How to cut better holes with your CNC plasma cutter

September 27, 2019

It’s not easy to cut perfect holes with your CNC plasma cutting cutter. The difficulty becomes greater as the hole diameter gets smaller, and especially so when it shrinks below 1 1/4”.

Some companies offer automated solutions to make this process easy and consistent. But you don’t always have access to machinery like that.

So how do you make beautiful holes without any defects on a regular basis? Here’s some tips:

Set a Pierce Height of 1.5 – 2.0 Times the Cut Height

Easy math for you to do here. Take the recommended cut height and multiply it by 1.5 – 2.0 times to get the proper pierce height to start at.

What Amperage Do You Set Your Plasma Cutter To?

Always choose the lowest amperage process that allows you to pierce the metal you need to cut. Your manufacturer has given you charts (or they should have) that tell you what amperage to set your plasma cutter at to cut the depth you want. You’ll likely have several choices. When you keep the amperage lower, this allows the torch height control and motion control to react well with the plasma arc. And when you set the amperage life lower, you also get a nice bonus of longer consumable life.

Follow the 60% Rule with Your Cut Speed

Whatever cut speed you use to cut the outside contour of your project, set the speed to about 60% of that when you cut your holes. You will get some dross on the bottom of your hole. However, this slower speed minimizes the hole’s taper. Some plasma cutters account for this automatically. Others need G-Code programming.

Set Your Lead-In Close to the Center of the Hole

You do this for three reasons:- It gives your plasma arc time to stabilize its pressure and energy so it cuts best – Your height control has time to index down to the cut height – You avoid creating a divot in the holeWhen you use a lead-in shape that’s straight and perpendicular to the hole you cut, you set yourself up for success from the start.

Finish Your Hole Right

Your hole should finish with an overburn at its end. Don’t lead out into the center slug, as this warps the shape of the hole and wastes consumable life. “Overburn” simply means staying on the hole radius about .150” to .200” past the lead-in point.

Enjoy Beautiful Holes

When you follow this tips, you end up with holes you’re proud of every time. Make sure you keep these tips in mind the next time you have to cut holes with a CNC plasma cutter.

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