Sunday, 31 July 2011

Laser cutting magic clock

One of the great things I'm finding about having a laser cutter is just turning an idea into a product in a few hours. Such an opportunity presented itself this evening.

After playing petanque down on the seafront at the Brighton and Hove Petanque terrain, I got chatting to Ray - a longtime founder member and one-time president of the club. Ray is selling his house and soon moving to France, to spend his days drinking pastis and playing the game he loves, so it seemed a fitting to use my new-found skills to make some kind of memento - something that incorporates plastic and boules.

The obvious answer, of course is a set of child's plastic boules! The slightly less obvious answer (and the option we finally plumped for) is an all acrylic boules clock!



We had a sheet of A4 mirrored acrylic so quickly knocked up a design - drawn in Flash, exported as .wmf, then loaded into Inkscape and finally saved as a .dxf. This then allowed us to import the shape(s) into NewlyDraw, ready for cutting.
It seems like quite a faff but actually makes sense: you do all your drawing and editing in Flash (I personally love the Flash IDE for drawing!) then save the result as an image. You use Inkscape to prepare the file - no drawing here, but you can split shapes up, put them onto different layers, simplify splines etc. Then save as dxf and import into NewlyDraw. We just use NewlyDraw as the cutter driver - no messing about: load the dxf to cut shapes from, move the laser head to the start position and hit go. That's it!

Heres' the outline drawing


And here's a link to the dxf for cutting.
After assembling, we did hit a few snags, but only because we're still waiting for a delivery of various sized clock movements, so only had one movement to hand. It shouldn't have been a problem because it's on an acrylic-faced clock, but it didn't take long for the problems to start mounting up....

... firstly, with our clock consisting of a layer of 3mm mirrored acrylic on top of a base of 3mm blue opaque, we had a 6mm thick clock. That doesn't sound like much. But our clock movement was designed to fix to a 4mm or thinner face. So we had to re-cut the bit of the boule with the numbers 0-6, making the hole at the bottom wider, so that the clock movement attached onto to the blue layer only.

Then we spend ages getting the hole right for the hour (spiral) hand.
The clock movement was supposed to have a 5mm shaft. It took no less than five goes for use to find out that the hole needed for a snug fit is 4.7mm (we went 5mm, 4.9mm, 4.8mm - oh, this is going to take ages, let's skip a few and go for 4.5mm, oh that's a bit too small, what about 4.6mm, bugger it, if 4.7mm doesn't work, we'll have to give up and go to bed).

So what's with the weird spiral movement and peculiar numbering?
Well, of course, it's a petanque clock - so it's fitting that it should go from zero to thirteen (scoring in petanque goes up to 13, not 12). The spiral hand allows you to tell the time still, even though it's got these extra digits. If you think of the spiral hand as the hours and the short, straight hand as minutes, it's actually quite easy to read the time - in the example drawing above, the clock is reading half past three. Whichever number is covered by the spiral hand represents the hours, the minute hand works as normal. The photo, by the way, shows the time as 01:35am, which is what time it was when we finally finished making the first, working clock!

And the zero and thirteenth hours?
To be honest, it's best just to ignore them - they were only put there to make the clock look cool ;-)