11/30/2006 - 5:00 pm - 6:30 pm Room:Marcello - 4503 (MSD Campus)

Step on the Accelerator in Autodesk Inventor®! Bill Fane - British Columbia Institute of Technology

MA35-2 The Inventor Content Center comes with a huge collection of stock components such as bearings,

bolts, bushings, and so on, that can greatly speed up the design process Question is: Do you still need to calculate the sizes of components you need? The Design Accelerator of Release 10 speeds up this process, while the new capabilities in Release 11 take another giant leap With the latest Design Accelerator, the design process now becomes performance driven You no longer need your engineering handbook to find the correct formula, then calculate the required sizes, then model the parts and assemble them Instead, you now simply enter the performance specifications and the Design Accelerator does the rest For example, you can design a V-belt drive simply by entering the input power and speed, the ratio, the loading factor, and the center-to-center distance The Design Accelerator automatically calculates the sheave sizes and belt quantity It then selects the commercial stock sizes and lengths that come closest to meeting your specifications and adjusts the center distance accordingly before inserting the models directly into your assembly Of course, if you change anything then everything updates We’ve come a long way from computer-aided drafting!

About the Speaker: An AutoCAD software user since 1986, Bill was a product engineer and manager for Weiser Lock in Vancouver, Canada for 27 years. Bill has taught AutoCAD and mechanical design at the British Columbia Institute of Technology since 1996 and teaches Autodesk Inventor at the Institute's Training Center. He has lectured on a wide range of subjects at Autodesk University since 1995. An active member of the Vancouver AutoCAD Users Society, he has written "The Learning Curve" column for CADalyst magazine since 1986, and writes about Autodesk Mechanical Desktop and Autodesk Inventor for Autodesk's Point A Toplines. He also writes for Inside AutoCAD Journal and Design Product News, and Cutting Tool Engineering. [email protected] Stay Connect to AU all year at www.autodesk.com/AUOnline

Step on the Accelerator in Autodesk Inventor!

NOTE This course is intended for intermediate users. I assume you have a working knowledge of Inventor, including sketching, constraining/dimensioning, solidifying, and assembling. It applies to Inventor releases 10 and 11. The basic functionality was introduced in release 10, while 11 expanded on it and changed the interfaces somewhat. I will deal with release 11. Once upon a time, a long time ago, ‘way back in the last millennium, when I went to school, the world was flat. Or at least, the drafting world was. We used paper and pencil to create engineering drawings in much the same style and format as the Romans had used. Yes, it was primitive, but somehow we (well, not me personally, but my generation) managed to build the 747 and the moon rockets. Next came CAD, which is a TLA (Three-Letter Acronym) for Computer-Aided Drafting. Actually, in the early days, there was some debate over whether the D stood for Drafting or Design, while a third camp argued for two Ds, as in CADD. Eventually, the general consensus evolved to Computer-Aided Drafting, because at the end of the day all we were really doing was to produce 2D drawings. As an aside, there should be no such job title as “CAD Operator”. They didn’t used to call us “pencil, T-square, set square and eraser operators”, did they? Then 3D parametric software arrived on the scene. It became much faster and easier to make changes and adjustments, and to play “what if” scenarios. We can perform stress and kinematic analyses, and we can test assemblies for proper fits and clearances. The D in CAD is shifting closer and closer to Design. This brings us to “functional design”, as manifested in Autodesk Inventor’s Design Accelerator. I’m not sure I would have chosen “functional design” as the description (hopefully most of my designs function), but instead prefer to think of it as “design by performance”. Let’s take a look at the design and drafting sequence in the development of a simple V-belt drive within a larger machine, as performed within a parametric modeler, or in paper and pencil for that matter. The basic steps would usually involve: 1. Determine the performance specifications to be met by the drive. This includes such things as the power, speed, service factor, life expectancy, and so on. 2. Decide to use a V-belt drive. 3. Perform appropriate calculations to determine the sheave diameters, V-belt length, whether or not to use multiple belts in parallel, and so on. 4. Check through the appropriate catalogs and standards to select the stock, standard components that come closest to meeting our requirements. 5. Produce 3D models of each component part and add them to our assembly model. 6. Produce 2D documentation as required. Inventor’s Design Accelerator does exactly what its name suggests. It accelerates the design process, in that it allows us to jump from step 2 almost directly to step 6. Let’s start with a quick demonstration of a V-belt design to help show this process. Our basic design assumptions are as follows: 1. Input: 50hp, 1750 rpm 2. Ratio: 4:1 reduction. 2 /7

Step on the Accelerator in Autodesk Inventor! 3. Narrow-series belts. 4. Approximately 36” centres. 5. Service factor 1.2 Now that we have the basic data, it’s time to apply it. The steps to be taken are as follows: 1. Within an assembly model, activate the Design Accelerator tool panel: click the down arrow beside the Assembly Panel title, and then select Design Accelerator from the drop list. 2. Click the V-belts tool. This brings up the Design tab of the dialog box of Figure 1.

Figure 1: The V-Belt Component Generator 3. Note that the Belt Mid-Plane button is pressed. Click on a suitable plane surface or work plane in the assembly. You can also set the mid-plane offset as desired. A preliminary representation of the V-belt drive immediately appears in the graphic screen. We will ignore it for now because it represents the leftover values from the last time the V-belt generator was used.

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Step on the Accelerator in Autodesk Inventor!

4. Click the down-arrow to the right of the Belt window. This brings up the unnamed dialog box of Figure 2. This dialog box will let us choose between Classical or Narrow belts, and the specific type within each category. Let’s go for a Narrow 5V Wrapped belt. 5. Returning to the main dialog box of Figure 1, we need to activate the scroll list at the right side of each pulley and select a style that is compatible with the chosen V-belt. 6. The first pulley is always the driver. Click on the second pulley to activate it. 7. Click on the “three-dot” button at the right end of the second pulley’s window. This brings up the Groove Pulley Properties dialog box (not shown). Enter 4.0 in the Ratio window, and then click OK to close the dialog box.

Figure 2: The Belt Type selector

We have now specified the main characteristics of our drive, and are ready to move on to the calculations. 8. Click on the Calculation tab to call up the dialog box of Figure 3 . 9. Use the drop lists to set the Type of calculation to be Design Number of Belts and the Load to be Power, SpeedÆTorque. This now sets things up so that all windows are grayed out except for the ones that are appropriate to our settings. 10. Enter the values as shown, and then click Calculate. 11. The values in the Results window will be updated, and suitable messages will appear in the message window. In our case the messages will indicate that a pulley used has a diameter smaller than the recommended minimum, but other than that the design complies with requirements.

Figure 3: The Calculation Window

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Step on the Accelerator in Autodesk Inventor! 12. Now let’s shift our attention to the graphic screen, where the preliminary representation has updated to reflect our specifications (Figure 4). In particular, notice the red crossed arrows at the centre of each pulley, and the double-ended one on the smaller (#1) pulley. 13. Using the cursor, click and drag the doubleended arrow. This causes the pulley to get larger or smaller. Meanwhile, the larger pulley also changes in order to maintain the specified ratio, and the Results window of the Calculation tab updates to the correct values. Figure 4: The preliminary representation of our V-belt drive 14. Increase the size of pulley #1 a bit, and then click the Calculate button. Repeat as necessary until the message window no longer complains about the pulley size. 15. The two crossed arrows can be used to change the locations and therefore the centre distance of the two pulleys. This may also affect the message complaining about pulley size. Did you notice anything interesting as you changed the pulley size and locations? They could not be dragged smoothly and continuously, but rather they jumped in finite increments. If we were doing this in AutoCAD we would think that Snap was turned on, but Inventor is far more cunning than that. As we change the pulley size, it automatically snaps to industry-standard stock diameters. Similarly, changes in pulley location and therefore centre distance are not a fixed increment but instead are calculated on the fly, based on the pulley sizes and industry-standard V-belt lengths. The preliminary representation is anatomically correct. Before you comment on how many steps we went through, and how long it took, remember that prior to the Design Accelerator you would have had to do all of this manually before you even looked at Inventor. 16. When everything is in order, click OK in the Design tab. Inventor will then churn for a moment or five (depending on the speed of your computer) and will automatically generate the two pulleys and the Vbelt as solid models in your assembly Figure 5. This is where you make money; how long would this have taken using standard Inventor modeling techniques? Each of the three components is linked as a V-belt drive, but each can also be edited separately as individual parts. You can thus edit the pulleys to add suitable hubs, bores, keyways, and so on.

Figure 5: The final model of our V-belt drive Houston, We Have A Problem… Uh, oh. I just noticed that I made an error while filling in the Calculation tab. The original specification called for 50 HP, but I did not change the default value of 1 hp. No problem; simply right-click on the drive in the browser tree or in the graphics window, and then select Edit using Design Accelerator from the context menu. 5/7

Step on the Accelerator in Autodesk Inventor! Hey, presto, we are back in the exact same dialog boxes as Figure 1 and Figure 3. I can change any of the specifications, including belt type, service factors, pulley sizes and locations, and so on. In our current case I’ll just change the input power to 50 hp, check the calculations, click on OK, and then watch in shock and awe as everything updates to add two more belts Figure 6. What if we decide we want to try to stick with a single-belt design? No problem; simply edit the drive and change it to an 8V belt and see if that works. Similarly, changing the centre distance may change the number of belts because of the changing wrap angle. Figure 6: The V-belt drive updated to the correct power I have shown a simple 2-pulley system, but any number of pulleys can be added, including idlers. As you have seen from this example, “functional design” as manifested in the Design Accelerator is powerful, versatile functionality. I hope you did not come to this class hoping to learn all there is to know about how to use it all; that would be like trying to summarize the Bible in a couple of paragraphs. For example, what I have shown you so far is about one quarter of V-belt design functionality. The total list runs to 47 topics, many of which could take several days to learn: •

Bolted connections

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Shafts: Shaft generator, Parallel splines, Involute splines, Keys, Cams

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Gears: Spur, Bevel, Worm

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Bearings: Rolling, Plain

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Springs: Compression, Extension, Torsion, Belleville

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Belts: V, Synchronous (Timing), Roller Chain

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Pins: Clevis, Secure, Joint, Cross, Radial

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O-rings

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Welds: 5 types

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Solder joints: 5 types

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Separated Hub joints: 3 types

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Step on the Accelerator in Autodesk Inventor! •

Tolerances, limits, Fits & Clearances

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Power screws

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Beams, Columns, Plates

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Brakes: 4 types

There is also a complete Engineer’s Handbook available for detailed calculations and analyses. GIGO As marvelous as the Design Accelerator is, don’t ever forget that it is computer AIDED design, not computerized. It won’t ever replace engineering training and experience. It is truly a case of Garbage In, Garbage Out. If your power, load, strength, and other values are wrong and do not match the real world then your results will be meaningless. In my sample case, for example, should I even have been using V-belts, or would a chain drive be more suitable to the application? There is a tendency these days to say “It must be right; it came out of a computer.” “Functional design” is a very powerful tool, but like any tool it must be used correctly. Some years ago I attended an Autodesk University session on finite-element analysis (FEA). At the end of the session, the presenter said that “low-cost, easy-to-use FEA would make good designers better and bad designers dangerous”, to which I say “Amen”. And Don’t Forget… www.autodesk.com/auconnect will connect you to Autodesk University content files. This includes course handouts, sample files, datasets, and the a/v files for over 100 presentations that were recorded live.

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