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View Full Version : Engraving. Would like to know what others are doing.



Joseph Shawa
10-04-2016, 6:21 PM
So I used the rotary tool to engrave a private label onto a wine bottle. I actually came out good but I have absolutely no idea how I got there. Strictly trial and error......had to drink LOTS of wine to get test right. : }

Now I am doing custom engravings on wine glasses. Every guest gets their face on their own glass....no more charms.
My first few attempts have been disastrous. Blotchy, faded, dark. Anything but good.

So I am going to make a check list of variables.

I would love it if anyone had any more variables and give input on what seems to work.

I also have questions if anyone can answer please do.

Tube Power:
I don't think that 150W is going to be a problem as it doesn't mark glass at it's lowest useful setting of 13%

Focal Length:
I have a lens that has a 3.5" focal length. ( I ordered a 4" but received a 3.5"....China)
The spot size should be between 2.5” .007” and 4.0” .012” So about .010? Anyone know how to figure this exactly?

In LaserCut, the "Half Bitmap" option breaks down the object into points/blocks. Is this some kind of dithering? Any specific variety?
Is it only for solid objects so that every point doesn't get lased? It isn't an available options for objects drawn within the program, only imports.
The "Simulate" function doesn't seem to hit every dot on the horizontal. You can see this if you really zoom in before the simulation is done. The red simulator line skips a dot once in a while but not with any regularity. Anyone?
As an aside, has anyone ever zoom in to an image in LaserCut? REALLY zoomed in? Strange code starts showing up instead of pixels.....think I'll stay out of that type of depth.

On an untouched .JPG or .BMP I just import into LaserCut and run the "Half Bitmap" operation and just invert and print as long as no pre processing. I need to compare that type of processing with the best from CD.
If I perform the "Half Bitmap" option it sets the scan gap as expected. With a Gap of .1 the simulation line is exactly right across the middle of each block on a 254 dpi CD image. So I can see that is correct on the Y Scan line.
I believe that this can be set to anything that divides evenly into the pixel size of the image. So if I enlarge and resample the image in CD and set the scan gap appropriately I should avoid banding?

If I run the "Half Bitmap" operation on the CD image there seems to be a lot more points in the image but I don't know what to make of them. And I can run it again and get even MORE detailed patterning. Anyone know what is going on?
There is also a "Dot Size' option in "Half Bitmap" operation. This seems to be like a resample but instead of DPI it is the actual dot size. Anyone? It makes big dots when set at 10 for example. I imagine that ideally it should be set to the same size as the dot size at 300DPI for instance (same as .1 Scan Gap).....OR should it be set to the Spot size of the beam? I cannot imaging the latter is correct as the spot size would change with Power and Speed settings.

It's getting so dang complicated!

And then there is the amount of grey and contrast in CD and more export options. I have read of the Gold technique and will try that when I get the machine figured out.

But for you glass engravers. Any tips? Cold glass. Wet glass. Wet paper on glass. I already read about these.
How to approach glass vs plastic? Shorter focal length? Longer? In focus? Slightly out? Speed? Number of passes at a lower setting maybe, so as to keep marks small?

Any other considerations?

I will test all of these and plan to make a big table but I can only imagine it would take an AWFUL long time to complete it. I hope to narrow it down a bit.

Finally, can Corel Draw X6 64 bit output directly to Engraver? If anyone knows how to get this working I would love it. LaserCut crashes too frequently.

David Somers
10-04-2016, 8:43 PM
Joseph,

Not too many of us have good results with glass. And by good I mean both good looking engravings AND consistently.

There are perhaps 3 or 4 folks I can think of here that have consistent results on glass.

The one I think I might focus on for now is Bill Cunningham. Do a search on him and you should come across a thread he did on his technique. Here is a link to a thread where he mentions this that might help you with the search.
http://www.sawmillcreek.org/showthread.php?39598-Lasering-Glass

I should add I have not fussed with it yet. Have not had the need. Though I should probably try it just to be ready.
I did have a nearby neighbor with a laser business who could get decent luck with glass, but with a few exceptions he really preferred to do sandblasting of glass for orders on expensive glass or for orders of more than a few glasses. He used the laser for small orders of a few pieces. I saw his best results with glass and the laser, and with glass and sandblasting and the sandblasting was considerably better. The depth of the engraving was better. The surface frosting was far more consistent. The edges were cleaner in most places. And his speed was considerably better on a glass by glass basis. He was using a used micro sandblaster. It was a Jetstream One from SMCsystemsinc.com.

Hope this helps!

Dave

Kev Williams
10-04-2016, 9:18 PM
I have 3 lasers, only one will engrave glass decent enough to suit me, my 40w Synrad LS900. If I run 70% black in photo mode, the results are so close to sandblasting that people can't tell the difference. Doesn't matter what power or speed or DPI settings either, although I do need ENOUGH power obviously. Once I'm in the power range, not much else matters. It's near perfect...

The 35w Synrad Explorer has no photo mode, but it does have a nearly endless variety of halftone, dithering and dot-by-dot settings. I spent 4 hours one day running thru all the various bitmap and halftone settings, using varying %'s of blacks and colors, at different speeds, powers, DPI's... Not once did I get anywhere close to 'sandblasted'. Way too much fracturing, even when it's obvious watching the beam hit the glass that the laser is spacing the dots correctly.

Two very similar lasers, completely different results. I have no clue as to why.

Then there's the Triumph, 80w glass laser. No pun intended ;)... Now, if I have thick enough glass, crank up the power and it'll melt the glass as it engraves it, and the results are stunning. But try that with anything less than 1/2" thick glass and I get shattered glass. All attempts at 'normal' engraving glass results in way too much fracturing. But- since I have no rotary for the Triumph and I rarely if ever engraving flat glass or mirrors, I haven't taken much time to better tune it for glass.

So, I'm one for three, even though I should be TWO for three. The Explorer SHOULD engrave close to the same, but it doesn't. One of these days soon I'm going to MacGuiver in the lens from the LS900 and see if it's all optic-related. Should be interesting. Just need to do it...

So then, all that said, how do I get good photo engraving on glass? BSSSZZZTTT.... I don't. Can't figure that out either. My LS900 won me a GoPro on this very board having engraved this extremely detailed photo I took of my basement shop, engraved onto NON-laserable black Rowmark no less...

345190 (if anyone cares, this is a link to the full-size pic. Hey, it still amazes me my laser did this!) http://www.engraver1.com/pictures/TheAbyss.jpg

Yet- I can't figure out how to engrave a simple face onto a piece of glass. No matter what I do, it doesn't work. Doesn't look right. If I engrave a negative of the same image, it still doesn't look right. I can't seem to get the shading or contrast right. A face ends up looking like a white silhouette with holes.

SO, all I can say is good luck, and if you do stumble on to the magic settings, please let us know! :)

Joseph Shawa
10-04-2016, 10:19 PM
Well, a good start.

I have a hand held microetcher as they are called. I wouldn't operate it anywhere near any machinery. That said, I wonder how well some kind of stencil would work.

Thank you!

Joseph Shawa
10-04-2016, 10:23 PM
Wow, I feel validated and hopeless in the same instant.

Well, I sure as heck will share everything I learn.

Thank you!

Seann Fordham
10-05-2016, 5:12 AM
I used to engrave lots of glass on an old universal v460 and used to engrave all our photo's with the help of photograve, but could never get glass to engrave photo's really well at all. We sandblast our glassware, but that doesn't do well with photo's (all the fine detail will get blown out).

Since getting a Trotec I've had to experiment with settings alot, and figured out that putting masking tape or sandblasters tape onto the glass prior to engraving will prevent that inconsistency and bits of flaky glass you can get when engraving glass normally and it also reduces the dot size on the glass a bit. I run glass photo engraving at 250dpi, 100% power and roughly 20% speed with a 2.5" lens, usually messing around with contrast and sharpening the photo considerably in corel draw makes a big difference in how the photo turns out (and a bit of experimenting on scraps).

Although I do all my photo engraving using the photo optimised mode in the driver (including the photo's attached), so I'm not sure how well this will work for others.

1st photo is a mirror (enlarged the photo so is a bit blurry), 2nd photo is a crystal award.

Ian Stewart-Koster
10-05-2016, 6:16 AM
I wish...

I fiddled with numerous settings - editing the photos in Photoshop, as well as Corel Photopaint, and rerunning it...

I did find a few hints on various websites re lasering photos on glass: keep proper halftones for fine substrates than can hold the dot (similar principle to screen printing ), and use a diffusion dither (not halftones) for substrates like glass, that can NOT hold a fine dot.

For editing images to laser on glass:
IN Photoshop, resize to actual size wanted, and 250-300 ppi.
Convert to greyscale, bump up the contrast a bit, then apply Unsharp mask at 500%, and 5 to 8 pixels.
Rerun unsharp mask at 150% and 2 pixels. remove background you don't want.
Then invert (make negative) and convert to Bitmap - or save as a jpg and do the converting with a diffusion dither in Corel, and invert it in Corel if you wish.

Run it via the laser in a pulses per inch proportional to the pixels per inch photo resolution - eg 250/500/750, not nay inbetween figures like 600, or 400, for instance...

However, I'm not yet content with any results - friends & family are happy - I am not!
I thought maybe you could download a trial of Photograv, but no luck.
I tried to download a trial of 1-touch-laser-photo, but it would not install or run due to a different windows dot net older file required.

So like you, it's back to the drawing board... but the wet paper idea does produce a sharper image on glass... :)

Joseph Shawa
10-05-2016, 8:48 AM
The white background on the award actually might be a great way of getting that needed contrast. Nice work.

Joseph Shawa
10-05-2016, 8:51 AM
Thank you for all of that. I will get to work and report back.

Ross Moshinsky
10-05-2016, 12:36 PM
Putting photos on glass should be a PREMIUM service. It's one of the more difficult things to do well in engraving. It shouldn't be a give-a-way or a gimmick. You're devaluing the market, devaluing yourself, and devaluing the industry.

If someone wants me to put a photo on glass, I'd first try to talk them into using acrylic as the results are better. If for some reason they won't, I absolutely charge them a premium for the service. This covers me editing and processing their photo and testing it at least once on a flat pane glass to make sure it's acceptable. I'd also charge extra because it's on a round vs on a flat which is a slower process and results in more headaches.

If you're giving something away, it should be to your benefit. That means it should be a glass with YOUR logo on it. I think you're going about this idea completely wrong.

Joseph Shawa
10-05-2016, 4:48 PM
LLLLOVE that shop!!! Great pic and engraving too!

Joseph Shawa
10-05-2016, 4:50 PM
I would have to agree but add that until I know what the heck I am doing and can assure a result I do actually give my time away BUT with no promises.
Once I get this down- and I plan to- then I can charge as needed. BTW, how do you know I am doing this for nothing? I don't think I mentioned my price. Have you been talking to my wife? It's for her party : )

David Somers
10-05-2016, 9:57 PM
Joseph!

In that case....double the price!!! What the heck. It is all in the family! <grin>

Joseph Shawa
10-07-2016, 1:17 PM
So I am trying to figure out the abilities of my engraver and have this question.

If I import a solid black square and set the scan gap then I know what vertical spacing will be.
How do I know what the horizontal spacing is between dots. Is this a setting that I can adjust with PWM in settings? (LaserCut)
Does it vary with speed setting? i.e. do the dots just get further apart when the head moves faster? Can't see that being the case...Or, I should say, I cannot imagine the laser not firing fast enough to be able to separate the dots even at speed=500....but I haven't tried or done the math.