Having already bought and assembled a MeArm kit from Makersify, I decided to use the open hardwire files from thingiverse to laser cut all the parts from 3mm Acrylic.
Thingiverse files. If your DT department in school is as awesome as mine, they’ll show you how to use the cutter so you can plan and cut your own designs.
I had some trouble with the .dxf files running in 2D design, so I printed the design out on paper first and then did all of the measurements, comparing it to the real mearm that I built in order to make sure the scaling was perfect. (If not, the servos won’t fit in the holes, and the bolts won’t self-tap)
I also cut a mountboard version for the students to see, and get to measure with vernier callipers to check the dimensions. (It turned out it had scaled wrong vertically, and the test-print would never have assembled as all the circular holes were ellipses!)
In order to build the robot, you’ll need a bunch of M3 bolts, and some Turnigy 9g micro servos. I picked up a load of servos cheap on ebay , at £11.99 for 4, which seems like a good deal. (I would get a spare set, in case you burn the servos out during a build!)
I used namrick.co.uk to get small batches of the screws, as they were by far the best deal I could find in the UK, cheaper by about £25 than all other dealers.
Once the students had done the inventory, they began to follow the assembly instructions, starting with the baseplate. Here you can see that the longer M3 bolts are used like standoffs in the assembly. You can also see the mounting holes to bolt on an arduino for controlling the servos.
We’ll keep you posted on the build as it happens, and then how to control it with scratch on the raspberry pi.