View Full Version : New Machine Build Need help

08-18-2010, 01:16 AM
Finished my table (4x8) last week and been cutting with limited success. Having issues losing arc. I've spoken with Dynatorch many times and they suggested adjusting the set point and cutting speed.

I cut out some letters from 3/16" mild steel flawlessly today (picture) but then spent hours trying to cut some much simpler pieces from a piece of 10 ga. steel.

For the letters (cut from 3/16" flawlessly) I used 80 amp consumables at 132 set point and 130 ipm. My plasma cutter is a Hypertherm 1250.

On the 10 ga. I used fine cut consumables at 50 amps, 76 set point and from 60 to 110 ipm (tried them all) and lost arc 29 times. I them switched to 40 amp and used 83 set pint and 35, 40, and 50 ipm. No combination worked.

The Hypertherm was grounded to the work as in the picture.

Is the window to keep the arc so tiny that I just never found the right combination?

Is there something else I should be looking at?

08-18-2010, 08:36 AM

Congrats on the new Dynatorch. It is a good machine with excellent support. Like anything else there is a learning curve to get up to speed. Here are a few tips. 80 amps is major over kill for 3/16 material. The general rule is to use the smallest nozzle size for the material. With fine cut nozzles 3/16 would be the upper limit or you could use 40 amp shielded. Don't change more than one parameter at a time when dialing it in.

I'm not sure what you are talking about when you say you are losing the arc? Is it going completely out? Is the machine abruptly coming to a stop with no arc? Is the torch crashing into the material and triggering the crash dector or causing motor overload either of which shuts off the arc and stops the machine?

In addition, a drop in air pressure while cutting will automaticly shut off the the arc and stop the machine. Before you begin to cut your part you should do a CUTTING air pressure check on the Powermax 1250 by turning the amperage dial to 0 which turns on the air flow to the torch.

Watch the green lights on the front of the machine and make sure they stay in the 70 to 80 psi range. This pressure must be maintained through out the cut. Check all air lines from the compressor to the machine.

Look in the 1250 manual for cutting charts for the consumables and material thickness, select the optium IPM and Arc Volts or (SP) on the Dynatorch. This will get you in the ball park. Here is a link to some troubleshooting info for cut quality and how the arc volts affect the cut.


Here is a link to the Hypertherm Webinar with some good info. They cover Hydefinition as well as the 'Air type' PowerMax systems. Click on Mechanized Plasma;


08-18-2010, 09:22 AM
Matching the power (amperage) to the materials you are cutting is important for best quality with a plasma system. A good rule of thumb with your Hypertherm Powermax1250 is to stay within these ranges with each consumable set:

FineCut consumables....max power 40 Amps, thickness range 28 ga to 1/8"

40 Amp shielded consumables....always operate at 40 Amps, thickness 1/8" to 3/8"

60 Amp shielded consumables....run at 60 Amps, thickness 1/4" to 5/8"

80 Amp shielded consumables....run at 80 Amps, thickness 3/8" to 3/4", thicker with edge starting.

You don't eleborate on losing the arc. If it is happing in intricate areas of the cut, such as sharp inside corners.....then you may be dwelling to long in these areas. If the plasma spends too much time in one area (speed to slow, corner dwell) then the arc voltage increases and can exceed the maximum sustainable voltage output of the plasma power supply, which will cause the arc to extinguish. To solve this issue, cut at a lower output amperage (with the fine cut consumables you can vary the amperage from 20 to 50, however it is best to stay under 40 Amps to optimize nozzle life. Another way to solve the issue, if lowering plasma amperage does not work...is to increase the corner speed or increase acceleration settings in your drives.....I'm not sure how this is done with the Dynatorch....but I'm sure Leon (Dynatorch) can help you out with this.

best regards, Jim Colt Hypertherm

08-18-2010, 11:22 AM

Good thought on the air. I just ran a check and it did remain in the 70 to 80 psi range also checked my dryer for fluids or and crystals, all good, and drained my tank. My compressor kicks on at 125 psi. and is regulated to 110 psi in the lines to the 1250. I watched the front panel through a complete cycle and it stayed at 70 psi. I did turn up the regulator on the HT a little to maintain 80 psi.

Thank you for your input. The lost arc is happening on straight cuts, curves, at times almost instantly. I have been using the settings from the HT manual and adjusting the speed down. Leon (Dynatorch) suggested 20 to 30% and Russel (Dynatorch) suggested 5 to 10 lower ipm.

I realize there is a steep beginning to this learning curve and appreciate your feedback. Looking forward to the time I can barely remember the frustration of clawing my way up. : )

08-18-2010, 11:28 AM
To troubleshoot the loss of arc....maybe wire a plasma start jumper....hold the start signal to the plasma on.....if the arc still goes out, then this will isolate whether the problem is in the plasma or the output from the Dynatorch.

For cut speeds.....use the "optimum" speed chart under mechanized cutting.....make sure you are using the mechanized shield on the torch. I vary from 20% lower speed (better edge angularity) to 20% higher speed (less dross) from the optimum settings. On torch height.....don't worry about the "book" arc voltage settings, rather, adjust voltage so the the torch to work distance is correct (settings listed at top of Hypertherm cut charts). Speed, THC calibration, voltage drops in cables, consumable wear will all affect the voltage readings....physical height is the important setting.

80 psi will do you no good....it causes faster electrode hafnium erosion. Use the Hypertherm pressure setting listed in the manual.....which I think is 70 psi dynamic (flowing).


08-18-2010, 02:42 PM

this sounds like my next step "wire a plasma start jumper....hold the start signal to the plasma on". Is there somewhere I could get more detail on how to add the jumper?


08-18-2010, 03:19 PM
Pins 3 and 4 on the rear panel interface connector (if you are using a machine torch only) are the start input to the plasma......connect these two pins together....the plasma should fire (assuming consumables are correct and air pressure maintains at 65 to 70 psi, and there is material under the torch with work clamp attached)......when you break the connection the plasma arc should extinguish. There may be a better way to make this connection in the Dynatorch interface.....perhaps they can help as well.

Jim Colt

08-18-2010, 06:00 PM
Try de-checking "stop on lost arc" and see if that corrects it. I have to run this way all the time until I get time to install a resistor in one of the motor connectors.

I know it sounds backward, or that the machine will keep running without the arc (it will) but the problem went away for me. I am getting noise input with the signal.


08-18-2010, 08:59 PM

Thanks I'll try that.

In fact when using the joystick to cut what ever motor was running when I lose arc continues until I do a e stop. If the torch is the active motor going down it raises my gantry off the track.

08-18-2010, 11:43 PM
Mines the same as WSS, i run it with the stop on lost arc box unchecked

08-21-2010, 03:48 PM
Thanks all, running with the "Stop on lost arc" unchecked solved the problem. DT suggested I add a capacitor from Radio Shack to the lower plug on the x axis motor. Seems this is a common problem.

Wonder why DT doesn't add the capacitor? That would have saved me a 5 days of trouble shooting and the tension that goes along with it.