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THC Active Delay?

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zj2203
Posts: 12
Joined: Sun Sep 04, 2016 10:47 pm

THC Active Delay?

Postby zj2203 » Mon Sep 12, 2016 3:30 pm

I have a Shopsabre sidekick table with a Hypertherm Powermax 85 and run WINCNC Controller

Can somebody please explain to me what THC active delay is and how it effects the cutting process/when should it be used?
I noticed it is on some of material thicknesses that were pre-programmed in my settings when I got the computer/table delivered.
Is this helpful to use when cutting thicker material? For example trying to cut 3/4'' with the 85.

Any insight would be helpful and appreciated. Thank you
Last edited by zj2203 on Mon Sep 12, 2016 10:14 pm, edited 1 time in total.

beefy
Posts: 1239
Joined: Fri Jan 18, 2013 3:19 am
Location: Melbourne, Australia

Re: THC Active Delay?

Postby beefy » Mon Sep 12, 2016 6:17 pm

I wouldn't use the word "helpful", it's more like essential, unless you manually enabled THC a short distance into the cut.

Assuming you have THC enabled before the cut commences.

The gcode gives out a command to fire the torch.
Now the system waits for ARC OK which is sent by the plasma cutter itself to indicate the torch has fired.
Unless quite thin steel, the torch fire command is normally followed by a pierce delay (NOT THC delay) to allow the pierce to complete.
After the Pierce Delay the torch will go down from pierce height to cut height
Then the XY moves start and the main cut commences.

Up until the XY moves, the torch voltage will be wildly fluctuating and normally be much higher than the SET VOLTS you have programmed for your THC. If your THC was immediately active at the beginning of the gcode it's going to think friggin heck, this voltage is way too high I'd better move the Z axis down to close the gap and reduce the voltage. Your torch gets driven down into a molten puddle (you starting to see why I use the word "essential" :D ).

The THC ACTIVE DELAY causes the THC to do zippo for this period of time. This delay normally starts from when the ARC OK is received. The length of this delay is totally up to you and you can find it by doing some test pierces / lead ins with the THC off, or you can calculate how long the THC ACTIVE DELAY should be by adding your Pierce Delay plus an amount of time that allows the torch to get down to cut height and be a small distance into the metal, by which time the voltage should have stabilised and is ready to be monitored by the THC. Thicker metal generally takes longer to pierce and has a slower cut speed, thus the THC ACTIVE DELAY needs to be longer to allow the pierce to complete and the XY moves to get the torch away from the pierce point, the molten slag mound, and into nice clean metal.

You could even use a stopwatch. Start it when the torch fires and stop it when the torch looks like it's cutting away from the pierce point and slag puddle. That time could then be used as a starting point for the THC ACTIVE DELAY for THAT particular thickness steel and the applied parameters (feedrate, etc).

Hope that helps,

Keith.
8 x 5 water table
Powermax 1250 with Duramax torch
Candcnc MP3000 / Mach3
Sheetcam
Geomagic Design 3D solid modelling
Coreldraw X5

zj2203
Posts: 12
Joined: Sun Sep 04, 2016 10:47 pm

Re: THC Active Delay?

Postby zj2203 » Mon Sep 12, 2016 9:47 pm

Keith,
OMG THANK YOU. Thank you for taking the time to respond to my post- this information is very helpful. My torch has driven down into many molten puddles :( but still works great. This will change the game. Thanks again.


beefy wrote:I wouldn't use the word "helpful", it's more like essential, unless you manually enabled THC a short distance into the cut.

Assuming you have THC enabled before the cut commences.

The gcode gives out a command to fire the torch.
Now the system waits for ARC OK which is sent by the plasma cutter itself to indicate the torch has fired.
Unless quite thin steel, the torch fire command is normally followed by a pierce delay (NOT THC delay) to allow the pierce to complete.
After the Pierce Delay the torch will go down from pierce height to cut height
Then the XY moves start and the main cut commences.

Up until the XY moves, the torch voltage will be wildly fluctuating and normally be much higher than the SET VOLTS you have programmed for your THC. If your THC was immediately active at the beginning of the gcode it's going to think friggin heck, this voltage is way too high I'd better move the Z axis down to close the gap and reduce the voltage. Your torch gets driven down into a molten puddle (you starting to see why I use the word "essential" :D ).

The THC ACTIVE DELAY causes the THC to do zippo for this period of time. This delay normally starts from when the ARC OK is received. The length of this delay is totally up to you and you can find it by doing some test pierces / lead ins with the THC off, or you can calculate how long the THC ACTIVE DELAY should be by adding your Pierce Delay plus an amount of time that allows the torch to get down to cut height and be a small distance into the metal, by which time the voltage should have stabilised and is ready to be monitored by the THC. Thicker metal generally takes longer to pierce and has a slower cut speed, thus the THC ACTIVE DELAY needs to be longer to allow the pierce to complete and the XY moves to get the torch away from the pierce point, the molten slag mound, and into nice clean metal.

You could even use a stopwatch. Start it when the torch fires and stop it when the torch looks like it's cutting away from the pierce point and slag puddle. That time could then be used as a starting point for the THC ACTIVE DELAY for THAT particular thickness steel and the applied parameters (feedrate, etc).

Hope that helps,

Keith.

beefy
Posts: 1239
Joined: Fri Jan 18, 2013 3:19 am
Location: Melbourne, Australia

Re: THC Active Delay?

Postby beefy » Mon Sep 12, 2016 11:20 pm

Ha ha, happy to stop you destroying your torch :lol:

I bought my machine torch some time after I bought the plasma cutter and here in "double the import price Australia" I paid $1100. Got to look after these precious torches.

Keith.
8 x 5 water table
Powermax 1250 with Duramax torch
Candcnc MP3000 / Mach3
Sheetcam
Geomagic Design 3D solid modelling
Coreldraw X5


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