Using a laser to mark wax coated drink cups - Page 1
Forum section: electronics / projects

author: rcourtney
author_rank: Contributor
timestamp: November 24, 2016, 03:59:51 am
content: Anyone have experience selecting a laser that can mark a drink cup?Can't change the integrity of the cup. (Can't make it leak)Can't contaminate the contents when filled. (Can't burn the paper)Must be machine readable from inside. (Think QR codes)

author: rcourtney
author_rank: Contributor
timestamp: November 24, 2016, 11:55:21 am
content: Interesting paper on control of the beam density.Forgot to mention how cups are made. Paper spools are first coated with a layer of wax.The product logo that can be any color is offset printed using a vegetable based dye.This is where we initially plan to mark the cup.The paper is then cut, formed and heat sealed.A final wax coating is applied to ensure the seals will not leak and to protect the printedimage.Reading reflectivity from the inside surface shouldn't be hindered from the color of the dyeon the outer surface.

author: Seekonk
author_rank: Super Contributor
timestamp: November 24, 2016, 12:11:38 pm
content: Can't contaminate the contents when filled. (Can't burn the paper)I was involved in building a machine that filled peanut butter jars, the lid seal. In production the aluminum seal is attached to the lid paper with wax. We had complex induction coils to heat the lid to separate it from the paper and seal it to the jar. This was a larger lid than had ever been done before. The trick was to seal it without getting the smell of burnt wax when the customer opened it for the first time. It might be a problem with how soon the cups are stacked.

author: rcourtney
author_rank: Contributor
timestamp: November 24, 2016, 01:56:20 pm
content: Neither the paper or the wax can be burned. Modification of the wax's optical property is.an ideal goal.Visible printing on the inside of a cup will freak out customers.

author: PointyOintment
author_rank: Frequent Contributor
timestamp: November 24, 2016, 04:54:45 pm
content: Quote from: rcourtney on November 24, 2016, 01:56:20 pmSo print using invisible ink, perhaps infrared or ultraviolet ink, and use the appropriate camera to read it. Or print some attractive pattern or design incorporating/disguising your data on the inside of the cup.

author: calexanian
author_rank: Super Contributor
timestamp: November 26, 2016, 07:41:35 am
content: Does it have to be a laser? How about some kind of ink jet printer the cup is held up to or some kind of automatic stamp, sticker, Or embossing of some kind.

author: SeanB
author_rank: Super Contributor
timestamp: November 26, 2016, 08:19:43 am
content: Use a continuous inkjet printer and UV visible ink. White in normal light, so invisible against paper, and the solvent will embed it in the wax. There are food safe versions available.Look at Linx printers, either new or used, and see what you find there. They will handle the printing on the moving paper spool, and are designed to do this kind of print with only a tacho signal of some sort, or a known speed line and a trigger pulse. Will be expensive, but will typically last a decade or more, and you only need to have a service kit installed every so often, and keep a good stock of the solvent on hand for refill, as you typically almost never use ink between services, unless you are running 24/7 printing a solid stream of characters onto the substrate.Still trying to get a scrapped one from the service guys ( or a dead print head) to tear down, but they are just too reliable, and so easy to repair when something dies. You have to be in the hundreds of millions of metres of print before something wears out.

author: LaserSteve
author_rank: Super Contributor
timestamp: November 26, 2016, 01:17:36 pm
content: My former employer will be glad to sell you a femtosecond laser with a high pulse rate to scribe the wax. It ablates rather then burns. You'll get opaque grey patches, if I guess right. When you don't burn or char, the only thing you get is opacity, diffraction, or a sort of grey /white color, you go from gloss to flat in something like wax.How to do the marking optics is up to you.Laser starts at 56K $ USD.Commercial "on the fly" bar code markers for paper use arrays of small carbon dioxide lasers. You wont taste the burn. Surface is brown or carbon black depending if power and pulse width is set to "like" or"love".Steve