The basic MPCNC rail assembly is done.

The picture above shows the basic plastic and steel foundation for the Mostly Printed CNC. It fits together pretty well. As I explained previously, some light sanding and filing was required to fit the hardware into the plastic parts.

The outer frame is 38” by 32” and is made of 3/4 inch EMT conduit cut to size. These steel rails fit into the plastic corner blocks. Then a roller assembly slides onto each of the four outer rails. Finally, two additional rails are attached to provide the X and Y holders for the soon to be built gantry and tool holder.

At present, without any final adjustments, these two center rails slide nicely back and forth on the outer rails and roller assembly. It’s not as smooth as could be achieved from proper linear rail, but pretty good.

MPCNC Rail Assembly – More Sanding To Come

As you can see from the lower left inserted picture, the center rails still do not have a symmetrical fit into the roller assembly. This is so for all four connections. I will have to sand the plastic shapes with my emery cloth and sanding jig, described previously. The shaping is very close, so I need a very light touch in the sanding. At present, if I were to try to properly screw done the locking part, I think there would be too much stress on the plastic because the conduit wall is not mating equally across the plastic shape.

Next to come will be the assembly of the Z-axis and tool holder, which will connect onto the basic MPCNC rail assembly at the center. With a short visit to Lowes today, I picked up a 12” piece of threaded rod, as well as a 5/16” connecting nut, which will make the vertical motion controller.

By the way, if you are picking hardware from Lowes or Home Depot, it is useful to download their supplier’s catalogs (in Canada, that’s Hillman or Paulin, respectively.) These catalogs provide additional information about the hardware, over and above what is on the big box web sites.