Hi,
I built the mpcnc primo and I noticed that my z-axis is skewed. According to the image with the spirit level the back of the cutter is lower than the front. I re(un)tightend all the screws of the core but nothing changed. Additionaly the marked bearing moves freely.
The x and y tube pairs have the same height and the problem is equal on any position on the printbed.
I appreciate any idea what I can try to change.
As I am a new user this forum I can just upload one image per post so I post the additional images as comments
Start by checking to see if the rails are parallel to the spoilboard. You can check both with a level to make sure you get the same reading, or you can measure down to the spoil board. You can also put a smaller bit (1/8" chamfer works well) and move it around the spoilboard to see if the height of the spoilboard changes.
Assuming the rails and the spoilboard are parallel, then you will need to tram your router. There are no tramming adjustments on the Primo. It is fixed by shimming the router in the mount. For my Burly, I shimmed using slices from an aluminum can. It has been suggested on the forum to use layers of duct tape on the router or the mount to do the shimming. That way the “shims” stay in place if the router is removed. You can increase the accuracy of your tramming by using a tramming arm like this one.
The usual sequence is to surface your spoilboard first (as gently as possible), then tram the router and then surface the spoilboard a second time. But in your case, assuming you can verify the rails and the board are roughly parallel, I suggest some tramming before the surfacing.
P.S. I liked your solution to getting multiple images posted. The period of time you are limited to one image is very short, and the restriction is to help eliminate spam.
Thank you very much! I didn’t now that shimming is a thing because I haven`t read anything about it in the documentation. I always thought either it fits or it is wrong. I will follow your advice and report the result 
The term “tramming” is the best search term to use on the forum for topics on adjusting the router angle.
Since we are dealing in PLA here with a lot of differently tuned printers it is nearly a necessity. If you take it seriously you (and everyone else is) are probably going to need a shim. 
