New Custom Built Frame- DSP Wavey Cut Lines Problem.

[Patrick34]

I have finally entered the testing phase of my laser cutting machine, which has been about 4 years in the making. This is a totally custom build inspired by Bart over at BuildLog.Net. I can fit and cut passed the edges of a 24"x48" sheet of plywood. I am running a AWC608 controller, 120W Puri laser tube,and CW-5200 chiller. All of my power/control hardware was purchased from LightObject.

The test cut was done with all squares running 100mm/s speed in 10% increments descending power from 100% (top - down). It took 5 passes to cut through on the 100%. The others were also cut through on the same pass. Judging from the draft on the sides, I am currently too close and my focal point is below the material. I gather this is the reason it took so many passes to get through?

My issue is the wavy sides on the squares of all the parts. Can this be caused from some setting I have incorrect somewhere?

I have one possible source of mechanical vibration which I can isolate. My air assist pump is currently mounted in the base of the frame. I can mount this on top of my chiller to remove the small amount of vibration it is causing. But the repeatable nature of cutting over and over on exactly the same path leads me to believe this is an issue with the DSP settings and has nothing to do with vibration.

Please don't be afraid to point out anything you think is incorrect. I have absolutely zero experience with laser cutting, (I am a Physics and MechEng major at the moment, and I have been programming CNC mills for years, so the physics of light and the machine itself are not foreign concepts to me). I need to understand the settings/ interface of the DSP as well as how to troubleshoot cutting problems. Right now I have no clue what settings to start to play with. I figured I could save myself hours of testing by asking here first.

[Tech_Marco]

Check the cartridge wheels, pulley wheels, and belt tension. It could be lose parts.

Marco

[Tech_Marco]

BTW, slow down the cutting speed , say 20mm/s see if it is still doing exact wave for line. If it did, most likely that it is hardware issue. Let me know how it goes.

Marco

[Patrick34]

It is not coming from the carriage or linear drive system. There is not any play in the rollers, belts, pulleys, ect. That was the very first thing I checked. You can push the carriage with your finger very easily. You cannot feel any sort of binding or pulsing in the movement. I can tape a marker to the laser head and move it around with the DSP controller to draw very straight lines. This waviness only happens when cutting with the laser.

[Tech_Marco]

If it happened only when laser is fired, then it seems an issue of electromagnetic field interference.
What kind of motor drivers and DC power supply are you using? Rating?

Try another sample without moving the last sample. Then, swap X,Y motor drivers and let it run again. Pay attention to to the route see if wobble line duplicated or in XY reversed (sort of)


Marco

[Patrick34]

Solved! It was caused from vibration of the air assist pump. I am guessing that the vibration, being a constant pulse combined with the laser pulse, was why it appeared to be wavy (constantly changing the location of the mirrors along the beam pathway as well). When I unbolted the air compressor and put it on the floor, the waves went away.

I was drawing lines with the air assist off. My bad.

The squares also cut through in 3 passes at 100mm/s instead of 5. And again, 100%, 90%, 80%, and 70% all cut through at the same time. On the first pass, the corners were cut all the way. I could see light through. From this I gather a speed around 30mm/s would cut in one pass? I still need to find where my focal point is relative to my tip. Do I optimize this to be in the middle of my stock, or always at the top or bottom?

Is this a normal speed? I am just up to about 32mA at 100% (120W on the sticker of the tube) which is the max I can safely run at according to the tube supplier. I am supposed to stay around 28mA to help extend the life.

What can I expect to cut through with 120W?

Thanks for the input Marco. I wanted to be sure of all the mechanical issues like you suggested before I got into any of the other possibilities.