[aaronbee]

I'm having cut quality issues.

The machine will just stop cutting properly. All the settings are the same, but changing consumables can cause it to go from cutting fine, to hardly cutting at all.

When it is working well, you can hear the cut quality. The air flow on the torch sounds nice and clean, and consistent, and has very little dross or top splatter. When it stops cutting well, the torch makes a louder air flow noise because less of the air is making it through the cut and instead is being blown out on the top side of the metal. The sound is also very rough and inconsistent. I say these things because I've watched it cut with a welding helmet on and the cut is v-shaped. Most of the metal isn't being removed. When it cuts well, the entire cut width is melted with a sharp vertical edge and the air blows right through it with very little, to no slag at all. When it isn't cutting right, some of the air blows back causing a lot of top splatter, an increase in heat across the metal, warping, and a ton of slag on the bottom of the cut. I'm guessing the dross on the bottom is because not all of the air is getting though the cut.

When it's cutting like this, increasing or decreasing the amperage doesn't fix it. Lowering the speed can help some, but it's still an awful cut with lots of slag. Increasing or decreasing the height doesn't seem to help. It's not like it's trying to cut a 1/4" off the metal.

Cutter is a Cutmaster A40. Cutting 16 gauge HR mild steel. Using a 60 amp tip. New consumables (electrode, tip and starter cartridge) . Cutting speed is 160ipm. Amps set to 40. THC target volts 107. psi is at least 80 to 85. air inlet at plasma cutter has a water separator in front of a motor guard filter. When the air is running through the torch head, I've put blank paper under it and it never produces any visible moisture. Now, in front of the water separator and filter, you get water in the air, but on the other side, I can't detect any.

I can't make any sense of it. It just doesn't seem like the plasma beam is getting all the way through the metal. At the setting listed above, sometimes it cuts just great. When it cuts like this, you can see the cut is rounded off on the top edges, it's V-shaped and has a lot of warp. The heat just doesn't seem like it's passing through a nice clean cut and being blown out the bottom.

What causes this? Why one set of consumables works fine (almost no slag at all) for 15, 20, maybe 30 parts, then a new tip and it all goes to crap. I can't get it to cut right again. Any helpful ideas welcome. Thanks.

[jimcolt]

I would suggest that you go back to the manual for your Thermal Dynamics A40....check out the mechanized cutcharts and follow them exactly in terms of which nozzle (tip) to use for best cut quality on each material type and thickness.

You state that you are using a 60amp tip running at 40 amps , 160 ipm on 16 gauge steel.....

1. If you are looking for best cut quality you should use the correct consumables for the material. Without having an A40 manual.....I would guess that either a 30 amp or 40 amp set of consumables would provide far better cut quality and consumable life on 16 gauge....and a 60 amp "tip".....should bve operated at or near 60 amps. Less amperage and you are reducing the arc energy density....which will make for a very ugly cut.

2. You mention arc voltage (so you must have a height control).....don't worry about the arc voltage that is listed in your manual....rather, adjust the arc voltage durring the cut so that the torch cuts at the physical height that your manual suggests. At 40 amps on 14 gauge...the torch should be cutting at around .06" (1/16") off the plate for good quality.

3. You don't mention what the consumables look like after a few cuts.....is the nozzle orifice damaged? Out of round, nicks in the orifice? If so....that is usually caused by piercing too close to the plate....or by allowing the nozzle (tip) to contact the plate during the cut.

I typically will get many hours of cutting, and average around 1400 pierces (on one nozzle) when cutting 16 gauge at 45 amps with my Hypertherm Powermax45.

Jim Colt Hypertherm

[aaronbee]

I would suggest that you go back to the manual for your Thermal Dynamics A40....check out the mechanized cutcharts and follow them exactly in terms of which nozzle (tip) to use for best cut quality on each material type and thickness.

You state that you are using a 60amp tip running at 40 amps , 160 ipm on 16 gauge steel.....

1. If you are looking for best cut quality you should use the correct consumables for the material. Without having an A40 manual.....I would guess that either a 30 amp or 40 amp set of consumables would provide far better cut quality and consumable life on 16 gauge....and a 60 amp "tip".....should bve operated at or near 60 amps. Less amperage and you are reducing the arc energy density....which will make for a very ugly cut.

2. You mention arc voltage (so you must have a height control).....don't worry about the arc voltage that is listed in your manual....rather, adjust the arc voltage durring the cut so that the torch cuts at the physical height that your manual suggests. At 40 amps on 14 gauge...the torch should be cutting at around .06" (1/16") off the plate for good quality.

3. You don't mention what the consumables look like after a few cuts.....is the nozzle orifice damaged? Out of round, nicks in the orifice? If so....that is usually caused by piercing too close to the plate....or by allowing the nozzle (tip) to contact the plate during the cut.

I typically will get many hours of cutting, and average around 1400 pierces (on one nozzle) when cutting 16 gauge at 45 amps with my Hypertherm Powermax45.

Jim Colt Hypertherm

I'm off from manual specs by +20 ipm, +5 arc volts, +10 psi, and using a 60amp tip at 40amps.

I'll adjust and try it again.

I always used a 60 amp tip assuming it would work up to 60 amps. I knew the orifice was larger, thus wider kerf, but didn't consider it not working properly at an amperage below 60.

As for tip life; not anywhere near 1,400 pierces or hours of use. That would be awesome. 200 is more like it. Yes, after 10 or 20 parts the orifice is damaged, out of round, with nicks. The pierce height is per manual spec, but where it is most likely to touch the metal surface is while cutting very small holes (.2"). It will pierce at .1800", then circle back round in a dive that will bring it close to touching the metal surface. I remember a post about g-code enabled macros (M101/M102) that would turn the THC on and off while cutting. I'm gonna try that as well.

Yeah, I eat up tips. I have a box with nearly 25lbs worth of wasted tips (I've weighed it).

[aaronbee]

Ok, I changed the setting to match what's in the Cutmaster A40 manual for a 40 amp tip cutting 16 gauge mild steel. Everything is per specs, pierce height, arc volts, cut speed, THC settings reflect everything... and it absolutely cuts better than it was. I'm gonna try to include some pictures. We'll see if I get it right.

The first picture is the first cut it produced with adjusted settings and brand new tip/nozzle, matching electrode. I'll take that all day long with a smile. I can knock that off with a wire cup in seconds. Perfect.



Also, turning the THC off in g-code on small holes stopped the tip from winding down and touching the metal as it cut. That's super. The macros I downloaded wouldn't work with my setup (maybe because they were older or something, but I replaced the code in them with "StartTHC() and EndTHC()" for M101/M102 and it worked perfectly. Super, great.

Now, how long did it last? I got 56 parts cut before the cuts started looking like those in the second picture.



56 parts is 504 pierces. It's a little over one 4X8 sheet of 16 gauge. I don't have the actual inches in front of me, but its around 4,400 inches of cut. Is that good? I don't know. At least it is cutting. It's a dime on each part in tips, roughly. You can see, though, that it starts putting out a lot of heat, it's warping the metal, you can see the slag on top, discoloration, etc.

So, I change the tip out, put another one in and 9 parts later, it wont arc right. It goes to fire and it acts like it does when it's not grounded. You get the pilot arc but no plasma. And it is grounded. The ground clamp is on the metal, the table is grounded to an 8 foot rod into the ground 4" from the table leg. The height is right. I checked it. The third picture shows the height next to two stacked quarters. The tip is just a little taller than that (.18") which is what the manual called for. The DRO on Z reads .18". But it won't fire. When it does that, I have to physically lift the metal up to nearly touch the tip to get it to fire. Otherwise it will just sit there and arc green and burn things up.



The last picture shows what the tip looked like after 9 parts (81 pierces, three of which wouldn't arc unless I manipulated it - unless I forced it to do it.)



If I have to change it after 9 parts, it starts adding a almost a $1 in cost to each part. I can't do that. Now, it's still cutting nice on the back side, but it won't take too much of that nonsense before it won't cut at all. I promise the second tip won't make it 50 parts working like it is. If I have to keep lifting the material up to the tip to get it to fire, it will destroy it long before I get to 50.

[jimcolt]

You seem to be making progress. From my experience....the cut height of .18" seems way too high. Are you sure that is not the recomended pierce height? I would pierce at (on 16 gauge) .12", and cut at .06" (1/16"). The heat shadows evidenced in your pictures shows that the height is too high.....and that the acceleration of your machine is rather sluggish. If there is a way to increase accel, deaccel.....you will see further improvement.

As far as the arc not transferring to the plate.....the pierce height may be too high.

The pic of the nozzle looks like there is a dent right next to the orifice....is it hitting the plate too hard? If so reduce the z axis speed....or somehow make it find the surface with less force. Any distortion of the nozzle orifice will affect cut quality. Nozzle orifice must be perfectly round.

If you had a Hypertherm...I could offer much better advice!

Jim Colt Hypertherm

[tinman13]

"If you had a Hypertherm...I could offer much better advice!" True statement!

But if he had a Hypertherm he wouldn't have these issues!

I can safely say that because I have been there and now have a Hypertherm!

As far as the arc transfer problem don't hold your breath for Thermal to fix it.....
They never could tell me what was happening or why.
At one point the changed the pilot arc board in the machine and it seemed better for a while, but it didn't last long.

I could go on for pages with the changes and issues with them but the surest fix is Hypertherm.

Your pierce height is right according to the specs but you will have to lower it to get a consistent transfer...... Then your nozzle life will suffer.
You can try slowing your travel speed and increasing the arc voltage to maintain cut height, Thermals specs aren't very accurate. The specs for the A120 are way different than for a 152 even though it's the same torch and consumables!
Good luck....... I would highly suggest contacting their tech support people if for no other reason than to make them aware there are issues.

[Mike 1948]

I've got a Cutmaster 52 thats been automated, so I can give you my thoughts.

I'm no "expert" but it sure looks as if you don't have a good ground. Could the ground clamp have a bad wire or a corroded/rusty faces on the clamp. I know car jumper cable don't work worth a damn when they get rusty.
I normally set my min THC height to about .09 to keep the tip from diving into the plate.
Also you may want to shift over to a shielded tip, it will protect the orfice from damage.
Just out of curiosity, what kind of machine and control software?
If all else falls, you have a 4 year warrantee to play with.

Good Luck
Mike

[aaronbee]

I've got a Cutmaster 52 thats been automated, so I can give you my thoughts.

I'm no "expert" but it sure looks as if you don't have a good ground. Could the ground clamp have a bad wire or a corroded/rusty faces on the clamp. I know car jumper cable don't work worth a damn when they get rusty.
I normally set my min THC height to about .09 to keep the tip from diving into the plate.
Also you may want to shift over to a shielded tip, it will protect the orfice from damage.
Just out of curiosity, what kind of machine and control software?
If all else falls, you have a 4 year warrantee to play with.

Good Luck
Mike

Everything looks fine with the ground. I think I tried using a shield cap once before, but it didn't work out well. I don't remember why. Probably just wasn't setting it up right.

I changed to a different type of electrode and it seems to be cutting better. I know assumption is the mother off all screw ups, but I assumed the electrode that came with it was the right one ...which it is, for manual cutting, but obviously I'm not using it manually. It lists a slightly different electrode for automated use. Devil's in the details, I guess.

About the only issue I still have with cut quality is on 22 gauge. It likes to warp up as much as a half inch and then pop back the other direction which spikes the volts and locks the torch height a half inch off the table. I've given up on that and started strategically placing neo magnets around the table to hold the metal down. Works fine as long as they aren't too close to the cut.

It's a table built with candcnc's stuff, mach3.