help with 5/8 powermax 85

[99guy]

So .... i need to cut some parts out of 5/8 plate. I usually do 16 gauge to 1/4 so ..... new deal for me. Testing looked like I was hard on tips piercing so I switched to edge start but i had this same problem when i pierced as well. At the end of the cut I'm getting a small spot at the bottom of the plate that either does not burn through or sort of re-heals itself, part wont fall out, and then leaves a little spot to hit with a grinder to clean it up.

PM 85 at 35 ipm, 85 amp tip shielded, set on 85 amps, .06 cut height and have confirmed that, gas pressure auto on the PM and have 125 psi at the inlet, new consumables. This pic was on a .3 perpendicular lead in and .1 perpendicular lead out ..... I've messed around with lead in, out, and over-burn without any real change .....

Any thoughts?

[sphurley]

1second delay? .18" pierce ht? I use at least a .3lead in and out and overcut when I can.
This was 1" (edge start) when I still had a PM65. Something is not right. I cut a lot of 1/2" using 65amp tips and you should have no issues on 5/8"

[jimcolt]

Place your lead in and lead out on a corner and you will eliminate this divot. It is likely due to slow acceleration on the lead in....the plasma is burning at the power level you set it at....but if the motion slows and dwells at the point where the lead in intersects with the cut edge (or the same thing at the lead out)....then expect that the plasma arc will reach out and form a divot. When the lead goes straight in and straight out (on a corner) this is not an issue.

If you are having issues with consumable life ("tips"....though there is no "tip".....so I suspect you mean shields and/or nozzles?) ...then you need to verify the piercing technique. Done exactly as the manual suggests....you can pierce 5/8" around 300 times before any damage will occur to a shield or nozzle.

Critical:
- Pierce Height. The manual suggests .18" pierce height for 85 amp shielded consumables on 5/8" plate. Are you 100% sure that your torch is piercing at .18" height? I suggest measuring the actual pierce height instead of relying on the accuracy of the machine. You can go higher on pierce height as well....as much as .24 inches will work well as long as your z axis gets down to the cut height before the exiting from the lead in to the cut path.
-Pierce delay time...as critical as pierce height. The manual suggests 1 second pierce delay...and this time should be measured from arc transfer (when the arc transfers to the material as sensed by current flow on the Plasma work lead) ....and there should be no x, y or z motion (torch stays at pierce height) until this times out and the pierce is complete (all sparks exiting the bottom of the plate before any movement of torch). Increase this time if you think the torch moves before pierce is complete. Some machines do not start this timing when current is measured at the work lead...and when this happens you may have to compensate for your particular machine.

Think about piercing with a Plasma torch. The arc fires...and starts melting steel.....all of the molten steel blows back at the torch until the pierce makes its way through the material. If the torch is too close.....some of that molten steel will enter the shield orifice.....and cause the shield to short to the nozzle.....this causes "double arcing" from the nozzle to the shield to the plate.....which will immediately cause damage to the nozzle orifice. A damaged nozzle orifice changes the shape of the arc....which will cause angularity and roughness on the cut edge (which I think I see in your pics).

Best regards, Jim Colt Hypertherm