The profile of my cut is not straight, plasma not strong enough?

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.

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

Quote:

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Originally Posted by 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

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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?

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.

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.

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.

Ok, I'll just make cambam do an opposite movement and give it a bit more amps. Thank you for your help, I'll tell you tomorrow if that helped :-) I'll give you all the details tomorrow aswell. Thanks again!

Ok, so I made cambam run in the CCW direction, gave it a 110 amps and it didn't do it right, but it made it better. Not sure what to make of it. Oddly, my machine doesn't do exact circles, it bends a little, as shown in the 7th picture. It goes a little to the left and up, instead of perfectly round circles. No idea why. As I said, I'm not even sure if steps per MM are set right. If I cut 28mm circle sometimes it cuts 27.60, sometimes 27.9, no idea what to make of it. So I made couple pictures that show how my machine is connected and such, the motor manual page, the name of the machine etc. basically everything I've got. Could you please check if everything's ok? I know it's a lot to ask for, but I feel like I'm walking in circles here with no idea where to go.

http://www.cnczone.com/forums/attach...8&d=1454847637 this is my stepping motor, got two of them, and it's not running smoothly. It jabs a bit (you saw the lines on the profile too). How could I fix it?

Last picture shows how the profile looked today. It was much better on square shapes, no idea why.

As for steps/mm, I'd like to ask you about that - my table is 2000x1000mm, and I know mach3 doesn't care about my table size, but I'm fairly sure 1 millimeter should be the same as 1 unit in my DRO, right?

My plasma is the 125H one, last column. I hope it's the information you asked for.

Well….. you’re all over the map on this one. Let’s deal with the process issue first.
What is your arc voltage setting? You have yet to tell me that, or to tell me if you have THC at all.

What material is on the table? Mild Steel, Aluminum ???

What is the kerf compensation for the plasma cut. Torch kerf will change with cutting current. This relates to the size of your part. Plasma is just like a circular saw in that you have to take into account the thickness of the cutting tool/blade. Every time you change the current/different size nozzle the kerf changes. Also, plasma is NOT as accurate as a water jet, laser or router.

Why 110 amps? Is there a process recommendation for 110 amps? Does the cut data for your torch/plasma cutter recommend a particular set of consumables with a cut current of 110 amps?

Dimension issues: EASY to check, not always easy to do.
Throw a large chunk of that 10mm on the table and clean it off (or some ¾” plywood, smooth side up) but it needs to be flat, not warped or bowed.
Strap a pen to the torch, TIGHT!
Tape some paper to the plate/plywood. Make certain it’s flat and doesn’t roll if you pass your hand over it.
Make the following drawings:
254mm square - Check for size
254mm diameter circle – check for size and check for round
Draw the largest RECTANGLE on the table that you can [or just the corners :) ] and measure the diagonals. They should be equal. As in EQUAL. If not, you have a machine square issue. {EDIT} which you may be able to compensate for in the software depending on how severe .
You may need to be a bit creative with your pen setup. In a perfect world you have a spring loaded pen holder or something that would allow the pen to float on the drawing surface.

In Mach3, tab motor tuning, set step pulse and dir pulse to at least 5.
I had a similar problem with my Stamos 85a plasma cutter. Your machine torch P80 is sheet and nozzles and electrodes are bad quality. You can try to improve cut by lifting torch on 5-6mm (cutting height), (8mm pierce height), when cutting ticker metal. Do Your self a favor and purchase a decent torch.

Hello
I also use the stamos 85a. I have had the same problem and help to change the nozzle.
Lakijano did you bay a new torch? Whose production and where?

In fact, I bought a new plasma cutter (Huayuan LGK 120 IGBT).The machine is also Chinese but much better than Stamos 85a plasma cutter.
With the machine I bought a 100A HD plasma torch (link: https://www.aliexpress.com/item/Hot-...66225.html?spm= a2g0s.8937460.0.0.755b2e0epJLQ9U).
Consumable parts are much better quality and longer lasting.

Quote:

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Originally Posted by lakijano

In fact, I bought a new plasma cutter (Huayuan LGK 120 IGBT).The machine is also Chinese but much better than Stamos 85a plasma cutter.
With the machine I bought a 100A HD plasma torch (link: https://www.aliexpress.com/item/Hot-...66225.html?spm= a2g0s.8937460.0.0.755b2e0epJLQ9U).
Consumable parts are much better quality and longer lasting.

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I would like to change the torch of my Stamos. I plan to buy the torch that lakijano suggested. I wonder if it will fit?