Used Hypertherm consumables needed.

[jimcolt]

Starting is probably not the issue after an electrode has been shortened by .030"...as the spring loaded starting mechanism likely still can push the electrode into contact with the inner nozzle bore. The issue I would be more concerned with is the distance from the end of the electrode to the inner bore of the nozzle after the cut is established....the dimensions insde the torch are critical and .030" is a big distance. This increased distance will increase the arc voltage (an increase of .030" in arc length will increase arc voltage 12 to 15 volts)......so if the torch is operated at a fixed height from the plate (as measured from the shield or nozzle)...the the voltage will be 12 to 15 volts higher.

Plasma systems operate at constant current....so if you were running at 60 Amps at 120 arc volts with a new electrode...then the power disipated at the arc would be 60 x 120 or 7200 watts. With the electrode that has been shaved by .030", then the voltage would likely be 12 volts higher....so the power disipated at the arc would be 60 x 132 or 7920 watts. This does put a larger heat load on the power supply as well as on the torch.

Of bigger concern would be if you were using an arc voltage based height control.....if the height control was set to maintain 120 volts in order to keep the torch to work distance at .062" from the plate......and you had an electrode that was .030" shorter....then the height control would attempt to maintain 120 volts by moving the torch .030" closer to the plate. I would expect plate collisions in this case.

The point is in regards to remanufacturing consumbles....if you are not able to maintain the original design and dimensions...then expect some other issues to occur...such as higher heat loads (reduced duty cycle or torch body overheating) or incorrect torch to work distance (which affects cut edge angularity and dross formation.

Jim

Originally Posted by AccuFast2D If the electrode is .03" shorter and the spring that maintains the electrode/nozzle contact still places the hafnium in the same start location. The .03" must be a huge difference in the performance in the spring. It is my understanding that the compressed air flow moves the electrode back when the ignition takes place and is maintained throughout the cut. If the distance from part to electrode is maintained why would it need more power? I believe that the electrode never touches the "nozzle" once the flow is established.

[Normsthename]

Normsthename, what consumables do you use other than finecut? Do you use the shielded or unshielded? Are you using a machine to cut or hand?

I mainly use finecut to cut 1.5mm (16swg) Stainless steel.
I do sometimes cut thicker materials and I use 40a and 60a tips shielded and my CNC Plasma has a machine torch fitted.

While I was searching the Hypertherm site I found that they have now bought out an update to the Powermax 1000 manual

http://www.hypertherm.com/library/files/Manuals/Operator%20Manual%20(OM)/Updates%20to%20manuals/PMX1000_Change1.pdf

This now lists the correct swirl ring for use with Finecut consumables.

Andy

[AccuFast2D]

Jim I am thinking we are not on the same page.

Unless we can prove the the decreased length of the electrode is somehow increasing the distance from the orifice because of the reduced spring pressure I still can't see your point. Let's say that I take off .03" off the nozzle tip (exit) and .03" off the electrode. The nozzle reduction would facilitate the electrode to work distance to be decreased from the original and therefore reduce the power required to make the same cut.

If the electrode is shortened from the cut side by .03" the work to electrode distance is still the same.

[AccuFast2D]

Thanks Norm. That is good NEW information. I see they finally included the oring part number also.

[jimcolt]

The spring pressure has nothing to do with electrode to nozzle...and electrode to work distance. Once air pressure arrives at the torch..the electrode retracts fully and seats....so if the front of the electrode has been faced off....that is how much longer the arc will be. The spring compensates for the faced off amount during the starting process...but during steady state cutting it has nothing to do with this distance! Whatever is faced off the electrode will increase the distance between electrode and nozzle during steady state cutting...this add arc voltage to the formula that detrmines kW output of the plasma power supply!

I doubt that there will be noticeable effect for hand plasma cutting....but I guarantee that cut edge angularity and dross formation will be effected in mechanized cutting where precise torch to work distance is necessary for best cut quality.

It is not the distance from the orifice (nozzle) that detrmines arc voltage...it is the distance from the emitter (electrode).

Jim

[AccuFast2D]

Again I disagree with the assessment. Although I have a hand held unit I don't see where there could be a difference in the basic function. If there is pressure from the incomming gas that would keep the electrode forced forward durning the flow why would it push the electrode back any further than the pressure on the spring required to allow the flow out the orifice. It is an almost perfect valve. There is no need to push the electrode further than to allow the gas to exit just elevating the electrode away from the nozzle funnel with the minimum distance required. I.e. similar distance from hafnium to the nozzle funnel. Therefore same work to electrode distance.

I agree that the cut quality may be changed but on 16 gage, 11 or 10 gage or even up to 1/4" I could cut with my new Hypertherm nozzle and my referb nozzles and put them side by side and I would bet that we couldn't tell the difference.

Originally Posted by jimcolt The spring pressure has nothing to do with electrode to nozzle...and electrode to work distance. Once air pressure arrives at the torch..the electrode retracts fully and seats....so if the front of the electrode has been faced off....that is how much longer the arc will be. The spring compensates for the faced off amount during the starting process...but during steady state cutting it has nothing to do with this distance! Whatever is faced off the electrode will increase the distance between electrode and nozzle during steady state cutting...this add arc voltage to the formula that detrmines kW output of the plasma power supply! I doubt that there will be noticeable effect for hand plasma cutting....but I guarantee that cut edge angularity and dross formation will be effected in mechanized cutting where precise torch to work distance is necessary for best cut quality. It is not the distance from the orifice (nozzle) that detrmines arc voltage...it is the distance from the emitter (electrode). Jim

[WSS]

A quick way to tell if it is stressing the Power Supply is to run it without the cover (if it is safe) and infrared temp the inverter and capacitors under the same load with both referbed and new tips.

[jimcolt]

You clearly do not understand the starting mechanism...and the position of the electrode during steady state (flow) conditions. As I stated...the electrode pushes back (up, away from the nozzle) during flow...not forward. There is an absolute need for the electrode to push all the way back and seat...this is to ensure that the distance between the emitter end of the electrode and the inside bore of the nozzle is held to the critical dimensions it was designed to. If you shortened the front (emitter end) of the electrode...you have changed this dimension.

I'm quite sure that what you are doing will work..the torch will fire and the torch will cut! I'm 100% sure that it will not cut to the specifications (ISO9013 cut quality specifications) that the torch was designed to cut at....and I am 100% sure that the arc voltage will be affected at a given torch to work distance.....meaning....to maintain the recomended torch to work physical distance..the arc voltage (arc length as measured from the electrode emitter to the plate) will be higher.

I see no need to argue this subject....hypertherm has over 85 engineers involved with the design and manufacture of these torches....we take huge measures to ensure that the dimensions that control the plasma arc are held to very tight tolerances...however I understand your desire to experiment and the need to get a little more life out of your consumables.

Best regards, Jim Colt

[Alan Bradford]

Hi,
Here is my 2 Cents worth:

Rule # 1) Dont argue with Jim Colt. He has forgotten more about Plasma Cutting than most of us know right now.

That said Rule#2) How do you gauge a good cut?

By the size of the customers smile !!!

If you are happy with the cut you get from the reworked consumables, and want to take the risk of damaging the torch, then I am very happy for you and
that is all that counts.
We like happy customers.

BTW In case you all dont know, Jim was my old boss at Hypertherm 16 years ago so I am biased, but I still dont argue plasma with him. I loose all the time.

[AccuFast2D]

Thanks for all the information. Will continue to study the matter.