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Originally posted by Garret H 11-01-2019

Originally posted by Garret H 11-01-2019

I was asked to make a mounting holder for an iPad on an exercise bike. At first I thought it would be a completely 3D printed affair, then we got the acrylic bender. So I decided to make the iPad frame out of formed acrylic, and then just 3D print an arm and mounting clamps for it.

My first step was to make a design, so I measured up the iPad and then drew it up in Fusion 360. With the iPad drawn I could then create the frame for it. To do this I made use of the sheet metal feature. This is a really awesome tool that I haven't really played around with yet. It lets you create bend "flanges" and then view the "flat pattern" of the part before its formed. I posted about it here: https://community.kamloopsmakerspace...bent-materials

The formed part and flat patterns in fusion 360:

Fusion created a DXF from this flat pattern, although I had to edit it in AutoCAD to remove the bend lines and clean up some doubled up lines.
I sent that DXF to the laser cutter and got cutting.

After it was cut I took out the new acrylic bender. A heating element in the middle heats up the acrylic enough that it can be easily bended. The extruded metal frame is cooled by recirculating water, not the most energy efficient set up but it worked well. I had to use the highest power setting and even then each bend took a few minutes to get the acrylic warm enough to be formable. It seemed to go pretty well, and I managed to get some forms with very small lips. One trick I learned was after the bend is made to move the work piece over top of the cool zone so you don't need to hold it for as long while it cools to the new set position.

The finished product turned out pretty well. In hindsight I should have cut some forming guides with the laser cutter to make sure it was totally square. I used a small 1x2 with a radiused edge to try and keep the bends from being too sharp and thin.

Then it was the printed parts. I printed out the pipe clamps as separate parts, and used PETG instead of PLA for these. The PETG worked really well, it had enough flex to open up around the pipe I was mounting it to. PLA would have shattered had I used it there. I used a T-shape that the arm can slide over to help hold everything together. I made sure that for this design the layers would be aligned to the part that flexes, so layer shear wouldn't occur when it bends.
Its really important that one puts painters tape on the print bed - this material sticks down extremely well.

The main arm was just printed out of PLA, I used support material for the T-slot so I could orient the part properly for strength.
Created assemblies out of multiple printed parts means not only do you need less support material, but you can orient each part correctly for strength. I've gone as far before as gluing multiple pieces that are oriented perpendicular to each other to maximize strength and avoid some of the strength problems that can occur with 3D printed parts.

I also used an extra part to make printing possible. This part should have been printed to the "as built" distance between the acrylic mounting flanges. As is I had to cut it down since the inside dimension of the bracket ended up being tighter than I intended.

3D printed parts are great for building in little smart design features, like recessed nuts that are held captive in a hex cut out in the printed part, and countersunk holes.

All the fasteners I used came straight out of our Fabshop consumables station. Since we have lists on the forum of all the bolt lengths I could design the part around those while I did the CAD work at home. Check out the fastener list in our consumables station here: https://community.kamloopsmakerspace...on-supply-list


After a little post print sanding and filing (whoops should have left some clearance!) I put everything together. It worked quite well.