Engraving Champagne Flutes

[Liesl Dexheimer]

A couple of months ago I laser engraved 2 champagne flutes. I noticed when I took them out, the text looked somewhat stretched. I wasn't sure if this occurred do to the shape of the glass or if it was because it was cheap glass. I made sure the glass was level in my rotary attachment. I'm also wondering if it somehow slipped without me noticing. Has anyone had any problems like this? Can you successfully laser engrave champagne flutes?

[Martin Boekers]

I have done quite a few flutes and most come out ok. I use a Libby Cobalt Blue glass which is nice.
I usually don't have the image come out streched, if anything it's compressed.

I have never had consistant resulst with a rotary device. One big issue it never returns to the same spot
if I decide it needs a second pass. It seems after all these years this product would be improved upon.

[David Fairfield]

The stretchy text is often the result of the geometry of the glass surface, or the glass configuration working against your graphic. I'm sure there is a mathmatical principle to explain it all, but the way I look at it is this-- your glass is a fun house mirror and your graphic must be distorted to look normal in the mirror. Not being mathmatically inclined, I use a trial and error process. A few glasses get wasted this way, which limits what sort of jobs I can accept. I never do antique glasses, or pricey crystal for example. And some glasses are not perfectly round from the factory and those give me so many rejects, I'm careful to catalog which glasses I can use, and which I can't.

Physical slippage in the glass usually results in compression, as the object doesn't turn with the wheels, its more likely to turn slower, than faster than the drive wheels. Although either is possible. Also if your drive wheel is rotating a wide base, and your flute is narrow, for example, that will throw off the graphic, too.

I agree with Martin. The laser rotary tool is a very imperfect design, due to inherent wobble slip and play, results are always iffy. I don't really understand why they can't make something that works like a lathe, to hold things precisely without slip.

Dave

[Joe Hillmann]

I agree with Martin. The laser rotary tool is a very imperfect design, due to inherent wobble slip and play, results are always iffy. I don't really understand why they can't make something that works like a lathe, to hold things precisely without slip.

Dave

The rotary that universal makes clamps the piece in nice and tight and you don't have to worry about the base being larger than the area you are engraving and it always goes back to 0 within 1/10 of a degree so you can run the same part multipul times if necessary, but it limits the size of what you can do with it so I often end up wishing I had one that is similar to to what epilog sells.

[Real Mercier]

Engraving glasses is a little bit more involved than flat pieces. I did a quick search and came up with this thread that may help. Start here.
http://www.sawmillcreek.org/showthread.php?111973-Epilog-Rotorary-conundrum/page2&p=1130447&highlight=Rotary+sizer

Also, you don't say which machine you have.

I hope that helps.
Real Mercier

[Mike Null]

All of the answers could be part or all of your problem but David's answer is the one I'd check first. A tapered object will always distort type and you can correct for that in Corel by using the envelope tool.

[Riki Potter]

I've had this problem when the setting for the rotary attachment are off, specifically the diameter. For our rotary attachment in the driver options under Paper you can select rotary attachment and the input the diameter of the glass your doing, if it's to big it will compress the text, to small and it will stretch it. I believe it essentially uses the diameter to figure out how far to turn the object on each step to keep it in proportion.
From what I've heard our rotary attachment functions a bit differently from the bigger brands, but this issue exists both on our laser and our diamond needle gravograph machine so it's something to look for.

[Martin Boekers]

That's interesting..... What if the base is a smaller diameter than the bowl size?
Effectively each diameter is turning at a different rate. One other issue with some
glasses the stems may not be perpendicular with the base which will cause it to
not be a circular rotation.

[David Fairfield]

I'm actually not sure about the base vs bowl size, now that I think of it. The glass is tilted in the rotary, so the face is horizontal, and the entire glass is turning at a constant rate, so umm, I'm confusing myself... :o But nevertheless, the trial and error process of warping the graphic to provide the results you want, will compensate for whatever is going on with the geometry.

Dave

[Real Mercier]

The math is actually pretty simple. Let's see if I can explain it. For example, let's say our glass is a tapered glass with a 3" opening at the top and a 2" bottom. What we need is the circumferences of the top and the bottom of where we want the graphic. To keep it simple let's use the whole height of the glass. The circumference is calculated using the formula pi * diameter (pi = 3.14). So for the top we have a circumference of 3.14 * 3" = 9.42", and for the bottom we have 3.14 * 2" = 6.28".

Now let's say we want our graphic to 1/4 of the diameter of the glass. regardless of the rotary type, the glass will turn 1/4 the circumference. For the top this will 2.36" (9.42" * 1/4), and for the bottom will be 1.57" (6.25" * 1/4). So you can see the graphic will be smaller at the bottom.

The compensation is a little trickier to explain, but I have written an Excel spreadsheet that does that for you. If you input all your dimension on the input side, it will tell you the dimensions of the distortion needed. Unfortunately the file is just over the file size limit for attachments. If you PM me I will try to send it to those who want it.

Real Mercier

[Dan Hintz]

Or you could use the simple math explanation I gave in the thread linked above ;)



Riki,

Ideally, you'd always have the largest diameter side being on the "Driven" end (the one attached to the stepper motor, assuming the other end is free-spinning) of the rotary. This isn't always possible. Either way, the sheet size should be set to the largest diameter and work from there.

[Martin Boekers]

214471
I'm actually not sure about the base vs bowl size, now that I think of it. The glass is tilted in the rotary, so the face is horizontal, and the entire glass is turning at a constant rate, so umm, I'm confusing myself... :o But nevertheless, the trial and error process of warping the graphic to provide the results you want, will compensate for whatever is going on with the geometry.

Dave

David I drew a quick sketch (I love the virtual segment tool! worth the admission price to X5 alone!)

If the bowl is 4" in Diameter and the base is 2" in Diameter each bowl travels 4" in the the space of 2"
that the base turns. So if I layout the text to the bowl size but the base turns at twice the rate. So it will
change the text dimension.

Think of it in terms of a bicycle gear system, when you change the gearing you change how many revolutions
you need to peddle to turn the wheel one revolution.

Hope this makes sense.

One more thing, when we are doing the layout it is in 2 dimensions, when we engrave it is in 3 dimensions.
What is flat that we design will now be curved. In affect if you look at it head on it will be visibly compressed
on the sides as they are now curving around and inflated in the middle as that is "ballooned" outward.

Now I know I have you confused!:confused:

[Liesl Dexheimer]

All very interesting explanations / observations. It almost makes me not want to engrave champagne flutes at all. I have more success with Libbey wine glasses and basic drinkware. I had a customer come in the other day with champagne flutes which I told her I could probably engrave. I'm hoping she doesn't decide to have them engraved though, (they are Lennox), don't want to mess those up. Not to mention she was mildly complaining @ having to pay $15.00 a piece (x2 pieces) for me to engrave them. Here's hoping she goes somewhere else or doesn't have them engraved at all. I love it when customers buy something expensive and then don't want to pay much for the service of having them engraved.

[David Fairfield]

Liesl, if you have the tool, might as well try to make it earn its keep. Libbey glasses are good, they seem to be made in a press that gives them symmetry. I get them by the case, need not worry about rejects, because they are inexpensive and plentiful. If a customer wants me to engrave their own glasses, I explain the issue of rejects and send them a photo of a comparible glass that might work. I'm sure the excell sheet would help mathmatically inclined people. I'm visually inclined so warping the graphic has become second nature, I can usually get the graphic correct within three tries. Sometimes the glass slips when doing the test shots, then its easy to screw up the graphic by accidentally compensating for slip, which doesn't repeat the next time you test the graphic and leaves you wondering what the heck?? :confused:

[Riki Potter]

Is the any particular reason to have the large end on the driven end? This is the way I normally put them in but I wouldn't think it would make a difference.

When you say the sheet size should be the largest diameter do you mean the largest diameter of the object or of the area your engraving? I measure around the area I'm engraving to get the most accurate read on it, but maybe I'm not totally understanding how the rotary attachments work.

[Adrian Hernandez]

If you own a chinese laser machine rabitlaser.com has tutorials and instructions on how to setup the rotary attachment.

I hope this will help you