My daughter came home a few weeks ago with a science project to build a musical instrument. Lucky me, she chose to make a violin. Now for anyone with an array of woodworking tools, this is probably an easy task, but for my meager supply of hand tools this was going to be a challenge. Standing in the wood aisle at Home Depot several days later and inspired by my lost jigsaw, I decided I needed a better plan. She is going to need to draw out her plans for me to cut from anyways, so let’s see if we can laser cut her project!
I’ve never laser cut anything before, but I know someone at www.outfab.com who was able to provide guidance and tips to get us going. The first thing I did was to go to their website and read through the FAQ and look through the gallery of stuff they’ve made to look for ideas. My daughter planned on using her violin as a model to design her project so we had something to look at. I showed her how to use my calipers, and she set to work sketching out her violin with measurements.
I decided that she should use Inkscape because it was free, seems fairly powerful and was recommended by Outfab. However, a few of its quirks with grids proved to be cumbersome to my daughter doing the drawings and for me fixing the drawings. In hindsight, I would have perhaps used a free trial version of the Corel Draw, but Inkscape is definitely capable of doing the job.
To make the drawing a little easier for her, I started with the template from Outfab and created a blank drawing in which I turned on the grid at 0.125” and set the snap options to snap shapes and vertices to the grid points. She would use that blank drawing from which to start all of her drawings. The biggest problem I encountered when checking her drawings is that if she moved a part the corners inevitably ended up off grid! We eventually learned to do one part per page and don’t move them. When you are ready to cut, you simply copy them to another drawing (sized to your target unit size) and rotate them to use as much of the space as possible while leaving the required margins around the edge of the wood.
Step 1: The First Cut Is the Deepest
The first part of the design that she tackled was perhaps the hardest part of the design—the neck of the violin.
After discussing several ideas, we settled on making it like a layer cake with piece of plywood creating each layer. She would have to design two different parts: an outer and an inner piece. The outside piece would have the holes for the bolts that act as tuning pegs. The inside piece would have a cutout where the strings could wrap around the bolts. I recommended that she draw the outside piece first, and then copy it and modify it to make the inside piece. I had her add holes that we could use to align the pieces to each other. Since we had space left to cut, she added the fingerboard to the drawing and we sent it off to get cut!
Step 2: First Cut Lessons Learned
Ok, so it didn’t go exactly as we planned. Fortunately, Toma at Outfab caught our mistakes before cutting. She drew the parts exactly as I would have done: she drew each arc, line, and circle individually and then grouped them to make a part. However, Toma showed me that if you zoomed in, you could see that these lines didn’t actually join in most cases and the parts wouldn’t have been completely cut out. He showed us a great trick to use in Inkscape located under the “Path” menu where you can “Union” and “Difference” objects from each other. So instead of thinking about it as drawing a part, we had to think more about it as “building” a part.
For example, see the drawing above where I drew interlocking teeth for a part. First, I drew the teeth and placed them where I wanted them. Second, I used Path->Union to join them. I made the teeth a little bigger needed because the “extra” part disappears. Now there are no gaps and this is actually quicker than drawing each line!
Step 3: Now We Really Cut Something
So these commands were great for new parts, but for the parts we had, my daughter had to go back and edit each line and join the parts together using “Edit Path by Nodes” command. (Thank you Google and all those Inkscape tutorials out there!) After fixing the drawings, and submitting them we got back our parts.
Step 4: Time to Glue!
I grabbed a piece of wood pounded a couple nails for thealignment holes and my daughter glued the cake together and we clamped it to sit overnight: Unfortunately, things still slid a little. Perhaps a better approach would have been to cut notches and slide a small piece in like a key or even to create a small jig.
Step 5: MORE Mistakes?
Now for the second mistake we made. The fingerboard looked right and even matched the dimensions she had written on her notes, but when we placed it on our model, you can see it is too short. We realized the dimensions she used were actually for the part sketched next to it. So a good rule to follow is to print out the parts to scale and lay them next to your model.
Step 6: Even More Mistakes!
So now it’s just a simple matter of designing a box with interlocking teeth and putting it together. When we got those parts back, however, some didn’t fit. So it is a good rule to also use scale printouts (or you can line them up in Inkscape) to make sure all parts interlock as expected.
Paper is cheap!
You can see in two of the pictures, we've actually cut out the part from the paper and put it in the existing parts to double check. Works great!
Step 7: One Last Hurdle
This had nothing to do with Inkscape or Laser cutting, but if you want to make something like this instrument, you need to know this. The bolts we used for tuning pegs turned out to be harder to use than I thought.
I thought we could simply wind the wire around the bolt and the tension would hold it in place. Wrong! So I tried to drill a hole through the bolt to feed the wire through like the real pegs, but without a drill press, I couldn’t manage to do it. So we went to plan B: wooden dowels (which I could easily drill holes in). These worked great until we actually tried to tune the violin. As I tightened the strings, the dowels started to crack under the strain (much like I was at this point). I finally stumbled onto the solution; I used a hacksaw to cut a flat spot into the bolt. Once I had a flat spot, it was just a matter of patience with the drill to get the hole I needed.