Inconsistent center Pierces - Older Powermax 85

[whizbang]

I have a Powermax 85 from early to mid 2000s that I bought used a few years ago and its been great with my CNC table. I had to add the CNC port and I had to replace the air filter bowl in the back when I got it but thats it.

I often use a quick pierce blip at the recommended pierce height to mark the center of holes I want to drill and tap. When I first started doing this it worked great, pierce marks were all perfect round dimples. For the past 6 to 8 mo I have noticed that the dimples are inconsistent, oblong, some are significantly larger/deeper and there is literally nothing different from a program standpoint between them. Ive tried with brand new consumables and it doesnt seem to make a difference. I have a 1/2" air line going to the machine, a cooler on the air compressor as well as a water separator and extra filter before the machine as well. The inconsistencies seem worse with thinner materials but I also marked 2 holes on 3/8" plate back to back with identical code and had one make a perfect mark and the next blow straight through the material. Ive also tried to adjust amps but no success in maintaining consistent marking.

I am wondering if there is an issue with an internal regulator or solenoid on my machine, any thoughts?

[adbuch]

Perhaps you are having some issues with your THC not maintaining your specified pierce height. Do you have an inline air pressure gauge directly at the air entrance port to your plasma cutter? If so, then is your pressure stable at around 100 psi with air running thru the torch and the machine cutting? You could also consider installing an Easyscriber in place of your nozzle/electrode and scribing your hole centers using a very small circle or an "X".

David

[weldguy]

It is possible that due to the age of your unit that the orings in the torch head are dry and/or shrunken and not sealing 100% which can prevent the air from flowing in the designed pattern and velocity which will affect how the arc is constrained. This could be why your arc is wandering on the pierce. I would replace all the orings and swirl ring. Also be sure you blip it for the minimal amount of time to get the hole cause once it blows that hole there is no material there and the arc will wander trying to go to ground and cause what your seeing.

[acourtjester]

I agree with Weldguy air direction may be causing your problem, "O" rings have caused similar problems for member before. I would also get some silicone grease to use on the "O" rings to help when changing consumables.

[whizbang]

Thank you all for the replies.

I should have mentioned that I am using the older 85 with the Duramax Machine torch I bought brand new 2 years ago. I have changed out orings at least once and I do grease them but I will first try changing out the swirl ring and if that doesn't fix it then I will also change out orings.

I do have an air gage at the port on the back of the machine and I hold steady at 100psi, especially during my center mark operations. Once in awhile on long (usually straight) cuts you can hear the air pulsate and the cut will be a bit jagged looking, air is jumping but only by 15-ish psi.

I see both the air pulsate and the wonky pierce blips even when THC is off. I am pretty confident in the height being consistent. I also blip for 0.5 sec or less depending on thickness of material.

I have an easyscriber and do occasionally use it if I have alot of holes to mark to save on some wear and tear of consummables but for 2 or 3 holes its so much faster to blip and not have to change consummables