Backlash compensation > does not compensate enough

[bloq]

Hey all,

i have been able to get really good results in small details with my 2.x laser with dsp / x7 and the x_unilaterism setting. Unfortunately this is not very fast
because the laser only engraves one way. When using x_swing there is some amount of backlash which leads to an uneven edge. I already
changed the belt on the x axis from mxl to gt2 because it should have less backlash but this did not have any visible effect. What i also tried is the
backlash compensation in the lasercard software (Engrave reserve offset). I tried the recommended value and other values but i was
not able to detect any changes in the engraving. Did anyone achieve good results with backlash compensation?

thanks a lot,
tm

[Techgraphix]

I also use GT2 belts now (Before T5...) and a LO-X7 and have not set any compensation, still have not a singe micrometer backlash. Not even when I used the T5 belts. When I engrave a vertical thin line it is straight and continue even under a strong magnifying glass. When magnified very much you can see which way the laser went (start and stop) but still without any shift horizontally.
You might check the belt tension. It has to have some tension but not like a guitar-string. Check if there is some freeplay in the coupling or timingpulley.
Do you use a reduction or is the motor directly coupled to the timingpulley? what kind of guiding-rails you have? If you use simple (V-grove)bearings on a rail you can imagine that the head will tilt when pulled to one side and in the opposite direction when it's pulled in the other direction.. I use HiWin linear guideways which do not have any freeplay.

Kees

[bloq]

Hey Kees,

thank you very much! Hmm this sounds like it is possible. Do you also have perfect results when lasering very small fonts?
I checked belt tension and it seems to be ok. I tried reducing the tension but it did not show any change. My x axis (i am talking
about) is connectet to the stepper directly. I use the standard makerslide with the v-reels. So this may be the reason? How
do you use the hiwin linear guideways? Do they use screws? Because you said you were still using belts.
You are in the netherlands, right? Where did you get them from? I live in germany so maybe you found a source in europe.

thank you!

tm

[Techgraphix]

Hi TM,
I even believe that they where from Germany You have to google for a local dealer.
I think the attached photo will give you a good impression of how my laserhead is mounted.. I see that this was still with the T5 belt..

The smallest what I engraved was with a beamexpander in the laserhead's tube with a 38.1mm lens: 0.2mm height (YES 1/5 of a mm) and with a strong magnifying glass it was readable and perfectly in shape...
Imagine that the average christmascard has a paperthickness of 0.7mm... I should be able to write 3 lines on the side of a postcard.... Aligning the postcard will be quite impossible however

BTW do you see my ultrasonic autofocus.. Only seen that on Trotec's ... The small switch you see on the side is to teach-in the sensor.. Only to be operated when replacing the lens.. works from 3-30cm with 0.05mm accuracy... good enough for laser IMHO..

Kees

[bloq]

omg! What an amazing setup! Wow. Do you have more images? i want that too : ) I am totally excited but have no idea how you put this in the buildlog laser ...

[Techgraphix]

I designed and build it myself.. It's apparently so good that 3 other guys came over to Appelscha to have a look at it and where convinced to skip all other projects and build the same laser.. two of them are working right now.. except for RF-lasers it can compete with 30.000+ euro lasers as it is.. Building your own laser doesn't mean it is cheap however, good materials cost a fortune.. I spend about 5500 euro's for all (including a CW5000 cooler, Airassist-compressor, ventilation etc..)
More photo's, some older, while I was building it... I have a LO-X7 controller in it so you might see an older DF212 or AWC608 but those are replaced..
The first one is one of the machines that is build by someone else (light blue frame)
The last is in present state (with LO-X7)

I have more pictures if you're interested.. From details etc.

Kees

[Techgraphix]

Just a few results from the past: a 10x10cm mirror (lasered from the back) and a 7cm Trespa disk with the Aztec calender... as you see: No backlash..
And both done bi-directional..

Kees

[bloq]

Wow. Thank you very much for sharing. This is nothing less than impressive. I would love to see more images of every detail
I guess you do not have a bom or something like that? Or even plans? If my (future) machine could do that i would be more
than happy . When i am in the netherlands for the next time - would you mind if i take a look at the machine?

tm

[bloq]

Regarding my problem i have checked a lot from belt tension to acceleration speed to several settings in lasercad. I am not even sure if this is a backlash issue. There is also no visible freeplay when i try to wobble the unit which carries the lens head. I attached a picture of two 1,5 mm lines. The left one is made with one way lasering and the right one with x-swing. You can see what i mean. There is a big difference in precision between both of them. Is this a matter of backlash and are there any ideas?

thanks

tm

P.S: When i use x_swing very very slowly (100 and with ppi set to 600) the results are very good. Does this point to backlash problems or is this something else.

[sshwarts]

This is always a good test for backlash... the snakes test.

Backlash Snake.pdf

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