Mis-match of lines when cutting circles

[Roger Lueck]

Example - I cut a circle in .25" acrylic, the point a which the cut line started and ended did not align, hence a small ridge resulted.

What is the cause of the mis-match of cut lines when cutting circles or other "closed objects" drawn with CorelDraw?

Thank You,
Roger

[Kev Williams]

It's not Corel, it's the part. Cutting acrylic heats it, which makes it expand. So when the laser gets back to the start/end point, that point's not in the same place- Read the 'lead-in lead-out thread for more on this--
Another factor I discovered, air assist-- the air pressure can and will move the material you're cutting! I only use air assist to reduce flame and move smoke, I just use wide-open 3/16" tubing with my diaphragm pump, it puts out a good volume of air but at very low pressure so it won't move the parts.

And then there's the beam itself, when it starts the cut, it has all of the material to cut thru at the beginning, and (just conjecture here), I'm thinking the beam may bend more at the start point than when it returns, making for a small 'new' cut. Like I say, just a guess, but someone may know! (Dave?) ;)

[Dave Sheldrake]

And then there's the beam itself, when it starts the cut, it has all of the material to cut thru at the beginning, and (just conjecture here), I'm thinking the beam may bend more at the start point than when it returns, making for a small 'new' cut. Like I say, just a guess, but someone may know! (Dave?) ;)

Kevs got it covered, on big sheets the heat in the sheet can make stuff move quite a bit.You would think that the beam makes a nice straight line through the materials but often it doesn't, it almost works like a drag knife with the bottom of the cut trailing the top by X amount. (the more power you have the less of an effect the *drag* has)

Either that or your driver for the stepper motors need adjustment for the step lengths.

[Roger Lueck]

Thank you for the replies, your responses are appreciated.
Roger