Lead ins Sheetcam

[adamsfab]

Hey guys,
I have a part with 4 holes in it, the holes are .30" diameter. Why does Sheetcam show that the lead in cannot fit in 2 of the holes, but does fit in the other 2? I have gone back to the cad drawing several times and checked to make sure all the holes are on the same layer, same size, etc.
Does anyone know what would cause this?
Thanks for any help.

[Xalky]

Try to shorten the lead-ins a bit. And try to have them start as close to dead center of that hole as possible.

[I Lean]

I've noticed sometimes a lead-in won't point toward the center of the hole if it's at one point on the circle, but will if I move it to another point on the circle. Example, with a perpendicular lead-in, it might angle down away from the center if I have it start at 3:00, but if I move it to 1:00 it will point to the center.

I have no explanation for it, but it might be something to mess around with.

[adamsfab]

I did shorten the lead in, but the only way it would create a lead in for those 2 holes was if the lead in was to small to avoid a crater mark. I am just confused as to why the other 2 holes, which are the exact same size, are able to accept a 0.20 size lead in , and the remaining 2 holes (same size) are only capable of accepting a lead in of 0.10" size. All 4 holes are 0.30" diameter.
.??????

[beefy]

I would ask that question to Les Newell himself (Sheetcams creator). I think you can sent a support ticket from the help menu. He said you have to identify yourself in the support ticket because the system has no idea where it came from. Sheetcam has a Yahoo support group where Les is always answering questions.

That problem's got me boggled, but anyway have you tried perpendicular leadins, making the length exactly half the diameter (=radius) of the holes. Les says this should put the pierce / start point smack in the centre of the hole. With a bit of luck it might even get rid of your problem. Fingers crossed.

Keith.

[Diverdude]

Check your circles and make sure they are one piece, I have found circles and shapes I thought were solid that had an unseeable break in them and that will not let sheetcam set an offset or leadin.

[adamsfab]

It would let me do perpendicular lead ins, I just have never cut those before. How do they turn out?

Thanks for all the help guys.
I will add a solution (if I find it) for members to find if they have the same problem one day.
It might be that the holes are segmented. I will check and get back to ya.

[beefy]

As far as how do perpendicular lead ins work, I've never done them myself.

Hypertherm has a write up about attaining cut quality on small holes. They recommend perpendicular lead ins but ONLY if your machine is rigid and has good acceleration, other wise arc leadins are recommended.

Keith.

[trucutcnc]

We typically use tangent lead in/out. Lead ins are set to half the hole diameter and lead outs are set to .1....Just enough to get clear of the edge. We run small holes about 20% slower than contours.