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Strategy for using 3d printing in your overall problem solving process when working towards prosthetic hand or hook solutions [tip's and trick's]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Strategy for using 3d printing in your overall problem solving process when working towards prosthetic hand or hook solutions [tip's and trick's]; published November 28, 2016, 18:40; URL: https://www.swisswuff.ch/tech/?p=6911.

BibTeX: @MISC{schweitzer_wolf_1571448767, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Strategy for using 3d printing in your overall problem solving process when working towards prosthetic hand or hook solutions [tip's and trick's]}}, month = {November},year = {2016}, url = {https://www.swisswuff.ch/tech/?p=6911}}


We all know that the reality of 3D printed parts are somewhere between close enough for rock and roll and utter crap. At the same time, there is a specific reason for that: they are totally available, and they are meant for testing - not for actual use.

I mean, telling people that 1100 USD is cheap for them if you print out their "3d printed hand" is mostly wrong - it costs only a few bucks to make a hand with PLA and it may cost just 100-200 USD to get metal parts. Not a lot more.

But really, you want a strategy.

Here is your strategy:

  1. The shape, size and function of any 3d thing is what is most difficult to achieve. From that, it also depends if you want that thing, or whether you will solve the underlying problem with a different strategy. Having a really close contact with that design, creation and development aspect is key. So, think it up, sketch it, get inspired on the internet, and try to end up with a useful STL file.
  2. So, rapidly approach the 3d shape problem, and also, break it down to small bits. Test cheap fast must be the ultimate priority. Reason is that printing large objects to test a small aspect of these takes far too much time and material. Also, even if you decide to get it large and realistically sized, printing really good quality is costly and time consuming so, reduce infill, reduce all supports, make it cheap and cheap looking, to maximize on output speed and keep material cost at a minimum. Print fast, not nice. Particularly if you are looking at several development cycles, a speed fest is definitely in order. So if all you want to know is whether a particular plate dimension fits a particular notch in an existing structure, print a small bit with that dimension and see if it fits. If all you want to see is whether the shape at all is cool, get that shape with as little time, cost and material as possible, from whoever you can get it from.
  3. Rapidly print a part and actually test it. Just see how it handles, how it fits, how it looks, how it interfaces. If you have the model, put it to use immediately. Go ahead and test it then and there. And you do not need the most advanced 3D printer for that, just one that gets the shape in plastic sturdy and precise enough for possibly gentle testing, regardless of whether the model is perfect in irrelevant ways. Even more: if the plastic model contains a bit too much bulk here or there, chipping it away to see if that improves the design is considerably easier if you already built it with only thin structural support. I just tore a few bits away from one thingy to see where that would take me, using a screwdriver and pliers. If you get a massive block, you may end up having to use a power tool for modifications. Remember, you are just shape testing, not making a final product, at this step.
  4. Revision time. Modify the design, where necessary, and go back to step 2.
  5. Cycle and re-cycle this. Steps 2-4 are called "rapid prototyping". If your setup works, you will be freebasing 3d shapes through a few cycles, getting closer to what you really want, which is extremely cool.
  6. Get the final version made. After you finished evaluating the shape, you may have a finall shape you want to get manufactured or printed, carved or made to last. You are left with more or less four options:
    1. Print the final version yourself, using one of the available devices that you have. Either you opt for a final material to last, or you remain aware that not all things need to last as long as you can get a number of them as replacement items.
    2. Print a final version yourself, using one of the available devices that you have and submit the resulting 3d model to all kinds of bench top post processing - filing, adding holes or parts, spray painting it, and so on.
    3. Get the final version manufactured or printed elsewhere: you do not need to own all these 3d printers in order to take advantage of them.
    4. Get it made elsewhere, then prost process yourself.

To find 3d models:

To get them printed:

And, this is not your strategy:

  • Someone wants to sell you one of these open design plastic print hands as "end user product" for a lot of money? Never pay too much money for such a 3d hand or device. If anything, go on Thingiverse, find the STL files that you need and upload them on Shapeways yourself to get the parts printed. Then assemble them yourself or get your next bike shop to do it for you. Why pay 1500 bucks if you can get it for 30.
  • Do not get, generally, a 3d printer to print final versions or wearables. Easy to print plastics are by far too fragile for actual prosthetic use, and good materials require more expertise and costly investments - best to have a cooperative solution work for you there. Of course, I make cheap support plastics for this or that application where the final product is totally OK to remain a cheap plastic piece - but a prosthetic arm usually requires better materials for end use or final product stage. Conversely, easing into a new thingy greatly benefits from cheap fast plastics.
  • Do not believe it when people tell you it cannot be done. It can always be done. But you may have to meander your own way to get where you want with a particular project.

Categories: 3D Printing

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