Question on vector cutting

[Bruce Clumpner]

I've got a question on something I'm calling it dot-gain when vector cutting acrylic... I'm new to engraving, just purchased an older epilog 35w mini that seems to be working pretty well...Anyway I'm finding that my vector cuts through 1/4" plus acrylic stock is not always at a perfect 90-degrees. Top of the sheet seem to shrink a bit away from the laser cut line, while the bottom of the sheet is on-line. I think it's producing something akin to dot-gain found when printing when the ink seeps into the paper producing a larger dot than expected. I figure the laser power heats the top of the sheet more than at the bottom, causing the acrylic to shrink.

Is this common? Is there any way to insure we get perfect verticals on vector cuts like this? How do you all make compensations for this? Is there a standard shrinkage rate for each material?

Any pointers gratefully accepted.

Bruce

[Mike Null]

Bruce

Welcome to SMC.

What you are experiencing is most likely the natural kerf of the laser beam as it cuts through your material.

I suggest that you focus the beam about half way down into the material. That should improve the situation but won't eliminate it.

Also check out the Epilog site as they have an abundance of tech info available.

http://www.epiloglaser.com/tech_library.htm

[Scott Shepherd]

+1 for what Mike said. The beam is shaped like an hour glass, so it's not straight and won't produce a true straight cut.

[Bruce Clumpner]

Scott & Mike,

Thanks for the info. Gee, I didn't figure the short throw of the laser between the mirror and material would result in such a variance. Considering the shape of the beam, I'll work on shifting the focus a bit more into the material.

bc

[Scott Shepherd]

Bruce, it's published somewhere. A 2.0 lens has about a 1/8" effective cutting area, so it's small. Shape that like a hourglass as well and it can be quite the angle.