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!