CAD Modeling Tips By Mike Rouen (PE Retired) 7 years being the “CAD” guy for the chapter

CAD Modeling Tips • “CAD” here covers both solid modeling and mathematical software. • A little on what kinds of tools are available at “EWB support” $ availability levels. • A little on why I use the tools I use. • A bit on how solid modeling CAD is used to support the chapter – not like it is used at work. • A trick or two on “doing the math”

CAD Modeling Tips • A little on what kinds of tools are available at “EWB support” $ availability levels. • Lets talk solid modeling first – Did a bit of looking on the internet preparing for this talk and was pleasantly surprised. Lot more out there than when I went looking 7 years ago. – The search was made easier by this page http://en.wikipedia.org/wiki/List_of_computeraided_design_editors

CAD Modeling Tips • Solid Modeler Operating system requirements – 1 of 59 would not run on Windows (it was Mac Specific). – 11 would run on Unix but that increased to 18 if Max Os X was included. – 3 ran on “other” systems, 1 of those was Mac only. – Windows rules in this genera. – Mac fans need not despair since Mac went to Intel processors, • a Mac is a Windows machine for the extra cost of the Windows operating system and willingness to reboot. • You can run a system emulator like “Parallels” to avoid rebooting but if you do, don’t expect support from the software supplier.

• Solid Modeler File transfer compatibility – DXF, IGES and STEP file types are well supported – TransMagic (transmagic.com) does 3D multi-CAD data exchange software products if you encounter real problems.

CAD Modeling Tips • The expensive guys like – AutoCAD, Autodesk Inventor, CATIA, Creo Elements/Pro (formerly Pro/ENGINEER), NX Unigraphics, SpaceClaim, Solid Edge, SolidWorks, etc. run in the $5000 a seat category and significant cost for yearly support. – Expect to be using this class at work, but unless your work allows use to support EWB, these folks are too pricy for the average EWB chapter. And if your work allows such use, can any one else in the chapter access and use the files? – Some have student versions, but I am focused on long term availability. To start with a $50 student version and face a $4000 price when you graduate and still want to support EWB some where is not a good path.

CAD Modeling Tips • AllyCAD, ($70), FreeCAD (Free), SolveSpace (Free), SketchUp ($600 but have non profit grants), TurboCAD ($1500), VeriCad ($680 with upgrades for $220). – Not all of these have all the functionality needed. For example FreeCAD is developing an assembly module but that capability is mandatory. – To my surprise, the software I have been using for 7 years is not on the Wiki list.

CAD Modeling Tips • Alibre Design (now Geomagic Design) ($2000 with $300/year for support). – Have two versions with various capability but their web site includes the claim that “Geomagic is very flexible - if you have specific or special needs, please don't hesitate to ask us about your options.” – Company claim is to "change the landscape of 3D mechanical CAD/CAM software by providing full parametric technology to anyone that needs it.“ – Recently acquired by 3D Systems, a 3D printer company. – When shopping for a software product you intend to use for long term support, this kind of information about company intent can be helpful.

CAD Modeling Tips • So what are the real needs? everyone know what this – 3D solid parametric modeling. Does means? – Assembly capability – Boolean operations capability – Sheet metal capability is nice but not mandatory – Parts library is time saver but reverse engineering parts to the level of detail needed is not to time taxing.

CAD Modeling Tips – 3D solid parametric modeling. • Most Parts are simple – And easy – Some are simple and hard

• Some are complicated

CAD Modeling Tips – 3D solid parametric modeling (continued) • Why all this complexity in a single part? • Because all of this is existing structure we could not change but had to work within. Consequently, I put it all in one part to avoid the complexity of a large Avoid unnecessary assembly.

assemblies

large

CAD Modeling Tips • Assembly capability – A necessity, actually where you work the most. • Most things built by EWB are things assembled and possibly modified in the field from simple or standard parts. • Seldom need drawings as we are communicating with – Our own people who can see what they need using the model – Work force in country that is very capable but do not work from drawings on a day to day basis.

CAD Modeling Tips • Assembly capability (continued) – Lets take this fruit drying cart assembly as an example

CAD Modeling Tips • Assembly capability (continued) – Specifically lets look at the wood structure – Now, all those words I have been using to describe this need to be written into the build procedure.

CAD Modeling Tips • Step by step instructions with illustrations from the CAD model that show what is being done and includes why things are done work well. Translation is an issue but that is true of everything we do. • Show the PDF of Fast Sand Filter build here • A good screen capture tool is necessary for this kind of work.

CAD Modeling Tips

CAD Modeling Tips

CAD Modeling Tips

CAD Modeling Tips • Put in fasteners last – just as you are doing build procedures. Their placement is important and until you think through the build sequence you don’t know exactly where they need to go. Over complicate the assembly if put in early. • Name assembly constraints – even in simple assemblies this is a real time saver • Build assemblies from subassemblies – this is a corollary to avoiding large assemblies.

CAD Modeling Tips • A little on what kinds of tools are available at “EWB support” $ availability levels. • Lets talk math software now – Did a bit of looking on the internet preparing for this talk and was pleasantly surprised. – The search was made easier by this page http://en.wikipedia.org/wiki/Comparison_of_com puter_algebra_systems

CAD Modeling Tips • Operating System – Not a windows dominated world here, about equal coverage between Windows and Mac. • Even the expensive guys have personal editions that are priced in reach. Maple ($239), MathCAD ($1195), Mathmatica ($295) • 19 of 28 listed are free.

CAD Modeling Tips • MathCAD has been my standard mainly because of its excellent handling of units. This is very important because – much of our standard material stock is in non-metric units and the world you are sending data to uses metric. – Units help you keep a calculation correct. – One of the free packages seems to handle units as well. It is Smath Studio – Mathmatica has recently added units handling but I have not worked with it enough to give an assessment. A free package that is like Mathmatica is Sage.

CAD Modeling Tips • Math Modeling Tips – Talk to yourself when building math models – you will have to set them aside for long periods of time and come back to them later. If you have talked to yourself you can find out what you did. If not, you often can’t understand what you did in a large model and will have to redo a lot of the thinking to get back to where you were. – Use your CAD system to find the values that feed the math models. Example is overturning calculation for the fruit cart. Actually tying the math model to the CAD model (as supported between Pro E and MathCAD) has not been necessary in any thing I have done – Calibrate your math model with test data. Essential step is your model is at all complicated.

CAD Modeling Tips • 3D Modeling Tips – Avoid unnecessary large assemblies – Generate step by step build procedures using screen shots from 3 D model – Fasteners last – Name assembly constraints – Build assemblies from subassemblies and subassemblies from parts.

References Solid Modeling comparison site

http://en.wikipedia.org/wiki/List_of_comp uter-aided_design_editors

Solid modeler file translation software site TransMagic (transmagic.com) Math Software comparison sites

http://en.wikipedia.org/wiki/Comparison_ of_computer_algebra_systems And http://alternativeto.net/software/mathca d/ http://www.3dcadtips.com/free-mathsoftware/

IrfanView is a very fast, small, compact and innovative FREEWARE (for noncommercial use) graphic viewer for Windows

http://www.irfanview.com/

CAD Modeling Tips • Math Modeling Tips – Good Unit handling is essential – Talk to yourself when building math models – Use your 3D Solid Model to find the values to feed the math models – Calibrate your math model with test data.

Chimney Top HX

0 Outside Air In Heated Outside Air In

1

Fruit Inlet

2

Hottest Air Out of HX

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7

6 Humid Air Out

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5

Re-circulated Air

Fruit Outlet

Fan outlet

CAD Modeling Tips