Tag Archives: laser mistakes

112: Three-Ply Acrylic

It’s kind of amazing that it’s taken me this long to get to this project; when 52 Lasers was first conceived, using three-ply acrylic was on the first draft of our potential projects list. Now, more than two and a half years later, I finally have a project that requires this unique material!

Rowmark's convenient visual representation.
Rowmark’s convenient visual representation.

Three-ply acrylic is similar to the two-ply acrylic I use very often, except the thin cap layer is applied to both sides of the main acrylic substrate. While most of the badges, magnets, and other pieces I make only need one side to be engraved, certain items like medallions or coins might need both sides engraved, and this is when you’d use a three-ply option. This month’s project is a great example.

 

A bunch of SCA tokens celebrating an elevation.
A bunch of SCA tokens celebrating an elevation.

A couple of dear friends of ours are part of a group called the Society for Creative Anachronism. While I’d like to explain what that is for you, I couldn’t possibly do better than the SCA’s excellent portal for curious newcomers. Dave got in touch and explained that his husband Jim was going to be recognized for his accomplishments in the Society, in a ceremony called an elevation. For the event, they wanted to distribute small tokens, in SCA appropriate colors, featuring Jim’s moniker in Chinese (凱曾, Kai Tseng) and the triple rapier logo of the Order of the Masters of Defense. I’ve always used wood for tokens that need both sides engraved up to this point, but it was far easier to get the colors Dave and Jim wanted by using the three-ply LaserMax acrylic from Rowmark.

When you’re engraving two-ply material, you don’t really have to worry too much about the back face; people aren’t going to be scrutinizing a blank back surface, so imperfections caused by the manufacturing process aren’t a big deal. That’s why two-ply materials only ship with mask on the front surface. Three-ply material has mask on both cap layers, and while you want to remove the mask from the side you’re engraving first, you definitely want to leave the mask on the bottom side. That’s because those vector cutting scars—plastic residue, honeycomb table impressions—are going to damage that side if you don’t. It’s okay to engrave the reverse side with the original side unmasked because you won’t be doing any high power vector cutting in that final step; it’s just surface engraving, which doesn’t cause those kinds of issues.

Red tokens placed upside down in the makeshift jig.
Red tokens placed upside down in the makeshift jig.

Conveniently enough, just cutting the shapes out in the first pass automatically creates a makeshift jig—or template—out of the leftover material. As long as you send the second half of the engraving data in the same exact positions as the first, all you have to do is flip the shape over and engrave again. Now, this requires a symmetrical shape, or else you’ll have to take flipping into consideration and cut extra pieces out of the material that will form the jig. You also want to remember to take the mask off of the flipped token’s new front side before engraving; firing the laser through that thin plastic layer will usually create a sticky mess.

With all of that in mind, it’s fairly simple to process three-ply material in a clean manner. You’ll still have to wipe down the edges with a light alcohol or a solvent similar to Goo Gone, but that’s usually the case with two-or-more-ply acrylics anyway. For how simple the whole process is, I still managed to muck things up, and I lost a whole set of twenty yellow tokens on the first pass due to a technical issue with the laser that I still haven’t figured out.

Unexpected markings ruined a whole batch of tokens.
Unexpected markings ruined a whole batch of tokens.

Once in a while, when raster engraving, the field I’m engraving will be speckled with tiny additional engraved dots. I can never predict when it happens, and just rebooting the system fixes it, but it always loses me a piece or two.

Token stacks.
Token stacks.

I also noticed with this project that my laser alignment isn’t perfectly perpendicular to the engraving surface currently; if you look a the picture of the token stacks above, you’ll notice the slight skew in the 1/8″ thickness of the tokens. I think this is due to a misaligned mirror #3, but it’s difficult to know for sure and I might end up having to replace the mirror #3 assembly with a factory-calibrated one.

If any of you have any tips for cleaning the laser-cut edges of a two-or-three-ply piece, any ideas on what might cause the rare engraving field speckling, or any suggestions on how to realign the beam path across the surface, let me know in the comments below!

21: Laser Etched Bricks

There are a number of important buildings in town slated for the chopping block and it’s not uncommon for people to ask for a brick to remember it by.  In chatting with some long time Aurorans, they have saved bricks over the years, but when they aren’t properly marked, it’s hard to remember which brick went to which building!

I’ve seen fundraisers where people sponsor bricks for walk ways, and their names are stamped or etched into them.  It can be a great fundraiser if you have the space to display them.  These types of projects are done with new brick, though, not old.  What could we do with brick that we’ve saved?

Enter: the laser.  Let’s see what happens when applied to bricks!

Brick and not brick etching side by side.
Paver and brick etching side by side.

I had two sample bricks – one is a paving brick that you could buy at any hardware store, and the second was from the old Aurora Train Station on South Broadway, which was torn down last year.   I really did mean for the tester to be done first, because it didn’t have historical value, but the “good” brick from the train station got etched first, whoops!  It worked out in our favor and I learned something new about paver bricks.

Coffeyville stamp
Brick from the old Aurora Train station.  The Coffeyville stamp is on top.

The Aurora Train Station was built in 1922, and all the bricks were stamped with the manufacturer’s name – “Coffeyville VB&T CO.”  During the early 20th century, Coffeyville, Kansas was one of the largest glass and brick manufacturing centers in the nation, and the Coffeyville Vitrified Brick and Tile Company made bricks from 1894-1930.  We didn’t want to mess with that bit of history, so we etched it along the edge, which would still be visible if displayed flat.  Because brick is a tough material, we etched the material heavily.  Raster power was set at 100%, and raster speed at 40%.

This is halfway through the second pass - the top is still light.
This is halfway through the second pass – the top is still light.

Interestingly, the laser didn’t so much etch the brick, but rather, it seemed to melt.  The result was a fantastic and unexpected glossy black color.  The wording wasn’t as pronounced as we liked after the first pass, so we did a second pass,  this time 100% power, 10% speed.  This really gave the brick the deep dark shiny black we were looking for.

The first one turned out so beautifully, that I almost didn’t do the paver – we proved it worked, right?  And the tester brick’s design was not nearly as well designed – I just put a bunch of typical fonts and some images to test out the capabilities.  So it wasn’t going to be pretty or saved for perpetuity.    Since I thought it would be a short post, we threw it in anyway.  This is  when I learned there is a difference between bricks, pavers, and “brick pavers.”

Concrete paver brick
Paver brick

The second etch was not looking the same at all.  Instead of black, the etch was turning whiter.  Thinking that bricks from a wall and bricks made for paving might have different glazes or treatments, I went to Google for the answer.  What I learned: Bricks are made of clay.  Pavers can be made of clay…but are more often concrete that’s been colored to look like clay.  The name “brick pavers” refers to the shape of the paver, not what it’s composed of.  So our paver brick?  Concrete.

I DO NOT RECOMMEND PUTTING CONCRETE IN YOUR LASER CUTTER.

As Wikipedia so much more gracefully says it, “Concrete is a composite material composed of water, coarse granular material (the fine and coarse aggregate or filler) embedded in a hard matrix of material (the cement or binder) that fills the space among the aggregate particles and glues them together.[2]”  We used the same settings as the second pass on the brick – 100% power, 10% speed.  Luckily the concrete DID etch, though it did make brighter sparks than other materials.  There didn’t seem to be any smell associated with it, either, so it was probably safe to be in the office with it. What we didn’t notice until the etch was done was the fine white concrete dust that got everywhere.  We have a more than adequate exhaust system, but there was enough dust that it damaged the lens.  The lens is what focuses your laser for cutting – scratches are no good.  Subsequent testing and cleaning shows the lens still does it’s job even with the light scratches around the edge, but it has now moved to the top of the replacement parts list.  That price tag is $300, ouch.  Do your research kids!

the halftone of the happy fire flower is sort of visible...if you look just right.
The halftone of the happy Fire Flower is sort of visible…if you look just right.

Under the laser, the different parts of the mixture act differently – some specks of black and white are mixed in with the gray. The result was not amazing. I think it would have been more successful if the concrete paver had been more colorful, or even painted.  Half tones didn’t really work as you can see from the fire flower, and the text is subtle.  I had the brief thought of trying Rub ‘n’ Buff on it, but the materials is all pretty coarse – it would be impossible to rub the excess off.  Either way, we will not being doing that again.

In the end, you got a “two-fer” – first time etching brick, first (and last) time etching concrete.  Looking at the paver now, of course it’s recognizable as concrete.  I feel a little silly for not realizing it from the get-go.  It was a mess, with so-so results.  Etching the brick, though, was a resounding success!

Check out that awesome gloss!

Check out that awesome gloss!