Lead Ins and finished cut out.

[larrycameron44]

Powermax 45 Torchmate AVHC
Hi all, can anybody help with a small problem I am having. I am sorry but the photo attached is not the greatest but on the bottom cutout, about half way along, you can see where there is a little bit cut out, where I assume the lead in created this or the finished cut as it drops out causes this.
Does anybody know how to limit this. I have tried using a 90 degree angle lead in and the arc angle with a 2mm lead in thats about 1/16 I think.
Any ideas would be appreciated

Larry
NZ

[jimcolt]

Larry,

I cannot see the anomaly in your picture...it is a bit fuzzy....and I have not had a beer yet!

Jim

[larrycameron44]

Ok I shall try again, try this one Jim. Its 1.6mm galvanized sheet metal. And I assume as the lead in or finish cut bit drops out the plasma arc causes this????
Help please!!

[jimcolt]

To determine if this divot is created by the lead in....cut the same part but hit the stop button before the end....if the divot is there then it is likely on the lead in.

If on the lead in, first make sure this divot is not in your cut drawing (probably is not).

-Next....go to your machine and see if you can feel any type of mechanical backlash (improper gear seating, etc)...as this can cause an over shoot in motion when truning sharp corners, creating a divot. If you have backlash that cannot easily be fixed ( a machine design issue) then re draw your lead-in as a radial (curved) lead in....thia often will eliminate backlash related divots.

- A divot like this can also be caused by exremely slow acceleration rates/cornering speeds. If you have the ability to tune your motion....work on increasing accleration and corner speeds to the maximum that your machine can handle without affecting the ability to stay on the cut path. Slow accel, slow corning casues the plasma torch to effectively stay in one place (on sharp corners) for too long.....the plasma is burning all of this time....reaching out further and further for metal, creating a divot. This is a reason that I like servo drives on my plasma machine....correctly set up they have incredible accel/decell capability.

- If this is determined to be caused at the end of the cut....check to see if you have a plasma off dwell in your set ups. Many machines / software use this function to allow the trailing bottom edge of the arc to catch up at the end of cuts, especially on thicker aluminum and stainless so the the parts will drop. On thin material, the motion comes to a stop then this dwell keeps the arc on for a time period...creating a large hole.

- best bet for a lead out...if your control and software can do it...is to program an overburn at the end of the cut. The overburn should go past the start lead in, staying on the original cut path for about .200", but shutting the plasma arc off at about .100" into this overburn. This makes for the cleanest end of cut transition.

- Do not program a lead-out that turns back into the scrap material, especially if the scrap slug is small enough to drop. This is tough on nozzle and electrode life.


Jim Colt Hope this helps!

[larrycameron44]

Thanks Jim, I shall check my Torchmate software and see what is available to change and see if I can stop this from happening. Its about the only thing that makes the internal cut outs look bad.

Cheers
Larry
NZ

[motoguy]

To determine if this divot is created by the lead in....cut the same part but hit the stop button before the end....if the divot is there then it is likely on the lead in.

If on the lead in, first make sure this divot is not in your cut drawing (probably is not).

-Next....go to your machine and see if you can feel any type of mechanical backlash (improper gear seating, etc)...as this can cause an over shoot in motion when truning sharp corners, creating a divot. If you have backlash that cannot easily be fixed ( a machine design issue) then re draw your lead-in as a radial (curved) lead in....thia often will eliminate backlash related divots.

- A divot like this can also be caused by exremely slow acceleration rates/cornering speeds. If you have the ability to tune your motion....work on increasing accleration and corner speeds to the maximum that your machine can handle without affecting the ability to stay on the cut path. Slow accel, slow corning casues the plasma torch to effectively stay in one place (on sharp corners) for too long.....the plasma is burning all of this time....reaching out further and further for metal, creating a divot. This is a reason that I like servo drives on my plasma machine....correctly set up they have incredible accel/decell capability.

- If this is determined to be caused at the end of the cut....check to see if you have a plasma off dwell in your set ups. Many machines / software use this function to allow the trailing bottom edge of the arc to catch up at the end of cuts, especially on thicker aluminum and stainless so the the parts will drop. On thin material, the motion comes to a stop then this dwell keeps the arc on for a time period...creating a large hole.

- best bet for a lead out...if your control and software can do it...is to program an overburn at the end of the cut. The overburn should go past the start lead in, staying on the original cut path for about .200", but shutting the plasma arc off at about .100" into this overburn. This makes for the cleanest end of cut transition.

- Do not program a lead-out that turns back into the scrap material, especially if the scrap slug is small enough to drop. This is tough on nozzle and electrode life.


Jim Colt Hope this helps!

Always finding useful information here. I'm going to make a few changes to my lead-ins and lead-outs, and see if I like them.

On another note...Sheetcam seems to always want to create the lead-in/out point on a corner. Do you guys like to start your interior cuts on corners, or straight areas?

[OTHill]

I always check my drawings and move all lead ins away from corners.

[motoguy]

I always check my drawings and move all lead ins away from corners.

I have been doing the same. On inside corners, anyway. With Sheetcam always trying to put the leadin in a corner, I wondered if I was missing something. I seem to have a much smoother transition in/out of the part if the leadin/out is on a straight (or large diameter arc) section, vs a corner.