Plasma vs Torch- Pros & Cons - Looking to buy

[txcowdog]

I have an opportunity to buy a CNC torch that has a 60" x 96" table that I expect to go cheap at auction. I want to convert it to plasma because I feel that is the better technology. Can someone weigh in on the pros and cons of each technology and which is the winner in your opinion.

Thanks for the input.

[Karl_T]

A torch is much cheaper, only for steel, and does thick steel well, up to 6" or more if you got a BIG torch.

Plasma cost WAY more, does several metals, and doesn't warp thin stock.

Karl

[txcowdog]

Thanks Karl. Appreciate the input.

[Redline]

What will you be cutting?

[txcowdog]

Hi Redline,
I will probably cut 1/8" to 1/4" mild steel. I am unfamiliar with torch tables and don't really understand why people still build them if plasma is a faster and cheaper method of cutting. The table I am looking at in an upcoming auction is an 8' x 5' torch and I was thinking of converting to plasma if that is the better all around approach to cutting.

[Alex S.A]

To the sort of material will be cut for you, the plasma will be better than torch, but you have to take consideration productive level, if you will go cut seldom torch will fit to your needs. You are going to have a lower cost.
The necessity to cut much material, outsourcing work and so on, plasma you'll be better coz it has got cut velocity higher then your production will be higher as well. The cost involved in plasma process are: Gas (you can use air compressor with line filter to eliminate oil, water and dust like this the consumable life will be the best as possible), consumables and electrical energy.

[Torchhead]

Just in pure time the plasma will cut the thinner materials 3 to 5 times faster. Kerf width will be smaller with plasma and less heat injection into the workpiece means less buckling. I would not even consider cutting 1/8" or less with an oxy torch unless that was all I had. I think plasma cutting for materials 1/2" and less is the best process. Over that it starts to be a toss up. A lot of production is still done up to 1" with plasma but the trade offs start to cross. To cut thick stuff you need really big plasmas.

Major differences from a CNC perspective is that you need to provide cutting speeds of up to 300 IPM for thin materials with plasma so you electronics design and approach (motors, gearing, power supply, etc) are different than if the table is made for pure oxy cutting.

I converted an old "tracing eye" oxy cutter to oxy and plasma and we had to toss all of the motors and control electronics. (We actually just kept the table and most of the mechanical components. The motors were tiny little DC motors with radical gear reduction but the top speed was about 20 IPM. It cut 4" steel with an oxy torch great but we had to get the speed up for plasma.

Just be aware the table you are about to buy may not work for plasma as is and may need extensive changes.

It's easier to convert a plane to a car than vise versa!

tom caudle
www.candcnc.com

[txcowdog]

Thanks Tom,

Your points are well taken. I will definately be cutting 1/2" or thinner so it looks like plasma is the way to go. The table I am looking at turns out to be not CNC, but manual so I will be starting from scratch converting it to a CNC machine. It is 90 miles from here so I will drive over next Tuesday and take some pictures that I can post if you can give me a little feedback on what might be involved in a retrofit. Thanks for the input.

[Torchhead]

Be careful in you accessment. The old manual tables for oxy cutting do not typically have precision linear components and are not designed for rapid moves of 300 IPM +. The value will be in not having to build the table part but you may be looking at a total replacement of bearings, tracks and adding all of the drive components. Just be aware you proabably won't end up with more that 25% of a CNC torch table.

Don't get much money involved in this especially if you have to load and tote it 90 miles.

If you get some pix you are welcome to send them to me and I'll give you the benefit of my having been-there-done-that level of experience.

[aaronpentz]

How much were you looking to spend on this project?

[txcowdog]

I passed on this table because it was an old manual table that had a lot of slop in it and would have cost a fortune to change all the slides to new technology. This was a 12' x 8' table and I imagine THK rails would have cost my left leg. Thanks to everyone that helped me make an informed decision and not get stuck with a money pit.