Hi-amp Fine cut ohmic clip problems

[34by151]

Having issues with Fine cut on a Hi amp torch with powermax 125
Note the consumables are different to the 45-105 ones

Was cutting 1.6mm core 10 and every few pierces the THC would get stuck in a collision mode
After many errors finally tracked it down to fine dust getting stuck between the shield and nozzle

The table is a downdraft

What seems to be happening was very fine particles of aluminium that were deposited on the slats were being blown back up during the the pierce.
These wedged in between the shield and tip creating a short and sending the torch into a permanent collision
The Ohmic was therefore seeing the short as a collision

Wiping the torch, going back to the pierce and restart go it it going again.
Anything from 2-10 pierces before another error
Most annoying as the sheet had around 800 pierces to do.

I cant recall cutting 1.6 Core 10 right after aluminium before
Short of blowing out the slats with an air duster after cutting aluminium, I cant think of another way of minimising the issue

As a side note the THC is servo controlled so the Pierce and initial cut heights are spot on book values (measured)
I also tried a Peck pierce, starting higher than normal and moving down to pierce height.
This seemed to extend the cycle a bit but not much.

In the end the sheet was estimated to take 1.25 hours took over 4 hours to cut. Wasted the better part of my day

PS I also tried using the Ohmic just for the initial height sense and disabled for collision during cutting.
This let each cut finish but would obviously cause and error on the next pierce.

I would have disabled ohmic all together but the floating head proximity switch decided to die the day before and had not managed to get a replacement fitted in time.

Not the best day in the shop

As a test I ran some of the same 1.6 core 10 using 45A shielded , no issues at all
Same material, just re-generated the gcode for 45A shielded

Anyone have any more Ideas on minimising the issue?

[adbuch]

Maybe coat the consumables with anti-spatter spray. Also, with brand new FineCuts it is recommended to set the cut height to around 0.075" to 0.080" for the first several hundred pierces, after which drop back to the 0.060" book setting.

David

[Rodw]

I wonder if pulsing the torch to generate postflow before you start cutting a job would help? It works on watertables to keep water out. You'd think it would be hard for dust to get in against a stream of air.
Also, can you test the ohmicprobe before starting a job?
some machines have a test probe button that checks for a shorted torch from rubbish in the nozzle. If the probe lights up there is a short.
QTplasmac config on Linuxcnc has these features...

[34by151]

The issue is the dust from previously cutting alloy sheet

The Duramax Hyamp does not use the same consumables as the Duramax 45-105 torches
The fine cut nozzle is more extended on the Hyamp

It seems to allow the dust to get in between the tip and shield
The dust is so fine you can hardly see it but can feel it


So I ran a few tests today
Swapped in a Duramax torch (not hyamp) this worked fine but not a solution as I cant cut at 125A

Replaced the failed floating head proximity switch allowing me to play with disabling ohmic

Added some code to disable ohmic after pierce
This will use ohmic for the initial height sense then relay on the proximity switch during the cut
This allows the cut to complete but will fail on the next pierce

Added some code to detect the failure on pierce
Upon detection
Turn on Alarm buzzer
Turn Alarm Light
Disable Arc
Move torch to the Tip Change position

Machine will wait for an operator input (pendant key)
Check the failure is now cleared
Move the torch back
Start next cut


This works well but does not address the issue with Hyamp Fine cut
big deal
Going to try firing the torch as high as possible and ramping down
Will have to do some some work on the piece for each material but not a big deal

Have to work out how to get the TC to pulse the air as well

[adbuch]

Perhaps contact Hypertherm directly to address your consumable issues.
David