I recently discovered that kerf bending is perfect for building small cases.
Take a pice of plywood, cut out a pattern along the curve you want to shape and apply some hot water to the outside face of the bend, et voila. The cuts weaken the integrity of the material making it able to bend without snapping. Well, I tried some more patterns…
For the transmitter case I tried dashed patterns. Unfortunatly the cuts were too far apart. The bend was under a lot of stress. I decreased the spread and it now bends very well.
pliability: very good
tensile strength: good
torsonal strength: good
normal strength: very good
This is a herringbone pattern. It does work quite well. I underestimated the waste of the laser so the pattern breaks in some areas.
pliability: good
tensile strength: very good
torsonal strength: very good
normal strength: very good
Here is a good old midevil cross pattern. It’s a little hard to bend but once it’s in place it holds up nice.
pliability: fair
tensile strength: good
torsonal strength: fair
normal strength: good
This is the diagonal cross pattern. I would’t reconment using it. It bends really hard and breaks very easy. The biggest problem is, it doesn’t evenly bend due to its diagonal grid.
pliability: very poor
tensile strength: good
torsonal strength: fair
normal strength: good
Here is my favourite one made out of a few rows of space invaders. It is very delicate but in the end it does bend.
pliability: fair
tensile strength: good
torsonal strength: poor
normal strength: poor
You can actually use whatever pattern you like as long as the pattern isn’t diagonal to the bend. Just tinker around a little. It all works to some extend. The problem with these tests is definetly the size of the bend. The radius is only 8 mm. The space invaders are a little too small for the laser I used. I could see this being awesome in a bigger scale.
If you want to try it yourself here’s the CAD file.
Very nicely done ,and the site is almost professional .
question: Have you experimented with stopped cuts using the laser ( e.g. a slit that DOESN’T go completely through , leaving the surface unmarred ) , rather like this : ————-^-^-^———. or is even possible? ( old wood worker with no laser yet )
Thank you anglo. You should be able to do blind cuts, at least you can engrave things. It’s probably just a matter of focus and/or speed of the laser. Unfortunately the folks at the universities workshop are rather strict about the settings of the machine making it impossible for me to try.
I guess for “just” bending wood all you really need is a table saw but the laser is perfect if you want to work with graphical patterns.
Yes, it bends!
So can you tell us the length of each cut line and the spacing between the parallel lines? Can you confirm when you use the water, I presume after the laser cutting? Then do you let it dry in the bent position? Do you think the length of the cut line the spacing between them should very depending on the radius of the bend? I’m experimenting with this technique as the spine of a book, nothing new but one thing I noticed is that the grain must be parallel with the cuts, basis woodworking, but even then I get failure or cracking of the 3mm birch plywood. Of course I’d like the spine to bend for a good long time without cracking. Thank you in advance.
Hey Brian,
the length of the cuts don’t matter. What matters is the spacing between the cuts. If the cuts are too far apart, it won’t bend, if they are too close, the whole thing becomes instable. There is some math to calculate this but I didn’t really bother. All in all it breaks down to the thickness of the material and the radius of the bend. You could check out the cad file to see how big my spacings are.
Yes, you would use water for the bending process after you made the cuts. The water softens the fiber of the wood so that it won’t break under stress. Bend it to your likes and let it dry in the bend state. It works even better if you’d use water vapor instead of just water.
For durability, you could glue some strechable cloth to the backside of the spine (the inside of the book). You could even pick your favorite color