By Peter Maxwell-Stewart
Ok so I’m just going to come right out and say it! I’m a little bit obsessed with my 3D printer. I love it. It’s so so useful and I use it pretty much on a daily basis. What do I make? Well really anything. I have made things as small as picture hooks, clips to stop the dishwasher rocking, toy rockets for my son and friends, fidget spinners for my nephews, climbing holds and even replacement lawnmower wheels.
For my latest project I’m trying to design a prosthetic hand for children with no full hand or fingers. Now there are quite a few designs out there and I could just print one of those from thingiverse but where’s the fun in that.
So I did a bit of research on how they work and the types of designs and in doing so I came across a new technique called thermoforming. Basically complicated 3D printed shapes need support to enable them to print, but with thermoforming you print a flat pattern and then heat the plastic back up after printing and bend or form it into shape afterwards, eliminating the need for support material. If you have done a lot of 3D printing you will probably appreciate how beneficial this is. For those of you who haven’t, support material can be a nightmare often ruining a print due to not releasing itself from the part or leaving blemishes in your design that take hours to remove. So wherever possible you try to print without them.
From then on it was fairly plain sailing. I could easily add the threaded connections and export it out as an .stl file or take it directly into my slicer program to prepare for print. You will see below the comparison between the folded and the flat model and the difference it makes in material and print time. This is proving very beneficial during this prototyping stage.
This got me thinking. Inventor and Fusion 360 have Sheetmetal functionality. The ability to create flat patterns easily. Thinking outside the box I started to redesign my hand using the Sheetmetal functionality inside Inventor and then took the flat pattern into Fusion 360 to add printable threads. (See my other blog for more details on this).
Okay so I actually had a few issues trying to get the part into Fusion 360. Yes it would upload the .ipt no problem, but as soon as I did that the Sheetmetal functionality inside of Fusion was disabled. So I thought okay I will make the flat pattern first in Inventor and Export that as a .step file. Unfortunately, that didn’t work either. An error message came up saying the part couldn’t be exported as a flat pattern. In the end I had to create the flat pattern in Inventor. Create a new sketch on top of the flat pattern by projecting all the geometry and then create a new part from that sketch and upload that into Fusion 360.
Below are some images of the flat part being printed, folded and finished.