Cad software thoughts

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jmcglynn
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Re: Cad software thoughts

Postby jmcglynn » 28 May 2010, 15:25

I started with Alibre several years ago. It was all I could afford (about $1,200 for the version I got at the time), and did an OK job although it crashed A LOT. It was really frustrating, I really wanted to like Alibre...I guess it's like your first girlfriend, you know the one that never shows up for a date. I designed a motorcycle gas cap that I sell as well as two different mc fork plan sets using Alibre. They have probably fixed the problems I had, and it might be a good way to go.

Tools like Rhino and SketchUp are limited, they aren't really parametric CAD. You draw something, and if you want to change it you have to edit the drawing. Parametric CAD tools like Alibre and SolidWorks have a "feature tree" so you can go to any operation and change its paramaters to change your design. It's REALLY powerful and well worth the time to figure out how to drive it. You can also base dimensions off of other dimensions. As a simple example, if you wanted to lay out bolt holes spaced at three times the diamater you can do it, and if you change the diamater the holes re-position themselves. If you have something based off of a hole location it will adjust too.

I switched over to SolidWorks and I really like it. It's not cheap (I think the important bits will run you about $4-6K), but it works really well.

Personally I'd stay away from any 2D-only drafting packages unless you just need to lay out some brackets.

There is a free 3D CAD tool that I just learned about. I installed it but haven't given it much of a test drive http://sourceforge.net/apps/mediawiki/f ... =Main_Page Most of the 3D CAD tools will exchange parts data using IGES or Parasolid or STEP formats. You can also mock up your suspension in 3D and move it through the travel to measure geometry changes.

Generally these 3D CAD tools work the same: Most parts are made by drawing a 2D shape and then extruding it, rotating it or sweeping it along a path to create a solid shape. You can also do the same operations to create a "cut". Combinations of these basic operations can get most things done. There are other operations of course, but this is the fundamental principle behind you you make most parts.

Most of the 3D CAD programs will create 2D drawings for you of your parts pretty much automatically. You can send these (in DXF format) to the local laser/water-jet cutter and have really accurate brackets made. Or you can print them out full-scale and use spray-adhesive to stick them to the metal stock. Snap-punch the hole locations and some reference marks around the cut lines, and cut it out on a small bandsaw. Works really well.


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