Engineering, meet Inkscape…Inkscape, Engineering

January 18th, 2008 by heathenx

I cannot count how many times that I have used Inkscape to do my job, which 90% of the time is totally unrelated to the graphic arts field. Case in point, yesterday I had to create some documentation to go along with a new product that I just finished designing a few weeks ago. In one of the illustrations I wanted to show a hand on an assembly tool used to aid in the assembly of this new product. Initially I didn’t know how I was going to pull it off. Drawing a hand around a product in my CAD system, although possible, didn’t seem like the tool to use to get the job done. AutoCAD and Inventor are very powerful applications but I needed something even more flexible. That’s when Inkscape came to the rescue.

Since I didn’t feel like I had neither the talent nor the time to draw a hand from scratch, I took a picture of my hand in the shape that I wanted it and traced around it in Inkscape. A cheating mans approach, perhaps, but I’ll learn in time to forgive myself. Adjusting the nodes or “nurbs” is much easier to do in Inkscape in my opinion and that comes from a guy who has been using AutoCAD for more than 20 years and Inventor since the start of the millennium.

When I was finished adjusting the shape of my hand in Inkscape, I saved a copy out as a plain SVG file. Since Inkscape has a sketchy DXF exporter at the moment I couldn’t use that option. I opened the plain SVG file in Adobe Illustrator :( and exported the image out as a DXF. Adobe also has a DWG exporter but DXF works just fine for me. After that I brought the DXF into my Inventor drawing, adjusted scale, tweaked some nodes, and I was done. The hand is a little rough but I think it will work perfectly fine in my final documentation.

Although Adobe gets a shout for supplying the bridge between Inkscape and Inventor, it was Inkscape that helped me with the brunt of the work. Since I’m the “decider” I’m giving Inkscape most of the credit here. ;)

7 Responses to “Engineering, meet Inkscape…Inkscape, Engineering”

  1. Richard Querin Says:

    Very cool. I’ve done similar things at work, using Inkscape to create certain graphical objects that are just too tedious to do in the AutoCAD environment.

    ps. Your fingers don’t look nearly as sausage-like as I had imagined. Did you get a manicure done specifically for this? ;)

  2. heathenx Says:

    Nope, no manicure. My hands are naturally that breathtaking. I often wear oven mitts to protect them. This has been a pain in the rear especially when trying to unzip my fly prior to a potty break. Or try holding a pencil with those things on. No, it’s not easy being beautiful. It’s a curse. You wouldn’t understand. :p

  3. Serge Gielkens Says:

    Interesting workflow. I bet it is quite unique although I have to admit that I do not have any experience with AutoCAD, Inventor (even never heard of) or Illustrator.

    By the way, what kind of tool is it anyway? I just cannot figure it out.

  4. heathenx Says:

    The tool is the “rod” that is in my hand. It is used to snap the white colored saddle into place over an aluminum extrusion. See the link below. I made a rendering of the product.

    Rendering

  5. Richard Querin Says:

    Okay. I’ve got a question. I’ve always wondered about the design of something like this.

    How do you decide the thicknesses of the saddle (like the flanges and main body of the saddle). Do you just pick some reasonable thickness, fab a prototype and try it out? I mean if you picked something too thin, it might be easier to install but wouldn’t hold as well to the extrusion – it might leak. How many prototypes do you try out? Or maybe you’ve got it down to a science. (ie. you do it with mathematical models etc.)

    Shed some light for a know-nuthin’ like me. ;)

  6. heathenx Says:

    Wow! That’s like me asking you how you design buildings. :)

    If you want a better understanding of how plastic parts are designed then head over to efunda and have a read of the “Plastic Design” category under the “Design Center”. They do a very good job of detailing plastic part design guidelines. There is quite a lot that goes into it.

    Material thickness is determined by the type of plastic and how I intend for the part to function. Part function is most important but proper wall thickness and coring have to be taken in account so that the part will mold accordingly. Applications like MoldFlow help me to analyze how a part will mold before I have a tool built. I watch for how material flows, where knit lines occur, how gate locations affect things, and how the part will shrink. Also, I can check for proper vent locations so that gases during molding can escape without interfering with the integrity of the part. Improper venting causes voids inside of the part rendering it weaker in that particular section. MoldFlow can help a designer (me) focus on the part while a mold maker can use it for proper tool design. Also, I can perform some light finite element analysis (rarely do I, anymore) if I think it’s needed to check part stresses (flanges). FEA is a science all to itself (I’m sure you know) so if you do not understand how to apply proper loads then you’ll get false information. It’s not my area of expertise so I try to use other methods to prove out a concept.

    Proper flange design can be a little tricky. Sometimes it takes a little math, a little analysis in CAD, a little prototyping, and a little experience (meaning failure so that I know what not to do). Making mistakes can be costly after a mold has been made. Just like designing buildings, I suppose. Takes a little foresight to minimize those easter eggs.

    Prototyping always starts out for me with a virtual concept in 3D in my CAD system. Once I have settled on a particular design I may choose to make a prototype. Part complexity determines prototype method. For instance, I may go with an SLA model from a 3D printer just so that I can evaluate size and function. From there I might make some modifications and prototype again or go straight to final tooling which will be a multi-cavity injection mold. Another method of prototyping might be a single cavity MUDD mold which is small and relatively inexpensive to build. I like to have things prototyped but I also have to be practical about cost. I also make my own prototypes at work. I have a mill and a lathe and I use them often.

    As far as keeping the part from leaking, much goes into that as well. Proper o-ring/gasket design is involved. Take a look at efunda again. This time o-ring design guidelines.

    Before I begin concepting a product I tally some guidelines. What must the part do? Who is it for? How much should this part cost? What color should it be? What material is most suitable? How will this part be made? Who’s turn is it to bring in donuts tomorrow morning? Is there a fresh pot of coffee? Did I wear these underwear yesterday? Is that a booger on my finger? What stinks? Is Verbal going to send in a listener tip this week? :)

  7. vidiot Says:

    Thanks heathenx for that link. In my daytime job I´m designing plastic parts, too
    I go through every video tutorial (no I´m at No 26) – I abandoned Corel Draw for Inkscape already and Photopaint for Gimp.

    Thanks for this great resource!

    Harald

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