Disclaimer: This is not an April Fool’s joke! The files for this print are available here.
As you may have guessed from last week’s post, I’ve been working to co-process motors so that prints can drive themselves off of the build plate (If you aren’t familiar with co-processing, please check out my first post here). Using last week’s lessons, I’ve switched motors and gone with a high torque full rotation servo motor, controlled by an Arduino (off the build plate) and simplified my design so that all it does is break the build plate adhesion by directly making use of the torque of the motor.
The first step of this experiment was designing to minimize build plate adhesion. There are 3 points of contact with the ground, which makes the part very easy to remove, but also can make leveling the build plate difficult, as you make have build adhesion issues. All of my previous prototypes could not get themselves off of the build plate just because they contacted the build plate too much and in non-ideal spots. The final iteration of this design reduces build adhesion and places the point of contact far away from the pivot point to increase the applied torque.
Another thing that you may notice is the hinge on the other side of the part. It consists of a hole with a disc on one side, sort of like the car wheel axle I designed, except the disc side of the hinge slightly rests on another face of the print job. Because the disc does not technically “contact” the part in my CAD file, the “foot” of the print job is free to pivot. When this prints, a small part of the disc will loosely touch the other part of the print job, and build up from there. The small contact is easily broken once the servo turns on.
The next design step involved being able to co-process the part easily, while still letting it be removable. The part does not fully enclose the servo, so the top brace can be easily broken to get the servo out. When the servo with the servo horn is placed in, the horn is oriented to be tangent to the top and bottom faces of the servo. When placed, the servo horn slides into its fixture and becomes fully constrained after co-processing.
After the co-processing step is completed, the printer will print over the servo motor because of its flat surface, which is why the shape of servos make them great for co-processing! This will secure the servo motor in place so that it is constrained to the piece it is mounted to. In future iterations, I will likely put a strip of blue painters tape on the servo so that I don’t damage the motor and so that the print sticks better.
After all that was done, the motor was plugged into an arduino and a slightly modified version of Arduino’s “Sweep” example was run, allowing the servo to break the build adhesion and release itself from the build plate.
And there we go! First successful test of co-processing a motor to get a print of the build plate is complete! You’ll see how I use this idea in a video coming next week!