My cnc isn't cutting sharp edges

[nikolakuzzz]

Hello, I'm pretty new to the CNC Plasma cutting thing, having recently built my own table. For now I attached to it the plasma i already had, Cebora Plasmaprof 120, but I'm having some difficulties while cutting, most notably it does not cut straight edges.



I'm using Mach3 and SheetCam, and the 5mm thick parts were cut with 80A. My axis calibration seems to be ok, with barely a milimeter of extra.
I'm grateful for your help in advance.

[acourtjester]

I would say your torch is not perpendicular to the table surface, or there is a problem with the plasma stream (air flow out of the torch).
Some have had problems with an "O" ring inside the torch with Hypertherm torches, I don't know about the Cebora if they have any. Also grud on the torch tip can effect the plasma stream too, or wear. If you have had pierced to close it can blow out the nozzle so it is out of round. You show one direction of the angle cut but the cut pattern and the angle seem to be in one direction I would look at torch angle first.

[Rodw]

I would check there is no play in any motion components or the torch slide. The inner corners are not consistent.

[weldguy]

I'm with AC on the air flow out of the torch. See how the bevel drafts in the same direction on opposing sides of the cut...that is the the direction of your air flow. If you were to rotate your nozzle in the torch 90 degrees you would see the bevel be on other 2 opposing sides I bet. This will be caused by the orifice in the end of the nozzle no longer being perfectly round.

This is often caused by moisture or oil in the air supply, incorrect cut height, the nozzle coming into contact with the material while cutting, running an amperage higher than the nozzle is rated for, and/or well as pierce delays being too long.

Cross all those items off your list and post back with another cut and let us know how it looks or post back with additional questions. Helpful folks here for sure.

[nikolakuzzz]

Thank you all for your replies, however, I think this is SheetCam/Mach3 problem, because when I run a gcode with my plasma turned off, I can see that the machine isn't making a good turn at angles. Could it be the speed or pause at the end of cut, or something related?

[acourtjester]

What you showed cannot be caused by the G-code. IF the speed is off the cut will either not go through the metal or produce large amounts of dross. Pause at the end is just that after cutting, not during the cut. Not cutting good angles as you say are a table movement problem. When cutting an angle you transition from one axis to another which is a direction change. Your image shows an angle cut from top to bottom. The torch or plasma steam is not perpendicular to the metal.

[robertspark]

what acceleration and federate were you running

acceleration too low imo / guess (with no info but a photo)

also remember cut direction is different for inside (holes) and outside (part) cuts

https://www.google.com/url?sa=t&source= ... NyPrgXm0HC

[nikolakuzzz]

It seems that I have found the reason for the problem.Too high cutting speed and my rules speed for angles was nowhere near good. I tried this few minutes ago with a feedrate of 5000 mm/min and 10/20/30% speed on angles. I feel like it can get even better, any tips?I'm mainly using 50A and 2mm sheet plates, if anyone could provide me with good rules and cutting speed, I'd be grateful.

[robertspark]

60% + high acceleration
3000 mm/s/s

[robertspark]

at 5000mm/Min, and 60% in the corners (angles less than 90 degrees you can get away with acceleration of 1250mm/s/s for a 2mm inner corner radius... given this is air plasma not laser or high Def plasma

[nikolakuzzz]

It's been a while and I just wanted to share with you how far I've gotten by now. You helped a lot guys, hopefully If i need you again in future I will receive the same attention

[acourtjester]

looking good it puts a smile on your face when things work out. have fun

[adbuch]

Nice work! I'm very happy to see that you are getting your system dialed in and making some nice cuts now.
David

[plasmanewbie]

Nice looking cuts, thanks for the progress update. These folks here helped me out a ton when I first started, just takes some time and experience to "click"