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View Full Version : Engraving glasses revisited (long)



Don Gares
11-03-2008, 10:42 PM
First of all I realize that there have been several threads concerning this subject and I think that I have read them all. I have a 40 Watt Pinnacle M Series machine and the related rotary attachment. I have been experimenting engraving beer mugs, flutes, wine glasses, etc. with reasonably good success.......probably not perfect but presentable as far as I can tell (never seen any done by other people). Obviously, I have not tried every combination of DPI, speed, and power but I have tried a lot of them with my best results being with 100 speed, 60 power, and 1000 DPI! Yes, I have found 1000 DPI to work the best but 600 DPI is almost as good. I have not been using any wet wraps or dish soap on the glasses.

Ok, now my questions:

1.) Most all of the posts that I have read recommend a dramatically lower DPI, why am I getting the best results with a high DPI?

2.) The previously posted speeds and power are all over the place but this may well be because of different powers of lasers. Does my settings sound in line and if not, what would you suggest?

3.) I have also seen liquid dish soap recommended several times. I would like to try this but isn't it a real mess dripping in the machine?

4.) My print driver has both a "Black and White" and a "3D" setting which the manual really does not fully explain the difference. For engraving on glass I have been using the "Black and White" mode, does this sound correct? In, fact, I have only found the "3D" to be useful on wood plaques. What am I missing?

All in all, if this knowledgeable group of individuals could shed some light any or all of the above it would be greatly appreciated by this person that has only owned a laser for about three months and had never even seen one before.

Cheers,

Don

Tim Bateson
11-03-2008, 11:49 PM
I can help with a couple of those questions:
1) Good question - I'd be interested in that answer myself.
2) Yes, you are correct every laser - even the same wattage is a bit different.
3) When properly applied, the glass will be slippery with a thick coating of liquid dish soap - not to the point of dripping or running - almost like an oily film.
4) Never tried it, but I don't think you want 3D for glass. That mode digs a bit deeper & may be too much power for the glass to handle or may weaken it. Again, I'd be interested if someone has tried it.

Hilton Lister
11-04-2008, 12:01 AM
I have a 25 watt Mercury and I get the best results at 1000dpi. 100% speed and 85% power. I do use sign-vinyl application tape as well though and often give the article a light sandblast before removing the tape. The tape seems to have quite a dense adhesive and will take quite a good blast. Indeed, you must make sure you have completely lasered through the tape, otherwise it is almost impossible to blast through the adhesive (at least, at the pressure I blast) Another advantage, is that you can actually see the crystallised deposits from the laser being blasted away during the process, leaving no shards.

Darren Null
11-04-2008, 12:52 AM
1) Possibly your software is reducing the dpi of the image on the way through. Don't know otherwise.

2) Sounds about right.

3) You don't use enough to drip. Smear it on with a finger.

4) Black and white turns the laser on to the power you specify or turns it off for the white bits. 3D uses the power you specify for the black bits, but steps down the power through various shades of grey (how many shades depends on the machine). With a specially-prepared graphic, it's possible to make a 3D image. It takes ages and I usually end up with charcoal. Technically, the image is 2.5D, because you can only fire the laser from one direction. Most of the laser manufacturers have some sort of demo; this is the first one I found on Google:
http://www.gemengraving.co.uk/laser_engraving.htm

With my 10W, 3D is nowhere near cost-effective...much quicker to vector cut layers of plywood for 3D. Your mileage may vary.

Frank Corker
11-04-2008, 7:45 AM
When it comes to engraving glass, I always put my settings on 1200 dpi, it results in a much smother finish. I always use thin paper with a dollop of concentrated washing up liquid which I smear with my finger across the glassware. On the Epilog rotary you have to be careful about having too much soap in the wrong place or the workpiece will slip.

Don Gares
11-04-2008, 12:32 PM
Ok, for a few hours this morning I have been trying many of the suggestions that I received and the end result was dramatically better than I had originally obtained. It appears, at least on my machine, that the increased DPI and dish soap is what moves the engraving from just "ok" to "great".

First I increased the DPI to 1000 and wiped the glass with dish soap and got great results. Of course I didn't know if it was the increased DPI, dish soap, or both that helped so I continued to experiment. The end result was that it was both.

In short I get my best results at 1000 DPI, speed = 100, power = 70, with the glass wiped with Joy liquid dish soap. This is with a 40 watt Pinnacle M Series machine. Of course, the drawback is that it takes 66% longer to engrave something at 1000 DPI than it does at 600 DPI.:(

All the replies were appreciated and I must say that this forum is probably the best that I have found, all subjects included (from gardening to lasers). So many forums get off subject with their replies but you people stray right on tract and that is definitely appreciated.

Thanks again,

Don

Richard McMahon
11-09-2008, 9:40 PM
I would love to know how you can get 1000 dpi from your laser. I have a home built one and the very smallest I can get my dot size seems to be about 0.006" or about 160 dpi.
My lens is a 2" focal length and I think that the smaller the focal length the better the dot size. i.e smaller
I usually engrave at about 300 dpi but lately I have reduced the size to 96 dpi with better results

I now have a sheet of granite to engrave for a memorial plaque on a headstone and I am just a little bit reticent about doing it with no test sheet and as such I am torn between doing it at 96 dpi or somewhere between that and 300 dpi.

for testing I usually use the cardboard from our local X-Ray department that the X-Ray negatives come in and it is coated but takes a good burn so I may use that as a test plate. They throw it away by the hundreds so you may try that as well if ever you want to try it. The plastic X-Ray sheets cut ok too and there are usually a few blank ones you can use for stencils etc which are free.
Does anybody else use them?

All my mirror tiles have come out ok and Photograv 3.0 has helped a lot but it is still a science to get it right.
Rich.

Mike Null
11-10-2008, 7:03 AM
I'm definitely in the minority here but I use a lower dpi (333) to get the result I consider best. What a I like is a frosted look without the micro-fractures.

If you want to practice get some window glass from the hardware store. It's cheap and will allow you to experiment with settings, masks and lubricants.


Additional comment: I usually run these twice at this resolution. 45 watts at 90 ips.

Albert Nix
11-10-2008, 8:53 AM
You guys have a lot more laser time than I do but it would seem like 1000 DPI would be way over kill. If you had a lens that could reduce the beam width to .001 the dots would be end to end at 1000 DPI so with the 1.5" lens that fires a .003" spot, would'nt 600 DPI give you a nearly 50% overlap on the dots? Or am I looking at this all wrong?
Al

Don Gares
11-10-2008, 12:11 PM
Okay, I can't argue with the math because it certainly makes sense so I just tried the various DPI's (300, 600, & 1000) on a piece of flat glass. All were engraved on a 40 watt machine at 100 speed and 65 power. I then scanned the engraved glass with a black mat board behind it and attached is the result.

As you can see the 600 and 1000 are dramatically better than the 300 DPI. What I found interesting is that the 600 and 1000 are basically a "toss up" with the 600 possibly being a bit better when engraved on this flat glass. OTOH, when I tried the same thing on a beer mug with my rotary attachment the 1000 was by far the best.

And yes, I had too much time on my hands this morning.:)

Don

Albert Nix
11-10-2008, 12:40 PM
I think I agree with you that the 600 may look a little better. If the math does work, then the 1000 DPI pass may have been over kill for that particular piece of glass. 1000DPI may be fine at a lower power setting. The mug may be a different grade of glass and be able to stand the pounding or a higher power setting (or slower speed) at 600 DPI. The reason I am so interested is that it looks like you have the same machine that I do and I like doing glass. Mine has mostly been glasses and mirrors. For the most part I also use 100P/60S 600DPI

Jack Harper
11-10-2008, 3:16 PM
Ahhhh, but what about a photo where you need to control gray scaling? Over driving the resolution may just make a photo lose all detail.

Bob Cole
04-03-2009, 4:55 PM
I was having trouble with glass engraving and still fine tuning. I first went by the settings in the ULS book and they came out horrible. Another post had the link to a colorfill demo on ULS web site and the settings for the 2.0 lens were:
pwr=100
spd (use your laser wattage, so if you had a 60 watt, put in 60)
ppi=500
img=5 (500dpi)

The kicker that modified how well it looks was having the mask on the glass and changing the black to grayscale of about 60%. I tried 70%, but it turned out better at 60%. I haven't tried any other % but wondering if either lower power or reducing the grayscale even more would help it out.

Using this formula got me the closest to the look of sandblasting (obviously without the depth).

My goal is to colorfill but all the rattle cans I try just don't work well. I also tried some Amaco for glass/ceramics and wasn't thrilled with that. The gold rubnbuff came out the best but still having difficulty getting it to look exactly the the picture on the tutorial page 3 and page 4.

I am getting a little nervous due to having 50 glass awards to do and still don't have my settings dialed in perfect. I may be expecting too much. Most people I show the samples to say that looks great before I tell them I am unhappy with it. Not sure if it is my obsessive compulsive behavior or what.

John W. Love
04-03-2009, 7:46 PM
Bob, I am with you on the colorfill of glass. I have tried dyes, inks, paint, rub n buff, etc. and just have not had any luck producing something that not only looks really nice, but also lasts. I do remember about a month ago somone posting about using craft paints from Michael's. Americana brand? Not sure if that is right or not. not sure exactly what the thread was about, but I am most certain it was within the last month.

BTW Bob, we are our most critical critic.

Dan Hintz
04-03-2009, 8:16 PM
Bob,

Hmmm, I think you have that backwards... you want 100P and a speed that matches your wattage (in your case, and mine, 60S). I use 60S/100P/333dpi with good results (though I'm still tweaking, as time permits). To use it your stated way doesn't work. Imagine someone with a 100W laser... they'd be running at 100S/100P (blowing 100W into the glass at 'X' ips), whereas someone with a 10W laser would run at 100S/10P (blowing 1W into the glass at the same speed).

I haven't yet played with anything other than pure black, but that's my next step. I believe most have received great results with 80-90%.

Bob Cole
04-04-2009, 12:49 AM
Please do as I am thinking, not as I'm typing. Or better yet, maybe ignore my posts.

I've corrected my post to reflect the accurate statement by Dan.

Mike Null
04-04-2009, 6:57 AM
Dan

That's not foolproof either as raster speed varies widely by mfr and model.

Dan Hintz
04-04-2009, 9:19 AM
Mik,

Understood, but it's a much better rule of thumb than what Bob was originally suggesting, don't you think? ;-)

Dave Johnson29
04-04-2009, 10:00 AM
I would love to know how you can get 1000 dpi from your laser.


Hi Richard,

The DPI is not related to dot size directly. It is how much the beam is stepped over each step.

With your 0.006" diameter (as are most 2" lenses) focused beam, with the dots touching you would get 167dpi on both X and Y for step over of 0.006". By increasing the dpi you get dot overlap so at 1000dpi each step over is only 0.001" and it takes 6 such steps to equal the raw 167dpi.

The dpi applies to both the X and the Y axis step-over. That's why Don said it takes longer to do 1000dpi than it does 600dpi.

Martin Boekers
04-04-2009, 11:59 AM
I find that 1200 dpi is more consistant for myself overall.

I do quite a bit of "front surface" engraving on black mirror from JDS always use soap the difference is amazing!

The on problem I have occasionally is that the glass will look engraved , but the "frosted effect" will vary depending upon the angle it's held. Sometimes when you look at it head on it will have slight "drop outs" (fully engraved but reflecting a bit different)

I've tried this with different dpi settings but still every so often it happens.

A second pass usually helps.

I can't do that with the rotary, as even if I leave the glass in place the second pass won't be registered.

Marty

Bill Cunningham
04-04-2009, 9:12 PM
Bob, I am with you on the colorfill of glass. I have tried dyes, inks, paint, rub n buff, etc. and just have not had any luck producing something that not only looks really nice, but also lasts. I do remember about a month ago somone posting about using craft paints from Michael's. Americana brand? Not sure if that is right or not. not sure exactly what the thread was about, but I am most certain it was within the last month.

BTW Bob, we are our most critical critic.

On plain text, and line art logos rubbing a little bit of white acrylic craft paint into the etch with your finger, and rubbing it off with a cloth within about 15 - 30 seconds, will whiten up the etch quite a bit.. I wouldn't use this on glassware that has to survive a dishwasher though, and may make a glass award look cheap! I run most text and art (not photos) using 100% power, 20% speed @ 400 dpi If it's just text, I run at 600 dpi
If it looks fine to me, I doubt if my customers will see a problem.. Sometimes we get Waaaaay over critical of our work. In years past, I've done rush jobs I've felt truly embarrassed about, and sheepishly handing over to the customer.. Then, the customer says something like WoW thats great!! Just what I wanted...

go figger..

Mike Null
04-05-2009, 7:28 AM
Dan

I think that it would work as an inches per second setting but as a percentage, no.

Machines vary so much, some are as low as 40 ips some are at 140 ips raster speed.

Dan Hintz
04-05-2009, 9:22 AM
Again, it's meant as a basic rule of thumb, a starting point, not a set value... just pointing out the backwards settings Bob originally mentioned.

Nick Napier
04-07-2009, 5:22 AM
Frank, You mentioned using thin paper and a little soap. What kind of paper are you talking about and what's it's purpose. I'm trying to laser some maple syrup bottles and looking to get the clearest lettering I can get. Any more suggestions?

Nick Napier woodworknick@yahoo.com

Bob Cole
04-07-2009, 1:16 PM
The type of glass really makes a difference also. The test piece I was using was a glass bottle for martini mixer (I happened to finish it off before I started this :) When I got as good as I could get it on that one, I went to the award and the award came out better.

The starting settings I put above seem to work fairly well and may translate pretty well to other laser wattages/systems. I went back and did some more testing and for my 60watt, using 100%black, my settings are 100pwr, 30spd,500ppi (500dpi). This looks very close to using the settings above without changing the black to 60-70%.

I also tested with a 1.5 lens and really didn't notice any improvement over the 2.0 lens that I use for most everything else. I had to clean the 1.5 lens more frequently due to the residue from lasering the mask.

I am using a red mask (not really sure the proper name) that is very sticky. I tried the mask with and without soap with no notice of benefit with soap. I also tried the paper with and without water. Once I added water to the paper, the paper started to bubble a little (not stick to the surface) and in those areas, there was a difference. I need to do some more comparisons between using the red plastic laserable mask and the paper mask to see if there is a difference. It would be easier for me if I can just use the paper as it is easier to work with. The red stuff is very sticky and I have to apply it like vinyl.

I am still having difficulty with color fill with using anything other than the gold leaf rubnbuff. I tried several different styles from the craft stores (Americana) but having difficulty with filling, then weeding without damaging the other colorfill or waiting for it to dry then cleaning up without having the fill get wiped off. I'm sure it is a technique thing that I am not getting but so far scoring zero. I have 20 crystal awards to do in the next couple of weeks and need to use a darker blue to fill it. Can't use the gold leaf.

Devon Jones
07-28-2009, 2:32 PM
i had a question how much soap do you put on the glass? i find that too little does nothing and when i put more then that on it turns white and messes it all up? i also wanted to know is it something in the soap that makes it look better in the engraving or just that it is a film over the glass that helps? if so is it at all possible to just use a stick of deodorant not the powder but the gell kind and just evenly wipe it over the part that you are trying to engrave? so it is a little more even and not as messy? thanks

Tim Bateson
07-28-2009, 6:32 PM
What type of soap are you using Devan? Using a thin layer of liquid dish soap keeps the glass cool to control the chipping/fracturing. That’s what the laser is doing to the glass & keeping it cooler minimizes over chipping or fracturing the glass – better detail.

Tom Bull
07-28-2009, 6:47 PM
The only thing that has worked well for me was wet (soaked) paper and engrave through it.

Brian Robison
07-29-2009, 11:59 AM
I use both, cheap dishwashing soap and a blue paper "shop towel" brand of paper towel soaked with water and squeezed out. I also use 600 dpi. I'm very happy with my results.

Bill Cunningham
08-01-2009, 9:37 PM
I keep a shot glass of dish soap next to the laser when doing glass, and just wipe it over the area with a finger. I find that it does not even make a difference if it drys out.. I think the soap, when it gets hit with the beam vapourizes, dampens down the chipping factor, and allows a much finer etch.. Particularly on small print.