- Plasma
9 Tips & Tricks to Improve Your Plasma Cutting
Sarah Mazlin
06 April 2021
Unlike welding, plasma cutting is not hard to learn at all, and there’s no messing around with filler metals or complicated settings. One of the hardest parts of plasma cutting is getting a straight line. Still, there are a couple of things to keep in mind to get the best cut possible.
1. Earth Clamp
Make sure you have a good earth. Like welding, plasma cutting machines come with a torch and an earth clamp, as you need to complete the electric cycle to ignite an arc.
You want to attach the clamp to a clean section of your workpiece. When you attach it to the workpiece, make sure it’s not the part coming off, as you’ll break the cycle, and the arc will cut out. If you’ve got a bad ground (dirty metal, not close enough, etc.), it can affect the cut quality.
2. Cutting Distance
Contact cutting tips are dragged along the surface of the metal as they go to create the cut. This often means that they wear out faster, as they’re directly exposed to any spark splashback or any stray metal going flying.
If you can, use a ‘standoff’ shield on the torch, this will hold your torch at a good height off the metal consistently and can help with the movement.
Every UNIMIG plasma cutting machine comes with a torch that has a standoff shield option, which extends the life of your consumables.
If you’re trying to cut through the maximum metal thickness your machine can do, having the tip flush against the metal can be more helpful, but in general, leave a bit of space.
3. Amperage & Travel Speed
When it comes to plasma cutting, your amps and travel speed impact each other. Technically, you could have your machine set to run its max amps for every single cut, and all you would adjust is the travel speed.
Running at full power all the time probably isn’t the best for your torch, so if you’re cutting thinner metal (like sheet metal), then turning your amps down to match that will still give you a good cut, you’d just slow down a bit. How do you know what’s a good travel speed though?
A good travel speed will mean that the sparks fly straight down from the cut, and your torch is running smoothly over the metal.
If you’re going too fast, you’ll have sparks flying back at you from the top of the cut because it’s bouncing off the metal that isn’t being entirely cut through.
If you’re travelling too slowly, the sparks will still shoot out from the bottom, but you’ll find that the torch gets stuck because more dross (the excess melted metal) builds up.
Find a good travel speed that matches your amperage.
4. Sample Runs
Doing a sample run along a piece of metal that is the same thickness as the one you’re planning to cut will help you perfect your travel speed. When you go to do the actual cut, you’ll have no issue and a clean cut with minimal cleanup.
5. Consumables
One of the main things that can impact a cut is the consumables inside your torch. It’s good to get into the habit of checking over your torch before you start cutting, as you’ll want to clean or replace any dirty or damaged consumables.
For example, metal slag covering any of the air holes, chipped, burnt or notched nozzles and electrodes will all lower the quality of your cut.
The other thing to keep in mind with consumables is making sure that they can handle the amps. If your plasma cutter maxes out at 80 amps, but your consumables are rated for a max of 60 amps, you’re going to burn through them fast.
Get consumables that are compatible with each other and your machine.
6. Dry Runs
As well as sample runs to check your settings, doing a dry run to make sure you can reach the whole way and be comfortable are also recommended.
While you can technically pause in the middle of a cut, you’re going to be left with a hole at the point where you restart. Checking that you can run the entire length of the cut without issue doesn’t hurt and will keep you from making any gaping craters in a piece that you had to stop and reposition on.
7. Perfect Your Shape
Freehand plasma cutting is fine, and it works, and if you’re cutting a squiggle, then it’s your only option. But, if you want straight lines or perfect shapes, then using a guide, stencil or other bits of metal for perfect lines is definitely recommended.
For straight lines, clamp down a straight-edged piece of metal next to where you’re planning to cut so that you can press the torch up against it. It’ll ensure that you get a dead straight line without wobbles.
For circles, UNIMIG has a circle cutting guide available for purchase that you can attach to the torch to get perfect circles.
Check out the Circle Cutting Attachments here
8. Don’t Start From the Middle of the Plate
Where possible, start your cut from the edge of the metal. If you start over the metal, the sparks blow back into the torch as it’s trying to burn through the metal, which damages your consumables.
If you have to start from the middle, angle the torch (roughly 45°) until it’s gone through and then reposition to 90° (or square) against the metal for the rest of the cut. Angling the torch means that when the sparks blow up, they’ll fly past the torch tip rather than into it.
9. Cleaning
Give your metal a quick clean and make sure there’s no burs or rough spots that the plasma torch will catch on; you’ll get an uneven cut that will need work to make it smooth. Checking for any bumpy patches on the metal you’re using for a guide (if you’re using one) is also a good idea.
You don’t want to be following a straight line and then find that it’s actually got a few hills and dips that have now transferred to your cut.
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