Here's the full 3D model:
The printer is a modified prusa-style system, with the Z axis riding on the X axis, and the Y axis actuating the bed.
The frame relies on M3 x 16mm bolts for almost every connection, with 4 M3 x 50mm bolts connecting the Z axis to the X axis, and a handful of M3 x 25mm bolts for the roller assemblies. The rollers used for each axis are a simple lasercut ring around a 6mm tall by 7mm outer diameter nylon spacer with 2 washers on either end. Here's a quick view:
The roller system also requires several eccentric spacers, which can be printed in just a few minutes. These eccentric spacers press the rollers into the rails of each axis and ensure smooth rolling action. Below you can see the eccentric spacer:
The whole motion system relies on these rollers and so far I've been very happy with how they're performing, although I've only tested them for around 20 hours of printing. I'm still waiting to see if or when the rollers wear down over time.
The motion system:
Lets go through how each axis works, starting with the Y axis.
The Y axis:
Here we can see the bottom of the printer and the Y axis mechanism with some components highlighted. The roller bearings are in red, the slide bearings are in pink, the rack is in orange, the base of the printer is in green, and the adjustable rail is blue.
The slide bearings and the roller bearings are attached to the bed of the printer and ride along the two rails. The slide bearings constrain the bed in the Z direction, and the rollers constrain the X and Y directions.
The left rail, in green, is the "static" rail, and provides a straight rail for the axis to ride along. The adjustable rail ensures a proper fit against the rollers, and can be adjusted to compensate for the kerf width of your lasercutter, which is not always consistent between cuts. The right side roller bearings also contain the eccentric spacers, and can be further tightened against the rail to provide additional stability.
In the video below you can see the Y axis moving:
I've found that the surface finish of plywood is not an amazing bearing surface, and the axis will bind if left unsanded or bare. Since hand-sanding the rails can introduce inconsistencies into the surface, the best and easiest option is to throw some low-friction tape on either the rail itself or the bearings for each axis, and everything should run fine. I've tested regular scotch tape, kapton tape, and even packing tape, and all have worked well.
Additionally, if you have access to a planer, I've found that planing the wood down to 5.7mm before lasercutting is the best option, and makes assembling the printer a very easy process as you don't have to adjust each axis to account for the width of the tape or inconsistent sanding. I'll put out a video near the end of the summer on my process for planing the wood I use.
The X axis:
The X axis is much simpler than the Y axis. Here we can see the X carriage system, with the roller bearings in red, the rear slide bearing in pink, and the rails/rack in green. The front slide bearing is another important component but is not shown, as it sits on the front of carriage.
The rollers ride on the inside of the frame, constraining the carriage in the Z direction, while the front and rear slide bearings are pressed against the rails and constrain it in the Y direction. The top roller contains the eccentric spacer for this axis, and must be tightened during assembly, as adjusting it requires removing the Z axis assembly to access it.
Here's a video of the X axis moving.
Here we see the top of the X/Z carriage. The Z axis rides on the front of the X carriage, and the front slide bearing...Read more »