8-Bit Blog: Right Tools for the Job November 05 2013
Small scale manufacturing often requires creating tools to make assembly easier. These tools are called "fixtures" or "jigs" and allow assembly workers to be more efficient, keep the product from getting damaged, or line up parts with a very tight tolerance.
One of our greatest challenges was the use of glue to put the lamp together. We had to apply glue on the inside edges, but we couldn't allow any to seep out the cracks, because it had the possibility to marring the finish. In order to prevent this, we built a fixture that squeezed the lamp together, closing up any gaps on the edges where the glue would escape. This was machined by CNC mills, and made to within a few 10,000ths of an inch.
We realized that the workers would need to rotate the fixture in order to apply glue to the various internal sides of the lamp. The head of the factory came up with a fantastic idea to mount the fixture to an old motor, which would remain off, but allow the worker to spin the lamp freely as they applied the glue.
Here's a video of the fixture in use. You can see the worker applying a small piece of plastic to every internal edge where he applies glue. These "cleats" provide a much stronger bond between each of the sides, and are the reason why the lamp could survive a fall out the 6th story window. We also installed a lever system with a piece of aluminum and rubber bands. This allows the worker to easily rotate the fixture between the four optimal gluing positions.
Once the five-sided box is together, we needed a way of gluing the sixth side on without applying any glue to the outside of the box. Our solution to this was to place cleats precisely on the inside walls of the lamp. This would result in a "shelf" where the worker could apply glue (see highlighted picture above). The final panel could then press down onto this shelf.
We CNCed another set of fixtures to ensure that these cleats could be applied with exact precision. The worker places a cleat into the fixture and applies glue, and then the panel is placed down precisely on top. This is one of the first steps in the production, so that the shelf is already in place when the box is put together.
Another common purpose for a fixture is to test the functionality of a component. Shortly after receiving the circuit boards, we found that an unsettling number of units had non-functioning LEDs. As a result, we decided to test every board before they were glued inside the lamp. The factory made the jig above, that allowed us to test all 3,000 boards, and send the broken ones back to the circuit board supplier (luckily there were only 50 or so in the batch).
After the circuit boards were tested, we had to glue them to the bottom panel of the lamp. This acts as the brain of the device: it contains the touch sensor, turns the lights on and off, and plays the sound through the speaker. It also needs to be precisely placed, as the speaker needs to line up with the hole in the bottom of the lamp (that way you can hear the sounds!). We created a jig that lines up the holes on the yellow panel and PCB, and allows the worker to glue the board quickly and precisely.
On the last day of my trip, I met up with our sourcing group for a party. It was the first time in a few years when their whole team could come together so it was a really fun celebration. We ordered a lot of great food including something called a "Dragon Egg". It was essentially fried dough filled with air. Very tasty...
The team we've been working with is called the Berkeley Sourcing Group. They're a great partner that's been helping us with finding factories, and making sure the product gets delivered on time. It's often challenging to find suppliers that work with you on a small scale, so it was great to have them helping us along the way.
Til next time...