All posts by Ryan

likes lasers, geometric design, typography, and video games

115: Rounded Edges

One of the first limitations of laser engraving I learned about was the right angle. On most (if not all? let me know!) laser engravers, the laser can only fire in one direction: straight down, perpendicular to the surface plane. This means that you can’t easily get beveled edges, rounded corners, or other nice depth effects you can get using a rotary engraving system like a CNC mill.

There are ways around this limitation, of course: a patron I spoke to at the Aurora Public Library‘s Makerspace suggested rigging smaller pieces of material at their own angles, allowing the laser to fire directly down at a skewed surface, creating the angled edge desired. I considered this process, but it only works if you are cutting a single straight line—any shift in the direction will pull the head out of focus with the section of material you’re cutting.

Focus matters, though, as I found out several months ago while cutting some badges for an event. I accidentally left the laser bed way out of focus when cutting one of these badges, and you can see how the laser didn’t cut through, and instead just created a rounded channel in the surface of the material, in the shape of the badge I’d intended to cut. It made me realize I could cut a shape normally, and then cut it again out of focus, to give the edge a soft curve.

The mistake that taught me how to round corners via unfocused engraving.
The mistake that taught me how to round corners via unfocused engraving.

So this month, I got around to testing that some more! I opted for some snowflake designs (sourced from freepik.com; thank you!) to give me plenty of edges to smooth and for general holiday goodness. The first step is to cut the piece normally, which results in the traditional sharp 90 degree edges you see in most lasered pieces.

Sharp 90 degree edges, standard for laser cutting.
Sharp 90 degree edges, standard for laser cutting.

Leave the leftover material in the laser bed, and do your absolute best not to disrupt its place. In fact, I suggest not touching the piece at all at this point and just telling the laser to fire again with new settings. Specifically, I threw the laser out of focus by telling it I was engraving on a 1.125″ thick material rather than a .125″ thick material. I’ve experimented with different unfocused settings, and can probably dial that in a little better, but 1″ is a nice easy number to get a decently rounded corner on a 2″ lens. I also sped up the laser a little bit because I didn’t want to overpower the edges when rounding them (while my speed settings won’t match yours exactly for a multitude of reasons, I cut the snowflake at 5.5% speed and then rounded the edges at 15% speed.)

The top side is now rounded; it's an imperfect process and looks a little rough up close.
The top side is now rounded; it’s an imperfect process and looks a little rough up close.

Since the rounding only happens on one side, you’ll have to flip the piece and round the edges again if you want to give both surfaces the same treatment. This is only possible if your piece has an axis of symmetry, and this is where you have to be very careful not to move your temporary jig. Once you’re done, you might have to clean the piece as firing a laser out of focus can produce a fair bit more detritus than firing it in focus.

Make sure to clean your honeycomb first, and wipe down any residue between each step. Oh, and use a clean cloth! Trust me!
Make sure to clean your honeycomb first, and wipe down any residue between each step. Oh, and use a clean cloth! Trust me!

As it turns out, even if you don’t move the makeshift jig at all, your second pass might be slightly out of alignment to the first. Why is this? Kerf—the width of the laser—means that your freshly cut snowflake might shift a fraction of a millimeter inside the jig. There’s a tiny, tiny little bit of give and it can sometimes be enough that the alignment is visually off. You can solve this by rounding one side before cutting, but you’ll still have to contend with this on the back half, and kerf didn’t affect my alignment nearly as much as another issue:

Much more alarmingly, I discovered while doing this project that pulling my laser out of focus by about an inch noticeably moves the laser’s aim. It’s not enough to ruin the project, but it is enough that I had to correct for it after several prototypes to get a nice even rounding. This aim issue as the laser focus changes is due to incorrectly calibrated mirrors somewhere along the laser’s path (totally my fault, as I foolishly adjusted them once upon a time and have been tweaking them here and there ever since) so if your mirrors are factory aligned like they should be you shouldn’t run into this issue.

Even if you don't move the piece at all between steps, kerf or poorly calibrated mirrors might cause your rounded edges to be misaligned.
Even if you don’t move the piece at all between steps, kerf or poorly calibrated mirrors might cause your rounded edges to be misaligned.

In the end, the rounded edges are a little rough looking, but if you get your settings dialed in (or would it be dialed out in this case?) you can get a nice smoothed edge that will catch light in a novel way for a laser cut item. I used opaque and translucent acrylic for this project, but I know this effect would look great in transparent and fluorescent acrylic as well. I can’t imagine it working as well with natural materials or microsurfaced plastic, but maybe I should experiment with that in the future!

If you have any unfocused laser tricks, or tips for keeping materials clean while processing pieces in multiple steps, let us know in the comments below! Happy holidays!

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!

111: Bottlecap Sign

The full bottle cap holder. Read on to find out how it was made!
The full bottle cap holder. Read on to find out how it was made!

It wasn’t all that long ago that the craft beer explosion happened, but it’s hard to think back to when beer—at least in my life—was a choice between Budweiser and Miller products. While I’m sure there’s debate aplenty about the community that formed around craft beer, you can’t dismiss all of the awesome artwork that community has produced. One of the best design ideas I’ve seen spreading around the Internet has been beer cap holders. They come in many sizes and shapes—usually states and countries—and are an artistic way to keep track of which craft breweries you’ve sampled fizzy drinks from.

The fact that most of these holders were laser cut was only part of the reason for my interest; many of the examples I saw had different amounts of studs to grip the bottle caps, and I wondered which one was the best solution. Sure, I could’ve done the research and stopped there, but that’s not nearly as much fun. A bottle cap holder I would make!

A stack of prototypes, some with six studs and some frightfully too small.
A stack of prototypes, some with six studs and some frightfully too small.

In my research, I learned that most pop caps (and the twist caps based on their design) have 21 teeth. Despite this, my first few prototypes had six studs. Once I realized they didn’t fit very well on the teeth of the caps I redesigned to include seven evenly distributed studs. I also experimented with stud design, settling on trapezoids after rectangles were too tight and triangles were just a little too loose. This mission to match the studs with the cap teeth would eventually cause me an issue: Goose Island’s caps have 27 teeth! Every other cap I had was only 21. While some size variance made some caps tighter and some caps looser, only Goose Island had to sit this one out. I hate geese anyway.

Bottle caps have feelings too. Look at how well the studs fit between the teeth!
Bottle caps have feelings too. Look at how well the studs fit between the teeth!

Once I had a single cap holder squared away, I spent an unreasonable amount of time trying to fit a grid of them into the word “beer”. I agonized over spacing, wanting to stick to some kind of grid without ending up with awkward, noticeable gaps. It wasn’t long before I realized I’d have to design my own letters based off of the grid rather than relying on otherwise well-made typefaces.

The initial design, with three caps per stroke. Way too big!
The initial design, with three caps per stroke. Way too big!
Another attempt, at a slightly more manageable size.
Another attempt, at a slightly more manageable size.
The final layout (apologies for how difficult it is to see!)
The final layout (apologies for how difficult it is to see!)

After a few attempts at grid-based letters that turned out far too large for the scope of this project, I ironically ended up back at a typeface: one I designed years ago based off of the bitmap version of Chicago present in Final Fantasy VI. Why not add a geeky touch? It also very easily solved the issue of making the letters fit on a grid due to its low resolution pixel quality.

Mounting holes and box joints.
Mounting holes and box joints.

Once I had the design complete, I whipped up a quick (and honestly lazy) box joint connection to hold two pieces together; the sign was very nearly three feet long and I couldn’t cut it out of one piece of oak ply. In hindsight, I should have engraved the sections of wood that held together each letter; they’re just a little too noticeable and wouldn’t be if darkened. I also inserted some small holes for screws that will eventually hold this a small distance from whatever wall it ends up on. A light sanding later and the finished piece was ready for caps!

Goose Island just had to have 27 teeth. Figures. Geese.
Goose Island just had to have 27 teeth. Figures. Geese.

…As it turns out, I don’t have many caps. I’ll fix that!

 

109: Edge-Lit Acrylic

I’ve been playing a lot lately with a new toy I picked up from Inventables: a powered LED strip for edge lighting acrylic. It’s made in particular to work in tandem with specially made acrylics that transmit light efficiently, but I’ve found it works really well with simpler transparent and fluorescent acrylics.

The first dual-layer design.
The first dual-layer design.

My first test was with transparent orange material sourced at the Aurora Public Library’s Makerspace—check it out if you’re local!—and it seemed appropriate to design a little sign for the space as the test. Because the LED strip is designed to snap to the edge of a 1/4″ piece of acrylic and I only had 1/8″ material available, I decided to split the design across two layers of acrylic. The front layer included all of the vector engraving and the back layer was just the main title text filled. The resulting look is striking, but using two transparent layers means you have to be extra careful not to let any fingerprints or dust get in between.

The short sign lit up easily.
The short sign lit up easily. Please ignore the Macbook!

Around the same time, I was working with a local artist to create some wall décor based on the classic Pac-Man maze. We agreed pretty quickly that the lit effect would look great and settled on some fluorescent blue acrylic. The first several tests confirmed that the two layer effect would be excellent; dividing the pellets, ghosts and other objects from the maze walls might not be very visible in the photography, but it’s a really neat trick when you’re examining the piece up close.

A small cross-section of the Pac-Man design in two layers.
A small cross-section of the Pac-Man design in two layers.

One concern I continue to have is whether a single LED strip will be able to illuminate the entire flourescent blue acrylic sheet—this piece is 16 inches tall, towering compared to the 4″ makerspace sign. A quick test on some scrap acrylic shows that the light visibly dims near the top, but I won’t be able to know for sure how the final piece will look until a last-minute shipment of materials arrives. Speaking of that, here’s a pro tip: don’t assume you’ve got all the materials you need until the day you’re scheduled to cut! Always check, even if it’s something you always keep in stock, like the black cast acrylic that was supposed to be the backing layer for the finished Pac-Man piece.

A later single layer test cut with rounded vector engraved maze walls.
A later single layer test cut with rounded vector engraved maze walls.

Edge lit acrylic is a great look, and I’m might have to investigate the “EndLighten” brand or similar substrates to maximize light transmission. I know I’m also going to be looking into portable equivalents; this hardware has to plug into a wall. I’m sure that’ll be a post in the future; until then, look forward to an update on this post with additional pictures of the finished Pac-Man piece!

This crazy square panorama shows how the lighting falls off near the top. We'll see how it looks in the finished piece!
This crazy square panorama shows how the lighting falls off near the top. We’ll see how it looks in the finished piece!