[planebuilder]

I have a weird problem. Trying to cut .020" old galv. roof steel, top side is rusty. I am using 40Amp tip, drag shield, amps set 30, Volts 160, 150 ipm, LCTHC .
If I try to cut it goes to Z.1, ( which is often actually just touching metal due to metal flex) fires, pierces, then arc stops, program stops.
If I program a prefire before the first pierce, like this,

G0Z.75
M3
M5
G0Z.1
M13
xxx rest of G code

It cuts great, and I can continue with as many parts/pierces as I want, only having to do the prefire once at the start of the first cut. I can continue to use this prefire if I have to, but I must shorten tip life?
When I try with fine cut tip, it doesn't work, It either stops after the first pierce or after an inch or two of cut.
What is happening?

[planebuilder]

I got the fine cut tips working. My M13 was like this

code "g0 G31 Z-3"
code "G92 Z0"
code "G0Z.697"
code "G92Z0"
code "G0 Z.1"
code "M3"
code "G4P0"
code"G0 Z.1"

Then I eliminated the last line from it "code"G0 Z.1"", even though it didn't cause a move from the Z.1 before the M3, I assume it caused a delay, with that last line gone, the fine cut nozzels work.
I still need the M3M5 pre-fire, actually I found there are 2 ways to make it work, use the M3M5 at the start, or lay another scrap of metal on the start point, once the cut starts and the machine is moving, pull the scrap away and it continues to cut many parts from that point on. If I stop for a minute to load more metal, I have to do the pre-fire or double layer trick to get it going again. I talked to a tech rep at HT, he had no idea why this was happening. Any ideas?

[planebuilder]

This is frustrating. I cut about 75 parts the other day, fine cut nozzle, with no problems. Yesterday I tried the same thing and it would cut 1/2 to 3 1/2 parts and just loose the arc and stop cutting half way through a part.????

[bytor]

Just a few thoughts that come quickly to mind. Check your work/ground connections at the table, the work connection at the 1250, the torch connection at the 1250. If the 1250 isn't sensing the arc transfer or the arc current, then it will not issue the motion signal or will interrupt the motion signal.

[planebuilder]

Bytor, thanks for the ideas, but i have checked everything numerous times. It's very strange, thicker metal doesn't seem to be a problem, I am wondering if the metal is too thin and "blows away" so fast the machine thinks it isn't there? Also, even the HT tech rep had no clue why a prefire or double thickness start helped, but I have tried with and without enough times to prove that it is needed on the thin steel? The fine tips are more of a problem than the 40 amp tips, so I am using the fine only when absolutely necessary.
Does anyone know if Jim Colt is still around?

[jimcolt]

Yes, I am still around! You can always contact me at Hypertherm ( [email protected] ) or contact technical service ( [email protected] ) for quickest response.

It is very common to have arc blowout (with any plasma) on thin materials such as 20 gauge. There are a few normal causes: 1. You have a pierce delay time that may be too long....torch does not start moving quick enough and blows a hole....arc voltage rises above the 180 volt threshold (power supply internal voltage limit) and the arc extinguishes. Be sure your pierce delay time is very small, or zero on very thin materials. Your operators manual has suggestions for pierce delay in the cut charts. 2. Pierce height is too high. (you can pierce anything thinner than 10 gauge at the recommended cut height of .060" 3. Using the hand cutting drag shield for mechanized cutting (use correct shield). 4. Your machine acceleration rate is too low (try increasing acceleration. 5. The above should all be carefully reviewed and optimized....however if none of them solve the issue then simply switch the front panel mode switch to the "expanded metal" position....and the pilot arc will automatically maintain until your machine reaches adequate speed to maintain the cutting arc. Jim Colt Hypertherm

Bytor, thanks for the ideas, but i have checked everything numerous times. It's very strange, thicker metal doesn't seem to be a problem, I am wondering if the metal is too thin and "blows away" so fast the machine thinks it isn't there? Also, even the HT tech rep had no clue why a prefire or double thickness start helped, but I have tried with and without enough times to prove that it is needed on the thin steel? The fine tips are more of a problem than the 40 amp tips, so I am using the fine only when absolutely necessary.
Does anyone know if Jim Colt is still around?