Epilog Express laser raster results not even

[jon heed]

Long time listener, first time caller.
While rastering I get lighter and darker areas of the text. The high/low points of text are darker/deeper, while the center is lighter. The effect is consistent across different fonts, sizes and materials. If I had to guess, longer delays between pulses allow deep/dark. Faster pulses required across center of text doesn't allow laser to recover. Anyone come across this?

Samples = Created in Coreldraw X6
Samples = 300dpi 70% speed/100% power & 600dpi 70% speed/100% power
Machine= Epilog Express 100W, (It has a Synrad 57-1 & 57-RF unit)
Tested power with PowerWizard of a 100% power vector file = 90-104W
Tested power with Powerwizard of a 100% power raster file = 30W

Jon

[Keith Upton]

Those all look like they were engraved into wood. I would say it's the wood grain that is giving you that effect. Try engraving on a solid substrate and see what happens.

[Bruce Volden]

+1 on what Keith said. Wood grain does certainly affect the "appearance" on light / dark areas. One reason I like to engrave on finished wood and then colorfill!

Bruce

[John Pletcher]

I agree with the previous two responses, the problem appears to be the material you're trying to engrave. When it comes to engraving wood, I get excellent results when using Cherry, Alder and maple. Once I had a client ask me to engrave his logo on pieces of furniture made from southern yellow pine and I got the same results you showed. Woods that posses a large difference in density between the early and late wood bands in the growth rings like southern yellow pine are not good for engraving.

[Jeff Belany]

+1 on what the others have said. I lasered in a hardwood lumber mill for 10 years and there were some woods that would do this a lot. No amount of power/speed would get a good result. Vector cutting some of this wood was almost impossible even using a 100W laser.

Jeff in northern Wisconsin

[Mike Null]

As a general rule, very general, conifers do not engrave well while many deciduous woods engrave very well. In my opinion, oak is an exception but so is cedar.

[Scott Shepherd]

Guys, I think you're all missing his point. It's not a variation on the grain area, it's a variation on the ascenders and descenders on individual words. Look at how the ascenders are darker than the other parts of the same letter.

It's a setting on Universal and Trotec's, but I'm not sure what parameter it is on the Epilog.

[Mike Null]

Steve

On closer examination I think you're right. I wouldn't discount the wood info but clearly, there is another problem.

[Michael Hunter]

It looks like a laser tube problem : recovery between pulses tends to take longer on a tube that is on its way out.

If you slow down to around 25-30% speed (and reduce the power accordingly) you will probably find that the problem is much reduced and maybe eliminated completely

[jon heed]

Thanks for the responses. When I first noticed the problem, I too thought wood grain. When it is grain, I can follow the grain in the wood and see where the depth of engraving is affected in line with the grain. That is why I made multiple samples (the separate one is maple) . That is when I noticed the defect repeated consistently on the ascenders/decenders.

Michael, I bought the machine with reserves to have the tube refurbished but was pleasantly surprised when it tested at such a high power. This RF unit in this laser is separate from the laser tube. Do you know if when the recovery between pulses is diminished, that it is an RF problem or gassing of the tube? What confuses me is vectoring lays down a very strong beam (not as strong as them manual suggests, but probably within 10%). It appears that rastering looses 90% of the power (estimate)

[Mark Ross]

I recommend everyone get a 10X eye loupe at a minimum, I also bought a deep blue USB 10X, 60X and 200X microscope to help trouble shoot things. We bake our wood before engraving which seems to help, but we have never had any good luck on pine. Hit a dollup of sap and it will look different.