[JerseyBill]

I am getting poor cut quality using the fine cut nozzle on 11 Gauge steel (.125). The cut has a scalloped appearance ( I will attempt to attach photos). The equipment is PowerMax 1000 with machine torch. It is used on a Torchmate 3. Generally I get good quality cuts using 60, 40 and fine cut nozzles. But most of the parts have been large and have more straight lines in the design. The parts I am having problems with are much smaller and have more curved lines in the design. The settings are 50 Amps, 83 Arc Volts, 90 IPM. I have tried changing settings such as air pressure, speed and pierce height with no improvements. I have also tried changing ramp speed and continuous contour speed. I have checked the gears for loose set screws etc. and checked the air supply. The original file was done in Rhino and exported as AI for toolpathing in SignLab. The file seems to be free from excessive nodes and is real clean. I've completed many projects using the Rhino to SignLab path and either AI or DXF as the file type with no problems. But they have all been larger parts with straight lines or very large curves. Any suggestions?

[jimcolt]

The scallops shown in the photo can be caused by:

- some sort of arc instability. Arc instability is usually du to incorrect speed....to slow or too fast....experiment with reducing and increasing the speed in about 5 to 10 % increments.

-Most often these scallops are motion control related. Put our hand on the torch while cutting the part (with the plasma on). Can you feel some roughness in the motion.....any motion anomaly will show in the cut.

-You don't mention if you have a height control. Incorrect height can cause arc instability (#1 above). This torch needs to remain at a constant .06" from the plate during the cut.

- Height oscilation. Again....with your hand on the torch during the cut...feel for z axis oscilation.


Last but not least....it is normal to have edge roughness....more so on thin material. Air plasma systems cut quality gets bettr as you increase thickness....and gets worse (angle and roughness) as you cut thinner. Without cutting your same part on my machine...it is difficult for me to determine if this is a normal looking roughness.

If you send me a .dxf fil with the part program I will cut it on my machine with the same consumables an power level...and will forward a photo of the edges.


Jim Colt Hypertherm [email protected]

I am getting poor cut quality using the fine cut nozzle on 11 Gauge steel (.125). The cut has a scalloped appearance ( I will attempt to attach photos). The equipment is PowerMax 1000 with machine torch. It is used on a Torchmate 3. Generally I get good quality cuts using 60, 40 and fine cut nozzles. But most of the parts have been large and have more straight lines in the design. The parts I am having problems with are much smaller and have more curved lines in the design. The settings are 50 Amps, 83 Arc Volts, 90 IPM. I have tried changing settings such as air pressure, speed and pierce height with no improvements. I have also tried changing ramp speed and continuous contour speed. I have checked the gears for loose set screws etc. and checked the air supply. The original file was done in Rhino and exported as AI for toolpathing in SignLab. The file seems to be free from excessive nodes and is real clean. I've completed many projects using the Rhino to SignLab path and either AI or DXF as the file type with no problems. But they have all been larger parts with straight lines or very large curves. Any suggestions?

[JerseyBill]

Jim,
Thanks for the suggestions. Yes I have a THC, not the best but works relatively well and certainly better than manual adjustments. It was supplied by Torchmate.
I read your list several times and had to admit that although I was certain the machine moved smoothly and all drive components were tight, I never attempted to verify that was true. So I rigged up a felt tip pen with duct tape and a block of wood on the side of the torch and ran the file. I was shocked that the pen lines matched the scallops in the cut metal. I ran the file several times plotting the toolpath to see if the scallops would be any different. They were all exactly the same. You have identified a major part of my problem. I rechecked the drive components and everything is tight with no play or slop anywhere. Thanks for your help and the offer to run my part file. For now, I need to resolve the machine movement issues before changing anything in my plasma setup. I will contact Torchmate to find out how to correct the movement and report back since others may want to know what the fix is. Thanks again. Photo of the pen lines is attached.

[jimcolt]

Great job troubleshooting. Often the pen tells a lot......however I have seen a few cases where the pen showed perfect contours....but the x-y motion was oscilating during plasma cutting. Sometimes the drive motors will pick up electrical noise from an inverter power supply...and can act like yours.

It could be a backlash or flex issue (mechanical) or it could be a drive tuning issue (accelerations, gains). Also look for things like loose mounting screws on the drive motors, bearings, etc.


Good luck and keep us posted.


Jim Colt

Jim,
Thanks for the suggestions. Yes I have a THC, not the best but works relatively well and certainly better than manual adjustments. It was supplied by Torchmate.
I read your list several times and had to admit that although I was certain the machine moved smoothly and all drive components were tight, I never attempted to verify that was true. So I rigged up a felt tip pen with duct tape and a block of wood on the side of the torch and ran the file. I was shocked that the pen lines matched the scallops in the cut metal. I ran the file several times plotting the toolpath to see if the scallops would be any different. They were all exactly the same. You have identified a major part of my problem. I rechecked the drive components and everything is tight with no play or slop anywhere. Thanks for your help and the offer to run my part file. For now, I need to resolve the machine movement issues before changing anything in my plasma setup. I will contact Torchmate to find out how to correct the movement and report back since others may want to know what the fix is. Thanks again. Photo of the pen lines is attached.

[JerseyBill]

Jim,
I talked to Mike at Torchmate today and he suggested that I check the bushings in the reduction pulleys. This is a stepper/belt driven table. It turns out that he is right and the bushings are worn. Just from tightening up the belts and closing up the gap between the spur gears and racks, I've reduced the amount of scallop by perhaps 50%. I should be able to improve a bit move once the bushings are replaced. But alas, unless I can stiffen up the stepper motor mounts, there will always be some scalloping. There is some flex in this area.

Many thanks for all of your help.