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Mark Powell
01-16-2005, 7:37 AM
Hi all,

I have been experimenting with different settings and preparation of the glass but I dont seem to be able to get the results Im looking for.
I am using an Epilog 35 watt Mini - 400dpi 40% speed 100% power with a mask.
I have also tried Rub & Buff to enhance the look but there does not seem to be enough depth to hold the paint in the engraving.
I seem to remember reading something about working with the laser out of focus. Is this an option?

Any advice apreciated.

Mark

PS: I am tring the above on Wine Bottles and Wine Glasses in the rotary attachment.

Jerry Allen
01-17-2005, 6:52 PM
Glass is weird stuff. Despite one of the previous posts, it is urban legend that it is a liquid, not that that is really important here. Glass reflects or passes a lot of the power, but what does hit and absorb heats that area quickly and explosively. At the extreme you may even crack the glass.

First of all, your power setting is too high and your speed is too slow. Glass kind of explodes under those conditions and at that DPI you are probably seeing some banding.
The art work is fairly important because it's difficult to get good resolution on very tiny stuff, say 6 pt. type. It will come out but the chipping reduces the fine lines. I generally outline my text which in most cases helps clean up the etch, but can sometimes work agianst you depending on the design.
I've had better results on bottles using 1000DPI, 100% speed, 50% power. Adding 50/50 soapy water and letting it dry and a damp piece of newspaper where you will be blasting will help a little.
However, if you have ever blasted with carbide grit, you are in for some disappointment. You will never get the fine surface and depth that carbide grit, say 100 or 150, is capapable of in terms of smoothness and depth. But there are a lot of drawbacks to blasting. It's messy, a real pain to create a mask and apply it without getting some blowby, and you have to protect the entire remiander of the bottle. Sometimes you get some tape lifting and hitting a small area that you didn't want to blast, and during the cleanup process, it's tough to keep from damaging a label. That can get costly if you are blasting a bottle of Dom Perignon.
I have not tried making a mask using my laser and then blasting, but it sounds like a real good idea. Normally exposing a Raysist mask (for instance), developing it, washing it out and waiting for it to dry is time consuming, expensive, and prone to minor problems.

Keith Outten
01-18-2005, 12:06 AM
I've tried several types of blasting material in various grits but the best quality I have achieved blasting is with glass beads. The quality is very good but not near the quality I get laser engraving glass. Using the wet newspaper technique laser engraving is just awesome but I haven't been able to do photographs like some of the ones I have seen posted here in this forum. Honestly I didn't think that photos in glass were possible, but there are a few people here who have been very successful with photos on glass.

Roy Brewer
01-18-2005, 3:05 AM
Mark,

You'll soon notice you have a broad range of recommendations when it comes to glass engraving. I mean that the recommendations will contrast sharply.

From Jerry's comments I assume he is using either a ULS or GCC which is much slower than your Epilog (not picking a fight, just trying to partly reconcile the differences in the following suggested settings).

On wine glasses (cheap through leaded crystal, all the same) I recommend on your 35 watt system 100% power, 30% speed and *always* use the soapy water "sopped", wet newspaper, 600dpi.
On (brown glass) wine bottles, I drop speed to 20% leaving power at 100%,600dpi.

Those settings should give you a very opaque white letter with crisp edges.

I agree with Keith that photos are tough on glass. A photo needs to "lend" itself toward being laser engraved and lend itself even more to be lasered on glass. This is where I've seen the best results. Save photo at 200dpi(250 on ULS,GCC,Xenetech), negative(inverted), run through photograv, engrave at above settings *but* at 200dpi(250 on ULS,GCC,Xenetech).

Jerry Allen
01-18-2005, 2:05 PM
Glass beads are pretty smooth, soft, and are more for cleaning and peening metal.
Aluminum oxide is much harder and sharper, and silicon carbide is even better yet because it fragments as it is cutting and presents new cutting edges, therefore lasting longer. It also does not create static electricity and glows while it is cutting, making it easy to see what is getting cut.
Glass is pretty hard stuff. Using 100-150 grit carbide you can barely see the texture of the etched surface when compared to what I have seen so far with the laser.
I would prefer to be able to use the laser because of ease of use, but for a deep cut or 3D cut that's simply out of the question.
Based on Roy's remarks, I will try some new twists to see if I can improve my laser output on glass. Yes I'm using a 25w GCC, so my previous speed comments were not valid in Mark's case.

Rodne Gold
01-19-2005, 10:19 AM
Hiya
A laser does more or less what a sandblaster does , it "hits" the glass with pulses instead of grit, The glass cannot vaporise like other stuff does , so the local heat generated fractures it , it does not chip it nicely like a sandblaster will do , its very much uncontrolled. What one really has to do is control the fracture and almost limit it to the spot size , the wet newspaper/ liquid etc does just this , it "concentrates" the heat hit and localises the fracture by cooling the surrounding glass. The problem with the paper method is that the paper often dries up and if you use any air assist , blows away. We have found that coating with undiluted dishwashing liquid and letting it dry is ideal -even tho dry It seems to absorb the heat just adjacent to the pulse and allows a controlled fracture. another strategy we adopt is lasering thru masking tape for small areas and paper based vinyl aplication tape for large areas. This seems to give a smoother effect.

I do not generally like laser engraving on glass , I have never seen it come out as well as sandblasting (I do both).
Where the laser scores BIG time is making masks on the glass , we use polyester based vinyl and laser engrave thru that and then blast for the best quality and depth. If you use the polyester , you can do 3d blasting and lasering. For 3d blasting , imagine a leaf with veins , what you do is vector cut the polyester and remove only the veins , you blast and after you have a reasonable depth , remove the leaf and continue blasting , and you get a smooth transition tween the veins and the leaf where the veins are deeper. You can selectively remove portions of mask to achieve a 3 effect and can do this on multiple levels. You can achieve a similar effect with the laser by 1st lasering the veins and then the leaf , but you laser the WHOLE leaf over the veins , where you lasered the veins stands out from the leaf.

The PPI (pulse per inches) of a laser , beam quality and spot size all come into play with glass. Using very high DPI's and PPI's will actually waste a lot of time and create a huge amount of overlapping pulses and induces a lot of stress into the glass. One can use various settings to achieve various effects , a high power with slow speed and a low DPI/ppI will give a rather coarse shattered type engraving. Low power , high speed and high dpi will give a smoother engraving with little whiteness , upping power will give more whiteness but might induce a lot of stress. All of this also depends on the composition of the glass and how it reacts to power pulse. What works on one type of glass can be a disaster on others. What works for one laser might be a disaster for another.
Photos work well with very gross half toning , you will never get the same effect as lasering on pex or marble etc with glass photos.
What we do with glass and photos is to either laser directly or thru a mask and blast. We use a piece of black acrylic behind the glass (either the glass is drilled and we bolt the 2 together or use a frame to hold both together)
We invert the image (like a negative) , run it thru a graphics package with a very course 1/2 tone and engrave it in reverse and then layer the 2. Comes out really nicely.
A tip to get a slightly better finish on glass is to go over the engraving with a steelwool pad to "smooth" out roughness and remove splintering and use a white gilders paste like rub 'n buff on it , the lasered glass holds the colour quite well (you can use other colours too , like metallics)

Regards
Rodney

Jerry Allen
01-20-2005, 12:26 AM
Thanks for all the good info form Roy and Rodne.
I was pretty dismayed at the "shattered" effect and noticed that it had a tendecy to flake off. That could be dangerous if ingested. I used a poly pot scrubber to clean it up a bit. That never happens when blasting. When I lowered the power and increased the DPI that stopped happening, but it still didn't look as good as blasting.

Mark Powell
01-21-2005, 6:01 AM
Thank to all for the level of information.:D
I have been back at it with renewed energy and a multitude of settings.
I have to say my results are a lot better than previous efforts.

Thanks again

Mark

gary bonard
05-14-2013, 12:26 PM
Hiya where can i buy the polyester based vinyl ?

Chuck Stone
05-14-2013, 5:59 PM
Hiya where can i buy the polyester based vinyl ?

LOL .. wow .. opened up an 8 yr old thread to ask!

Not sure what 'polyester based vinyl' is, but if you mean a polyester
adhesive, I get mine from Papilio .. they have different versions for
printers, but it works well as a mask and there's no worry about
the vinyl.
You can also check with bumper sticker suppliers, as many of the
bumper stickers are polyester. You can get plain 8.5 x 11 sheets.
I think I paid $30 for 100 sheets, but that was a closeout. Don't
even know if it was a good or bad deal.. I just needed 'em!

Dan Hintz
05-15-2013, 7:10 AM
Chuck,

He's talking about the non-PVC based vinyl (polyester-based)... safe to cut in the laser, can be dye-sublimated, etc.

You can pick it up at most vinyl supply houses, same as the other stuff... though selection may be slightly more limiting.

Chuck Stone
05-15-2013, 1:38 PM
Chuck,

He's talking about the non-PVC based vinyl (polyester-based)... safe to cut in the laser, can be dye-sublimated, etc.

Ah.. I thought all vinyl was based on vinyl chloride, and the chloride was the problem.
But I'm not a chemist.. and don't pretend to be one on the internet