Need Help!- problem with lines not cutting straight after engraving

[geekinesis]

I have a ls3040 (rabbit 3040)
After a job engraving acrylic which lasted about 10 minutes I have now found that when cutting anything lines are not straight. There is a small kink in each line and lettering has a kink along each edge. Circles don't join without a kink in the line.

I am assuming this is a mechanical problem rather than software as I have tried two computers and haven't changed any software settings. I am more confident with electronics than mechanics so don't want to start experimenting with adjustments without advice.

I am not sure what needs adjusting, if anything, and would appreciate some ideas as to what might be causing the problems.

[zax15uk]

It does sound like a mechanical problem, try reducing the speed to see if it fixes the problem (stepper motors have more torque at lower speed).

If you can disconnect the motor cables you will be able to move the head (optics housing) back and forth by hand to feel where the problem is. It could be contamination build up or damage to a belt/gear pulley.

Zax.

[geekinesis]

hi thanks,
i just lowered the speed, to 10mm per sec, and yes the problem is solved at that speed. I noticed the long axis (y?) has a different method of adjusting the belt to the x. I cant quite work out how it works just yet. The belt on the shorter (x?) axis seems fine, and looking at the cuts, the play appears to be restricted to the longer axis.

I think when I was engraving something must have vibrated out of place but I am not sure what it is yet.

[geekinesis]

i have managed to get the speed up to 30mm sec now with some adjustments to the belt tensions. I know where the problem is now so its just a case of adjusting things until I know which adjustments have an effect.

The long engraving job seems to be the cause of the adjusting screws vibrating loose, and the belts becoming slack. I suppose this is because of the constant fast movement along one axis.

I think the belts shouldn't be too tight either I found out.

thanks zax

[zax15uk]

Glad you found the problem. As far as adjusting the belts, it's one of those things you learn the feel for but is difficult to explain.

The 'standard' adjustment would be to have them so you can't easily pinch them together at the mid point. It is also important to keep the drive and idler gear pulleys aligned so the belt stays centered, otherwise it will bind and add additional load on the motors.

Zax.

[SkipW]

And occasional lubrication of the rail bearings may prevent problems down the road also.

[geekinesis]

I was wondering about the bearings. What should I use to oil them?

I have experimented a bit. I have loosened the belts to the maximum and then tightened the adjusting screws a few turns until the belts just start to feel tight. This gives the smoothest travel on the axis but anything above 35 mm/sec starts to affect the alignment of the cuts and I get drift along a straight cut. Under 35mm/sec everything is perfect.
The problem is If I tighten much more, the bearings and the general metalwork vibrate and this affects the line being cut.
Its funny but the table has vibrated since I got it, which I assumed was normal. Its a bit of a novelty to have a silent lasercutter now.

I am not sure how to get a perfect balance yet between tightness of the belt and lack of vibration. I guess its an inexact science and like you say, i will develop a feel for what works

[SkipW]

Here's some posts that discuss lubing the x and y rails.
http://www.cnczone.com/forums/showthread.php?t=63767