[Normsthename]

Homebuilt Plasma machine
THC300 Torch Height Control
Hypertherm Powermax 1000 Plasma with machine Torch.
Finecut Consumables used for thin sheet.
Sheetcam programming software

Is there anything I can do to improve my floating head setup.
I mainly cut 1.5mm (16swg) stainless steel with finecut consumables and I get problems with the floating head flexing the sheet too much before it trips the microswitch.
Even after the head has risen to its 2mm piercing height the nozzle is still touching the sheet and it sometimes burns the nozzle out.
Today I burned two nozzles out within 5 minutes of each other, not cheap at £6 a throw
It is fine when it pierces over a slat and the thin sheet does not flex.
I have the offset set in Sheetcam and I have had to resort to raising the offset by an extra .5mm which is not ideal.
I have seen some 'Non-contact' devices to sense the initial height, are these any good?
Any other ideas much appreciated

Thanks

Andy

[Torchhead]

Homebuilt Plasma machine
THC300 Torch Height Control
Hypertherm Powermax 1000 Plasma with machine Torch.
Finecut Consumables used for thin sheet.
Sheetcam programming software

Is there anything I can do to improve my floating head setup.
I mainly cut 1.5mm (16swg) stainless steel with finecut consumables and I get problems with the floating head flexing the sheet too much before it trips the microswitch.
Even after the head has risen to its 2mm piercing height the nozzle is still touching the sheet and it sometimes burns the nozzle out.
Today I burned two nozzles out within 5 minutes of each other, not cheap at £6 a throw
It is fine when it pierces over a slat and the thin sheet does not flex.
I have the offset set in Sheetcam and I have had to resort to raising the offset by an extra .5mm which is not ideal.
I have seen some 'Non-contact' devices to sense the initial height, are these any good?
Any other ideas much appreciated

Thanks

Andy

1. The non-contact IHS solutions are expensive and need constant tweeking based on the material. There are ways to measure distance with infrared (like a camera does) or via capacitance but both are costly or inaccurate (or both) it's hard to resolve variances of less than + - .020 across different surfaces and under varying conditions. At the very least you would need to "calibrate" the sensor for a given sheet of material. While in your case, where you cut a lot of the same type, that might not be too bad, but most shops cut a varity of material types and with different surfaces.

2. I cut a lot of 16ga material and to get around the deformation problem I added an adjustable "bias" spring that counter balances the weight of the torch so now I can adjust to provide a feather touch on thin material. It does require you keep the slides of the floating holder clean and lubed. Problem solved. It also helps to have the cut grid spacing tighter so it has more support.

3. The addition of a an ohmic sensor tip would appear to be the solution but it has two major disadvantages:
a. It can malfunction on dirty , rusted, oily or painted material. If it does you can cause damage to the torch. To prevent that you have to have torque feedback on the torch motor. On the THC300 system where the Z motor is the THC lifter motor, measuring the motor current accurately (on a stepper especially) and feeding it back to the control software (MACH) would cost a lot of electronics.
b. The typical ohmic sensor uses the material as one side of the conductor. Since it is at Plasma (dirty) ground, the circuit then connects the noise of the plasma ground (at logic levels) over to the control electronics. The THC300 is isolated from the logic side to block conducted noise and an ohmic sensor not hooked up properly would cancel the inherent isolation of the THC. In short it could result in erratic operation all the way to damage to the THC electronics.

For a few thousand bucks you can have a stand alone THC solution that has either ohmic or torque feedback sensing but you will lose the ability to use the "lifter" for any Z level control. The bias spring is a lot cheaper and works well.

TOM caudle
www.CandCNC.com

[Kipper]

Hi Andy, I just took delivery of a CDE THC controller...Preliminary tests without having the torch live shows great promise....yet to be seen how it copes with actual use...I'll post back once it's actually cutting stuff.

URL for manual here

[Normsthename]

I cut a lot of 16ga material and to get around the deformation problem I added an adjustable "bias" spring that counter balances the weight of the torch so now I can adjust to provide a feather touch on thin material. It does require you keep the slides of the floating holder clean and lubed. Problem solved. It also helps to have the cut grid spacing tighter so it has more support.

Thanks Tom
I did think about adding a spring to counterbalance the weight of the torch and holder

Hi Andy, I just took delivery of a CDE THC controller...Preliminary tests without having the torch live shows great promise....yet to be seen how it copes with actual use...I'll post back once it's actually cutting stuff.
URL for manual here

Kipper, I will be very interested in seeing your setup

Andy

[Serafin]

Hello, I'm starting my cnc for plasma I wonder if you could send me pictures about your bias spring system, I can't even figure it out, besides english is not my first language, [email protected]

Thank you!

[millman52]

Hello, I'm starting my cnc for plasma I wonder if you could send me pictures about your bias spring system, I can't even figure it out, besides english is not my first language, [email protected]

Thank you!

Attach spring(s) that has adjustable tension to almost off set the weight of your floating head.

Then the weight of the floating head doesn't deflect thin material. At least not as much.

If your torch head + floating head assembly weighs 10# Put enough tension on a spring, pulling up on the floating head to almost balance it out.

Hope this helps some