[Stnq]

Hello,
I have a problem with my plasma cutter, running on mach3 software. Everything is leveled and straight, it's ok when I cut 2-3mm steel, but when I go to 10mm, it rarely cuts it like it should, more often than not it's something like in the first picture. When cutting straight (like squares) it's ok, when cutting arcs and circles it makes this...angled profile? No idea even how to name it. I use Stanko plasma machine with 130A limit, I tried to cut it at 70 and square looks OK, circles do not. I ramped it up all the way to 120 and it produced similar results. I have 4 bars of air and I have no idea how to approach this problem. I do not have experience in this field, I'm setting it up for my friend. Thank you for all the help.

This is the G-code I use for 66mm circle:



( circle_test 3/15/2016 3:36:09 PM )
G21 G90 G64
G0 Z-2.0
( move to the X,Y location of first toolpath )
( Profile1 )
G0 X67.4195 Y53.8378
G1 F500.0 Z5.0
( pierce height )
G0 Z5
( torch on )
M3
G4 P1
( plunge to cuting depth )
G1 Z5.0 F500.0
G3 F400.0 X66.3032 Y49.7447 I1.4884 J-2.6047
G2 X70.75 Y33.0 I-29.3032 J-16.7447
G2 X20.125 Y3.7716 I-33.75 J0.0
G2 Y62.2284 I16.875 J29.2284
G2 X66.3032 Y49.7447 I16.875 J-29.2284
G3 X70.3964 Y48.6284 I2.6047 J1.4884
( torch off )
G4 P0.5
M5
( small delay - s )
G4 P0.5
G0 Z-2
M30

Can't see anything wrong with it, or with the machine. I'm simply lost.

[bytor]

As for the bevel angle, first blush is the Arc Voltage it too low, but I have a few questions.What is the direction of the torch when cutting - clockwise or counterclockwise? Scrap is always to the left of the direction of travel.
Is the plate level and square with respect to the torch? Was this cut performed with brand new fresh consumables? If not, what is the condition of the nozzle? Perfectly round?
As for the dross/slag at the bottom of the part, does it chip off easily or is it a grinder only removal?
Rule of thumb is 10 amps per mm of cut thickness. Try 100 or 120 amps for cutting this and mind your feed rate.
The lag lines in the beveled part seem very pronounced. These are usually motion related and may be inherent to the design of the table (Motors, rails, controller) or may be an indication that you need to perform maintenance to the motion systems (pinions, rack, bearings).
Coming back to the bevel and direction of travel, Outer dimensions are cut clockwise, inner dimensions are cut counter-clockwise
Edited for clarity

[Stnq]

As for the bevel angle, first blush is the Arc Voltage it too low, but I have a few questions.What is the direction of the torch when cutting - clockwise or counterclockwise? Scrap is always to the left of the direction of travel.
Is the plate level and square with respect to the torch? Was this cut performed with brand new fresh consumables? If not, what is the condition of the nozzle? Perfectly round?
As for the dross/slag at the bottom of the part, does it chip off easily or is it a grinder only removal?
Rule of thumb is 10 amps per mm of cut thickness. Try 100 or 120 amps for cutting this and mind your feed rate.
The lag lines in the beveled part seem very pronounced. These are usually motion related and may be inherent to the design of the table (Motors, rails, controller) or may be an indication that you need to perform maintenance to the motion systems (pinions, rack, bearings).
Coming back to the bevel and direction of travel, Outer dimensions are cut clockwise, inner dimensions are cut counter-clockwise
Edited for clarity

Hello, thank you for your reply.
I'm not sure about the direction of the cut, I think it's CW (according to cambam). Yes, all is leveled in relation to the torch, besides even if it was a bit off, I don't think it could produce such..odd results, right?

It chips off fairly easily, one hit with a hammer usually removes a large chunk of the slag.

The speed which was used in this cut was 350, don't know if that's too fast or to slow.

Lag lines probably are from the motors, but they're not the issue, I can live with them.

It was cut for the inner part, so it should go CCW, yes? I'll change that tomorrow.

But I did try to cut the metal piece with 100+ amps and it still produced this 'profile'.

This cut was performed with fairly new consumables in very good condition. I'll perform a cut with brand new consumables tomorrow and post results.

So you're basically saying it's amp related thing + CCW motion instead of CW motion?

[bytor]

Well, you haven't told me your arc voltage, but I would be first concerned with the direction of travel and the condition of the consumables. For example, attached is a picture of a flange.Attachment 312606. The bolt holes and the inner diameter hole (numbers 1 and 2) are cut counter-clockwise. The outer diameter (3) is cut clockwise.

I am unfamiliar with the cut data for your torch, but to give you a comparison, a Hypertherm Duramax hyamp torch cut data is:
100 amps cutting current, 155 VDC arc voltage, 77 Inches per minute feed rate (1955 mm per minute)
ThermalDynamics specs:
100 Amps cutting current, 110 VDC arc volts, 67 Inches per minute feed rate (1701 mm per minute) - [ Personal note - I find the arc voltage here to be a bit low at that speed]
ESAB PT37 torch cut data:
100 amps cutting current, 150 VDC arc voltage, feed rate is a variable here 77 to 100 Inches per minute (1900 to 2425 mm per minute)

I'm not sure what your torch specs are.
Ensure when you change the consumables that you change the swirl ring or gas baffle unless it is designed into the cut tip as with the TD torches.

Regarding the dross coming off easily, this would indicate that you are traveling a bit slow
Here is something you can do as a test. Set a piece of 10mm on the table a couple feet long. Make a manual cut along the edge about 1/4" in from the edge. Cut the full length of the sheet. Compare the edge of the scrap that dropped to the edge of the plate on the table. The scrap part should have a bevel to it.
Unless you are using a reverse gas baffle that pushes the air in the opposite direction, then the scrap is always to the left of the direction of travel.

[Stnq]

Wait, I'm not sure I explained what my problem is clearly enough. Or I'm not understanding the answer. I'm not even an amateur in this, I just happened to be there when my friend got his cutting table and here I am trying to set it up.

So my problem is that the 'profile' (I'm not even sure this is a right name for it) has an angle, when it should be straight. So instead of my first picture, it should look like this one I've attached.

Is this related to cutting direction and amps I'm using? I'll have all the specs of my torch tomorrow, all the documentation is there.

[bytor]

Yes, we are speaking about the bevel angle on the edge of the part. Direction of travel is important as plasma torches are designed to swirl the gasses - in your case air - in a particular direction so as to give the part a flat edge.
I see this issue most often at ship yards that have a dual torch arrangement and cut mirror parts.