Tag Archives: laser engraving

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!

60: Tech Engraving

The notebook before we put it under the laser.
The notebook before we put it under the laser.

My first tech engraving experiment was quite a few years ago, when Brenn asked me to engrave his new Macbook with a geometric pattern.  It turned out great, but I haven’t really had the opportunity to carve things into technology since.  That’s why I was thrilled when a local friend, Reddy, asked me if I could laser engrave an illustration into his own Macbook.

Brenn's LaptopWhile Brenn’s design from a few years ago was dense, complicated, and meant to hide cosmetic damage on the lid of the laptop (which it wasn’t that successful at) the finished illustration for Reddy’s laptop was a clean line drawing that left much of the lid clear. This was a huge relief as the macbook measurements had changed and I was hoping to avoid having to design tightly around the apple at the center again.

The way light reacts to the engraved areas makes it difficult to photograph.
The way light reacts to the engraved areas makes it difficult to photograph.

The actual process of engraving the aluminum surface is interesting because it doesn’t matter how much power I fire at it (up to my maximum forty watts), it will only lightly mark the surface. Running a finger along the surface after the engraving is done and you can hardly feel the lines. Even more interesting is how light reacts: the engraved portions of the surface will either appear darker or lighter than the untouched surface  depending on the angle of the light source you’re near.

The engraving is so light that you can barely feel it.
The engraving is so light that you can barely feel it.

The tech engraving I’ve done so far has been raster engraving; I wonder if vector line patterns would engrave any differently. Conveniently, another local friend—Mark—has dropped off several left-over pieces of various Apple products for me to test engrave, so I have some more experimenting to do!