Map-engraved / heart-inlaid coasters

As a present for my wife this year, I made a set of heart-shaped coasters to commemorate key times/places in our past — where we met, were married, adopted pets and had kids. Each coaster has a map, a heart inset at the key location, and a description on the back. It was a fun project using a few techniques I thought others might find useful, so just a quick post to walk through it.

I used 1/4″ MDF with maple veneer but the engraving covers the full front of the coaster so you could really use any light-colored wood with minimal grain pattern (you kind of want a blank canvas). The heart insets are translucent red 1/8” acrylic, actually part of a pack I actually got for Valentine’s last year! I was worried that insetting the half-thickness acrylic into the coaster might be an awkward fit, but it worked great. The backs are 2mm adhesive cork that I use a lot for tabletop projects.

The Hearts

I started with a simple vector heart shape and scaled it to the target size of the coaster (4.5” square works for most mugs and glasses). I then scaled copies to three additional sizes:

  1. One inset 1/8” for the cork backing.
  2. A small one 1/2″ square for cutting the hole for the inlay.
  3. The small one outset .007” for the acrylic, which (when flipped over) made a snug fit into the hole.

I use Inkscape for most of my designs. Inset/outset from the “Path” menu is the freaking best feature ever — the only trick is that the size of each step is a global setting, so be sure to double-check under Edit / Preferences / Steps / “Inset/Outset by” to be sure it’s what you want. Seven thousandths of an inch is about perfect for the kerf I get on most 1/8” and 1/4″ wood and acrylic. I’m sure it varies a little but not enough to worry about. Remember to flip the insert over before pressing it in, which takes care of the every-so-slightly-conical cut you get from the laser.

The Maps

OpenStreetMap is a fantastic resource — community-produced and openly licensed, even for commercial distribution (attribution is required; see their guidelines for details). There are a bunch of ways to use the data; this is the process I finally worked out for my purposes:

  1. Navigate to the area you want to capture and zoom in/out as needed.
  2. Export the map as a PDF:
    1. Click the “share” button on the right side of the screen.
    1. Check the “Set custom dimensions” checkbox and select the desired area. Select more area than you need; it provides some wiggle room and we’ll clip it out later.
    1. Set the format to “PDF”.
    1. Play with the “Scale” setting to get a final image that works for you. I found it easiest to start with 1:5000 and adjust from there.
    1. Click Download.
  3. Open the PDF in Inkscape and make edits (remove landmarks, reposition street names, etc.) if needed.
  4. Paste your shape (in my case the 4.5” heart) and position it over the map.
  5. “Select All” and choose Object / Clip / Set to clip the map to your shape.
  6. Optional: I pasted in another copy of the 4.5” heart with a wide stroke, which made a nice outline.
  7. Under the File menu, choose “Export PNG Image”. Make sure “Drawing” is selected at the top and then export.
  8. Finally, open the new PNG file in Inkscape, add additional elements (i.e., the cut lines for the heart and inlay hole) and save as an SVG ready for the Glowforge.

All that work to massage the map into a bitmap (PNG) is worth it — the Glowforge handles the engraving super well.

Printing and Assembling

Printing requires three Glowforge runs, one for each material. For the wood, I used the “Thick Maple Plywood” settings and they worked great, engraving with Draft Photo / Convert to Dots with default settings except two passes instead of just one. The acrylic worked fine as “Medium Red Acrylic”. For the cork I configured “uncertified” material with a height of 2mm; engrave at speed 80 / power 10% and cut at 400 / 100%.

After pressing in the inlays, I poured on two coats of TableTop Epoxy, sanded off the drips, stuck on the cork backs, and that’s a wrap.

I really love working with the maps — such a neat way to personalize stuff. Hope folks will get some use out of the technique, and if you give it a try, let me know if I can help out. Kachow!

Rummikub on the Glowforge, a Journey

This summer our neighbors introduced Lara and me to Rummikub, which despite the weird name turns out to be a super-fun game played with a set of 106 tiles numbered 1-13 in four colors/suits plus two jokers. Tile games like this should be as nice to look at as they are to play — but our friends’ set is this awful 1990s sickly off-white plastic pile of junk, with jokers that looked like evil scary clowns. Ew. I set out to design something better on the Glowforge, sure I’d have it done in a few hours.

A few months later and I finally have something I’m mostly happy with. It’s not an incredible heirloom treasure — but it is nice and we’ll have a good time playing it. I learned a bunch of new techniques, and I suppose it’s healthy for the universe to put me in my place every once in awhile. Hopefully you’ll learn from my tribulations and make a set for your family, or at least enjoy a few laughs at my expense as you read along.

The Design

I chose to stick with the original tile size: 38mm high by 26.5mm wide. I could easily fit 6 rows of 13 tiles onto the bed of the Glowforge (about 280mm x 457mm working area), overflowing two rows of 13 and the two jokers onto a second piece, leaving a reasonable amount left over to recut any goofs. Measurements in hand, I set about creating the files in Inkscape. I eyeballed the radius for rounded corners and after looking at dozens and dozens of fonts went with … Arial Bold. Don’t judge.

The tiles are grouped into four colors, but in the original set each one just has the same circle under the number. I decided to represent each group with a symbol as well: circle, square, triangle and starburst (I can play endlessly with the corner count and spoke ratio of Inkscape’s “star and polygon” tool). Because I’m not a monster, I replaced the scary clown joker with a happy face (Wingdings character code 0x4A). Lastly, I added a Script MT Bold “N” for the back of the tiles. The “N” is for Nolan — I considered adding some form of our family crest but couldn’t find one I liked for the space. (New project: figure out how to draw a simple vector crest!)

For material, I used quarter-inch thick MDF board clad with cherry veneer on both sides. On my Glowforge Basic, I used 800 / 80 for engraving and 120 / Full for cutting. Feel free to use and alter these SVG files however you like:

Double-Sided Engraving

Engraving tiles on both sides presents an interesting challenge on the Glowforge; it’s tough to align designs precisely on a physical piece. Within a design, alignment is no problem — I can easily cut the tiles and center the numbers and shapes inside them. But getting the “N” engraved on the reverse side of already-cut pieces is a different story. The smaller the target piece, the harder it is to get exactly right; 106 individual tiles would be a nightmare!

This approach is the simplest and most effective I’ve found for the general alignment problem. But lucky for us, there is a super-cool trick that works for aligning front and back engravings for any shape that is symmetrical along its North-South axis — like our tiles! Details are in the link, but in brief it works like this:

  1. Create your design with the elements for both sides aligned as desired. In the rummikub SVGs, every tile has an “N” stacked right on top of the number and shape. Choose different colors for the front and back elements so that Glowforge groups them into distinct engraving steps.
  2. Fix the material to the Glowforge bed with tape or clips or whatever. This doesn’t have to be super-strong, but it should keep you from accidentally bumping the material once you’ve started. It’s really important that the material not move between steps!
  3. Upload the design and configure settings for the cuts and front-side engravings. Set the back-side elements to “Ignore” and run the print.
  4.  Open the lid, flip each cut piece to expose the back side, then place it back into its hole in the base material. It can be a bit tricky to pull the pieces out; I use a large hat pin to get a grip inside the cut.
  5. Now configure the settings to engrave the elements on the back and ignore the others (including the cuts), and run the print again. Note that when you close the lid and the Glowforge rescans the bed, it may show the elements out of alignment. This is a lie! As long as you don’t move the physical material, your second print run will cut aligned with the first.
  6. Tada! Perfect alignment on every tile.

Adding Color

Each tile “shape” has its own color. I chose red for the star, blue for the triangle, yellow for the square and green for the circle — plus black for the two jokers. I used this super-cool technique to apply color to the tiles neatly and absolutely love the result.

Pretty much everyone uses some kind of masking tape to cover their material and protect it from scorch marks that the laser can otherwise leave behind. When you buy “proofgrade” material direct from Glowforge it comes with a mask already in place; something like this item at Amazon does the trick for other stuff. It turns out that you can take advantage of this mask to fill in engravings with color as well.

With the masks still in place, I first cleaned ash and residue from each tile using baby wipes. This is a messy job and requires some care so that you don’t get the masks too wet; they need to stay adhered to the tiles for the next step. Then I just painted over the front side of each tile using acrylic paint from this set. Because the engraving is dark, it took a few coats to cover — four for most colors and five for the yellow. I let it dry for about ten minutes between coats, and then an hour before peeling off the masks. This was incredibly satisfying — the edges came away clean and crisp, and the color is bright and bold.

The last step was to cover the tiles on all sides with a few coats of clear enamel spray. The final result is a durable, nice looking set. Woo hoo!

Wait, this all seems fine?

“Seems” is the operative word here. The above is a textbook example of social media whitewashing — it’s all true, but skips over all of the not-so-pretty goofs and gotchas along the way. To wit:

Ghosts in the design

106 tiles, each with one cut and three engravings, is a lot of Glowforging and takes quite a bit of time (about two hours). The first hiccup came about two thirds of the way into this session as, seemingly at random, some of the engrave elements were just skipped. I couldn’t figure out a pattern to this so just wrote it off as “some bug,” maybe because of the large number of elements, and built new files to remake the ones that had been messed up.

Unfortunately, the “bug” kept showing up on some (not all) tiles every print, which was increasingly annoying as I quickly burned through my extra material trying to complete the set. Finally, as I was moving tiles around in the Glowforge interface for yet another run, I happened to notice that some of the engraving elements were showing up just a little darker than the others. WTF?

It turns out that, at some point during the dozens of copy/pastes involved in this design, I double-pasted some of the engraving elements — the elements that were showing up darker were actually two identical copies, one atop the other. And when a design has overlapping filled vector shapes, Glowforge just ignores the overlap area. I can’t find this documented anywhere, but it does show up in the community support forums with some regularity. Anyways, when I finally got the files fixed up, everything started working as intended.

Burn marks

A few of the tiles ended up with a weird pattern of burn marks along the edges on the back. I think there must have been something about the position of the tiles on the honeycomb tray that the material sits on in the Glowforge bed — some kind of reflection during the cutting process. It’s possible that I could have dialed down the power and still cut through the material without that side-effect. Anyways, while the aesthetics weren’t that horrible, part of the game is selecting tiles from a face-down draw pile. Unique patterns on the backs would be the equivalent of using a marked deck of cards … whoops! So I remade them.

Paint bleed under the mask

I actually expected this to be much more of a problem than it was. On a few of the pieces, the mask detached just a bit from the tile, causing the paint to bleed outside of the engraved area. I initially thought I might be able to scrape or sand off the extra, but that didn’t work very well — bits of the paint sort of smeared across the tile and it just looked bad. This only happened on a handful of tiles, so I just remade them instead of continuing to fight it.

Light and dark

The material I used has cherry veneer on both sides, but if you look closely one side is notably darker than the other (this was consistent across all the sheets of this stuff). I used light for the fronts, dark for the backs. Once I applied the masking tape, though, it was no longer clear which side was which. And after I got all the way through and was setting up to apply the enamel, I realized that I had flipped the sheet for a whole group of the tiles. And of course, the same thing about marked cards applies here — if you know that half of the green tiles appear lighter in the draw pile, it doesn’t make for a very fair game. I was just able to squeeze enough space out of my extra material to remake these too … whew.

Not the enamel too!

After this seemingly endless process of remaking and repainting problem tiles, I finally had a complete set. Home stretch! All that was left to do was to apply a few coats of clear enamel spray to protect the tiles during play. I’ve had trouble in the past with the enamel sticking the pieces to whatever they were sitting on (in this case a big piece of pressboard). My wife suggested that I put a penny under each tile to hold it just off the surface. A great idea, but because it was only 40° outside where I was painting, I was going to have to move the tiles inside to dry in a warmer environment — the pennies were just too slippery to stay in place during this move. Instead, I put little one-inch pieces of non-stick drawer liner under each one. Two coats on the fronts, wait for them to dry, flip them over, two coats on the backs, shuttling back and forth inside and outside, Bob’s your uncle.

Or not. Apparently tripling the dry time for the enamel (and touch-testing the tiles of course) was not sufficient. When I picked them up (thinking the project was completely finished, mind you) I discovered that the drawer liner was sticking to the tile fronts, leaving grey bits embedded in the enamel as they pulled away. Nooooooooooo! Through my tears of frustration, I used the flat side of a sharp knife to scrape off as much as I could — carefully touched up the paint where it had been damaged — and resprayed the fronts with two more coats of the enamel. The end result actually was fine — the scraping left notable marks at first, but the enamel coats fused together and left the final products looking ok.

Twist the knife

This last is just funny. As I was writing all of this up, I realized that the game wants tiles numbered 1-13 and I had created 1-14. Certainly better too many than too few, but come on.

I don’t remember any project where everything went exactly to plan. But this one takes the cake for sheer number of own-goals. Ah well … they will be fun to play with, and I will use both of those new techniques again for sure, and I can’t help but think of the old saw that a bad day fishing beats a good day working. Amen to that.

Inlays on the Glowforge

I just finished this coaster using cherry-clad MDF with red acrylic inlays; both materials from an assortment I got from my valentine (she knows me well!). A few new techniques here that I had a lot of fun with.

The design was inspired by tiles we saw a few years ago at the Alhambra, created in Inkscape by composing a bunch of variations on a sixteen-point star. I am still a rank amateur with this app but am blown away by its power. The second and third rings were each created by overlapping two 16-point stars with different “spoke ratios” (the radius of the outer points divided by the radius of the inner point) and then taking the difference between the two areas. For the third ring I also trimmed out a circle so you got the five-sided end result.

the round-bottom points in the outer ring were created by distributing triangles and circles around the same circular path, breaking all the paths apart, and unioning each touching triangle and circle. That union bit at the end was critical to get a single cut around the edge.

I cut the design from the cherry sheet along the red lines in the screenshot, and engraved the circle in blue. I also cut out a solid circle the same size to act as a base. The trick from there was to cut the acrylic pieces so that they’d inlay perfectly into the wood.

This is way more complicated that you might imagine! First of all, the laser cuts with a tiny but meaningful “kerf” (the width of the cut itself). The kerf is different from material to material, which is why I added that little stub of red cut line outside the circle in the Inkscape screenshot. The width of that test cut measured .014″ using my calipers, which meant that the cutouts were really .007″ bigger than my design. Inkscape came to my rescue again with an “outset” feature that expanded all the shapes for the acrylic cuts.

But wait, there’s more. It turns out that the laser doesn’t make a perfectly vertical cut. It’s actually a cone shape with the point focused on the top edge of the material. This means the bottom of the cut is just a little bit wider that the top, screwing up the inlay fit. BUT (and this is cool), if you flip and reverse your design, you cancel that out and get a perfect match. This was super-simple given my symmetric design; I just flipped over each piece of acrylic before pressing it into place. I have to say it was deeply satisfying having each inlay just click into place so beautifully.

Since this was going to be a coaster, I poured two coats of clear epoxy resin over the whole thing, sanded down the drips and then cut out (thanks again Glowforge) a circle of self-adhesive 2mm cork for the bottom.

I’m quite proud of the end result! A lot of work for a simple coaster, but now that I’ve figured out the quirks, new designs should come together pretty quickly. So many neat concepts packed into that Glowforge.

Love the translucence in the material; maybe next project should be a candle lantern?
Before the epoxy pour, which shows off the fit a little better.