Automatic Dough Shaper - Blog #9 Mechanical Construction Part 2 and Design Changes

There's only one week left and my project is not as close to being finished as it should be, so I've had to make some design changes and cut out functionality.

PyCNC uses almost all of the raspberry pi's GPIO pins so that it can do CNC milling or 3D printing, but this poses a problem for my project. The roller, oven heating, and the arm to move the pan into the oven are all extra parts. I've been trying to figure out how to incorporate this functionality into the PyCNC code as it is, and I've finally come up with a solution. I don't have an extruder, but since the extruder command is just the same as any of the other axes (step and direction outputs to a driver board), I can use that for the roller control. Next, in order to control the arm that moves the pan into the oven, I need at least 3 GPIO pins. PyCNC has 4 pins set aside for servo motor use (which comes from the reprap option to use servo motor control). I'm pretty sure that these pins actually aren't used, which gives me just enough to control the arm and 1 pin left over to heat up the oven. This is where I start cutting corners. Instead of using a thermistor to measure the temperature, I'll just figure out how long it takes to heat the oven to 350 F and have it turn on that long. It will work well enough to bake cookies.

I don't know how to change the PyCNC code to also run the oven heating and moving the pan into and out of the oven. But I learned that in Linux you can do multiple commands in one line, you just have to separate each command by a semicolon. So I'll run two programs, one right after the other. The first will be a PyCNC file that will have gcode instructions to roll out the dough and then cut the shapes. The second program will preheat the oven, push the pan into the oven, and remove the pan.

On the mechanical assembly side of things, I got the x-axis mounted and the roller almost completely mounted.

The motor for the x-axis sits inside a little box and the other end is connected to the opposite side of the platform. It's nailed into a block that is glued (with dowels) into the base.

I also had to have a little corner cut out by the motor so that the cutting head would have enough room near the edge.

I made a little shelf for the z-axis motors to sit on, but the hole I drilled was terribly crooked.

So the shelf got re-built and mounted on two rods. But it wouldn't slide very well in one direction, so I removed one guide rod. I may end up just drilling the holes bigger.

For the roller, I bought a wooden rolling pin and took it apart.

The roller assembly (as pictured) has a few flaws, so I'll explain how it works when it's fixed.