Waves in engravings

[MBS]

We have just set up out 100 watt CO2 laser and have tried to engrave a few things and are having trouble. There are waves in the pieces of material we are engraving. We have tried different speed and power combinations and have had the same result everytime. There is a picture attached of what i'm talking about. If anyone has any advice or has had this problem before your help will be greatly appreciated. Thanks alot.

Waves

[Tech_Marco]

You better post the original image and the front view of the work done byyour machine. The picture attached really can't tell much. Also, send picture of your machine from inside out so we know what you're running with.

[baccus61]

It helps to know a little bit about your machine first.
Is it a glass tube laser or an RF one.
Do you have belts or anti backlash drive screws.
What software version do you have
Etc.
etc.
etc.


If you have toothed belt drive then are these waves the same width as the teeth on the toothed belt?
If they are then it looks like the belt is riding up the edge of the pulley and dropping back into the trough for each tooth which gives it a fast/slow action but is not discernible until you engrave something. How does it cut? You probably wouldn't notice any difference if it was doing this while cutting because you always select a greater power to cut through the work. If you back off the power so it just cuts through then it would probably show up as a dotted cut or perforated cut.
How tight is your belt?
Is it loose or is it VERY tight?
I would check the alignment of the belt on the pulleys first before I went elsewhere for an answer.
Let us know how you get on.
Rich.

[MBS]

Our machine is a Transon TS1390. It has a glass laser tube that is water cooled. The software we are using is called Lasercut 5.3. There are belts that move the laserhead on the X and Y axis and the table can be moved up and down by a belt driven system. The tension on the belts seems moderately tight, but i am not sure what the correct tension should be on the machine. I moved the laserhead back and forth and noticed it started to hit the lip on the end of one of the the pulley as i moved it to the right, but never skipped any teeth. I dont think the waves are spaced the same as the teeth on the belt. There are screws that allow the belt tension to be adjusted. Heres some pictures of the machine we are using.

[Tech_Marco]

Please send the image of the original art work to compare. Otherwise, really can't tell what was the output suppose to look like! Post the image file as an attachment, would you? If you can, can you re-send the output image as it's so blurry to view.

Also, I want to know whether the 'wave' is happening to 2d (X,Y) or is happening to the Z (the deepness). It's kind of hard to see it from the picture you sent.

As I told you, grounding is very important to a CO2 machine. Make sure you double check if there is a good grounding on the machine and to the outlet. The power supply of the CO2 MUST be properly grounded. Check the HV cable see if it got some physical damage as 'arc' could occur if the HV cable worn out

Also, do a few basic tests: cut a square box and circle and check if the 'wave' is happening. If it can cut straght line, it may not be mechanic issue but the DSP card or other electronics part issue. Well, let's do it step by step

[baccus61]

OK. Now you show the bigger picture I think I know the answer.
You are engraving along a piece of wood that has growth rings very close together. The wood there is denser and not as easy to engrave as the softer wood surrounding it.

If you can, get a piece of birch ply and try that. Or in fact, another piece of wood that doesn't have the growth rings as close together as the piece you are engraving. Try it a bit further up the wood where the rings are more spread apart and see if it does the same thing with them.
This is the reason that manufacturers make the special laser ply because it has an even surface and density that a good engraving needs.

The belts should be tight enough so that there isn't any sag in them but not as tight as a guitar string. As long as there isn't any sag then that should be tight enough. About as tight as you can stretch it by hand would be good enough.

Hope it helps.
Rich.

[MBS]

We have tried grounding the machine to some of the plumbing in our building and have had the same results. The manual shows a metal rod that was hammered into the ground with a wire attached to it going to the machine itself, as well as a grounded power cable going to the machine. Would that be a better ground if we did something like that? The waves are in the X and Y axis. There are very tiny strips of material that the laser is not taking away. I have tried the exact same thing that I did on the plywood on a piece of wood similar to particle board with no growth rings in it and had the same result. It can cut a circle fine with no issues at all. It is only in the engraving mode that it makes the waves. The belt tension looks ok to me. Thanks everybody for all of your help.

[baccus61]

Hmmm. Interesting.
Have you tried changing the dots per inch for the engraving method or scan lines per inch? I'm not quite sure of the terminology in the manual.
Do the waves have the same frequency or amplitude as the size of the belt teeth or is it different all the time. I mean, does the wave size change if you change any settings or does it remain the same if you change something. You have tried to change some settings, haven't you?
What do you have the Laser pulses set to? Is it 20KHz or a lot less. This is set to 10KHz to 20KHz for a glass tube laser.
If you do change any settings then be sure to save a copy of the old ones before you do as it's very easy to go too far and not get back to where you originally were. Use paper and pencil and write them down. Make a hard copy just in case.
It is an interesting problem.
What setting are you using for engraving. Are you using the Stamp mode? This mode causes the laser to reduce power coming to an edge and increase going away but your engraving doesn't have any edges internally so it probably won't be that. Can you do a screen grab of your settings?

I use MWsnap for my screen grabber as it's free and you can use it to just grab a portion of the screen or a whole window etc etc. It's very good. Found here...

http://www.mirekw.com/winfreeware/mwsnap.html

Just grab the settings and post here so we may better have a look.

Rich.

[MBS]

We have tried changing the DPI and have got the same results. I dont think the waves are the same distance apart as the teets on the belt. The gaps are very small in the workpiece, the gaps on between belt teeth look much bigger. I just hooked up a seperate ground to go from the machine to a grounding rod and i saw a better result, but there are still gaps being made. I honestly do not know what the laser pulses are set to. I dont know where to go in Lasercut 5.3 to change that setting, if it can even be changed in that program. Or is that a setting that i need to change in the machine itself? We are not using the stamp mode, just the regular engraving mode. Our computer that operates the laser is not hooked up to any internet at the time, but i will try and get a screenshot for you to see. Thanks again for all the help.

[Tech_Marco]

Check the mirrors and the lens see if they are in locked position.

[MBS]

We have checked on the mirrors and they seemed to be loose and not locked down properly. After tightening down the locking screws on all of the mirrors we have gotten the same results. Here is a picture of a cut circle after we tightened the mirrors. There are some waves in parts of it that dont look right.

[Tech_Marco]

Ok, it seems that it may be the controller issue.

Do this if you can handle it (with care): engrave the same file on a piece of wood or something that used to cause the wave result. But listen carefully. Remove the cable that connecting to the "IN" of the CO2 power supply to by pass the power control from the DSP. Then jump a cable in between the "In" and "5V" of your CO2 power supply to enable FULL power output (dangerous). I suggest you add a momentary button to to the jumper wile to switch on/off just in case something happen. Or, be ready to pass the Big Red Button on the machine to shut of the machine if over power.

If the result is still wave, it could be the power supply or it could be the machine. But if it ended good, then it's the DSP card

Hope this may help you to solve the problem

[Yepez]

We have checked on the mirrors and they seemed to be loose and not locked down properly. After tightening down the locking screws on all of the mirrors we have gotten the same results. Here is a picture of a cut circle after we tightened the mirrors. There are some waves in parts of it that dont look right.

How did you solve this issue? I have the exact same problem.

Please I need some advice.

[waltfl]

Hi
to change the settings for the laser go to lasercut in option the system then in manufacturer settings and there you see the setting for the laser it should be set see atachement.
greetings
walt

We have tried changing the DPI and have got the same results. I dont think the waves are the same distance apart as the teets on the belt. The gaps are very small in the workpiece, the gaps on between belt teeth look much bigger. I just hooked up a seperate ground to go from the machine to a grounding rod and i saw a better result, but there are still gaps being made. I honestly do not know what the laser pulses are set to. I dont know where to go in Lasercut 5.3 to change that setting, if it can even be changed in that program. Or is that a setting that i need to change in the machine itself? We are not using the stamp mode, just the regular engraving mode. Our computer that operates the laser is not hooked up to any internet at the time, but i will try and get a screenshot for you to see. Thanks again for all the help.

[waltfl]

Hi all
after installing the new lasercut 5.83 I have waves too not as big but disturbing like you see in the picture
I have changed the settings for the scan gap in all variation and the speed and power but the waves are allways there.
maybe it has to do with the dithering in lasercut I have used from 0.01 up to 0.0000001.
with the same picture I did not have the probleme with the previous version of LC .
maybe someone knows whats the reason.
I have clean and checked the optics and the belts too.
greetings
walt