In this episode, Jim Colt, an industry veteran from Hypertherm, talks about Torch Height Control on a CNC plasma table. Visit https://www.maverickcnc.com/ for more information on all of our plasma cutting tables.

The fully integrated torch height control is critical to excellent high-quality plasma cuts. Maximizing consumables life with Arc Voltage Height Control equals saving money! How to work within the budget when running a light industrial CNC plasma cutting table.

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Video description :

Hi, Jim Colt here with MaverickCNC. Nice little table here, this is a 5 by 5, they also are available in 5 by 10 and 6 by 12 sizes. Very good motion control and everything.

One of the features that I like to talk about, with a lot of CNC plasma cutters and machines is the importance of torch height control, also commonly known as THC. It’s a very important function for plasma cutting that a lot of people don’t realize and there’s still, there are a lot of machines out there on the market that are sold with no torch height control, in other words the torch always stays at a fixed height so it’s not always exactly the right height off the plate and there are also machines that are sold with some really simple, what I call stand alone torch height controls and those are height controls that don’t really integrate and don’t communicate with the CNC control, the motion control, the electronics and the software.

On this MaverickCNC the torch height control is actually what I call an integrated height control so it’s actually treated as another axis so there’s the x axis and the y axis that move the torch around and the z axis, the up and down axis controls height and it’s very critical. A couple of things that happen with torch height control is, the torch, before it fires, it has to come down to the plate, has to contact the plate and locate the surface of the plate. That kind of zeros the height control. The height control then, before the torch fires, retracks to what is known as the pierce height. Pierce height is different for thin material than it is for thick material, it’s very critical for consumable life to be at the correct pierce height so the torch then fires at the pierce height and then indexes quickly down to the cut height – a physical distance between the torch and the plate where it cuts best, the cut height is always lower than the pierce height.

As soon as the cut height is reached, then x and y motion start and the machine starts cutting it’s part. As soon as it gets up to speed, another height control function called arch voltage control starts to take over and that’s reading the feedback arch voltage between the electrode and the work piece while your cutting and that’s what maintains real time height with an integrated THC and that’s what gives you superior cut quality and excellent consumable life. Another important feature of the torch height control is something called ohmic contact and that’s the way the surface is sensed on the plate.

So if you have a CNC machine that does have torch height control but uses the Hypertherm retaining cap like this as opposed to this retaining cap, this retaining cap has a connection for a wire called the ohmic connection wire so every torch height control system has to have a method of finding the surface of the plate. If you don’t have that wire on the front of the system your going to be using either torque sensing or what’s called floating head sensing, it’s a micro switch in the torch head that allows the torch to locate the surface of the plate.

Now if you’re cutting very thin material and you can kind of emulate it right here, if your cutting thin material, the torque that’s needed for that contact type sensing might deflect the plate down a little bit like this and then when it retracts to try and go to pierce height it’s at the wrong height, it’s minus the amount you deflected the plate. With ohmic sensing which is on all MaverickCNC machines, with ohmic sensing you’ll have this cap on here, there will be a wire connected to it, it uses a very light touch with electrical contact or ohmic contact that does not deflect the plate and so when it retracts to the pierce height it’s at an accurate, very accurate height. That dramatically improves consumable life and as a second aside benefit because it knows the exact height it is off the plate when it indexes down to cut height and starts cutting, it’s at the correct cut height too.

So ohmic contact is a much more accurate means and it’s definitely necessary and an integrated torch height control is the way to go for CNC plasma cutting

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