This instructable guides you through the basic process of laser cutting veneer for marquetry purposes and hopefully covers some of the terminology and tips that I found useful. It was initially used to create a kindle case for my wifes birthday and then the tiles and board for my tile game.
Marquetry is the art of applying wood veneer to an item to create a picture or a pattern. The designs can be very detailed and intricate which would be tricky to cut out by hand. Accurate and repeatable cuts make for work that is particularly well suited to the laser cutter.
If you're in Nottingham, UK and would like to know more about this subject then come along to the Nottinghack space tomorrow night where I'll be giving a small workshop
Step 1: Calculating Laser Kerf
When the laser cuts it vaporises a small piece of wood directly under the cutting head and this cut has a width. The width will vary depending on the power of the laser, the speed of the cut and the material you are cutting in to.
James Williamson has written a great post about how to calculate the exact width of a laser cut. His method shows that cutting 10 stripes of veneer side by side allows you to bunch all the kerfs together and take a much larger, easier, reading of the amount of material lost. I calculated that the kerf for this tile setup was roughly 0.1mm and I used this figure while designing the tiles and veneers.
Another thing to consider is that the laser does not create parallel cuts. As the laser penetrates the wood the power drops off and the cut actually becomes narrower. This leads to '\ /' shape cuts in the wood. The veneer I used was only .6mm thick and this effect was still visible, the effect is very noticeable in the material I was adding the veneer too. This can be used to our advantage to create 'male' and 'female' parts. By cutting a mirror image of the veneer parts and cutting those it is possible to create parts that compliment each other. When the piece is 'flipped' back up the right way the edges of the two cuts can be aligned to make '//' edges.
Step 2: Compensating for Laser Kerf 1
The Outset Method
Inkscape has a specific function for drawing an outline around an existing path.
1) Start by drawing the shape that you want to cut out. This is the shape that you will cut into the base material and will make a pocket that you insert the veneer into.
2) Convert the shape to a path. Select the object then click Path -> Object to Path. You will notice that my object now has a node in each corner.
3) Make a copy of this shape, this copy will be modified to become the veneer outline.
4) Setup the outset step required. Go to File -> Inkscape preferences, this will open the preferences window. In the left hand menu scroll down for the Step settings. In here is a value for the Inset/Outset distance. This is measured in pixels so convert your distance to pixels (0.1mm = 0.354 px) and close the preferences
4) Enlarge the shape by clicking Path -> Outset
This will give you an enlarged version of the initial path. You might wonder if 0.354 pixels is actually going to make that much difference but it you stick 5 pieces together that's already 0.5mm gap which starts to become noticable.
Step 3: Compensating for Laser Kerf 2
The stroke width method
Stroke width is the thickness of the line within the drawing. Using this method provides you with a pocket that is slightly smaller than the original image and a veneer that is slightly larger, complementing each other perfectly.
1) Take the desired shape, this time starting with it as a path.
2) Open the fill and stroke panel, Object -> Fill and Stroke
3) Set the stroke width to match the kerf that you are compensating for.
4) Now convert the stroke to a path, Path -> Stroke to Path, this will give you two paths in one object, one around the inside of the shape and one around the outside.
5) Split the two paths, Path -> Break Apart, and set the fills and strokes to something sensible (no fill, 0.01mm stoke for this).
The smaller of the two paths is the one to use as a pocket outline and the larger path is the veneer outline. The pocket will be made slightly larger because you are cutting the inside of it and the veneer will be slightly smaller because it is the outside being cut. Don't forget to mirror the veneer design and flip the cut shapes to make for an extra snug fit.
Step 4: Cutting the Shapes
I used standard wood glue and a cocktail stick. Fill the pocket with a small coat of glue and then use the cocktail stick to smear it evenly across the surface. Position the veneer nicely over the pocket and press the two together. Wipe off any excess glue that comes out from under the veneer and clamp the whole thing down. This is important as the veneer can warp and lift out of the pocket so keep the item under pressure until the glue has dried. I also wrapped the tile in silicon paper to stop the stack of tiles sticking together.
Sand the tile with progressively finer sand paper until the veneer and the base material are flush and smooth, then oil or varnish the item for your preferred finish.
Step 5: Knotted Tile Game
Now a quick plug for my game. I made a game, I'm pleased with the results. It's no Settlers of Catan but it is a nice simple little game that you can play with your parents and grandparents.
It is available for free download so you can print one out, play it and tell me what you think.
For more information and the download please visit my blog