[trdcelica]

Hey guys,

Long story short, I purchased the infamous red and black 60w co2 laser from eBay (knowing it would need work). Upon receiving it I discovered what they claim is a 60w tube is actually a 40watt tube... so I knew some work had to be done.

I took the machine almost completely apart and installed a real 60watt tube, new power supply, upgraded mirrors, lens, and bearings. Overall, the final product came great for my needs... except for circle cutting!!!

Thus far I have done the following for tuning purposes:

• Laser bed was aligned with laser head to ensure even spacing across the platform in the X and Y directions
• Aligned X and Y beams so they are square
• Double checked all bearings and timing belts so they are tight
• Adjusted the beam so it hits the surface as vertical as possible (pretty darn close to perfect)
• Spent about an hour tuning the X and Y e-steps. After an hour of cutting more 20mm squares than I know what to do with, I get numerous measurements at 19.94, 20.04, 19.97, 20.01 etc. So for the most part, +/- .05mm in the X and Y.... not bad for a Chinese stepper machine.
• And for less wear and tear on the machine, I decreased acceleration speeds to about 50-80mm/s
• Cut software - RDWorks V8

So, with ALL that tuning, I still cannot cut a circle if my life depended on it. The circle starts fine, and then will add about .5mm to the area facing the back left corner of the machine. I am cutting circles in both oak veneer and acrylic to test/measure this. My cut speeds are slow, 5-8mm/s at 80-90% power.

My 20mm circle test will measure around 19.99, 20.04, 20.03, and then spike to 20.48, and then come back down to 20.0mm (on the same circle).

The same .5mm ovality issue is consistent across all different sizes of circles. And since I mainly cut 3mm - 5mm circle, this poses a pretty large issue for me.

I am totally out of ideas, well kind of, a part of me thinks that somehow the X and Y beams are not aligned? But when I check them, they look fine according to my square. Maybe there is a trick to aligning them?

ANY help is appreciated. I am so out of ideas... at this point in time anyone telling me to dump a bucket of water on it while it is turned on may be a good idea!


THANKS!
Mike

[otromar]

Hi Mike, apologies for my english, I think about the 20x20 square... for me is too small to wipe the errors of steps.
I am just thinking... Is too crazy try a bigger square, and then you can minimize the error of drivers ?
Martin.-

[trdcelica]

Hi Martin,

You English is fine! Thanks for the reply. I'll give a bigger square a shot today and report back. I am open to ANY ideas. Thanks for replying so quickly.

Thanks!
Mike

[trdcelica]

Hi Martin,

I am pretty close now, about .2mm off on my 5mm circle. I cut a 100x100 square and noticed my e steps needed more tuning than I observed at 20x20 squares. For the circle being within .2mm.... I'll chalk that as a win and "close enough" for a cheap chinese machine. Thanks!

[Dean448]

I wouldn't be so sure that accuracy will be maintained. I found that the temperature of the cooling water slightly changes the location of the beam. A slight change in the beam has a significant effect on accuracy. I found the beam to be less accurate then the steppers.


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[trdcelica]

Hi Dean,

I am using a chiller on my setup. I'll run a few test cuts and check to make sure the laser is hitting straight down on the material. I'll let you know how I do.

I wouldn't be so sure that accuracy will be maintained. I found that the temperature of the cooling water slightly changes the location of the beam. A slight change in the beam has a significant effect on accuracy. I found the beam to be less accurate then the steppers.


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[trdcelica]

Hi Dean,

Does the attached pictures help? The cuts on my X axis are flat and perfect. What you see here is the Y axis cuts, it's pretty obvious the cut isn't flat. That's the best I have been able to get it. I'm open to any advice.

Thanks!!!!
Mike

I wouldn't be so sure that accuracy will be maintained. I found that the temperature of the cooling water slightly changes the location of the beam. A slight change in the beam has a significant effect on accuracy. I found the beam to be less accurate then the steppers.


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[trdcelica]

Here is a prime example of the issue....

Hi Dean,

I am using a chiller on my setup. I'll run a few test cuts and check to make sure the laser is hitting straight down on the material. I'll let you know how I do.

[Dean448]

That's a poorly cut circle indeed. Notice the step between start and end of cut? I also had that problem and eliminated it by improving alignment in the pulleys. In my case the belt was slightly riding up the outer flange causing it to not cut accurately.

You know your cutting a decent circle when you can rotate the cut out circle a full 360 degrees in the area it was cut from.

Does this machine have a precision slide that has ball bearings in it. If not you should find a way to add them. In the end you might fully rebuild the machine


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[trdcelica]

I 100% agree, no way I can make a product on this machine and sell it with circles that off. Yes, my rails are equipped with ball bearings.

The machine can cut a perfect square, engrave beautifully, but not perform a circle. The problem is much less noticeable in 20mm and larger circles.I am really out of ideas.

[TehPepper]

To get good circles on my G350 I have to actually loosen off the Y axes belts.

This also applies to any cuts that start and finish at the same sport but start and finish from different direction on the y-axis.

[mysticusa]

Hi Martin,

I am pretty close now, about .2mm off on my 5mm circle. I cut a 100x100 square and noticed my e steps needed more tuning than I observed at 20x20 squares. For the circle being within .2mm.... I'll chalk that as a win and "close enough" for a cheap chinese machine. Thanks!

are you using RDWORKs by any chance?

[trdcelica]

Yes I am. I only have RDWorks installed. I have tried importing DXF circles from other CAD software, and the results are the same.

I am running out of ideas... lol. Mechanically the machine is solid... it has to be a software issue (least I would hope).

[mysticusa]

if you dont have any mechanical issue as i stated in my comment on another topic, you can try this if you havent already,

1) if you have done any user menu (on the main window) adjustments (transform, path optimization, backlash appy fix, backlash compensation values etc...) reset them to 0
2) now there is a cut optimization icon (see top toolbar where it says bmp, next to it is a square, third one looks like triangle... thats the one)
3) in cut optimization menu, unselect everything, choose up to bottom in drop down, and set BLOCK HEIGHT to max value (say 300 as my machine was 500x300), important no tick box should be selected! and no path optimization in the laser start options...
4) now draw a rectangle 450 mm by 250mm (if you can?, or whatever the max you can do but not the max machine can as it tends to cause problems near edges)
5) measure the rectangle...
6) go to file / vendor settings (password rd8888 or RD8888)
7) click READ on the bottom. select X axis, click "..." menu top right side
8) a window will pop: enter your drawing and measured values for machine to adjust stepper motor (for X axis, 450 is draw size, but measured size will be different, say 449 or 451.. etch)
9) do the same for Y axis as well
10) click WRITE on the bottom menu
11) Draw the same rectangle again, measure again? if you dont have real backlash issue (on the rail, or belts too tight or loose, or anything rubbing/draging etc) your rectangle will close. draw a circle, and it should close as well, but check cut optimization menu, and make sure everything unselected and block value of max or not smaller than your max drawing length in an axis...

I had the similar issues as well, fixed the tensions on Y axis belt, had to adjust stepper motor position on the X axis as its belt was rubbing against the rail when it was going further away from the stepper motor of the X axis... once all backlash issues rectified, and found the block value/cut optimization options by accident, my problems sorted

sort of... as i have tube fading away issue now due to silly chinese using used or bad tubes on shipment... but this is a totally separate issue...

Good luck and report if it works man...

[trdcelica]

Thanks for the detailed reply mystic! Gonna give it a shot now.

[mysticusa]

Good luck man, i was pulling my hair for days for this circles issue, etc... i first started to look for mechanic issues... which i found a few... mirror 2 would misalign itself, figured damn spring screws were not tight and cause mirror plate to wobble and misalign... then on side of mirror 2 there is cable belt (protector kind of thing) would move the mirror at certain positions due to mirror fixings touching the plastic cover belt thing... then hearing belt stretching on Y axis... then X axis belt rubbing against rail etc... i thought my issues were mechanical, which i had a few but they didnt fix the drawing anomaly... then thought wrong values in vendor settings for stepper motors would be the issue... but main issue which i accidently found was cut optimization options, while trial/error all options... unselected it all fixed it all problems... those options in there changes the starting positions, and if you added any backlash compensation in the USER section, it would distort the images... cut optimization messes starting point, and backlash compensation distorts the image by adding incremental moves... which i see on your pics that i also had! so more settings i used more messed up it became, until i reset everything... and accidentally while trying options in the cut optimization option, finally made the breakthrough... block value and the unselected all option in the menu did the trick...

[trdcelica]

I think I may be bald soon lol. It is good to know that someone else is out there who has also experienced this problem, lol. Now, unfortunately my 20mm circle is at 19.2 on the X, and 19.8 on the Y lol. I am going to have to go to Lowes tomorrow to get more wood.... I was't able to cut the full 700x500, so maybe I have more cutting to do at the appropriate size. I'll keep an eye on that cut optimization factor, I bet that may have something to do with it.

When I first got this machine, the circles were PERFECT. And the Y belts were super loose, I mean so loose that I couldn't believe the machine worked. Then it blew a bearing on one of the Y rails, I replaced it. It cut circles again for about a day... then... just started getting catywhompus.

[mysticusa]

Make sure
you unselect/reset all backlash options in the USER menu if you added,
reset transform values if you di?
undo backlash appy fix if you selected etc...

all these adds to the problem and complicates it.

draw a rectangle, first dont do circles... find correct drawn/measured values for the stepper (of course if you dont already have any mechanical issues)
and check the cut optimization menu! very important as it messes the starting and ending points! and backlash adjustments/transform options in the user menus are distorting the circles/or any drawing exactly like your cut stuff...

drawing biggest rectangle helps you minimized the error factor for stepper motors... just dont do the 700/500 do 680-690 / 480-490 otherwise these machines complain about some other problems... ones you get good X and Y axis movement, you will have perfect circles as well...

[trdcelica]

Mystic you are the MAN!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ! Seriously, wow!!!!!!!!!! It works man, it freaking works. I had to tweak some settings, and my final cut optimization was not like yours, but hell in the end, it cuts a damn circle. Mystic I owe you one! You got me in the right direction!!!!!!!!

For anyone whoever has a similar issue....

1 - Follow what Mystic said below about clearing any custom settings
2 - Cut a LARGE piece of wood and calibrate it. I started with 450mmx450mm measured, adjusted stepper settings, re-uploaded, then cut that same square at 425mm, measured, rinse and repeat until it is good to go.
3 - Check "Blacklash reapy optim" in the Output settings tab on the right of the main menu (no idea what it does, but it seemed to help).
4 - Grab a bolt (I used 8mm), draw an 8mm circle, cut it, and see how well it fits.
5 - Start messing with "Cut Optimization" settings. I cut about 15 8mm circles, checking certain boxes, using different drop down options, etc, and settled on the final settings (see attached photo). Tweaking these settings here will bring the circle to life.
6 - Final calibration was done via the good ol' guess and check method for User - Other - Backlash settings. In my original circles I knew I had a Y axis problem. I just picked an increment, cut an 8mm circle, changed the increment, re-uploaded, cut, checked it,etc. Adjusting these backlash settings created the final touches on my circles. This made them round.

In the before and after attached pics, there are four 3mm circles and 1 8mm circle.

Fair warning to everyone... do NOT be in a rush to do this... I cut about a total of 40... 8mm circles until it was right.

Hope this helps anyone in the future... I give all credit to Mystic. Attachment 317596Attachment 317598Attachment 317600

[mysticusa]

Well done mate... Dont play around with backlash adjustments too much, they cause distortion just like your first image squashed circle

I m setting the block height to 50 or more (original value is 50 and it seems to work well) i have no idea what the block handle does and no where there is any info about it, but it fixed my issue!

Congrats again... and good luck, glad these settings helped you find your own fine tune...

Also try large circles/squares, because if you have small problem, it will be amplified in a bigger circle... you may need to tweak your block setting based on the size... backlash appy does fix unfinished circles but it can also cause distortion, be careful adding or playing with backlash values...