center pierce holes help?

[Les Newell]

I just ran your job with that post and it appeared to work. One thing I noticed is that your 'centre punch' tool has a pierce delay of 0. If you have arc sensing this is fine but if you don't, the torch probably won't fire.

[regpye]

I just ran your job with that post and it appeared to work. One thing I noticed is that your 'centre punch' tool has a pierce delay of 0. If you have arc sensing this is fine but if you don't, the torch probably won't fire.

I probably don't have arc sensing, so what should I do?
When I run the file, the torch goes through all the motions correctly, just doesn't fire when it is supposed to do, then moves on to the next hole and misfires again and so on.

[djreiswig]

What cutter are you using? The arc sensing he is referring to would be an arc ok signal from the cutter to let the program know that the plasma arc has transferred and it is cutting. If you don't have this signal you need to add time to your pierce delay to allow the arc to begin cutting before it begins movement. I would think a second would be a good start.

[regpye]

What cutter are you using? The arc sensing he is referring to would be an arc ok signal from the cutter to let the program know that the plasma arc has transferred and it is cutting. If you don't have this signal you need to add time to your pierce delay to allow the arc to begin cutting before it begins movement. I would think a second would be a good start.

The cutter I am using is suppose to be for hand held use only, it has no special features except it has low frequency pilot arc.
Unimig Viper 30
It is only a 30 amp machine, but works very well for my purposes, I use mainly 3mm (1/8") thick mild steel for most jobs.
If I add pierce delay time, what amount should I try, I have no idea?

[djreiswig]

I would start with one second and test. If it doesn't pierce, add 1/2 second and try again. It's going to be trial & error until you figure out what works.

[regpye]

I would start with one second and test. If it doesn't pierce, add 1/2 second and try again. It's going to be trial & error until you figure out what works.

Thanks for that, it worked fine.
I tested a few times and found that 0.55s works the best for me, at 1s the holes are too deep.
I must remember to place the first centre punch hole in the scrap area, because it is pretty deep compared to the ones that follow

[djreiswig]

Wonderful. Yeah, it's common for the first one to be deeper because the post flow air isn't running.

[regpye]

Wonderful. Yeah, it's common for the first one to be deeper because the post flow air isn't running.

After getting it all working, I didn't realize how useful this feature is. have used it several times now and all have been successful. Saves a heck of a lot of drill bits because the metal has not become real hard like it does when plasma cutting a hole. Can make a nice clean hole now with a drill bit.
Most of my small holes are 3mm (1/8")

[Les Newell]

The first time I tried this I thought I'd use a carbide stub drill to pilot the marked hole. The mark is still hard so I thought the carbide drill would last longer. It actually only lasted a couple of holes before chipping. Lesson learned! I use plain old HSS or cobalt now. Cheap and easy to re-sharpen.

[regpye]

The first time I tried this I thought I'd use a carbide stub drill to pilot the marked hole. The mark is still hard so I thought the carbide drill would last longer. It actually only lasted a couple of holes before chipping. Lesson learned! I use plain old HSS or cobalt now. Cheap and easy to re-sharpen.

I have had no problem at all in drilling the centre punch marks. They don't seem to be any harder than the rest of the material, but a very different story on holes that I have cut right through, they are as hard as hell, makes my drill bit go red sometimes.
Maybe if I use a different steel I could have problems with the centre punched marks too. Been lucky so far.

[Les Newell]

I think it also depends on the plasma. My Hypertherm 45XP punches pretty deep even at the shortest on time and 35A. It won't fire reliably much below 35A on my normal cutting consumables. I don't do enough marking to warrant changing out consumables just to mark drill holes.

[regpye]

I think it also depends on the plasma. My Hypertherm 45XP punches pretty deep even at the shortest on time and 35A. It won't fire reliably much below 35A on my normal cutting consumables. I don't do enough marking to warrant changing out consumables just to mark drill holes.

I must be lucky I think. I now do a lot of punch markings as I need a lot of small holes that are best drilled out. I don't have to change the amperage on mine because the machine is a low power machine, and the holes are perfect each time, just a nice mark in the right spot and done very quickly, just a little flash and it is done. I originally setup a pause so I could change the amperage down when punching, but found I didn't need it, so it makes it easier for me.