Z-axis not perpendicular


I have assembled my MPCNC very secure. Everything has the right dimensions, is rectangular and running smooth without backlash. Only one problem, the Z-axis in one direction is not 100% perpendicular with the table, its hanging a bit (about 2 mm) skew in the middle assembly, see the pictures.
Played with the tension of the bolts, but that doesn’t help. Anyone an idea/suggestion what I can do more?


How big is your cnc and are your outside rails perpendicular with the table?

It’s 800 x 600 mm, rather big but it is standing like a rock with 25 mm stainless steel conduites with a wall thickness of 2mm.
Yes it is perpendicular. Checked everything at least five times, heights, lengths, diagonals, perpendicularity, rectangularity…

That is a new one.

Can you put up a few pictures at different angles of you middle assembly. I have a feeling something is missing.

Is that tool mount sitting perfectly flat on the z rails… Looks like its twisted like the holes were drilled not totally vertical.

Or a piece that warped slightly when printing?

I’m thinking the spacer is missing or the z rails are not parallel.

Thanks for all your replies.
I am afraid my camera on this short distance has a little distortion. There’s nothing twisted nor is there any friction.
The spacer is on it’s place too. I spent hours checking everything and I don’t get it. Tomorrow I am going to disassemble the middle part so I can check on bad prints. The prints are in PLA so the chance of warping is small, but you never know…
The Z-axis is perfectly straight and with parallel rails.

I think I know what’s wrong. Took the middle assembly apart and it appears that the XY-parts are not printed right-angled from the printbed. There’s a mm play on the height of 10 cm of the part so I think it turns out to 2 mm play in the Z-rails.

At least, I hope this is the cause. I printed this XY parts at the end of all needed prints and did some printer maintenance before because of the 12 hours printing session. It seems I did something wrong with the printbed guidance that causes this little deviation.

Printing once again now…
Thanks for your thoughts.