Last week, I tried co-processing some electronics into my 3D printed part. Before that, I used co processing to get the printer head to push my part off the build plate, and in another experiment I made the part lift itself off the plate. In this week’s experiment, I tried combining those two ideas to create some more motion on the build plate.

The print job almost activating upon completion.
The print job almost activating upon completion.

This week, my experiment ended up failing. But that’s ok, because I learned a lot from it. Here’s what I took from my experiment:

1. Build plate adhesion forces are stronger than you think.

Have you ever had issues trying to remove your part from the build plate? It’s pretty difficult sometimes. Because each time we level the build plate it will be slightly different, it is fairly hard to get an approximation of those forces. The print bed is supposed to be stuck to, and sometimes that is a problem! The motor that I used had a fair amount of torque, but it wasn’t enough to get the print moving, because the wheel was so stuck to the build plate. The main body of the print, that houses the motor and electronics, only has 3 points of contact with the build plate, and each one is very minimal, but it was the wheel that got caught and stopped the motor from turning.

Take a look at the wheel design of my part. The reason why this is not just a simple cylinder is so that the wheel can actually provide some force to the ground once it is driven. When the wheel is upright and in its original orientation, the “bumps” that you see along its rim are tangent to the bottom of the build plate, allowing it to print well. When the wheel is rotated, the bumps create a larger working radius at points, giving the wheel some grip on the build plate, and slightly lifting the rest of the part off of the plate. However, this only works if the motor can break the build plate adhesion forces to begin with!

The CAD model for the build plate roller.
The CAD model for the build plate roller.

2. Designing to account for tolerances has its price.

Although this is not clear in the video, the motor actually slipped out of its mount once the switch was activated. Although it didn’t disengage from the wheel, it does present another issue. I had played with the dimensions of many of the “sockets” in this print, including the motor hole, the axle hole, and even the battery case and switch fittings, and just because of the tolerances of the printer (about .2 mm), the results varied from the motor not being able to fit at all to the motor sliding too easily. Printing isn’t perfect as a manufacturing process, and has its limitations just like any other manufacturing method.

3. Be careful about friction and 3D printed parts.

In previous iterations of this print, I had a much more complicated printed assembly that was supposed to walk off of the build plate, and had a couple 3D printed four-bar linkages and gears to actuate the walking mechanism. However, this design fell through just because there was way too much friction between the printed assembly components to drive easily. If you are concerned about friction between components, space them out more. However, this comes at a price, because it means your parts will be lower tolerance and may not function as nicely as you want them to.

An initial prototype for a print to walk off the build plate. It didn't work because of too much friction.
An initial prototype for a print to walk off the build plate. It didn’t work because of too much friction.

4. Failure IS an option

In general, don’t be afraid that you won’t succeed. That’s the point of research and experimentation! If it doesn’t work, things were still gained from the experiment, and that’s great!

Designed to roll itself around on the print bed. Unfortunately, it didn't.
Designed to roll itself around on the print bed. Unfortunately, it didn’t.

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