[Normsthename]

I have been trying to cut some 1.2mm Brushed Stianless Steel but I have a problem with burn marks where the machine starts and finishes the cutouts (See Photo)
The triangle shapes are approx. 30mm long on each side and the holes are 7mm diameter.
I think it is when the machine finishes when it burns the material.
I use Sheetcam and have a generous lead-in but because the part falls down between the slats I cannot have a lead-out or the machine loses the arc and stops
When I cut the large parts out I had a 35mm lead-in to ensure that it did not burn the material when starting the pierce, but it still made the burn mark when finishing.
Any ideas how I can stop the burn marks?

Thanks

Andy

[plain ol Bill]

Norm I don't know why you can't use lead outs. I think you have the CandCNC THC3000 don't you? If so the tip saver should allow lead outs. I see the need for a water table too to help eliminate discoloration.

[Kipper]

I feel your pain....What speed are they cut at.....Just wondering if it lingers too long as it finishes.

[Normsthename]

Thank for the replys

I see the need for a water table too to help eliminate discoloration.

I already use a water table!
I am not worried about the discoloration, it cleans up with a bit of scotchbrite or simillar

I don't know why you can't use lead outs. I think you have the CandCNC THC3000 don't you?

I have a Campbell THC300
If I use a lead-out, won't the machine stop when the inner part falls thru' the slats losing the arc???

If so the tip saver should allow lead outs.

What is tip saver?

What speed are they cut at......

I use a Hypertherm Powermax 1000 with finecut consumables, cutting speed for 1.2mm is 3810mm / min as recommended.

Andy

[Alan Bradford]

Hey Norm,
I am not sure how the Hobby grade machines work, and if that have advanced set up parameters.
In the more advanced industrial CNC's (Hypertherm, Burny, MG etc) you can reduce your lead out to as little as Zero length. As soon ad your part drops you want the arc to shut off.
If you leave it on after the part drops, the arc will attach to the outer part of your piece and continue to cut until the Arc shuts off, or you streach the arc too far.
You can actually program a negitive leadout.
This stops the torch before the end of the cut.
This is for torches that require a second or two to shut off.
The PowerMax 1000 shouldnt need this feature.

This is also why you do not finish the cuts. The part drops out and the arc goes out befor the end of cut.
The machine stops and requires a Restart to continue.
If your CNC has a parameter 'Arc Off Time' that lets the machie run a given time after loosing the arc, this will help with the Restarts, but will not help the extra cutting done at the end.

This is what I call 'Programming Choreography'
It takes a little practice to get it working right.

Good Luck,

[C.Michael]

Andy, change your lead in to a smaller size..maybe 7 mm.Why waste the cutting of 35 mm when all your doing is getting the torch to start away from the edge..when Mach sees the good arc signal it will move the torch..but have the same 7 mm as a lead out..when you are moving at 3810 mm a minute,it is only a fraction of a second for the torch to move that last 7 mm of the lead out..by the time that the thc senses the lost arc and then tells mach to stop and then mach finally stops, you will have traveled that 7 mm without loosing any steps ..it works fine with me and trying it is the best thing to see if it works for you..Mike