Getting Y axis rails parallel

New here.

I followed the table mounting instructions but my y axis rails are 1/16 out of parallel from end to end, with another 1/16 bow in the middle.

Wondering if this acceptable, what your setup is like, and general advice.



@joekorman Welcome to the group, Joe. I think you can do better than 1/16", assuming that your measurement technique is good. (No offence intended). The “bow in the middle” is particularly weird. I’ve lost track of what the instructions say, but once you have attached the back corners, jog the machine in Y, to close to the next foot position, then attach that foot. Continue until you have reached the front. If you have done this already and your rails are not parallel, I would give it one more shot.

Finally, you may want to check the rails for straightness. There is no way that they should be bowed.

We followed the steps in the assembly instructions, which matches @gwilki 's description above. I did notice that some of the screw holes are on an angle and some are straight. Perhaps put the down screws in first if you didn’t do it that way already? Just thinking it’s less likely to pull in crooked that way.

Good luck!

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Hi, did you ever get this solved? I have the same issue except for the bowing.

Hello! I just assembled my CNC and it’s been challenging so far. I also have an issue aligning Y axis. I see that the X axis rail and the Y gantry is not 90 degree (Lesser than 90) when I tighten all M8 bolts. If I tried to align the back, I will have to exert an effort, which I think is not right. I tried following the instructions on alignment. I have the X all the way to the back, but still the back feet are are not aligned and Y axis narrows going to the front. I found a work around by loosening the M8 bolts (X axis rails & Y Gantry connection). I have tried carving and Its kind of working right now, but I am not sure if this is normal to this machine? I want everything tightened down as much as possible. I think the X axis and Y gantry angle is the root cause. Not sure if I miss a step or the shoulder brackets are not 90 degrees ?

Jeesh! That the assembly can’t come together correctly unless bolts are purposefully left loos certainly doesn’t sound right to me. Perhaps there is a particular sequence they need to be tightened in?

I think it’s time for you to get in touch with the Sienci Labs staff, as this sounds wrong to me.


I have assembled my machine (the original Mk 1) and gone through the calibration process. According to the results, my machine is running quite accurately… but not perfectly.

After re-reading your post, I measured to see how square both of the Y-rail to X-rails are, and have noticed that on both sides and in both axis (vertically as well as horizontally) they are quite a bit off (several degrees). I am planning to shim under the steel brackets that adjoin the X-rail system to the metal plates to see if this can correct things. Once I’ve done that, I’ll rerun the calibration process.

Incidentally, I needed to do this to my other woodworking machines to bring them as close as possible to perfect, so I have no compunction in doing this with my CNC.

I’ll let you know how things go.
Marty Schlosser

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Thanks again Marty. I certainly appreciate any updates to how things are going for you if you don’t mind taking the time to do that.

Take care, Greg