plasma torch high frequency

[gordon stephenson]

Hi, Everybody,
Im sure this will have been asked before but I can't find the posts, i have the Powermax 45 and am delighted with it. I have been asked by a member on a UK forum if it causes any damage or does any harm to consumables at all to fire the high frequency with the torch in the air and not cutting metal. I don't ever do this but it would be nice to have a definitive answer. This question is not restricted to Hypertherm but all plasma cutters in general.
Thanks in advance guys,
Best regards Gordon.

[mechanic416]

Hypertherm does not use high frequency to start the arc. Yes it does cause excess wear to the consumables.

"Most" but not all plasma cutters have a timing circuit that will limit the pilot arc to a few seconds. If it does not since a ground to start cutting the pilot arc will go out.

Also if you keep pulling the trigger over and over in time it will overload the pilot arc circuit and you will let out the magic smoke.

[jimcolt]

To correct Mechanic, Hypertherms Powermax systems use a starting system called "Blowback start", which uses a spring loaded electrode to break a short circuit, creating a high intensity spark that ionizes the gas and starts the plasma arc. All of Hypertherms high end industrial plasma cutters (HSD130, MaxPro200, all HPRXD systems) use a high voltage, high frequency discharge between the electrode and the nozzle (inside the torch) to ionize the gas, starting the plasma arc.

The high frequency starting method which was used in all plasma systems for many years (1957 thru the present) was the original way to start a plasma. The Blowback method was invented by Hypertherm in the early 1980's in order to reduce costs, weight, complexity, and electrical noise in portable plasma cutters....primarily hand torch systems.

High Frequency start is very reliable, but can create electrical noise in the form of RF (radio frequency) that can effect the performance of computers and sensitive electronics. High frequency start is used in all of Hypertherms high end mechanized plasma systems because it allows us to manufacture torches and consumables to the utmost levels of precision, (electrode, nozzle, and gas flow concentricity) which provide the tightest cut tolerances (angularity, dross).

Blowback start allows the plasma power supply to be less costly, is a reliable starting method, and makes low cost plasma cutters smaller and lighter. An added benefit is that the system does not produce the high frequency RF noise that the industrial systems do.

There are many low cost import plasma cutters that still use high frequency start technology.....as most are copies of older technology.

Now......do not confuse high frequency with a pilot arc start! Most high frequency start plasma torches can support a pilot arc. All blowback plasma torches can support a pilot arc. A pilot arc is essentially a non-transferred plasma arc that can be fired in air. When a Hypertherm Powermax torch is triggered away from metal....you see a strong, bluish flame exit through the nozzle orifice....that is the pilot arc. The pilot arc was introduced in plasma torches in the early 1960's.....it allows the torch to rapidly burn through rust, dirt, primer, etc to allow the main cutting arc to complete the circuit to the material being cut.

Firing a pilot arc in the air serves no useful purpose. It will very rapidly erode the nozzle orifice.....which will effect cut quality. Different design plasma cutters will have varying effects to consumables when there are a lot of non transferred pilot arcs. The better designs have minimal effect as they have very carefully controlled and monitored pilot arc gas and amperage levels......others (read older technology) will destroy the nozzle and electrode rapidly.

Hope this answers the questions!

Jim Colt Hypertherm

Hi, Everybody,
Im sure this will have been asked before but I can't find the posts, i have the Powermax 45 and am delighted with it. I have been asked by a member on a UK forum if it causes any damage or does any harm to consumables at all to fire the high frequency with the torch in the air and not cutting metal. I don't ever do this but it would be nice to have a definitive answer. This question is not restricted to Hypertherm but all plasma cutters in general.
Thanks in advance guys,
Best regards Gordon.

[mechanic416]

You are not correcting me, you are just adding on to what I started.

And I didn't think he was asking about "high end industrial plasma cutters" as most people don't have them with a hand torch.

[gordon stephenson]

Thank you for your rapid and very informative replies mechanic416 and Jim Colt. Once again i grateful for the help and education provided by this forum, And Jim Im still blown away by the power of my 45 and consumable life is truly excellent,
Thanks to everyone, Gordon.

[jimcolt]

Sorry Mechanic, bad choice of words.....I was adding to what you stated. I mention Industrial Plasma systems and their use of high frequency start....because there is a place for that technology. Many on these sites compare air plasma cutting with mechanized laser cutting....the proper comparison with closer productivity and quality is with high definition class plasma and laser.

Jim Colt

You are not correcting me, you are just adding on to what I started.

And I didn't think he was asking about "high end industrial plasma cutters" as most people don't have them with a hand torch.

[rufi]

hello Jim,

can you guide us how to filter the HF from going into the digitize input of the motion controller? it is an 24v npn input. thanks in advance.

-Rufi

To correct Mechanic, Hypertherms Powermax systems use a starting system called "Blowback start", which uses a spring loaded electrode to break a short circuit, creating a high intensity spark that ionizes the gas and starts the plasma arc. All of Hypertherms high end industrial plasma cutters (HSD130, MaxPro200, all HPRXD systems) use a high voltage, high frequency discharge between the electrode and the nozzle (inside the torch) to ionize the gas, starting the plasma arc.

The high frequency starting method which was used in all plasma systems for many years (1957 thru the present) was the original way to start a plasma. The Blowback method was invented by Hypertherm in the early 1980's in order to reduce costs, weight, complexity, and electrical noise in portable plasma cutters....primarily hand torch systems.

High Frequency start is very reliable, but can create electrical noise in the form of RF (radio frequency) that can effect the performance of computers and sensitive electronics. High frequency start is used in all of Hypertherms high end mechanized plasma systems because it allows us to manufacture torches and consumables to the utmost levels of precision, (electrode, nozzle, and gas flow concentricity) which provide the tightest cut tolerances (angularity, dross).

Blowback start allows the plasma power supply to be less costly, is a reliable starting method, and makes low cost plasma cutters smaller and lighter. An added benefit is that the system does not produce the high frequency RF noise that the industrial systems do.

There are many low cost import plasma cutters that still use high frequency start technology.....as most are copies of older technology.

Now......do not confuse high frequency with a pilot arc start! Most high frequency start plasma torches can support a pilot arc. All blowback plasma torches can support a pilot arc. A pilot arc is essentially a non-transferred plasma arc that can be fired in air. When a Hypertherm Powermax torch is triggered away from metal....you see a strong, bluish flame exit through the nozzle orifice....that is the pilot arc. The pilot arc was introduced in plasma torches in the early 1960's.....it allows the torch to rapidly burn through rust, dirt, primer, etc to allow the main cutting arc to complete the circuit to the material being cut.

Firing a pilot arc in the air serves no useful purpose. It will very rapidly erode the nozzle orifice.....which will effect cut quality. Different design plasma cutters will have varying effects to consumables when there are a lot of non transferred pilot arcs. The better designs have minimal effect as they have very carefully controlled and monitored pilot arc gas and amperage levels......others (read older technology) will destroy the nozzle and electrode rapidly.

Hope this answers the questions!

Jim Colt Hypertherm

[rlitman]

I'd start with the basics. Ferrite chokes on all your inputs and good shielding.

[jimcolt]

Industrial CNC Plasma machines that work with high frequency start plasma cutters have:

- Optically isolated inputs and outputs.
- A required earth ground rod driven close to the cnc machine.
- All interconnecting cables for plasma, torch height control, cnc control and drive amplifiers and motors are shielded cables with the shield drain wires connected directly to the earth ground cable, other end is not connected.
- Sensitive signals are also protected with RF chokes and / or Ferrite beads.
- CNC controller must be of industrial hardened design made for working in shop environments around inductive equipment. It is not recommended to use an office computer or PC to control the machine.
- All cables must have excess length removed (control cables, power cables, work cable, torch leads, etc.) so there is no coiling.
- Torch leads should be routed in a non conductive power track, separated from any other machine cables.
- Input line power for the cnc control and drive electronics should be filtered with a UPS or power line conditioner, filters.


All or some of these things will often solve electrical noise issues related to the use of a high frequency start plasma cutter. If your system is using an air plasma cutter, then it usually is easier and more cost effective to switch to an air plasma cutter that uses Blowback start technology, such as Hyperther's Powermax (45 through 125 amps) systems. Jim Colt

hello Jim,

can you guide us how to filter the HF from going into the digitize input of the motion controller? it is an 24v npn input. thanks in advance.

-Rufi

[rufi]

thanks for the info. We are already doing most of what you have suggested. The problem is that now we are going to use HF based plasma system from hypertherm and we still need the digitize signal to detect the material, and we have to somehow isolate it from the HF and HV. can you suggest what we can do (relay, LC filter, etc) to remove the HF/HV from the digitize signal which is a 24v dc npn signal. I hope I am clear about the problem we are trying to solve. Thanks in advance.

[jimcolt]

I would recommend working with the supplier of your cnc control that is having an issue. I suggested all of the most common methods of controlling RF and EMI type noises, if your electronics are being affected then that is where the noise suppression will need to be addressed. Jim Colt

[ccawgc]

If you are trying to use a auto height controller. You need to talk to that manufacture tech support.
You might have everything you need and not know it. If you can't figure out who made it. or who supports it.
Pictures of the CNC , height control and table serial number labels. Maybe we can point you in the right direction.
BUT please start your own thread. you will get better help.