Welding Tips and Tricks

I've never seen a plasma cutter, except on videos. I get the impression it's for gross cutting but have also seen it used on CNC plasma tables for detail work, but that's aided by the CNC's ability to move at set speeds and near absolute accuracy. When the cutter is in human hands, how does that affect the cut?

Recently I had to cut out numerous 3" long notches on lengths of 3/4"x1/8" angle iron. I believe each side of the angle iron is called a "web", and the notches were the removal of the entire 3" web section on one side of the angle iron leaving the remaining adjacent web that now is just flat stock. To do this, I made the perpendicular cuts at the ends of the 3" web I wanted to remove, but then had to use an angle grinder with cutting disk to remove the spine of that web which was a dangerous operation. It required me to get my face real close to the cutting disk to see what I was doing and that was a bit scary. Once the 3" section of web was removed, I cleaned up the spine cut so the remaining flat section was truly flat.

Could a plasma cutter do this job assuming that I could jig up a guide and just move the tip along a guide to cut out these notches? Would the dross left by the cut cause me to spend much time cleaning that up?

Also, is there a real difference between a Hypertherm and an Everlast plasma cutter? The thickest material I'm ever likely to cut is 3/8" so I'm looking at low amperage units.

For something like your describing a plasma would be ideal. There are a lot of recent discussions about the importance of air quality and getting the air as dry as possible for the best results. Since you live so far out I would recommend sticking with a good hypertherm unit. It will give you the best possible results with the least amount of worry weather it's going to perform on a regular basis.

Depends on the operator. If your like me you're a little shaky you may not be perfectly accurate but for most things it will be close enough with a grinder. I'd go with the hypertherm power max 45. The parts availability is better and service and I've heard nothing but good news about hypertherm. Just practice cutting on some scrap or something, get your amperage and speed right and you should get pretty good.

Its a bit like oxy cutting only better.
Cut quality really does lie in 3 things, the operators abilities and dry air of the correct pressure, condition of the cutting tip.
It takes a bit of practice to get your angle and cutting speed right, once you've nailed that, easy..
A jig will give you repeatability and speed.
A lot of people who aren't cashed up make patterns out of ply to cut around, on the ones I have used there is about 4mm between the edge of the torch and the centre of the cut, so you need to allow for that when you set up a guide or make a pattern. Then there's the buggers that can freehand cut to within .00001" with their eyes shut or be artistic and cut out something Michael Angelo would be proud of.
From what I've heard you won't go wrong with a Hypertherm.
The wife won't let me sell a child or kidney to afford one over here.

Cheers

First......when you ask how accurately can a plasma cutter cut, most readers instantly think of a hand held air plasma.....others will think of an air plasma cutter mounted on a small cnc cutting table (small is 5' x 10' or smaller). A few that may work in an industry that does metal fabrication will think of high definition plasma cutting often with multiple fully automated torches (up to four cutting simultaneously), perhaps beveling capability to 45 degrees, and tables as large as 40' wide x 300' long.

Totally different expectations and quality / cost output from each.

Hand plasma cutting is only as accurate as the operators skill. Generally you are cutting by following a soapstone line.....and the human hand is nowhere near as accurate at following a path as a computer controlled cnc machine.

Air plasma cutting by hand generally will get you into the plus or minus about 1/16" for a good operator, a little worse with less experience. I have seen some amazing artwork done by hand with plasma torches....from someone with great artistic talent. Compared to oxy-fuel....plasma requires far less training, uses no flammable or high pressure gas cylinders, and generally cost a fraction of the cost per foot of cutting with oxy-fuel. And....you can cut aluminum, stainless, copper, brass....any metal.

Air plasma mounted on a low cost entry level cnc machine will get a bit of variation in tolerances depending on the plasma cutter as well as the capability of the cnc. Generally the non-shielded low technology import plasmas mounted on a low cost 4 x 4 cnc machine with no automatic height control will get you tolerances in the range of +- 1/16", but with varying angularity which adds extra cost through necessary grinding and cleanup after cutting. The higher end brands (Hypertherm Powermax as an example) mounted on a better quality cnc with full featured height control can get you parts with virtually no cleanup, with tolerances in the .015" to .025" range, relatively square cut edges and good hole quality (minimal taper on holes, but round and bolt ready). Expect the Hypertherm torch consumable parts to outlast the low cost imports by 4 to 10x .......which accounts for more consistent cut quality and lower cutting costs. An unshielded import torch may get 100 to 250 pierces.......the shielded Hypertherm style torches will get 600 to 2500 pierces (depending on technique and power level/material thickness) per set of consumables.

High Definition class plasma systems have been around for over 20 years in high production industrial applications.....cannot be hand held and are only installed on high end precision cnc cutting tables and robotic applications. These system are designed to run 24/7, can produce nearly perfect holes and square edges on steel plate from gauge to 2" thick, and hold tolerances to perhaps .010" to .020" depending on material and thickness. These systems on a 6 x 12 cnc machine start at about $80k and go to well over $1 million for large, multi-torch machines as found in John Deere, Caterpillar, Shipyards, large steel service centers worldwide.

So....no easy answer for plasma tolerances....though I suspect the original poster was referring to hand cutting with an air plasma. You may be happy with a low cost import if you are a hobbyist with occasional use.......though the drawbacks are with high consumable use, sketchy support (you will never get to talk with the factory techs!, only the importers service department....if any.), and reliability historically is of issue. If you don't mind spending the money for a plasma with factory free support, lower operating cost and high reliability, then look at the major brands for a plasma that your kids will inherit! Jim Colt Hypertherm

jimcolt wrote:First......when you ask how accurately can a plasma cutter cut, most readers instantly think of a hand held air plasma.....

Jim
I don't use plasma cutting equipment currently, however I always enjoy reading your responses and learning from someone who's been in the industry for many years.

For the record, in case any users don't know, Jim Colt works at Hypertherm, and has no hidden agenda in answering any questions people ask about any brand/type of plasma cutter.

Also of note, you won't find much variety from a Hypertherm unit in most of the shops I've been in that do serious amounts of cutting, as they are simply one of the best.

Sent from my SM-G900V using Tapatalk

Hypertherm is the only way to fly, IMHO. Buy once, cry once.

Lightning wrote:Hypertherm is the only way to fly, IMHO. Buy once, cry once.

I agree. I was all set to buy a Chinese plasma cutter that was advertised at $100 off. But their website didn't recognize the discount, so I just said the hell with it and saved up a bit more money and got a Hypertherm Powermax 30 Air. Love the built-in air compressor, and it's a beautiful cutting little unit. I'm happy.