Intermittent Cut problem Thermal Dynamics 40

[Nando586]

Hello,

First post here on this forum. Looking for help.

I'm Fernando from Southeast Michigan. Running a Langmuir Systems Crossfire XL with automatic Torch Height Control. Using water table with SterlingCool Plasma Cut Fluid. Thermal Dynamics Cutmaster 40 with Thermal Dynamics 7-7507 single stage air filter at the input of cutter and 2 HP / 20 gallon air compressor. Designing with Inkscape and using Sheetcam for G-Code generation.

I've had the machine for about a year and half and I just started seeing a new problem that I haven't been able to figure out. I am uploading a picture of a straight line cut for review.
My jobs start out fine but somewhere in the middle of any given cut path the cutting process doesn't seem to penetrate completely for a short distance and then starts to work perfectly again and the cut path finishes without any errors. This problem is random. I can run any particular job to completion without any errors and then run the same job again only to have this issue pop up.
I can see the automatic torch control operating as it should (moving the torch up and down as needed due to material bow and flex).
Settings are as follows:
16 gauge sheet metal, 30 amps @ 175 ipm, Pierce height = .25 ", Cut height = .125", Pierce delay = .6 seconds.
My cut height is a bit higher than most but it has provided a good quality cut.
Cut speed was determined by multiple cut lines at different speeds. 175 ipm seems to be the best at this thickness.

I've confirmed with Thermal Dynamics that the in-line filter that I'm using is sufficient to prevent any moisture from my tank from entering the cutter. I also inspected my torch consumables for wear.
I ran two large jobs today with multiple different parts and the problem is popping up intermittently which is making it extremely difficult to remove some of the cut pieces. Any input would be greatly appreciated.

Fernando

[djreiswig]

Do you have a pressure gauge at the inlet of your cutter? Could the issue be a drop in pressure right before the compressor turns on? I'm not sure what the settings are on your compressor and what the requirements are for your cutter, but that's what I would check first. Also, make sure you attach your work.lead directly to the material and not just to the table slats.

[acourtjester]

where is the steel you are using from? There may be a problem with consistent quality of the metal. If the part us unusable have you tried to cut the same area to see if the problem is just in that location? Have you tried to increase the amps of the plasma, I use Hypertherm and would cut with higher than 30 amps for 16 Ga.

[Nando586]

Do you have a pressure gauge at the inlet of your cutter? Could the issue be a drop in pressure right before the compressor turns on? I'm not sure what the settings are on your compressor and what the requirements are for your cutter, but that's what I would check first. Also, make sure you attach your work.lead directly to the material and not just to the table slats.

The pressure gauge shows 100 psi consistently while the torch is "on". At idle the pressure at the input of the cutter is at 115 psi. The specs for the cutter require a psi from 95 to 125. So long as the input psi is within this range the internal regulator inside the machine will regulate the psi down to around 70 psi. So 70 psi is what is available at the torch.
I am attaching the work lead directly to the material.

[Nando586]

where is the steel you are using from? There may be a problem with consistent quality of the metal. If the part us unusable have you tried to cut the same area to see if the problem is just in that location? Have you tried to increase the amps of the plasma, I use Hypertherm and would cut with higher than 30 amps for 16 Ga.

I'll have to check on the material type. I don't remember if it's hot rolled or cold rolled. The problem has appeared at different locations in a workable are of 25" X 33". I did increase my current output from 30 to 34 amps with no success. I have also reduced feed rate from 175 to 150 ipm with again no success.

[acourtjester]

Good show other member may add other things to check, what you have checked are thing that have effected cutting, so it looks like it is another thing. Keep plug at it, when you do find the reason please report it so others in the future who have similar thing can read about it.
Have you touched bases with Langmuir to see if a member there has any help?

[Nando586]

Good show other member may add other things to check, what you have checked are thing that have effected cutting, so it looks like it is another thing. Keep plug at it, when you do find the reason please report it so others in the future who have similar thing can read about it.
Have you touched bases with Langmuir to see if a member there has any help?

Yes I have contacted Langmuir. Waiting on response.

[weldguy]

I think your just right on the cusp of it cutting and any inconsistency anywhere is causing it to not cut through from time to time. If you look at the speed chart for your plasma TD suggests a speed of 140ipm @ 40 amps on 16g mild steel if I am looking at the correct chart for your particular plasma. You were cutting at 175ipm @ 30amps, I am honestly surprised this problem hasn't happened sooner. Are you using different cut charts than I am seeing or are you developing your own speeds and heights as you go?

[Nando586]

I think your just right on the cusp of it cutting and any inconsistency anywhere is causing it to not cut through from time to time. If you look at the speed chart for your plasma TD suggests a speed of 140ipm @ 40 amps on 16g mild steel if I am looking at the correct chart for your particular plasma. You were cutting at 175ipm @ 30amps, I am honestly surprised this problem hasn't happened sooner. Are you using different cut charts than I am seeing or are you developing your own speeds and heights as you go?

Hello,

Thanks for the input. The speed chart for my plasma cutter recommends approximately 200 ipm at 30 amps on 16 gauge steel. I arrived at 175 imp at 30 amps based on multiple test cuts that I performed when I first got the table. Too slow a speed resulted in a wide kerf and a lot of dross. Too fast and not enough penetration with poor cut results. I worked my way to 175 ipm where the results where the best.

I diagnosed the problem this last weekend after more troubleshooting and I hadn't gotten around to posting my results. The issue was my modification to my table. The Langmuir Systems table that I have is entry level and does not have an ohmic feature. Whenever I cut small designs that are no larger than 12" square the machine works fine. But when my designs are larger and more intricate the machine tends to drag the torch tip and hence cut lines don't finish were they're supposed to. On initial height sense the torch tip will push the material down too far if there is any flex and that messes up IHS so when the torch retracts it thinks the top of the material is at a point lower than it really is.
So my solution to that problem was to design an ohmic circuit and install it on the machine. The circuit works fine but somewhere along the way the software that runs the table is picking up an input from my circuit and interfering with the automatic torch control feature of the table.
I just ran a batch of different parts/designs without the ohmic circuit enabled and I ended up with cut lines that did not finish (hopefully I can cut them out by hand to save the job). Then as it was cutting a second part in that same batch the tip dragged on the material and pulled it off to the side. Cutout ruined ($$$).
So now I'm going back to enabling my ohmic circuit and making some adjustments to my settings to see if I can tweak it just right. It tasks me and I shall have it! Lol!

[weldguy]

Thanks for posting back, glad you have it sorted out. The chart I was looking at was for the A40 which I suppose is an older machine that the 40 amp unit that you have. Is this the unit you have? How do you like it?

Thermal Dynamics Cutmaster 40.PNG (126 KiB) Viewed 5330 times

[Nando586]

Thanks for posting back, glad you have it sorted out. The chart I was looking at was for the A40 which I suppose is an older machine that the 40 amp unit that you have. Is this the unit you have? How do you like it?

Thermal Dynamics Cutmaster 40.PNG

Yes that is the one that I have. The machine is well made and Thermal Dynamics is a trusted brand. It came with a 4 year warranty as opposed to 3 years from the others. Before I retired I was in the industrial electronics repair industry and plasma cutters and welding machines were some the equipment that I used to repair. Being from the repair side gave me a good perspective on these machines and eventually when the warranty runs out I'll be able to repair it myself should the need arise.

[acourtjester]

You sound like a good guy to have on the site when plasma cutter problems come up

[weldguy]

Yes that is the one that I have. The machine is well made and Thermal Dynamics is a trusted brand. It came with a 4 year warranty as opposed to 3 years from the others. Before I retired I was in the industrial electronics repair industry and plasma cutters and welding machines were some the equipment that I used to repair. Being from the repair side gave me a good perspective on these machines and eventually when the warranty runs out I'll be able to repair it myself should the need arise.

Very nice. Those machines have caught my eye and judging by your cut speeds it packs more of a punch than the TD units I have had experience with. I am very interested in trying one out. Thanks for the reply.