The Design

The machine was supposed to be a low-cost CNC, but the cost did pose some problems, which were the lower quality of the materials. We could say that the quality of the materials was uncontrollable, which in turn proposed the idea of adding control to the machine so that it could be calibrated accordingly. The assembly of the machine is definitely going to be a process, but let’s assume others will have fun with it.

The Motor

So with that in mind, I started the design of the gantry. As mentioned, the gantry had diameter adjustment within the gantry with screws, which can be used to adjust the play of the gantry.

We were using 28BYJ-48 stepper motors for the plotter. When I had that motor in my hand, I found out that the motor had some peculiarities:

1. The motor shaft was comparatively smaller compared to NEMA 17, which I had previously used, so I had to change the design to mount the pulley other than the motor shaft.
2. The motor shaft had an up and down play, which came with the design of the motor. I needed to make a fixer that prevents the up and down motion of the shaft.

These were the challenges that I faced when it came to materials while designing the plotter, which I fixed by adding a fixing part at the top of the motor connecting pulleys and tightening it down to the board.

Core XY

The machine is using Core XY kinematics because the gantry needs to be as lightweight as possible. If the weight on the gantry is light, the machine has to run on these stepper motors, so I had to make the gantry as lightweight as possible.

Also, the moving belts of the machine have to be linear with no angle deviation to control the unbalanced forces, so the strings have to be straight. I needed to add a string tightening option to the machine to keep the string in adequate tension.

The Base

The base of the machine was built in plywood, which was 2D milled. I arranged the components on the base and 3D printed the parts of the pulleys and assembled them.

The End Effector

The end effector of the machine was actuated by a servo motor MG90 Pro, and the mechanisms were 3D printed. In the end, I felt curious and inclined the Z-axis gantry for fun. No other reason at all, but yeah, it worked. I tested the 3D printed design on different 3D printing clearances and found a clearance that really worked for the machine.