How small a hole can you plasma in 11 ga?

[Stuff-Builder]

Hey all,

I'm looking to bring some of my manufacturing in-house (really in-garage...) and I want to build a plasma table.

Most of my parts are out of 11 ga or 7 ga hrs sheet. I've got some holes and details - like logos - that are as small as 1/8" ID. The precision isn't important though I would like the cosmetics to be descent. Is anyone cutting parts like this? These parts are currently laser cut and the cut quality is between ok and beautiful, depending on which shop does the work.

I'm considering a Hypertherm Powermax 1000 or 600, but I want to confirm I'm not shooting for the impossible.

Any advice would be appreciated.

Thanks, Scott

[Torchhead]

You can't cut a decent hole even with Fine Cut consummables in 11 ga smaller than about 1/2" (unless a round hole is not your goal) Cutting detail with plasma is sorta like sculpting with a chain saw...very tricky. If you are looking for that kind of precision then conventional (read: affordable) plasma is not the best approach. Plasma can do some pretty neat stuff given the right setup and artwork but when the piece gets below about 16" in size you will start to see problems. You are, after all, vaporizing metal with a 30,000 deg flame and blowing it out with 70 PSI of air! Proper cutting with plasma is a dance of cut gap, feedrate, dry air, and several other factors. On small close cuts you never get to the proper feedrate and the quality suffers.

Before you waste a lot of money see if you can find someone with a CNC plasma and get them to cut one of your common products.

I think you will stick with laser or abrasive waterjet if cut quality is important.

I have cut miles of decorative steel in all thicknesses of material. I have a Hypertherm 1000 and a good table and Digital THC (Mine (:-)) and I have probed the limits of the process. I refuse to cut anything where the holes have to be accurate or round if they are less than 1". Decorative stuff is easier because you can always say "hey, it's SUPPOSED to look like that" but logos are another story. They have to be clean and accurate.

Tom Caudle
www.CandCNC.com

[Stuff-Builder]

Tom, thanks for the input.

I'm a bit bummed out now. I was planning on moving to plasma cutting and it appears that may not be a possibility. I know lasers are multi 100K machines, though I don't have a feel for water jet cutters. I imagine they're not low-cost items. I know the nozzles are wicked-expensive, and probably the abrasive is costly as well. Maybe I could get the one off American Chopper when they get a fancy new one for the next season...

Scott

[Torchhead]

Sorry. I think it's better to hear the truth rather than some table mfg's marketing tripe. Laser for metal cutting is very expensive. You can't do it with a one of the small 100W jobs. It's the domain of YAG and huge 2KW lasers that fill a room with just the power supply. Abrasive water jet is a close second on cost. The pump has to be able to put out 40,000 to 65,000 PSI. It's takes a BIG electric motor (and lots of KWH) to spin a pump that alone can cost $15,000.

What we do for small holes in sheet material is to to let the plasma "peck" a hole by just doing a pierce and use that as the centering for a drill process done off the table. You could get fancy and rig a dual head machine with a drill (CNC Drilling) but you still have the problem with cutting detail. It's not the electronics or table accuracy but rather the plasma process itself. Cutting close detail where the material left is not sufficient to absorb the heat of close cuts results in some nasty looking cuts.

Tom Caudle
www.CandCNC.com

[Stuff-Builder]

"The truth hurts. Not as much as jumping on a bicycle without a seat, but it hurts."



Based of what I've been reading, I could probably to all the outside profiles on my parts just fine. The 1/4" thru-holes would be a challenge, and it sounds like the logos just aren't possible. I could switch to sticker logos, but the cut ones look awfully cool.

All good information to know.

Thanks, Scott

[DISCONNECTED]

Torchhead is right conventional plasma is great for artsy stuff and by all means it an awsome process.You could probably do better with hi definition plasma at a major cost.

[duraflap]

So how does "CNC High Defination Plasm" differ from regular cnc Plasma?
Thanks
Dennis

[Torchhead]

Cost is about 10X that of conventional plasma and requires expensive gases for some materials. I thinner material using fine cut tips gives almost as good definiton as High Def.
When you get to thicker materials you can start to see a difference.