Large Assembly Strategies - Mastering Autodesk Inventor 2015 and Autodesk Inventor LT 2015 (2014) 

Mastering Autodesk Inventor 2015 and Autodesk Inventor LT 2015 (2014)

Chapter 9. Large Assembly Strategies

Working with large assemblies is more manageable than ever before with the Autodesk® Inventor® software's Express mode tools. Using Express mode allows you to open a large assembly four to six times more quickly than opening the same file using Full mode. Combining Express mode with the use of tools such as shrinkwrap and substitute level of detail (LOD) representations improves performance and minimizes the time spent waiting. Substitute LODs allow you to swap out complex subassemblies with single substitute parts of less detail, all the while maintaining model properties and an accurate bill of materials (BOM).

Although each design department may have a different view on what a large assembly is, everyone can benefit from the large assembly tools and strategies discussed in this chapter. You can create fully functional digital prototypes ranging from 10 to 100,000 components if you approach the task with an eye to the topics covered here.

In this chapter, you'll learn to

·     Select a workstation

·     Adjust your performance settings

·     Use best practices for large assemblies

·     Manage assembly detail

·     Simplify parts

Selecting a Workstation

Ensuring that you have an adequate system to accomplish the type of design work you intend to do is an important, but often overlooked, step in achieving successful large assembly design with any parametric modeler. Understanding the capabilities and limitations of your computer and then budgeting for upgrades is a crucial part of working in today's design world.

If you consider the time you spend waiting and the loss of work experienced when working on an undersized computer, you will likely determine that a workstation upgrade will pay for itself within a year. If you budget for upgrades every two years, you could argue that the upgrade is paying for itself in the second year of use. Although this scenario might not fit your situation exactly, it demonstrates the idea that operating costs (hardware and software alike) should be budgeted and planned for and always measured against lost work and downtime.

Physical Memory vs. Virtual Memory

When your system runs low on physical memory (RAM) and requires more to complete an operation, Windows begins writing to a portion of the system hard drive known as virtual memory to continue. Virtual memory is often called a pagefile.

When considering a workstation for doing large assembly design, it should be your goal to work in RAM as much as possible because when Windows begins to write to virtual memory, you will notice a considerable drop in performance. One of the weakest links in terms of speed on even the most adequate workstation is the hard drive. Accessing data from RAM can be thousands of times faster than accessing data from the hard drive. Therefore, one of the best ways to beef up a workstation is to simply add more RAM.

If you are running an older computer or you skimped on RAM when you upgraded, you will notice that as you attempt to load large assemblies or drawing files of large assemblies in Inventor, you quickly use up available RAM. You will find yourself waiting for Windows to write data to the hard drive and then read that data. Although the unknowing user might think that Inventor has suddenly become slow, you should understand that no application can overcome the hardware and operating system limitations upon which it is installed.

Autodesk recommends a minimum of 12 GB of RAM for working with large or complex assemblies, with 24 GB or more being ideal.

Hardware

Hardware upgrades are an important part of any design department. Budgeting properly and knowing what components to allocate more money to can make these upgrades more manageable. Dollar for dollar, you should give priority to the components described in the following sections, in the order listed.

RAM

When it comes to RAM, the more your system has, the better it will handle large and complex assemblies in Inventor. You can use the number of unique parts in your assemblies (unique parts as opposed to multiple instances of the same part) as a general rule of thumb when determining how much RAM to consider. Here is a list of recommendations based on unique part count:

·     More than 5,000 unique parts: 6 GB of RAM

·     More than 10,000 unique parts: 12 GB of RAM

·     More than 15,000 unique parts: 18 GB of RAM

·     More than 20,000 unique parts: 24 GB of RAM

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Calculating the ROI of New Hardware

It's often hard to convince management (especially nontechnical managers) that you really do need that new computer to get your job done. After all, you're currently getting your work done, right? So why do you need the faster computer? This is where a return on investment (ROI) calculation will come in handy.

Let's say you routinely have to open, modify, and print large assembly drawings. To calculate the ROI, follow these steps:

1.  Measure how long it takes to complete this process on your old machine.

2.  Look at some benchmarks or talk to others who have faster machines, and make a conservative estimate of how long it would take you to do the same operations on the faster machine.

3.  Subtract the second number from the first. You now have your time savings per operation.

4.  Multiply this by the number of times in a day or week you perform these tasks.

5.  Multiply it by an hourly rate for your industry (you can always use your hourly salary) to get the dollar savings per time period (per week, month, and so on).

6.  Now you can take the cost of the new system and divide it by this cost savings per unit of time. This gives you the amount of time it will take to pay off that new computer.

Furthermore, once this time period has passed, you are actually making money because you are saving the company money once the investment has been paid off. When you can show that the hardware will pay for itself relatively quickly, you should have fewer problems convincing management to upgrade your equipment.

Another consideration for the ROI is who will inherit your old system. Generally, some person in the office will also benefit from a faster system, even if they run general office applications. For instance, if the receptionist is required to access many documents quickly across a network while assisting customers and other office staff, there is a good chance that your old CAD station will improve the ability to do so. Because this key person is the first point of information for so many people, the ROI is exponential. Passing old workstations to the shop floor to allow shop staff to access digitally stored files quickly is another way to achieve ROI and justify workstation upgrades.

You can check the specifications of your motherboard to determine how much RAM your system can accept. Many RAM manufactures, such as Crucial (www.crucial.com), have utilities on their websites that will look at your system and tell you the RAM configurations that your system can accommodate.

Graphics Cards

In the past it was generally recommended that you consider an OpenGL (developed by Silicon Graphics) graphics card that was tailored for CAD stations via a custom driver. Graphics card manufacturers and CAD developers worked together to produce and certify cards and drivers to offer the best results. With the introduction of Windows Vista, Autodesk began developing Inventor to work with Direct3D (part of Microsoft's DirectX application programming interface). Inventor 2015 was developed to work with versions of DirectX not available on earlier operating systems; therefore, Windows 7 with a graphics card compatible with DirectX 10 or newer is recommended.

With the move to Direct3D, using OpenGL and custom drivers is no longer necessary. I recommend that to find the best card for your workstation, you buy the card with the best performance within your budget. You can research cards by using a DirectX graphics processing unit benchmark website such as PassMark (www.cpubenchmark.net).

Gaming Cards for CAD?

In the past, high-performing gaming cards were not recommended for CAD applications because the drivers were developed for different purposes, and they often performed poorly when running CAD software. Now, though, with Direct3D not relying on custom drivers, gaming cards may very well offer the best performance for the dollar.

To ensure that Inventor has the optimal settings, select the Tools tab, click Application Options, and select the Hardware tab in the dialog box that opens. Inventor will automatically detect the appropriate level for your card, but you can set it manually to influence system performance if needed. You can choose from the following settings:

1.  Quality This setting sacrifices system performance for better graphics presentation. If you're running Windows 7 or Vista, anti-aliasing is turned on to improve the visual quality of the graphics display. For machines running Windows XP, there is no difference between Quality and Performance.

2.  Performance This setting favors system performance over graphic presentation. If you're running Windows 7 or Vista, anti-aliasing is turned off. This is the default setting.

3.  Conservative This setting uses the same graphics processes as Inventor 2009 and earlier. Options such as Visual Styles and Realistic Appearance Materials are not available.

4.  Software Graphics This setting uses software-based graphics processing instead of hardware-based processing. The setting is often used to troubleshoot issues with a graphics card.

For more information and recommendations on graphics cards and other hardware, refer to the following website:

www.inventor-certified.com/graphics/

Hard Drives

Inventor files are segmented, meaning that the graphics are separate from the feature information. When an assembly is first opened, only the graphics segments are loaded. When you edit a file, the additional data is loaded at that time. This makes a fast hard drive important for performance.

Another aspect of hard drive performance stems from file storage and workspace setup. In Inventor, working from your local drive is the preferred method, and Autodesk has often recommended that you avoid working on Inventor files across a network (although many or even most Inventor users do work across a network without issue). The reason for this is simply the number of files that you might be editing at one time. For instance, a change to a large assembly could potentially modify hundreds of part files, requiring all those files to be saved at once. Doing this across a network, particularly one with latency issues, may result in file corruption if the files are not saved correctly. Autodesk Vault is set up to store files on a server and copy those files locally when checked out for editing. When working in this manner, Inventor has a higher performance requirement than standard office applications, and the hard drive workload is heavy. Therefore, it may be worth it to consider upgrading your hard drive to a faster drive.

Processors

When considering processors for an Inventor 2015 workstation, the chief question should concern multicore processors. As a minimum, you should consider a dual-core processor even though Inventor is not truly a multithreaded application. (Multithreaded means that the operating system or the application will spread the processing load across the processor.) If you opt for a dual-core processor, you can still take advantage of it because Inventor will run on one core and other applications will run on the other. There are parts of Inventor—such as InventorViewCompute.exe, which computes drawing views, and Inventor Studio's rendering engine—that are multithreaded, so if you work with large or complex drawings or plan to do a lot of image and animation rendering in Inventor, you will likely benefit from more cores.

Working with Performance Settings

Whether or not upgrading workstations is an option, you should ensure that your system is set up for optimal performance for working with large assemblies. A number of options in Inventor will facilitate this.

Express Mode

Express mode accelerates file opening for large assembly files by not loading all of the assembly tools that Inventor offers in Full mode. Once an assembly file is opened in Express mode, you can click the Full mode button to enable the additional tools when necessary. This simple but effective mode switching can allow you to access your large assembly files an average of four to six times more quickly.

One of the primary differences you see when using Express mode is that you cannot edit components in the context of the assembly file. That is, when you right-click a component in the assembly, you will not see the Edit option. Instead, you will need to right-click and choose Open and then make the edits to the component. Once the edits are made, they will be reflected in the assembly, even though it is still in Express mode.

To open an assembly in Express mode, you first need to enable the Express mode option and then save the assembly file so that the additional Express mode information will be included in the file. You can enable Express mode by selecting the Tools tab, clicking the Application Options button, and then selecting the Assembly tab in the dialog box that opens. Select the Enable Express Mode Workflows option and then set the File Open Options to a unique file threshold that fits your typically large assembly and workstation. For instance, if your workstation typically struggles when you open an assembly that references roughly 400 unique files, you'd set this number to 400.

You can also bypass the unique file threshold and use Express mode to open an assembly file with fewer unique files by browsing to the file, selecting it, and then clicking the Options button in the Open dialog box. Here you'll see the Open Express check box, which will force the file to open using Express mode regardless of the unique file number. If the Express mode check box is grayed out, the file needs to be saved with the Enable Express Mode Workflows option enabled first to include the Express mode information in that file.

Working with Drawing Settings

Generating and hiding lines when creating and editing drawing views in Inventor can be some of the most processor-intensive tasks in Inventor. To help ease the demand on the system when you're working with large assembly drawings, you should be aware of several settings. You can find these settings by selecting the Tools tab, clicking Application Options, and selecting the Drawing tab in the dialog box that opens, as shown in Figure 9.1.

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Figure 9.1 Drawing application options

Display Line Weights

The Display Line Weights check box enables or disables the display of unique line weights in drawings. Deselect the box to show lines without weight differences. Line weights will still print correctly, even with this box selected. Deselecting this box will speed up the performance of your drawing during edits and annotation work.

View Preview Display

The options in the Show Preview As drop-down box set the type of preview you get when creating a view. All Components is the default, but you will find that selecting the Partial or Bounding Box option will improve performance because Inventor will not be required to create and update the preview as you drag your mouse pointer around the screen. The preview setting does not affect the drawing view result. Bounding Box previews a simple rectangle during the view creation, and Partial previews a simplified representation of the view. Bounding Box is the most efficient.

When using this option, you can still preview the assembly if you'd like by selecting the Preview check box in the Drawing View creation dialog box, but the default will be a simple bounding box. Using the Bounding Box option is suggested if you find yourself waiting for the preview to generate during drawing view creation.

The Section View Preview As Uncut check box will also provide some performance improvements when selected. This option will allow Inventor to display the section view preview as unsectioned in order to be more efficient. The section view will still be generated as normal.

Enable Background Updates

When background updates are enabled, raster views are created temporarily until the computation is complete. This is indicated by green border corners on the views and a green view node in the browser. Raster views are simplified placeholder pictures of the view, used to create and place the view quickly so as not to slow you down when creating views of large or complex models. Precise drawing views are calculated in the background while you work with raster views.

You can hover your mouse pointer over the drawing view node in the browser to see the percentage of compute progress. Heavy view computation is spread over multicore processors using InventorViewCompute.exe, as is evident in the Windows Task Manager.

While a view of a large assembly or complex model is computing, you can continue to create other views or annotations. However, some tools are disabled during view computation. These tools are listed here:

·     Automated Centerlines

·     Auto Balloon

·     Project Geometry

·     Hidden Annotations

·     Model Features

Drawings containing raster views can be saved and closed while background computations are still working. If the drawing is closed during background updates, the updates will stop and be restarted the next time the drawing is opened.

BOM Views and Performance

In an assembly file you can enable a Structured BOM view or a Parts Only BOM view using the BOM editor. However, if you have both views enabled, you will likely notice that your large assembly drawings take longer to open. Therefore, you should generally choose not to have both views enabled.

Memory Saving Mode

The Memory Saving Mode option sets the way Inventor loads components into memory during view creation. When this option is selected, Inventor loads components into memory before and during view creation and then unloads them from memory once the view is created.

Although memory is conserved using this mode, view creation and editing operations cannot be undone while this option is enabled. You'll notice that the Undo/Redo buttons will be grayed out after a view creation or edit. This option will also have a negative impact on performance when you're editing and creating views because the components must be loaded into memory each time. Because of this, you should consider setting this option as an application setting only if you always work with large assemblies.

It is generally preferred to set this option per document by selecting the Tools tab, clicking Documents Settings, selecting the Drawing tab in the dialog box that opens, and then setting the Memory Saving Mode drop-down list to Always. Figure 9.2 shows the default setting of Use Application Options.

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Figure 9.2 Drawing Document Settings

Shaded Views

Also in the document settings, you can adjust the way that shaded views are displayed. Setting the Use Bitmap drop-down list to Always, as shown in Figure 9.2, improves performance by applying raster shading as opposed to a vector style. The difference impacts the display but typically does not affect printing.

You can also adjust the bitmap resolution; setting it lower conserves memory and speeds up performance. The default is 100 dpi. Setting the dpi to 200 or higher will invoke a prompt, warning you that increasing this setting for large assemblies may not be possible.

Troubleshooting Graphics Issues and Crashes

It's often difficult to determine the source of graphics issues and graphics-related crashes without knowing how to isolate and illuminate some of the variables. One of the best ways to do this is to go to the Hardware tab of the Application Options dialog box and set the Graphics Setting radio button to Software Graphics.

This setting uses Inventor, rather than your graphics card, to render the on-screen graphics. Therefore, any graphics anomalies that exist while using this setting can be attributed to something other than the graphics card. If you set this option to Software Graphics and your graphics issues go away, your video card (or video card driver) is mostly likely the cause. If the issue returns when you set the option back to the recommended setting, then you should look into updating or rolling back your graphics card driver or getting a different graphics card that handles Inventor graphics better.

Keep in mind that this is a just a test, and I don't recommend running Inventor using the Software Graphics setting all of the time, since it will cause Inventor to run slowly.

Working with Model Display Settings

When working within the modeling environment, you can adjust several settings to have a positive impact on performance. You can access these settings by selecting the Tools tab, clicking Application Options, and selecting the Display tab in the dialog box that opens, as shown in Figure 9.3.

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Figure 9.3 The Display tab in the Application Options dialog box

Appearance

All of the various display options can be controlled as application settings or as document settings. Using the application settings allows consistency across all of the documents that you work with. Document settings will adopt the settings that were used when the document was saved.

Not all settings are controlled by the Appearance option, but you can define useful settings such as displaying the model in orthographic or perspective view and what visual style you want active.

Display Quality

Setting the Display Quality drop-down shown in Figure 9.3 to Rough will speed up performance by simplifying details. Navigation commands such as zooming, panning, and orbiting are particularly affected by this setting. If you find that the rough display is not to your liking, you can toggle back and forth according to the size of the assembly model you are working with.

View Transition Time (Seconds)

The View Transition Time (Seconds) setting controls the time required to transition smoothly between views when using zooming and viewing commands. A zero transition time takes you from the beginning view to the end view instantaneously. For instance, if you were zoomed in on a small component and wanted to zoom to show all components while this slider was set to zero, you would not see the gradual zooming out. While this might provide a gain in performance, understand that it can make display changes concerning position and orientation less clear, with the result that your adjustments would appear somewhat erratic.

Minimum Frame Rate (Hz)

You can use the Minimum Frame Rate (Hz) setting to specify how slowly the display updates during zooming and orbiting commands. It may be hard to see the effects of this option on a normal-sized part or assembly because the views will typically update more quickly than the rate of this setting, but with large assemblies the results become obvious as components are dropped from the display during zoom and orbit updates. Here is a quick description of how the slider setting corresponds to the frame rate:

·     0 always draws everything in the view, no matter the time required.

·     1 tries to draw the view at least one frame per second. (Inventor will simplify or discard parts of the view if needed but will restore them when movement ends.)

·     5 draws at least five frames per second, 10 draws at least ten frames per second, and so on, up to a maximum of 20. Using the maximum frame rate of 20 will speed up zoom and orbit operations and give you the best results for large assemblies.

The settings in the Display tab can affect the performance of the system as well as the user's comfort when working in Inventor.

Working with General Settings

The following sections describe a few general settings that you can adjust to help the performance of large assemblies. You can access these settings by selecting the Tools tab, clicking Application Options, and selecting the General tab in the dialog box that opens. That tab is shown in Figure 9.4.

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Figure 9.4 Default application options

Update Physical Properties On Save

When checked, the Update Physical Properties On Save setting, located in the Physical Properties area on the right side of the dialog box, recalculates the mass properties of the model when you save the file. This ensures that mass properties are up-to-date. Setting this to Parts Only will ensure that the parts are all up-to-date without requiring you to wait on the recalculation for large assemblies. Note that this setting is disabled altogether by default but is recommended to be set to Parts Only if you find it helpful. Note too that the same function can be performed manually from the Bill Of Materials Editor and the Manage tab.

Undo File Size

The Undo File Size option, on the lower-right side of the dialog box, sets the maximum size of the temporary file that records changes to a file so that actions can be undone. It's typically required to increase the size of this setting when working with large models and drawings because each undo action is typically a larger calculation. Autodesk recommends adjusting this in 4 MB increments.

Enable Optimized Selection

The Enable Optimized Selection setting, located on the lower-right corner of the dialog box, improves the performance of graphics during prehighlighting in large assemblies. When the Enable Optimized Selection setting is activated, the algorithm for the Select Other function filters for only the group of objects closest to the screen. If you click through this first group of objects, the next group is considered for highlighting.

Status Bar

The status bar displays information concerning the number of files being accessed by Inventor, at the bottom-right corner of the Inventor screen, as shown in Figure 9.5. The number to the left is the total number of occurrences of all components in the active document. The next number is the total number of files open in the Inventor session.

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Figure 9.5 The status bar

Using the Memory Probe

Included in your install of Inventor is a utility designed to monitor memory use for your system. The MemProbe utility, shown in Figure 9.6, looks at the Inventor process and displays its use of physical and virtual memory. It can often be useful in troubleshooting issues of capacity and slow performance. You can find this tool at the following location: C:\Program Files\Autodesk\Inventor 2015\Bin\memprobe.exe. You might find it useful to create a desktop shortcut to it, if you find yourself using it often.

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Figure 9.6 The MemProbe utility

Working with System Settings

You can adjust several settings in the operating system to help with performance. Inventor users commonly set the pagefile size to twice the amount of RAM to gain performance. There are also many visual effects that you may have grown accustomed to that actually cost you resources. If you are serious about turning your workstation into a large-assembly workhorse, it is advisable to disable these features.

Adjusting the Virtual Memory Paging File Size

To change the size of the virtual memory paging file in Windows 7, right-click the Computer icon and choose Properties. On the System Properties tab, click the Advanced System Settings tab, click Performance Options, and, finally, under Virtual Memory, deselect Automatically Manage Paging File Size For All Drives. Then click Change.

Windows 7 is set to an Automatic or System Managed paging file size. If you choose to set a Custom paging file size, you should refer to the recommended size that the dialog box offers and set the minimum and maximum to the same value to minimize fragmentation of the paging file if it needs to expand. Figure 9.7 shows the Virtual Memory dialog box.

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Figure 9.7 Setting the pagefile size

Setting Virtual Memory

Search the Internet and you will find hundreds of incorrect theories as to how to set the values for your virtual memory. One of the major myths is that you should set the initial and maximum to different values. If you are dedicating a portion of your hard drive for a pagefile, why start it small and then let it grow? Just provide the maximum amount of space you can and let it be.

Disabling Common Visual Effects

Windows provides many options to set the visual effects of your computer. Many of them have a surprisingly high impact on performance when memory is scarce. Here are a few you might consider disabling in order to conserve resources:

1.  Screen Saver To disable the screen saver, you can right-click your desktop and choose Personalize; then set the Screen Saver option to None. While you are working, screen savers are just another running process. You may want to set the Power Saving Mode option to turn off the monitor after a certain amount of time. If you use an LCD monitor, understand that screen savers do nothing to save an LCD screen.

2.  Visual Settings Many of the fade and shadow settings used in Windows look nice but come with a performance price if your system is on the slow side. To adjust these settings, you can right-click your desktop and choose Personalize; then select the Windows Classic theme.

3.  Screen Resolution If you're fortunate enough to have a nice, large-screen monitor, you probably have set up the screen resolution to maximize your space. However, this may be working against your large assembly pursuits. Experiment with setting the screen resolution to a lower setting such as 1024×768 to see whether you gain any performance when working with large assemblies.

Large Assembly Best Practices

Oftentimes, Inventor users don't think about large assembly performance until it has already become an issue with the model on which they are working. It is possible for two Inventor users working on two identical workstations to create two seemingly identical models, and yet those two models might perform in dramatically different ways.

If the first user has been mindful of large assembly management all along, his model and drawings will be much easier to open and work with. If the second user concentrated only on her design and gave no thought to the memory demands of the files she was creating, her model will be slow to open and work with and ultimately more likely to cause application crashes and data corruption. When the next job comes along, user 1 can reuse his model to create a similar design, whereas user 2 will likely re-create the assembly model because she does not trust the integrity of the first model she created.

Understanding where performance savings can be gained as you create the model will pay off once the large assembly is created and will make it much more manageable to work with along the way. And of course, a large assembly model can be revisited and cleaned up according to best practices to make it more manageable as well. Either way, having a model that is manageable and can be reused for similar work in the future should always be your goal.

You should be considering assembly performance when creating and editing a model, when opening the model, and also when detailing and annotating the model.

Working with the Model

You can use several methods to ensure that your large assembly will not become unmanageable. It is important to remember that the term large assembly is subjective. To you a large assembly may be 200 components, whereas it may be 20,000 to someone else. Either way, following best practices ensure that you are developing good procedural habits and are prepared for the day when you are asked to design a much larger assembly than you typically do today.

As was discussed earlier in this chapter, hardware limitations might be an obstacle that you cannot overcome even if you follow every best practice, but you'll need to follow these practices to know that for certain. Conversely, even if you have a workstation that is extremely capable, you will still benefit by developing good work habits and making your models easier to handle on less-capable workstations of others you collaborate with.

Improving File Open Time

It is a good practice to shut down Inventor and other Windows applications if you will be leaving them for an extended period of time. Closing these applications can allow the system to free up memory “leaked” by drivers and subroutines that take up memory when executed but do not release it when finished, even if you don't use those functions again.

When working with large datasets, shutting down the application and reloading the model can be time-consuming. There is a default setting on the File tab of the Application Options dialog box that saves the last-opened assembly and its component files in cache. You can also define a specific file to be kept so that you can work with others and maintain the benefits of the Quick File Open setting for a specific assembly.

Reducing Assembly Constraints

Using subassemblies within upper-level assemblies can reduce assembly constraints. The importance of this concept cannot be overstated. Reducing assembly constraints can eliminate the number of redundant calculations Inventor must make to solve your model, and therefore it pays off immediately in that respect. The improved organization and ability to reuse components already organized into subassemblies is a benefit that may be realized in the future.

To reorganize an assembly that has not been created using subassemblies, you can use the Demote option. To explore this concept, let's make some changes to an assembly:

1.  Open the file mi_9a_001.iam located in the Chapter 9 directory of your Mastering Inventor 2015 folder. If you have not already downloaded the Chapter 9 files from www.sybex.com/go/masteringinventor2015, please refer to the “What You Will Need” section of the introduction for the download and setup instructions.

Although not a large assembly by anyone's standard, this assembly has been created without using subassemblies to demonstrate the ability to demote components into subassemblies from the top down. Currently, this assembly has a total of 31 constraints being used at the top-level assembly. Your goal is to restructure this assembly into three subassemblies so that you can reduce constraints and create subassemblies that can be used in other stapler designs.

2.  At the top of the Model browser, you'll see the words Assembly View with a drop-down arrow next to them. Use the drop-down arrow to change the browser view to modeling view.

Assembly View Displays assembly constraints and connections nested below the assembly components, as well as in the Relationships folder. Part modeling features are hidden.

Modeling View Displays all assembly constraints and connections in a folder named Relationships at the top of the browser tree. Each part's modeling features are displayed below the part.

3.  Click the plus sign next to the Relationships folder found at the top of the browser tree to display the list of all the constraints in the assembly.

4.  In the Model browser, select all the components with a prefix of 100.

5.  Once you've selected those components, right-click and choose Component  Demote, as shown in Figure 9.8.

6.  You are presented with a Create In-Place Component dialog box, where you can specify the name of the new subassembly, the template file, the file location, and the default BOM structure. Enter 100 for the name, set the BOM structure to Phantom, and then click OK.

Phantom Subassemblies

Setting a subassembly as Phantom prevents it from being listed in the bill of materials while still allowing the parts contained within the subassembly to be listed.

7.  Click Yes in the warning stating that assembly constraints will be moved with the demoted components, shown in Figure 9.9.

This warning simply states that any constraints between the 100-series parts and the 200- and 300-series parts will now be redefined to be between subassembly 100 and the 200- and 300-series parts. The constraints between the 100-series parts and other 100-series parts are maintained in subassembly 100.

This is important in large assemblies because it can significantly reduce the number of constraints used. Consider the five components you selected to demote in the stapler. If these components all had just one assembly constraint, each relating it to some part that will not be in the new subassembly, those five constraints will be discarded.

Continuing with the example, you should now see the subassembly named 100.iam in the Model browser. Because of the restructure, you will need to ground the assembly so that it cannot be accidentally moved. Then you can continue to demote components into another subassembly.

8.  Right-click 100.iam and click Grounded to set it in place.

9.  In the Model browser, select all the components with a prefix of 200.

10.Right-click and choose Component  Demote.

11.Enter 200 for the name, set the BOM structure to Phantom, and then click OK. Click Yes in the warning dialog box.

12.Repeat the steps for demoting for all the components with a prefix of 300 until your browser looks like Figure 9.10.

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Figure 9.8 Demoting components to a subassembly

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Figure 9.9 Restructuring components warning

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Figure 9.10 Subassemblies created by demoting

If you look in the Relationships folder at the top of the browser tree, you'll see that the number of constraints that exist at the top level of the assembly has been reduced considerably.

You can also restructure components by dragging a component listed in the assembly browser, either in or out of a subassembly browser node. Moving components up out of a subassembly is called promoting rather than demoting. Because you can promote or demote unconstrained and underconstrained components, you may need to edit the subassembly and ensure that components are constrained properly within that subassembly.

Assembly Constraint and Adaptivity Options

There are three Application Options settings to be aware of that can impact assembly performance. When working with large assemblies, you might want to have all three of these options deselected. You can find them by selecting the Tools tab, clicking the Application Options button, and then selecting the Assembly tab. The options are as follows:

·     Enable Relationship Redundancy Analysis

·     Enable Related Relationship Failure Analysis

·     Features Are Initially Adaptive

Adaptivity

Too many cross-part adaptive features can cripple the performance of even a modest-sized assembly if used without discretion. As discussed in Chapter 8, “Assembly Design Workflows,” adaptivity should generally be turned off once the adaptive feature or part is created.

Often features and parts are made adaptive during the early design stages of a model, when changes are made quickly and you want many parts to follow these changes. Turning off the adaptive status in the part ensures that your assembly performance will not be affected. If the adaptive part needs to be edited, you can turn on its adaptive status so that you can make adjustments.

Many times parts become adaptive by default when a new part or feature is created in an assembly, because a reference sketch is projected from one part to another. You can disable this by clicking Application Options on the Tools tab, selecting the Assembly tab in the dialog box that opens, and then deselecting the Enable Associative Edge/Loop Geometry Projection During In-Place Modeling option under Cross Part Geometry Projection.

You can also hold the Ctrl key while selecting individual edges for projection into your sketch. This works only when you're selecting individual edges. Selecting a face will build an adaptive relationship. Either technique will create fewer accidental adaptive parts but may require more manual effort in projecting geometry across parts.

Selection Tools

When working with a large assembly, combing through all the many parts within that assembly that you want to select for a given task can be time-consuming and difficult if you attempt to locate them using the standard Pan, Zoom, and Orbit methods. Instead, make yourself familiar with the options in the assembly selection tools.

You can use selection tools to suppress sets of components based on such factors as size, internal components that are not visible because of the presence of external housings, and so on. For instance, to maintain performance, you may not want to load all the internal components into memory when they are not important to your current design task. Once you've selected the internal components, you can suppress them and create an external-part-only level of detail representation. If you haven't created level of detail (LOD) representations before, you can find information on how to do so in Chapter 8.

Another use of assembly selection tools is to create view representations in the assembly to aid in the creation of views in the drawing file. As an example, when you place a view in the drawing using a design view that was created with the All In Camera tool, only the components in the screen view plane are calculated. This increases performance and memory capacity. Figure 9.11 shows the available selection tools.

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Figure 9.11 Available selection tools

The following selection tools are available:

1.  Select Component Priority Sets the selection to pick up the topmost structure level of components. If set, this will pick up subassemblies and not their children.

2.  Select Part Priority Sets the tool to select parts, no matter what their subassembly structure.

3.  Select Body Priority Sets the tool to select solid bodies within their parent part file, no matter what their subassembly structure. This option works best when using the Modeling view. When using the Assembly view, the Find In Browser option does not work.

4.  Select Feature Priority Selects individual features rather than the parts that contain them.

5.  Select Faces And Edges Allows you to highlight and select faces or the curves that define those faces.

6.  Select Sketch Features Allows you to highlight and select sketches or the curves that define those sketches.

7.  Select Visible Only Selects only visible components in a selection set.

8.  Enable Prehighlight Displays prehighlighting when your cursor moves over an object. This does not affect the Select Other tool, which always shows prehighlighting.

9.  Invert Selection Deselects all components previously selected, and selects all components previously unselected.

10.Previous Selection Reselects all components in the previous selection set.

11.Select All Occurrences Selects all instances in the current file of the selected component.

12.Select Constrained To Selects all components constrained to a preselected component or components.

13.Select Component Size Selects components by the percent set in the Select By Size box. Size is determined by the diagonal of the bounding box of the components. Click the arrow to select a component and measure its size to use as a scale. Figure 9.12 shows the Select By Size dialog box.

14.Select Component Offset Selects components fully or partially contained within the bounding box of a selected component plus a specified offset distance.

15.Select Sphere Offset Selects components fully or partially contained within the bounding sphere of a selected component plus a specified offset distance.

16.Select By Plane Selects components fully or partially intersected by a specified face or plane.

17.Select External Components Selects external components based on a percentage of the component's viewable surface.

18.Select Internal Components Selects internal components based on a percentage of the component's viewable surface.

19.Select All In Camera Selects all components in the current view screen based on a percentage of the component's viewable surface.

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Figure 9.12 Select By Size dialog box

Using the Feature Selection Filter to Select Work Planes

It can be a major pain to try to select a work plane while in a busy assembly file. To make it easier, use the Select Feature Priority filter or the Select Faces And Edges filter. Your cursor will no longer select parts but only features, making it easy to select even the most obscured work planes.

View Representations

View representations are often used in large assemblies to navigate to a predefined viewing angle so that you do not have to tax your system with heavy graphics regeneration. For instance, if you have an assembly that contains an entire production line of material-handling equipment, you may find it difficult to orbit around to the backside of the assembly to complete a simple task such as selecting a face or just looking at the assembly. If you set a design view before orbiting and then set another once you have orbited to the desired view, you can then easily toggle between the two views of this assembly, thereby increasing performance during navigation between these predefined views.

View representations have other large-assembly benefits as well. When creating a drawing view of a large assembly, you can specify a preset view representation and reduce the time it takes to create the drawing view. If you have turned off the visibility of some components in the assembly view representation, the drawing view can generate even faster and provide you with a clearer and more concise view. Of course, if you already have the assembly open when creating the drawing view, the components are likely already loaded into memory.

Another way that the experienced Inventor user may use view representations is to navigate the Model browser. For instance, if you set up a view representation to zoom in on a particular subassembly so that you can navigate to that component quickly, you can save that view representation while the entire model tree is rolled up and only the subassembly of interest is expanded. This browser state will be saved within the view representation.

Once a view representation is created, you can right-click it and choose Copy To Level Of Detail to copy the view representation to an LOD representation. This allows you to transfer the visibility settings from the view representation to the LOD where they will be suppressed. In this way, you do not have to duplicate the process of turning parts off.

Find

Navigating a large-assembly Model browser can be a chore. To help with this, you can employ the Find tool to define search criteria for constraints, components, features, sketches, and welds. Searches can be saved for future use and recalled as needed using the Open Search button, shown in Figure 9.13.

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Figure 9.13 The Find tool in an assembly file

You can access the Find tool in the following ways:

·     From within a file, click the binoculars icon in the Model browser.

·     In the Inventor Open dialog box, click the Find button.

Opening the Model

One of the most important aspects of working on a large assembly file is being able to open the file. Although this seems obvious, many Inventor users seem to approach opening a model as an afterthought. Consider it in this way—if you were tasked with carrying a pile of stones up a flight of stairs, you would probably be unlikely to attempt to carry them all up the stairs at once. But this is exactly the kind of heavy lifting you are asking your workstation to do when opening a large assembly.

To allow your workstation to make multiple trips when opening an assembly file, you will use LOD representations. You create LOD representations by suppressing components in an assembly. Once the LOD is created, you can access it the next time you begin to open the file by using the Options button, shown in Figure 9.14. Once the assembly file is open, you can unsuppress components as required, and those components will then be loaded into memory. You can also specify a default LOD so that the assembly opens to it without your having to use the Options dialog box every time. This is done from Application Options on the Assembly tab. You'll learn more about creating LODs later, in the “Managing Assembly Detail” section of this chapter.

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Figure 9.14 Opening LODs

If you need to open a large assembly that has not been properly managed, you may find yourself having to locate or skip a number of parts and subassemblies. This can be a tedious task, but the Skip All Unresolved Files option in the File Open dialog will bypass locating missing components and load the members of the assembly that can be located automatically.

LOD in Subassemblies

Often, you might create a complex assembly model as a stand-alone design because you need to insert that model into an upper-level assembly as part of a larger system. Because the original design was required to generate production drawings and an accurate BOM, it includes all the components in the design.

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However, because you will be placing multiple instances of this subassembly, you want to avoid placing it at the full level of detail. You might create an LOD in the subassembly where all internal components, all external hardware, and all internal and external fasteners are suppressed, leaving only the external housing and frame components.

LOD representations of subassemblies can be accessed from the Options button in the Place Component dialog box when you are placing them into upper-level assemblies. By placing a subassembly at a reduced level of detail, you have created a much smaller, top-level assembly file and yet still have the ability to pull an accurate BOM even from the top-level assembly.

Working with Large Assembly Drawings

Although large assembly files require some forethought and management; so do the drawing files of these large assemblies. Because Inventor generates the line work from the models that you create views from automatically, it is easy to take for granted the large number of calculations required to do this. Stop for a moment and consider all the hidden lines, sectioned parts, and so on, that Inventor has to consider in order to render your drawing views accurately.

It is for this reason that you will want to adopt slightly different techniques than those you use to make part or small assembly drawings. If you have not yet worked with Inventor's drawing environment much at this point, you can find more information specific to Inventor drawings in Chapter 12, “Documentation.” Keep in mind that many of the options mentioned in this section are covered in more depth in Chapter 12.

Working with High-Speed Raster Views

You can enable an option to create raster views for large or complex models. When enabled, a draft preview of a drawing view will be displayed while the precise drawing view is calculated in the background. Raster drawing views enable you to continue to work and annotate the drawing while the precise calculation of a drawing view is completed.

To enable a raster view, you can use either of two methods. One creates a raster view until the view calculation is complete, at which time it converts to a precise view. The other option maintains the view as a raster view until you choose to make it a precise view.

To enable temporary raster view creation, select the Drawing tab of the Application Options dialog box and then select the Enable Background Updates option (toward the bottom) to use raster views. By default this option is not selected. This setting will create the view as a raster view but will allow the raster view to convert to a precise view when the calculations are complete.

To create views that persist as raster views, you can select the Raster View Only check box found at the bottom of the Drawing View creation dialog box, as shown in Figure 9.15. To convert a raster view to a precise view once it has been created, you can right-click the view and choose Make View Precise. You can convert it back to a raster view by right-clicking again and choosing Make View Raster.

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Figure 9.15 Creating a raster drawing view from an LOD

Raster views are indicated by green corner glyphs in the graphic window and by either the green circular arrows icon in the browser if the view is calculating toward becoming precise or a red slash across the view icon in the browser for a static raster view. If you place your cursor on a calculating raster view icon, you'll see a tool tip showing the progress of precise calculation.

Several features are not available or will work differently while the precise views are being calculated and the raster view is displayed. This alternative functionality is intended to handle the situations where the less-detailed raster views might cause confusion or problems.

These features are not available for raster views:

·     Automated Centerlines cannot be created for raster views.

·     Auto Balloons cannot be used for raster views.

·     Model Features cannot be selected as edges in raster views.

These features work differently for raster views:

·     Tangent model edges are always shown in raster views, and their properties or visibility cannot be edited.

·     Interference edges are not shown in raster views.

·     Reference Parts might have incomplete geometry in raster views.

·     Hole Tables are not available to use the View and Feature options for raster views.

·     Thread Annotations are not displayed in raster views. New or existing thread notes are attached to thread features after views turn precise.

·     Printing when a drawing includes raster views provides three options: You can print the current precise views, wait until all views are precise, or cancel the print. However, I do not recommend you print raster views because geometry on printed raster views can be different from the final precise views.

·     Export to AutoCAD DWG, DWF, DXF, or PDF cannot be completed for a drawing with raster views. If a precise view calculation is in progress, a progress bar is displayed. You can wait until the calculation finishes or cancel the export.

·     Save and Close for drawings containing raster views can be executed as expected. If the file is closed and reopened, the raster views are automatically recalculated as precise.

Creating Large Assembly Drawing Views

When creating drawings of large assemblies, it is advised that you do so from an LOD representation already created in the model. Doing so reduces the number of files Inventor is required to access to create and update the line work in the view. To create views from assembly representations, you specify the representations you want to use in the Drawing View dialog box, as shown in Figure 9.15 earlier. Keep in mind that when browsing for the file to create a view of, if you use the Options button in the Open dialog box to specify the representation, you will reduce the time it takes to create the view.

Although using LODs will help with drawing views, be aware that because Inventor employs a global bill of materials, as soon as you place a parts list, balloon, or other annotation referencing the bill of materials, the number of files loaded into memory increases to include all of the parts in the bill of materials. This situation somewhat defeats the purpose of the LOD tools, but currently no solution is available.

View Preview Display

If you find yourself waiting for the preview of your assembly to generate before being able to proceed with view creation options, you will want to change the preview display to use bounding boxes and then enable the preview on files as required on a case-by-case basis by clicking the preview icon shown at the bottom left of Figure 9.15. Note that enabling/disabling the preview is an option only when using the Bounding Box or Partial option. To find this setting, select the Tools tab, click Application Options, select the Drawing tab in the dialog box that opens, and look in the View Preview Display section.

Reducing Hidden Lines

Hidden-line generation can be one of the most memory-intensive aspects of creating a drawing view. Generally, with large assemblies it is not desirable to show the hidden lines of all components. Instead, you typically will want to enable hidden lines for just those components where hidden lines add clarity.

Rather than selecting the Hidden Line style in the Drawing View dialog box, first create the view with no hidden lines. Next, locate and expand the view you just created in the browser, and select the components you intend to be shown with hidden lines. Right-click the components, and choose Hidden Lines.

You will be prompted with a message box informing you that you are changing the view style to show hidden lines and that any children of this view will be granted an independent view style based on their current setting, as shown in Figure 9.16. The result will be that only the components you chose will be displayed with hidden lines.

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Figure 9.16 Managing hidden lines

Creating Title Block Logos

A sure way to slow down your drawing's performance is to create an unnecessarily complex title block. If you have included a bitmap of your company logo in your title block, ensure that the bitmap file is reduced in resolution and file size as much as possible. You can use any photo editor to do this.

Once you've reduced the bitmap file as much as possible, consider embedding the file into the title block rather than linking it. Although linking the bitmap does give you greater flexibility in updating the logo independent of the title block, Inventor will be required to locate the bitmap each time the drawing is loaded. To embed rather than link the logo bitmap, simply deselect the Link check box when inserting the bitmap.

If you have pasted the logo in from Autodesk® AutoCAD® software, ensure that the logo is as clean as possible. You may be better off removing the hatches from the logo in AutoCAD and then adding them using the Fill/Hatch Sketch Region tool in Inventor.

Reducing the Number of Sheets and Views per Drawing File

Although it is possible to create a large number of sheets in a single drawing file, it is generally accepted that this is not good practice. Instead, you should consider making a new file for each drawing sheet when possible. Or at the very least, keep the number of sheets per file as low as possible. There are two primary reasons for doing so.

The first reason is simply to keep the file size down. If you have a drawing of a large assembly file that includes four sheets and has a file size of 80 MB, you could split this into two files, each with two sheets and a file size of approximately 40 MB. In this way, you do not need to load the extra 40 MB in sheets 3 and 4 just to make an edit to sheet 1.

The second reason to minimize drawing sheets is so you are not guilty of placing all your eggs in one basket. Creating multiple tab or sheet files in any application can be risky. Imagine you created a load calculation spreadsheet and you developed the habit of adding a tab for each new calculation you do rather than creating a new file for each calculation. If the file becomes corrupt, you've lost all your calculations rather than just one set of calculations. The same thing could happen with your Inventor drawing if you habitually create new sheets instead of new files.

Managing Assembly Detail

In Chapter 8, you learned about creating LOD representations within your assemblies to reduce the memory requirements of working with large assemblies. Here you will consider how you can use these LOD representations to handle large assemblies more efficiently.

LOD Strategies

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All Inventor assemblies have four default LODs predefined and ready for you to use. Learning to use them and creating your own LODs is an important part of working with large assemblies. The default LODs are as follows:

1.  Master This LOD shows your assembly with no parts suppressed. You can think of it as the highest level of detail for any assembly.

2.  All Components Suppressed This LOD suppresses everything within the assembly. You can think of it as the lowest level of detail for any assembly.

3.  All Parts Suppressed This LOD suppresses all parts at all levels of the assembly, but subassemblies are loaded.

4.  All Content Center Suppressed This LOD suppresses any component in the assembly that is stored in the Content Center Files directory as designated by the IPJ (project) file or the Application Options settings.

When opening a large assembly, you can use the All Components Suppressed LOD to quickly open the file and then manually unsuppress components as required. However, it is more practical to create your own LODs and use them to efficiently open your assemblies. Consider creating intermediate LODs based on your design process.

For a closer look at LODs in action, follow these steps:

1.  From the Get Started tab, choose Open.

2.  Open the file mi_9a_002.iam from the Chapter 9 directory of your Mastering Inventor 2015 folder.

3.  Expand the Representations folder and the Level Of Detail node in the Model browser if they are not already expanded.

4.  Right-click the Level Of Detail header and choose New Level Of Detail. Change the name from LevelofDetail1 to MediumLOD.

5.  In the Quick Access toolbar (along the top of the screen), click the selection tool drop-down list (see Figure 9.17) and set your selection focus to Select Component Priority if it is not already.

6.  Using the same drop-down list, now choose Internal Components, shown in Figure 9.17.

7.  Set the slider to 85 percent and click the green check mark.

8.  Right-click anywhere on the screen, and choose Isolate to get a better view of the components you selected. Your screen should look similar to Figure 9.18.

9.  Now you'll bring back one component to add to your selection set. Select the component called MA- 001:1 in the browser, right-click, and choose Visibility. You should see the motor subassembly become visible.

10.Select all the components on the screen. You can use a crossing window to do this quickly.

11.Right-click and choose Suppress.

12.Right-click anywhere and choose Undo Isolate to bring back the visibility of the remaining unsuppressed components.

13.Save the assembly to ensure that the changes to your newly created level of detail are recorded.

14.Switch back and forth between the master LOD and your MediumLOD to observe the differences.

15.To modify MediumLOD, activate it and suppress any component you'd like; then save the assembly.

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Figure 9.17 Selecting internal components

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Figure 9.18 Isolated internal components

In the preceding steps you used selection filters to quickly select the internal parts and then used the Isolate tool to toggle the visibility setting of the unselected components. Then you suppressed the visible components. Understand that it is the Suppress option that creates and modifies LOD representations. Changing visibility affects only view representations and has no impact on the LOD. When you've finished experimenting with this file, you can close it and continue to the next section.

Substitute LODs

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You can use substitute LOD representations to trade out a large multipart assembly with a single part derived from that assembly. Substitute LODs improve efficiency by reducing the number of files Inventor is referencing and, if created from other LODs, can also reduce the amount of geometry required.

For example, in the blower assembly, you could create a substitute LOD from the entire assembly and then place that substitute into a top-level assembly as needed. You would certainly gain some efficiency by doing this because the top-level assembly is referencing only one file. However, if you created a substitute from MediumLOD, you would be maintaining an even higher level of performance in the top-level assembly because all the internal geometry that was suppressed in the creation of that LOD would be omitted.

To create a substitute LOD, follow these steps:

1.  From the Get Started tab, choose Open.

2.  Browse for the file mi_9a_003.iam located in the Chapter 9 directory of the Mastering Inventor 2015 folder and click Open.

3.  Expand the Representations folder and the Level Of Detail node in the Model browser if they are not already expanded.

4.  Double-click MediumLOD to set it as the active LOD if not already done.

5.  Right-click the Level Of Detail header in the browser and choose New Substitute and then Shrinkwrap. Notice that Inventor is asking you to specify a filename, a file template, and a location to create this file.

6.  Enter mi 9a 003 Substitute 100 for the name in the New Derived Substitute Part dialog box and leave the template and file location at the defaults.

7.  Click OK. Inventor opens a new part file and takes you directly into the shrinkwrap process, bringing up the Assembly Shrinkwrap Options dialog box.

8.  In the Style area at the top, ensure that the Single Composite Feature option is selected. The following are the descriptions of each of the four available options:

Single Solid Body Merging Out Seams Between Planar Faces Produces a single solid body without seams. Merged faces become a single color, where required.

Solid Body Keep Seams Between Planar Faces Produces a single solid body with seams. Colors are retained.

Maintain Each Solid As A Solid Body Produces a single part file with multiple bodies. This is the closest approximation to an assembly.

Single Composite Feature Produces a single surface composite feature and the smallest file. Colors and seams of the original components are maintained. The mass properties of the original assembly are stored in the file for reference.

9.  Ensure that the Remove Geometry By Visibility check box is selected.

10.Select Whole Parts Only.

11.Play around with the slider, clicking the Preview button to see what is removed.

12.Set the slider to 78 percent.

13.Under Hole Patching, select All.

14.Ensure that Reduced Memory Mode is selected at the bottom of the dialog box. When selected, this option allows the derived part to be created using less memory by not including the source bodies of the assembly parts.

15.Refer to Figure 9.19 to check the settings and then click OK.

16.Click Yes when asked about the mass properties. Note that Inventor closes the derived part file and returns to the assembly and that an LOD named SubstituteLevelofDetail1 has been created. You can rename it if you like by clicking it once and then a second time.

17.Save the assembly.

18.Double-click MediumLOD to set it as active and compare the substitute LOD by clicking back and forth between the two.

19.To see that the substitute shrinkwrap is a surface model, click the View tab and choose the Half Section View icon from the drop-down list on the Appearance panel.

20.Click Workplane2 in the Model browser.

21.Right-click and choose Done.

22.Choose End Section View from the drop-down list on the Appearance panel to turn off the section view.

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Figure 9.19 Deriving a shrinkwrap LOD

Figure 9.20 shows the substitute LOD as it appears in the browser.

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Figure 9.20 Substitute LOD

Recall that all LODs maintain an accurate BOM listing. To confirm this, select the Assemble tab, click Bill Of Materials, and interrogate the BOM to see that even though the substitute LOD consists of a single part, Inventor still maintains the BOM information for the entire assembly. You can close this file without saving changes and move on to the next section.

Subassembly LODs

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Subassembly use is where LOD representations really begin to pay off in terms of performance. Once LOD representations have been created in your assembly, you can switch the LOD in the subassemblies to match in three ways:

·     Place the subassemblies into a top-level assembly with the matching LOD by using the Options button.

·     Switch the LOD manually in the subassembly in the Model browser.

·     Use the Link Levels Of Detail tool at the top-level assembly to automatically set the subassemblies to the matching LOD.

In Figure 9.21, all of the subassemblies contain LODs named Frame Layout, Exhaust Connection, and Harness Layout set up within them. These LODs were linked using the Link Levels of Detail tool, as indicated in the browser by the LOD name shown in parentheses next to the assembly name.

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Figure 9.21 Nested LODs with a consistent naming scheme

You might take this concept one step further and edit your assembly templates to automatically include standard LOD names already in them. This way you do not have to create the LODs, but instead you can simply activate them and then suppress parts as required to “fill them out.”

Recall that Inventor specifies your template location on the File tab of the Application Options dialog box. Note that this can be overridden in your project file. Check this by selecting the Get Started tab and then clicking the Projects button, and look in the Folder Options section of the Project File Editor that opens. If a path is specified there, that is where your templates are located. If it shows = Default, the path found in Application Options is where your templates are located.

In the following exercise, the subassemblies all have LODs created in them. These are called Bolts, Washers, Nuts, and Galvanized. Each subassembly was configured with these LODs set up as described in the previous exercise. The top-level assembly has three LODs created, called Bolts, Washers, and Nuts. Although these LODs have been created, they have not been configured and currently do not differ from the master LOD. The following steps take you through the linking of the Bolt LOD at the top-level assembly to the Bolt LODs in the subassemblies:

1.  From the Get Started tab, choose Open.

2.  Open the file mi_9a_004.iam from the Chapter 9 directory of your Mastering Inventor 2015 folder.

3.  Expand the Representations folder and the Level Of Detail node in the Model browser.

4.  Double-click the LOD named Bolts to set it active, or right-click it and choose Activate.

5.  Click the Assemble tab, expand the drop-down list for the Productivity panel and choose Link Levels Of Detail.

6.  Click Bolts in the Link Levels Of Detail dialog box.

7.  Click OK in the Link Levels Of Detail dialog box and click OK to accept the warning that the assembly will be saved.

Note that the subassemblies have all been set so that the Bolts LOD is active in them. If one of the subassemblies did not have an LOD called Bolts, it would be left at its current LOD. You can continue this exercise by repeating these steps for the Washers and Nuts LODs if you'd like. Note too that each of the subassemblies has an LOD called Galvanized in which all parts that are not galvanized steel have been suppressed. You can create an LOD called Galvanized in the top-level assembly and then use the Link LODs tool to suppress all the parts not made of galvanized steel. You can also set different instances of a subassembly to display differing LOD representations.

Using LOD Naming Conventions

There is an infinite number of naming conventions for LODs, including the one suggested here (High, Moderate, and Low). Making LODs that have certain parts of the design turned on can be useful as well—for example, Frame Only, Frame & Transmission, Transmission Only, Conveyors Off, No Robots, and so on. If you give them descriptive names, other users can select the appropriate LOD for the work they need to complete.

Simplifying Parts

It's often suggested that things be made as simple as possible but not simpler. This is a good concept to keep in mind when creating models in Inventor. Adding extraneous details to common parts can have a negative impact on large assembly performance. Of course, if the part file is to be used for fabrication, then a certain level of detail is required. Oftentimes, though, we create models of common parts to be used in an assembly for the end goal of getting an accurate bill of materials. Assembly performance could most likely be improved by reducing the amount of detail in those types of parts.

Removing or Suppressing Unneeded Features

Reducing the number of edges and faces in a part is a sure way to minimize the size of the part file. Removing fillets and chamfers for purchased parts is a good way to eliminate extra faces. If you have common parts that are used in large numbers throughout your assemblies, you might consider creating two versions of these parts: one version for use in large assemblies and another for use in creating production drawings and Inventor Studio renderings. In Figure 9.22, you can see two versions of the same part. The file for the part on the left is approximately 600 KB, whereas the one on the right is less than 175 KB.

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Figure 9.22 A simplified part

In the following steps, you will derive a simplified version of a part and set the part numbers to match so the two files report the same in the BOM and parts lists. To create a simplified part, follow these steps:

1.  From the Get Started tab, choose Open.

2.  Open the file mi_9a_010.ipt from the Chapter 9 directory of the Mastering Inventor 2015 folder.

3.  Click the end-of-part (EOP) marker in the Model browser and drag it to just below the feature named Revolution1 (or right-click Revolution1 and choose Move EOP Marker).

4.  Change the appearance to Default (at the top of the screen in the Quick Access toolbar, click the Appearance drop-down arrow and scroll for Default).

5.  Do not save the part.

Figure 9.23 shows the end-of-part marker being placed above the existing features.

6.  From the Get Started tab, choose New.

7.  Choose the Standard.ipt template to create the new file and click the OK button.

8.  In the new part, right-click and choose Finish Sketch if required. This might not be needed if you have your Application Options setting set up so that a new sketch is not created automatically when a new part is created.

9.  On the Manage tab, click the Derive button on the Insert panel.

10.In the resulting Open dialog box, browse for the file mi_9a_010.ipt located in the Chapter 9 directory of your Mastering Inventor 2015 folder and click the Open button.

11.In the resulting Derived Part dialog box, choose the Derive Style option called Single Solid Body Merging Out Seams Between Planar Faces as the derive style.

12.Click the OK button to create the derived body.

13.In the Model browser, right-click the part name mi_9a_010.ipt and choose Suppress Link With Base Component. This ensures that the derived part will remain in the simplified state when you set the original part back to its fully detailed state.

14.Click the filename at the top of the Model browser and choose iProperties.

15.Choose the Project tab of the iProperties dialog box and enter mi_9a_010 as the part number. This ensures that as you use the simplified part in an assembly, it will have the same part number as the original part and report an accurate BOM.

16.Save the file as mi_9a_010_simple.ipt.

17.Return to the original part (mi_9a_010.ipt).

18.Either close the file and click No when asked to save changes, or drag the EOP marker back to the bottom of the Model browser, reset the part color, and then save the file.

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Figure 9.23 Using the EOP marker to simplify the original part

As a result you will have two files representing the same part. Both will be listed as the same component in the BOM, but the derived component will add far less overhead when used over and over in an assembly. Note that if the original part were to require a revision to the overall length, you would want to edit the simplified part file and unsuppress the link so that the changes are carried through. You can place both files in an assembly file to test this workflow if you'd like, or you can close these files.

The Bottom Line

1.  Select a workstation. Having the right tool for the job is the key to success in anything you do. This is true of selecting a large assembly workstation. You have learned that for optimal performance you should strive to keep your system working in physical memory (RAM).

1.  Master It You notice that your computer runs slowly when working with large assemblies, and you want to know whether you should consider a 64-bit system. How do you determine whether your system is adequate or whether it's time to upgrade?

2.  Adjust your performance settings. You have learned that there are many settings in Inventor and in Windows that you can use to configure the application to work more efficiently with large assemblies.

1.  Master It You want to make your current workstation run as efficiently as possible for large assembly design. What are some ways to do that?

3.  Use best practices for large assemblies. Knowing the tools for general assembly design is only half of the battle when it comes to conquering large assemblies. Understanding the methods of large assembly design and how they differ from those for general assembly design is a key to success.

1.  Master It You want to create adaptive parts so that you can make changes during the initial design stage and have several parts update automatically as you work through the details. But you are concerned about how this will adversely affect your assembly performance. How do you keep your performance level high in this situation?

4.  Manage assembly detail. Inventor includes several tools to help manage assembly detail so that you can accomplish your large assembly design goals.

1.  Master It You want to reduce the number of files your large assembly is required to reference while you are working on it and yet maintain an accurate bill of materials. How do you do that?

5.  Simplify parts. Creating highly detailed parts may be required for generating production drawings or Inventor Studio renderings, but using those high-detail parts in large assemblies may have an adverse effect on performance.

1.  Master It You want to create a lower-level-of-detail part file for common parts to be reused many times over in your large assemblies but are concerned about managing two versions of a part. How do you avoid versioning problems?