Tag Archives: red

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!

74: Rotary Fixture

Last weekend, I snuck a piece of hardware out of Eagle Engraving, Inc. while there was a lull in production. The hardware in question? A rotary fixture for our laser that allows us to engrave on cylindrical objects! I’d like to say they didn’t notice at all, but in reality they were totally cool with it and their resident laser ninja Monica even helped make sure that I had all the parts needed. Thanks again, Eagle!

The rotary fixture, slightly askew to account for the glassware's edge.
The rotary fixture, slightly askew to account for the glassware’s edge.

After installation and calibration, I first ran several tests on a piece of glassware that had sloping edges. Because the engraved surface of the material still has to remain parallel to the path of the laser carriage, I needed to use some shims to raise one side of the rotary fixture until the glassware’s surface lined up with the system.

Several engraving tests on one glass show off how images can be warped by bad diameter settings.
Several engraving tests on one glass show off how images can be warped by bad diameter settings.

The first several engravings helped me determine how important the diameter measurement of the glassware is.  Early on I was imprecise, which resulted in the round “Made in Aurora” logo used for the test appear as an oval.  3.0″ felt like a nice round number, but the glassware’s actual diameter at the center point where I wanted to engrave was actually 2.96″.  That kind of precision was required to prevent image distortion.

A close-up of the Planet Express glass.
A close-up of the Planet Express glass.

I used transfer paper to soften the engraving—several of my previous experiments with glassware showed that glass has a tendency to chip during engraving and create a harsher surface than necessary.  The transfer paper, while troublesome to remove, provided a filter that resulted in a smoother engraving, as visible in the difference between the Planet Express glass and the Shield glass.

A close-up of the Shield glass.
A close-up of the Shield glass.

The final piece we engraved was a red ceramic mug provided by Eagle for testing—it’s pictured in the featured image above, sporting a Hydra logo.  It was much easier to engrave thanks to a consistent diameter across the entire surface of the mug, unlike the glassware.

While Jennifer and I picked up a handful of cylindrical objects to engrave, we were only able to engrave cups and glassware due to an unforeseen lack of hardware: the rotary fixture includes one internal cone that holds the bottom surface of the cup and one external cone that fits inside the open top of said cup. You can use two internal cones to hold shapes that don’t have open tops (like the drum sticks I wanted to engrave!) but we didn’t have those handy.

Three round logos done right!
Three round logos done right!

While I’ve had to return the rotary fixture to Eagle since then, I do look forward to “stealing” it again in the future and, possibly, owning my own down the road.