Messages

881

General Mach Discussion / Re: Physical buttons for plasma

« on: November 22, 2016, 03:44:14 AM »

If you extended the lead and air pipe you will probably need more air pressure to allow for the added loss in the longer hose.

882

General Mach Discussion / Re: Physical buttons for plasma

« on: November 21, 2016, 01:50:52 PM »

I will strip it off the machine and connect the central adapter plug direct to the original connections and see how it behaves, if it is ok then I may see if I can suspend overhead in some way, do you have any pics of how you did it?

Nah, too crude for pics - it just loops up from the torch to a bungee cord loop hanging from the roof truss, then back to the rear wall, down and into the plasma under the table.

883

General Mach Discussion / Re: Physical buttons for plasma

« on: November 21, 2016, 12:28:52 PM »

Yes, very happy with the cuts, much better than I had hoped for especially after the initial headaches

Yes I have cut a load more tests this afternoon and all perfect. 3mm, 4mm and 1/4 Alu, 2mm, 3mm, 5mm and 8mm stainless and 10 and 12mm steel.

I bought the machine torch because it would allow me to use the plasma manually on boats or things that wouldn't fir on the plasma with the hand torch and leave the machine torch on the table itself, as you say they are not cheap, £300 plus if I recall.

Yep, the Hypertherm CNC torch was about £500 I recall, It takes seconds to pull my hand torch off the table as the cable is suspended overhead not in the energy chain.

Glad its just the torch - must be a reason, hopefully something simple and fixable, is it returnable?

When it works it's a blast int it It opened up a whole world of possibilities for me.

884

General Mach Discussion / Re: Physical buttons for plasma

« on: November 21, 2016, 08:37:58 AM »

Those cuts look ok, so the hand torch works and the machine torch sucks?

Maybe a short inside or blocked air passages maybe.

I'm still running the hand torch as the machine one was a fair bit more cash.

885

General Mach Discussion / Re: Physical buttons for plasma

« on: November 21, 2016, 06:37:56 AM »

Thats not good.

Surely the divider card is only active/important when the THC is on?? Or does that send the ArcOk signal too? Still it should not affect the double arc issue.

Have you tried manual cutting with the drag tip again - it may be a problem in the plasma box??

886

General Mach Discussion / Re: Physical buttons for plasma

« on: November 21, 2016, 05:06:45 AM »

Jim is 99% right all the time, good guy.

Yes alu is a bitch, I hate the stuff on the plasma.

Cutting the castellations off a drag tip is what i did on the little 30XP unit as it has no machine torch - it works, try it.

HyperT recommend never cutting Alu on the 30A parts as they are not shielded either, i only use these for fine detail on stainless 1.2mm sheet.

Sounds like your on the way hopefully (did i say get a hypertherm ?? )

887

General Mach Discussion / Re: Physical buttons for plasma

« on: November 21, 2016, 02:14:49 AM »

Very odd, is there no help from TecArc?

Is there a support group? I can't see one on PlasmaSpider although i would certainly ask over there.

888

General Mach Discussion / Re: Physical buttons for plasma

« on: November 20, 2016, 04:52:52 PM »

does look like double arc or failing to switch to full arc maybe.

if you have a clamp ammeter stick it round the work return cable, thats where my current sensor sits, see if it registers full current when messing around.

Even when working right, it can (and does) blow a nozzle sometimes, for no reason it seems, not usually as bad as yours - that is really destroyed. Mine tends to slightly blow out one side - it still cuts but has uneven angularity to the cut. Other times I can go for ages on one set of consumables.

Are you 100% certain there is no water in the air - put a bit of polished metal or a mirror under the nozzle and trigger the air flow for a minute or so, any muck will show up.

889

General Mach Discussion / Re: Physical buttons for plasma

« on: November 20, 2016, 03:41:45 PM »

Ok, good the THC is off, one less thing.

Pilot arc is still HF but the arc is inside the torch and not from torch to metal. It won't be the issue though i think as all it might do is cause PC or motion problems and you don't have that it seems.

From the ESAB site...

Double Arc

A double arc is a condition which allows the nozzle to stay in the plasma circuit. As described, the nozzle should only be in the circuit during the pilot arc phase. If left in the circuit, the nozzle will carry cutting amperage which will destroy it.

Double arcing is caused by:

Standing pierce. The torch has to be positioned close enough to the work-piece to allow the pilot arc to contact the plate, so the main arc can transfer. Pierce spatter is ejected at a shallow angle during the initial pierce. As the arc penetrates the material the spatter becomes more vertical. This debris may connect the plate and nozzle, keeping the nozzle in the circuit even when the relay opens to remove it. This scenario may damage the front end of the torch.
Torch in contact with the plate. Cutting thin material. All automatic torch positioning systems utilize some initial height sensing method to position the torch above the plate. One method is the touch and retract method. The torch travels until it makes contact with the plate and retracts to the initial start height utilizing a timer or encoder. If the touch is not sensed properly, the torch may still be in contact with the material due to springing up or material warping. The nozzle will remain in the plasma circuit carrying cutting amperage, damaging it.

Pilot arc malfunction. This can occur if the pilot arc relay circuit fails to remove the nozzle. This can happen either with a shorted relay or resistor. Again the nozzle is left to carry more current than intended, damaging it.

Preventing the Double Arc

Double arcing usually occurs during the piercing sequence.

Some techniques which can help avoid double arcing are:

Creep move. The cutting machine is programmed at a reduced speed to begin machine movement on arc transfer. This speed is usually 5 to 10% of normal cutting speed and is for a given time period. Pierce spatter is being ejected away from the nozzle during this time. This reduces double arcing possibility.

Torch rising during standing pierce. On arc transfer the torch begins to pull away from the work- piece. This allows the pierce spatter to clear the nozzle. This retraction continues for a timed period, and then lowers to correct cutting height after the machine is moving at cutting speed.

Higher than normal initial height pierce (standing pierce). This allows the pierce spatter to miss the nozzle reducing the chances for a double arc. This method of prevention is the least effective.




So....
if you manually trigger an arc in free air, you should only see a low power pilot arc, not the full cutting arc, does your unit have current display? As there is no metal to complete the circuit, the unit should not switch to full power arc, just the pilot, if not  then maybe a dodgy pilot arc relay etc. You probably won't see this when manually cutting.

I would definitely not exceed the rated power for a nozzle/electrode, in fact my 45A unit cuts best at 43A, go figure

890

General Mach Discussion / Re: Physical buttons for plasma

« on: November 20, 2016, 08:00:34 AM »

I can't seem to find much as to how that torch strikes the arc - it says it does not use HF but does not say it is blow-back start (hypertherm) or something else.

Have you grounded the plasma to the sheet or the table - use direct to the sheet, at least to start with, this rules out poor return issues.

What thickness steel are you playing with? If its <12mm I would not bother moving the torch while piercing as it will not help, my little 45A will pierce 12mm without moving, just.

Have you any recommended settings for pierce and cut? There is no point in trying random settings here, there is usually only one setting for piercing a certain thickness of a certain type of metal.

Yes, my system has a built in lag (caused by THC, BOB, Mach3) of around 0.3s so until my book tells me i need more than 0.3 I set zero delay. Thinner (<3-4mm) metals need no extra delay. I think i used about 1s delay on 12mm.

What sort of dead-band do you have on the THC, mine is +/- 1v i think, so it does nothing in that area.

The best cut is achieved at the maximum setting for the nozzle in use so if i use a 45A set, i get the best cut at 45A although it will go down to 20A, if i use the 30A set i get the best cut at 30A although it will go much lower, all to do with arc energy density. Air pressure is a fixed setting and needs to be maintained without loss or it drops out.

How are you obtaining cut speed and voltage(height)??

To set mine up for a new material, I turn off THC, set my cut height as per book, then cut multiple straight lines maybe 150mm long with various speeds, looking at dross, cut quality, kerf etc, one of the lines will be better tan the rest - that one is the right speed. Then I cut one more line at that speed and this time monitor the arc voltage on screen (THC still off) - this now gives me the correct voltage.

Both these values are then plugged into the G-Code and the THC and away we go, sometimes a little tweaking is needed but it works. I tend to always have one eye on the screen where it shows Z height when cutting - i am watching for a sudden drop in z height immediately after the THC kicks in - this indicates my voltage wants tweaking a little as the Z gap cant physically change (sheet warp) in such a small distance therefore it must be consumable wear or just a wrong voltage.