overlap on lead in

[Larry1958]

Hey, I just noticed the overlap feature on lead in lead out. I was told by one of the guys on the floor to use overlap on circle contouring to reduce the tool marking on start and finish of contours. I have never had to do this before. I have always use a tangent approach with a smaller arc to do this, but there is almost always some kind of dwell mark at the start, and end point. I used the overlap at .1 but still have a mark, although it is less noticeable. Call me stupid, but why would you use this feature anyway? It seems to me that it would just create another mark where the overlap would end with the new setting.

[88Matt]

Depends on the tool, material and what u r trying to do. I have used it on tephlon before to smooth it out.

[Larry1958]

Thanks. Would you want to do this as a default setting then or are there any negatives?

[Guest]

I use this regularly for clean blends, I will use it in conjunction with a helix up and down as well when finishing a wall and floor.

 

It is not a default, I set it when I want it

[Thee Dragracer1951]

I use it as a default. I set it at .005. Works great.

[Larry1958]

o.k., I tried it and it seems to just be leaving the same mark only at the new end point. I think I am having some backlash issues with the machine, or the part is moving a little while machining. I am machining Black Delrin using double sided tape. I trammed the part after machining and only reads .001 T.I.R. on the bore, but the mark is very noticable.

[Guest]

how much of a finish cut are you taking?

 

Backlash could be an issue as well.

[Larry1958]

I am taking a .010 finish cut w/.05 overlap.

[Guest]

I'd lean towards machine issue then.

 

Might try a slower feed rate and see if it helps.

 

Also might want to check and adjust the backlash in the machine

[Span]

One trick I've found useful for holes is to set it to (hole diameter-tool diameter)*Pi. This will give you a full spring pass with no extra leadin/leadout.

[MLS]

A couple more instances where it works well.

 

Interpolating bushing holes(Sounded crazy to me when I saw another guy doing this) with comp to control diameters, some machines leave a tiny nipple. Enough to cause a headache when installing the bushing.

 

On machines with spline compression calculation for high speed functions, it will leave a small nipple on the surface relative to the tolerance set in the parameters.

[Elmer Fudd]

Span,nice,I like. Dan

[Programinator]

quote:

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I think I am having some backlash issues with the machine

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larry is it a fadal?

[doyleg]

I have to use the overlap because at higher feedrates the machine will slur and leave a "nipple". So I either have to slow down the feedrate or do an overlap. The overlap is better.

[jeff]

I have it set to .05" by default.

DO you have multiple passes turned on with a spring finish pass?

This will leave virtually no mark at all.

 

Great for Keyways,holes,etc....

[PeterM]

On finish Id"s I set the lead in/out to 120/180 deg., you can chain a point in the center of the hole, NOT use entry line and enter a rad just a little smaller than the hole size, set the use entry point in the lead in/out and Mastercam will calculate the line length for you. For external features where I am getting unacceptable in/out marks, I either create small(.003) rads on the corners, and lead in/ out from there, or if the contour dictates, I will create entry/exit arcs at the midpoint of a rad that are larger the the rad, chain those arcs as part of mt toolpath then turn infinate lookahead to OFF. This make a nice gentle entry exit for the tool and will practically eliminate any marking. I do that only on an as needed basis.