Merging modern software development with electrons and metal
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Notes On Creating The End Effector

I created my end effector mostly using “Spaceclaim Light”, officially known as DesignSpark Mechanical (DSM).  Since my goal was to create something I could use as quickly as possible, I have not spent the time to become an expert user.

The DesignSpark Mechanical Background

Electrocomponents (parent company of RS Components and Allied Electronics) offers a variety of free tools and other design resources (such as forums) on their DesignSpark website.   The most impressive tools are:

  • DesignSpark PCB, based on Easy-PC from Number One Systems
  • DesignSpark Mechanical, a carefully cut-down version of SpaceClaim.  DSM is a very powerful program, but lacks key features (such as useful import and export formats; assembly constraints also appear to be missing) needed to replace SpaceClaim, SolidWorks, SolidEdge, and such for hard-core mechanical design.  On the other hand, with features such as IDF import, DSM appears to be a good match for creating 3D PCB designs.

Electrocomponents is betting their costs will be more than covered by increased component sales and much better awareness (in other words, I’d say the cost of DesignSpark.com is a much better use of marketing money than direct advertisements).

Creating Parts

Creating parts in DSM reminds me of creating parts in SketchUp, except that SketchUp is really oriented towards architecture, while it’s clear DSM is meant for mechanical design.  I like being able to easily input exact dimensions.  It’s neat being able to push and pull 3D parts.

I didn’t have much difficulty creating my simple parts.  The hardest was figuring out how to create the cones for the vacuum grippers (I created a triangular sketch, then revolved it 360 degrees around the center axis – it did take a few experiments to figure out the exact sequence of mouse clicks).

I’m still not a fan of the Microsoft ribbon interface.  I don’t care for it in MS Office, and I don’t like it any better in DSM.

Assembling Parts

Well, my parts aren’t really assembled.  I got so frustrated trying to assemble them I was tempted to go back to Alibre Design (now Geomagic Design), but since this isn’t a real design, I just moved them by eye until I was happy with the layout.

At least you can move components (groups of parts) by selecting the top level component; if you’re not careful, you’ll end up moving just a part of the component.

Since DSM is so new, there is very little community support, and the documentation is pretty skimpy.  All I could find on making assemblies is this brief tutorial (see Section 3; I’m pretty sure all that’s happening is the part is moved, with no constraints) and in the FAQ (see How Do I Make Assembly Models?).

What I want to do is set assembly constraints such as making planes parallel, aligning axes, and such.  From my searching, it appears SpaceClaim has an assembly constraints toolbar; I couldn’t find anything similar in DSM.

Getting The Result Into WinCAPS III

I will be using my model in the Denso WinCAPS III robot simulator, which can only import DirectX and VRML files.  As is typical of most MCAD software, DSM does not export to VRML.  However, it does export to STL, and fortunately there are a number of STL to VRML converters.

I used meshconv to convert to VRML; its documentation isn’t great, but it’s not too hard to use.  For example, to convert fixture.stl to fixture.wxl I used this command line:

meshconv.exe fixture.stl -c wrl -o fixture -vrmlver 2

Conclusion

Based on my small project, I’d say that if you’re hoping for a free replacement for the professional MCAD programs, you’ll be disappointed in DesignSpark Mechanical.  But if you’re looking for a SketchUp-style program oriented towards mechanical, especially electro-mechanical, design then check it out.

I may have to tweak my model bit for different simulation situations; I think that will be pretty easy to do.

Sometime I need write an update about the low cost MCAD market, since there have been a lot of changes, including the introduction of DSM, and Autodesk buying Delcam (which may lead to changes with the free PowerShape-e MCAD software).

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