I can only describe the MPCNC Middle Assembly as both functional and artistic.

Putting together the MPCNC middle assembly was a brain teaser. I had seven pieces of plastic that looked like a jigsaw puzzle with not picture on the box, and no outer edges. It took a few hours of thinking before I understood what Ryan Zellars had done in this creative design.

The mental breakthrough came for me when I understood this was more about pipes than plastic parts. What I was really trying to accomplish was to get eight sets bearings to fit around four pipes. Once I had this idea in mind, the rather complicated assembly instructions suddenly made more sense.

The first step was attaching the bearings to the plastic parts, again keep the bolts snug but not fully tightened down. Then came lining up the plastic parts and bolting them together, in some cases vertically, in other cases horizontally Again, by thinking in terms of fitting pipes through bearings, it was easier to visualize.

Another aspect which makes the middle assembly hard is that you are working on two different levels to accommodate the spacing of the middle rails.

MPCNC Middle Assembly – Physical Challenges

Once you get past the mental blocks, the only real physically challenges relate to fitting bolts through holes in plastic parts. Most of my holes needed a little bit of widening with a round file. I wanted the bolts to fit snuggly without being forced. My thought was that forcing bolts through the holes would weaken the plastic parts and come back to haunt me later.

Sadly, I also discovered that some of my 1.25” bolts were actually 1.5” in length. The lesson here is that when you take parts from a bin at Home Depot, don’t assume that all the parts in the bin are the same. I supposed customers mix them up. You should check each bolt as you remove it! Fortunately, I was able to arrange things so that I used the proper sized bolts where there was limited clearance, and the longer bolts where there was more space.

Also, it is important to orient the bolts correctly, especially those holding the bearings for the inside of the Z or vertical axis. The heads of the bolts take less space than the nylon locking nuts. This orientation is necessary to provide space for the threaded rod to run through the Z lock nut.

Lastly, this MPCNC middle assembly requires two 1.75” bolts, which I could not find anywhere. In the end, I just used a hack saw to cut down a couple of 2.0” bolts. Remember to put a nut on the bolt before cutting it. There are two reasons for this. First, the combination of the head and the nut gives you two places to clamp down for the cut. Second, the nut on the bolt is used to repair the thread end after it has been cut.