I found recently something wrong in my x axis movement.

General CNC CNC Routers
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1

I found recently something wrong in my x axis movement. When the axis is in motion from one end to the other end of the table it is not drawing a straight line, but more a sinusoidal line. It’s amplitude is very small, approximately 0.3 mm both horizontally and vertically. Not much, but cannot etch PCBs.
Can it be no parallelism of the ball screw and linear guide?

2

It could be due to all of the acid you have poured onto your CNC machine in a vain attempt to etch with it.

3

I believe, if I understand you’re thinking, that you are correct. Sounds to me like there is some play in a linear slide.

4

I had a similar problem. The problem was in the ball screw. I had lubrified the axe with grease and the balls seemed like glued to each others. After cleaning all, i put some thin oil and now have straight lines. Hope this hepls in any way and sorry for some english mistakes…

5

@Jose_Lobo your English seems to come across just fine don’t worry so much about it. :slight_smile:

6

eheheh… thanks Kyle but still don´t know if its “x axe” or “x axel” or none of them…cheers

7

After some reading and investigation…now i know it´s “X axis”… :wink:

8

Something I had to look up is the plural of axis. It is axes, oddly. The English language doesn’t make much sense sometimes.

9

the path over the work surface is given by the rails; I don’t know your machine; if you are using two metal rods to the sides of the screw; an overtighten nut may induce it to one side when rotting CW and to the opposite side when rotating CCW; of course, your rods must be too thin, or the x-axis too long for the rails diameter. Or the forces on the tip of the router bit are too high for the rods diameter
I had the same problem with my router (doing ellipses instead of circles) and I resolved that adding an anchor at the middle of the lower rod.
You may try to reduce those forces by placing the PCB higher.
See http://www.cncroutersource.com/do-it-yourself-CNC-router.html

10

Thanks for your responses.
@Nelson_Trujillo ​​: my machine is currently made from plywood, 16mm linear rails, and 1605 ball screws. What I see different comparing to the drawing from the link you mentioned is that my x axis rails and ball screw are not in the same symmetry plane. But the machine itself is very solid and sturdy. I planed to use this construction to precisely predrill holes in flat Aluminium profiles and replace plywood with metal parts.
I think that the most possible issue (might be not only this) is the non parallelism between linear rails and ball screw, also will check if all axes are perpendicular to each other. My Z axis linear rails are close to 50cm long and I consider to cut them down, as I never needed more than 25cm up movement.
Ball screw seems to be OK. What surprised me is that Y axis is doing precisely well, although its length is ~80cm, while Y is ~60cm and draws the jerky line. @Krzysztof_Foltman ​​ It is indeed a jerky line. Niezbyt mocno, ale poszarpana :wink:

Update:
The ‘sinusoidal shape’ of the line with 0.2-0.3mm amplitude is repeating every 5mm, which is in relation to the 5mm ballscrew thread installed on X axis.