November 2012

This is a tale of a father-daughter project. Like most projects that you design from scratch, it took longer than originally anticipated but it was worth doing in many ways. You’d think that as a scientist and engineer who has done nothing but research and development for my entire career, I’d be used to this by now and I guess I am; I don’t get upset when projects run on and on. But I never have learned to estimate the timeline of one either.

Anyway… As soon as I joined the Tulsa FabLab, Erin immediately envisioned making her own set of custom game pieces for Catan. She wanted to cut them out of wood and maybe make a box to put them in. I started immediately; she would have also if she hadn’t been taking 18 hours this semester in engineering so she can be excused for not doing most of the work herself.

I found the basic shapes on and made some modifications. She took that file and made some refinements of her own and I then took it back and made sure the line widths were what they should be to make the laser cut or engrave.

I designed a gift box for them all to be stored in and she came up with some initials to be engraved on the top. Then, the day before Thanksgiving, we went to the FabLab where I had reserved two hours and cut it all out.

I really enjoy these collaborations; there are a fairly limited number of things that dads and daughters can both really enjoy doing together and this is one that works for us since we’re both engineers.

As to the woodworking aspects of the project, there is much to say. The game pieces are flat which makes this the perfect project for a scroll-saw or laser cutter. In fact, one day when laser cutters become the same price as scroll saws, they will take over that market because they not only do the same job but do it perfectly as well as offering the option of engraving (by burning only the surface).

The gift box is another matter. Because the laser cutter is basically a high-tech scroll saw, the project either has to be made out of only flat pieces or require some work with other tools after the pieces are cut. The latter is nothing new to woodworkers, in fact all real projects are like that. For the propeller-head crowd that flock to laser cutters, that is a bit of alien thought. I was on a timeline and really didn’t want to bother with creating a groove that the box bottom could slide into so I just cut the bottom to the real outside dimension of the box and glued it on. It’s plywood so that should be OK.

But first, a word on plywood. I bought a sheet of stuff at Lowe’s and it is the crappiest piece of material I have ever encountered. The 4×8 sheet was flat when I bought it (and, after all, isn’t that what plywood is engineered to be?) but as soon as I cut it into laser-cutter-sized pieces, they warped a bit. HOW CAN PLYWOOD WARP? That’s the one thing it is NOT supposed to do!

Anyway, I put the piece on the cutter and forged ahead. The first pass is usually the engraving pass where the laser head goes back and forth over the wood in a raster pattern and burns the top surface at low power. Some wood is vaporized and so there is definitely a change in thickness that you can feel but mostly the burning turns the wood black and makes an image. In my particular piece of crappy plywood, the veneer was so thin that it just burned through to the next layer. Strangely, the thickness was just enough to burn off the veneer but not char the next layer (which the guys up at the FabLab had never seen happen) and as such, it looked a bit weird. The second layer had some sort of light-dark pattern in it (like spalting) which showed through in the images and made them look completely strange. I did not have enough time to run it again since somebody was waiting to use the machine after me so I just took them home and decided to stain them.

So we took them home and applied some stain. I used whatever I had laying around from my last project and we brushed it on pretty thick and immediately tried to sort-of squeegee it off the top surface and leave it in the engraved parts to make them really dark and enhance the contrast. This mostly worked.

As to the joints, finger joints are a natural for the laser cutter and I very much like not having to have my fingers so near the cutter like you do when making these on a table saw. And, since the thing is so precise, they fit perfectly. At least in the finger-width dimension. The design assumed a full ¼” of plywood and of course it was less than that so the fingers were too deep, leaving some of the finger sticking out beyond the box. This is easily remedied by a disk sander but my daughter decided that it was fine the way it was. She does not have the typical woodworker’s aversion to this sort of thing and so I agreed to leave it.

This is where a ‘parametric’ design tool would be handy (the high-end CAD systems are like this). You would tie that dimension to a user input and, after measuring the material with a caliper, you would enter this and the design would adapt accordingly. But I didn’t have that software.
Another interesting phenomenon that I did not expect was the smoke marks on the “exit” side of the laser beam. The material sits on a metal honeycomb and air is pulled downwards through the machine to pull the smoke out as well as hold the material firmly in place. In my case, since the plywood was warped, as soon as one piece was cut out, there was no more partial vacuum to hold the piece flat and it warped upwards which let the smoke swirl around a bit underneath the material. This left smoke marks on the underside. Again, this is easily sanded out which we did.

This plywood took stain very strangely. One side blotched worse than anything I had ever seen. The “good” side would blotch in long lines that must have corresponded to something underneath the veneer but was most annoying. But it was not annoying to my daughter; she was totally happy with the result and therefore so was I. My alternative was to start over. We had put a sealer coat of shellac on the game pieces before the stain but for some reason I forgot to do the box pieces.

Again, my daughter was satisfied. Together we bought some brass hinges and a latch and installed these. I let her do most of this and one of the hinges ended up really crooked. We thought about it and decided to let this stay as it was and not try to fix it – mostly because she was returning to the university and wanted to check the project off her list. This is a gift so she needs to have it done and wrapped very soon.

After a number of coats of blond shellac, it looks pretty darned good – even in spite of the lousy plywood. And a good time was had by all. So, shop time, daughter time, and something completed. Check, check, and check. That’s something to be thankful for – and on the Thanksgiving holiday too!



Just for the record: last Wednesday 11/7.  Visual aura – no headache.