Oxyfuel CNC Torch Height Controller

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23 May 2016 01:15 #74964 by Marcin_ose
Hello Friends,

Marcin here from Open Source Ecology - opensourceecology.org.

We are going back to the next iteration of a CNC torch table and want to install an automatic torch height controller - for oxyfuel cutting.

Does anyone have experience with building an oxyfuel torch height controller?

Thanks,
Marcin

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23 May 2016 10:24 #74973 by cncbasher
with oxy it's more a question of keeping the torch at a predetermined height , and perhaps fit an ignighter at the tip.
far easier than a plasma , and add some extra outputs to switch solinoids for gasses etc . you need to be able to cut the gas
under estop etc , if the torch is fixed it's far easier , finding suitable gas solinoids is possibly the hard part .

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23 May 2016 10:30 #74974 by andypugh
I imagine it would need to be a capacitive system?

I do have some experience in building a capacitive measurement system from scratch, and it wasn't all that difficult.

I used a small centre-tapped pulse transformer as two legs of a bridge:
The layout was similar to this one:
ccphysics.us/henriques/p202lab/capfromdistance.htm
Except that I excited the system with a few kHz of AC and the resistors shown in that picture were the coils of the pulse-transformer.
If I was doing it nowadays then the excitation and measurement would be done by an Arduino. Those had not been invented 25 years ago when I built my Cam Plastometer.
Reading that page, I am not sure why I used AC. That page suggests that DC measurement can be used.

If using AC you need to rectify a very small voltage. An op-amp can be configured to act as a perfect diode, and a second amp in the same chip can be used to boost the voltage to the required range for an A/D converter.
en.wikipedia.org/wiki/Precision_rectifier

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23 May 2016 10:40 - 23 May 2016 10:51 #74975 by cncbasher
sorry yes Andys correct ,a Capacitive system would be the way to do , done easily with an arduino , i have seen some code on the internet for capacitive height control .
you can also use a LVDT linear pot , and a hoop resting on the plate , but this can be troublesome if your cutting small parts or
the mechanics of the hoop become stuck , these problems drove me nuts at the time
a infra red height sensor will do the same thing , so long as you focus the spot outside of the cutting area

Although you have all this covered on your Wiki pages it seems Marcin.
opensourceecology.org/wiki/Sensing_Distance_from_Work_Piece
Last edit: 23 May 2016 10:51 by cncbasher.

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24 May 2016 09:03 #75027 by Marcin_ose
Andy and others,

There is good information on our wiki already - but I came to this forum to see if anyone has done something similar.

From our wiki at opensourceecology.org/wiki/Sensing_Dista...uel_Torch_Technology

this one is referred:

www.rutex.com/us/index.php?productID=117

At $99 that is reasonable.

DIY route appears incomplete here, and is cheap.

opensourceecology.org/wiki/PSoC_Torch_Height_Sensing

The preferred route is of course to prove and opensource an Arduino circuit.

Marcin

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24 May 2016 09:32 #75028 by cncbasher
theirs a number of ways this can be done , but it's totally different than using Plasma ,
you could isolate the cutting tip of the torch and use that as your cap sense , for example , then take the output straight into Hal
using the THC Comp , and do all the rest inside linuxcnc .

or as you suggest using an arduino

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12 Sep 2021 16:10 #220337 by rajsekhar
Hello..everone.
I am trying to make a oxyfuel machine..and a THC. I am planning to measure distance using laser..
Can anyone share any case using laser..and the adruino codes??

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12 Sep 2021 18:56 #220356 by Marcin_ose
We are doing a capacive height sensor that is located behind a shield. Using Marlin 3D printer firmware, which has built-in height control. See wiki.opensourceecology.org/wiki/CNC_Torch_Table_v19.10

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