Cut quality issues 20 Gage CR steel Hypertherm 65

[rcktscientist]

I have been using my Torchmate Plasma Table/Hypertherm 65/BobCad software for thicker material building car frames, brackets, etc. Just started using it for art projects, 20 gage cold rolled. I see folks with crisp cuts on thin metal, trying to get there. Basic settings are .1 delay, .06 torch height, 128 V (sample on), AVHC on, tool width set at .060, lead in .125 90 degrees. Material is 4 inch square and fine cut nozzle. Model A grill is about 3 foot, cut at 45 amps 400 ipm, note divots at lead in and poor corner cuts, so I drew a part and ran trials. Here are the details of the trials, trial number, Amps, Speed.
1, 35, 400
2, 30, 400 Didn't cut through
3, 35, 450
4, 35, 350
5, 30, 350
6, 30, 300
7, 30, 250
Biggest issues are the small holes aren't round, probably due to lead ins, and the bottoms of the V's aren't sharp. I will be continuing trials, make test piece with bigger holes and lines as some of my designs have lines so lead in will be 0. I am open to using 18 gage or even 16 if that's what it takes.

BobCad and Cam may be an issue, I see it doesn't have some specific sheet metal settings other software has, especially lead in and out.

Any tips or recommendations would be appreciated.

[djreiswig]

On thinner metal I use a really short pierce delay or even none. Pierce at cut height so you don't have the delay lowering to cut height. On the grille, I always try to make my pierces where they will be less visible. Shoot for corners or tips instead of in the middle of a long straight cut.

[rcktscientist]

Thanks, good tips. I will do some more trials.

[adbuch]

I cut 20 ga. with my Hypertherm Powermax and 45xp at "book specs" using FineCut consumables. If you are cutting many smaller details, it helps if you can set your corner acceleration to around 0.03 to 0.05 G. Also make sure your consumables are in good condition. For new FineCuts, it is recommended that the cut height be set to around 0.070 to 0.080 inch for the first several hundred pierces, and then back to 0.060" for the remainder of the cuts.
David

[acourtjester]

You may want to check your table for wobble, the motion may not be a tight as it should be. With a fine cut nozzle you can use a shorter lead in/out.I think this was 18Ga.

[adbuch]

I use perpendicular lead ins.

[adbuch]

I also agree with Tom. Your circles look out of round, and some of your edges jagged. Perhaps check for slop in your table due to loose or worn belts, gears, etc.
David

[weldguy]

At the speeds you are trying to cut you will need a very tight, solid, well tuned machine to maintain good definition. Not sure how old your Torchmate is or what condition it is in but in my experience 250 ipm is about as fast as I would want to run that table or everything will look sloppy. I am not trying to knock your table, this is actually very common.

With that being said I would set your speed to the max speed you feel your table is able to operate at smoothly (250 ipm or lower I expect) and draw a 24" straight line. Cut one line with THC off and with the height set to a measured .060" and while cutting dial back your amps until the sparks are not shooting straight down but rather trailing behind a little bit under the plate. This will be a decent amperage for your selected speed.

Cut another straight line with your new speed and this time turn your THC on and set your volts a little higher to start with. Dial your THC setpoint voltage back until the THC can maintain a measured .060" cut height. This is your ideal arc voltage.

Use these newfound settings on a more intricate cut and see how it goes and let us know.

[rcktscientist]

First, thanks for all the help, cuts getting better. Disclaimer: I switched to Fine Cut Nozzle but didn't change the shield. Correct shields coming tomorrow, it may make a difference, Adbuch, I'm not concerned with speed so I'm going with the Low Speed Fine cut settings. That keeps it at 150ipm and is much more stable. weldguy, yes, the machine was jerky at high speeds so I'm changing to lower speed specs. Table is about 7 years old but has had very little use until I retired last year from the defense industry, which kept me hopping. I have questions about your post. I have a water table and it's difficult to see the sparks below the sheet. Also, the machine is under the table so it's a bit hard to adjust AMPs when cutting. I will raise a piece on blocks and give that a try. I assume what you call THC is AVHC on my machine. I believe I understand the last part but when you say dial back the voltage, I was not sure I can do that on the fly, will have to try. Also, I have to type it in so at 150ipm there is not much time.

More insight and questions:

I tried to cut the same sample with slow fine cut and Sample Voltage off, set to 71 per spec. Inside features cut OK but would crash when cutting the border. With sample voltage turned on the machine jumps to around 123 volts. Maybe this is because I'm using the incorrect shield?

Problem persists at bottom of the V's, I'm looking for a way to adjust corner acceleration on the Torchmate or more likely in the BobCad Cam settings.

Air Pressure/Flow: My hand-held torch is susceptible to air pressure, so I assume the same of the machine torch. Spec shows scfm, but that's hard to measure. I have 2 large compressors, so I assume volume isn't a problem. Book says 85psi inlet but doesn't vary it for 30 AMPs to 65 Amps, is this right? I also don't have a pressure gauge near the machine but will add one. I suspect it's higher than 85 though. Have you all seen much effect from higher inlet pressure?

[adbuch]

You should use matched consumables for optimum results.
David

[weldguy]

I have questions about your post. I have a water table and it's difficult to see the sparks below the sheet. Also, the machine is under the table so it's a bit hard to adjust AMPs when cutting. I will raise a piece on blocks and give that a try. I assume what you call THC is AVHC on my machine. I believe I understand the last part but when you say dial back the voltage, I was not sure I can do that on the fly, will have to try. Also, I have to type it in so at 150ipm there is not much time.

Yes, your AVHC is what I refer to when I say THC. If your table is operating smoothly at 150 ipm then just go with the setting from the Hypertherm Low Speed Finecut Mild Steel chart and you should have a great starting point and save some time not having to test for yourself.

I tried to cut the same sample with slow fine cut and Sample Voltage off, set to 71 per spec. Inside features cut OK but would crash when cutting the border. With sample voltage turned on the machine jumps to around 123 volts. Maybe this is because I'm using the incorrect shield?

I am unsure whats going on there. With AVHC turned OFF sample voltage is irrelevant, the machine only needs to sample the voltage when AVHC is turned ON. We need to gain a better understanding of your system, I have no experience with Torchmate systems. I would think that turning sample voltage on your AVHC would be turned ON. Do you see a defined ON/OFF button/switch for the AVHC system so we can turn it OFF and forget about sample voltage for now?

Air Pressure/Flow: My hand-held torch is susceptible to air pressure, so I assume the same of the machine torch. Spec shows scfm, but that's hard to measure. I have 2 large compressors, so I assume volume isn't a problem. Book says 85psi inlet but doesn't vary it for 30 AMPs to 65 Amps, is this right? I also don't have a pressure gauge near the machine but will add one. I suspect it's higher than 85 though. Have you all seen much effect from higher inlet pressure?

Your Powermax 65 will adjust the air pressure automatically internally, you need not worry about anything other than feeding it with a solid 100psi all the time. It is suggested to install a pressure gauge at the inlet of the Powermax 65 to confirm you have 100psi and that it never drops below 85-90 psi when cutting, a solid 100psi in all the time would be ideal. Post a pic of the front of your POwermax 65 so we can see your dial settings and LCD screen if you get a chance.

[rcktscientist]

Thanks again for the quick responses.

I received the correct shields and ran the last test with them. Very little difference, HAZ seems less, a little sharper and dross is good. It is almost acceptable now but I'm going to un trials to see how small a feature I can successfully cut, minimum lead ins, pierce delay, lines that have no offset, etc. I will also continue to research if I can control acceleration on BobCam and test that.

Additionally, I've added 2 pictures of my pressure near the machine and front of the 65 for settings. The pressure is 115, so I'll turn down the shop regulator to 100 until I get a dedicated regulator installed if you think that's optimal.

[ROKCRLER]

Turn your right hand knob to the second position on the machine..

[adbuch]

Turn your right hand knob to the second position on the machine..

Good call!! That one jumped out at me right away.
David

[rcktscientist]

Thanks, I changed the position, but it doesn't appear to make much difference. The local rep told me it didn't matter, but the 2nd position seems right. I need to cut some expanded metal soon for my wood fired oven chimney cover and Argentine grill, so I use position 1 for them.

Getting better. I don't know how folks get perfect tips in stars without filing. Even with a mill you get the tool radius. I've gotten rid of most of the ovality at the tips. Maybe increasing corner speed for these? BobCam adjustments page is attached.

Lead ins and outs and ovality are my biggest concerns. I may need to slow the speeds down on the circles and ovals. All trials are 30AMPS, 150ipm, .06 cut height, .09 pierce height and .1 pierce delay, per the book. As I strayed from these it seemed to get worse.

14 0.2 lead in and out 90 degrees
15 0.1 lead in and out with a .15 offset dial in position 1
16 Same as 15 but position 2

Offset seemed to help the circles, but the star is worse. I've also attached the BobCam page for leads.

Suggestions on improving these issues?

[adbuch]

Your last set of circles look greatly improved. Keep at it.
David

[weldguy]

Knob position won't matter unless your cutting expanded metal in which you already know to use position 1 for. In fact for new users I suggest position 1 as the arc will not extinguish when newbie things happen making problems worse.

Definitely big improvements in your cuts. I would suggest eliminating the lead outs, often the part drops out at the beginning of the lead out and your just cutting air.

You will never get crisp points in the negative of the star but the star that drops out should have crisp points unless your machine is slowing down too much in the direction change.

Not sure why your circles are so much better, the first set def look like you have a loose pinion gear or something. Did you find a loose gear or something and fix it or did the circles just get better?

[adbuch]

Not sure why your circles are so much better, the first set def look like you have a loose pinion gear or something. Did you find a loose gear or something and fix it or did the circles just get better?

That's what I was thinking as well. It shows quite an improvement between the last two photos and it's hard to believe that was simply from a minor setting change. But - stranger things have happened in the past, so you never know.

OK - I just took another look at your post above. You say the only change you made from 15 to 16 sample piece was changing the position of the knob from position 1 to position 2. So apparently the expanded metal setting vs. continuous cutting setting did make a difference for you.

David

[rcktscientist]

The trial 14 had longer leads and no lead out overlap. It may be the photo, but the last 2 aren't that different, Regardless, I still need to tweak circles and arcs a bit, probably with slowing down further in these areas. Additionally, I took your advice and used no lead out, much better. I cut these today, still need some tweaking in both my art and settings, but I've come a long way in a few days thanks to your assistance, greatly appreciated.

[adbuch]

I think these cuts look fine for what you are creating - artistic rustic pieces. Keep it up.
David

[weldguy]

That's great, happy to be of some help. Your cuts look much better so far