View Full Version : Raster Quality.

Pete Thomas(UK)
11-27-2008, 11:35 AM
I have just picked up a job that means rastering on glass tumblers. I have just noticed that the quality of the rastering is a bit odd. There are occasionally sections where the glass has not been lasered for maybe 1/4 of an inch. This may happen 3 or 4 times across an bit of rastering 2" wide.

I also noticed on close inspection that occasionally the laser would go beyond the drawn rastered area for about 1/16 ". Not leaving a clean marked edge.

I have cleaned the lenses, the encoder strip, cleaned and greased the running track, Found that the x belt was a little loose and retensioned it.

The overshooting of the raster area is considerably better but it still misses the odd bit of glass. I am running at 75 speed 100 power,600 dpi, on tempered glass. Coating the surface of the glass with liquid soap.

Any suggestions what it may be?

The laser head does rock a bit on the track. Is this normal. Is it adjustable?

Any Ideas greatfully received.

Epilog 24TT 35 watts.

Frank Corker
11-27-2008, 1:02 PM
Pete your settings aside (I engrave glass at 45sp 100pwr and that's with a 45w) the only one time I ever had problems of it not lasering was with the encoder strip. The only other thing I can recommend you do is remove the flat lead that feeds the encoder strip, turn it over and change ends, this might help getting a good connection. The lead has same connection both ends.

Stephen Beckham
11-27-2008, 7:26 PM
Only other thing that I've seen that might cause this is the ribbon cable in the I beam bar. Two ways to check - 1 - move your glass item to other end of bed (if there is a crack in the cable at the bend, by moving the head over, that part of the ribbon cable won't be flexing).

The second way is to flip the cable - now I've got a Mini 24. I'm not sure if you model will allow you to flip the cable.

Good luck..

Pete Thomas(UK)
11-28-2008, 9:43 AM
Thanks for the suggestions Frank.

I have cleaned everything, regreased the x axis etc. I have atached an image of what I mean. The left hand side of the engraving has the ragged edge. It is possible to see where the laser over shot. Strangly this appears only to be when the laser distance being fired is reducing. The right hand side of the image is perfect.

I also tried just lasering a triangle and the same effect happened.

Peck-any ideas?


Mike DeRegnaucourt
11-28-2008, 12:08 PM
Hi Pete,

Are you using the rotary attachment? If so, I've encountered some similar problems when using the rotary attachment and the glass slightly slipped while rotating. I think it was because the glass was not actually heavy enough.

I have also encountered glass engraving issues because of inconsistencies in glass densities. I did several glasses all using the exact same settings and one of the glasses came out poorly. I chalked up the problem to non-uniform glass density for that particular glass. Grabbed a different glass and it engraved fine.

Dave Johnson29
11-28-2008, 12:18 PM
I have cleaned everything, regreased the x axis etc.

Hi Pete,

A couple of comments. Unless your manual states "grease" from a mechanical standpoint, it is not a good idea to use grease on the rails. If the axis end slides on a bar, they usually use a Delrin or Teflon pad to slide on and grease will slow up movement. Even worse is if they use a Nylon pad as some grades of Nylon absorb moisture and swell slightly.

However if the book says, "grease" then ignore me :):) and have at it.

Maybe try for a little more belt tension too. Do you have a tension gauge?

The other thing, what about putting a Vector line on top of the problem edge so after rastering it cleans the appearance up a little

Pete Thomas(UK)
11-28-2008, 3:32 PM
I spoke to a Chris at Identify(UK) and followed his suggestions. Set the Dpi to 150 and try again. This showed the individual laser paths quite clearly on acrylic. I was vescoring a triagular shape. As the head approached the left hand limit of its travel the engraved lines stopped being parallel and some went over the top of others or where the next path was to be. This then showed as gaps on the lasering. Tried this top corner of the table. If I did two triangles at the same, time the right hand one which had no deceleration of the head lasered fine. The left hand triangle was c--ap. As I went further across the table the better it got. On the right hand side even doing just one triangle it was fine.

Conclusion:- The linear track must be worn/ sloppy allowing the head to move enough to make a difference. Tightening the x axis belt had helped considerably, so had re greasing the track(only for a limited amount of time).

Solution:- Remove the linear bearing track, turn it over and reassemble. One hour job.

Works fine now where it gets most use. I will need to get a new track/bearing slide some time soon. Any one out there bought one recently and knows what it will cost?

Thanks for all the advice and suggestions.

Pete T

Bill Cunningham
11-29-2008, 10:00 PM
I tip I got from Epilog, is when 'greasing' the track, you really only want to grease the bearings in the head. Put a small amount of the white grease on the track, then slide the head back and forth along the X track to work the grease into the bearings, THEN clean all the grease off the track, if any grease remains on the track, it will only collect crud and cause problems.. The side bearing are perm lubed, and the track only needs cleaning..

Scott Shepherd
11-30-2008, 9:49 AM
Just for the record in case someone looks at this in the future, I had a problem with our Epilog rotary where it would completely skip a line or two of engraving (randomly of course). Replaced the motor on the rotary axis and it resolved that issue.

I know it's not your issue, but it might help someone troubleshooting in the future.