All Caged Up

After finishing last week's blog I encountered another long string of 3D printing failures on my own printer. We did have a snowstorm one day, but other days the weather was fine, and I have no idea why the prints all failed. I had thought previously that temperature or humidity could have been an issue but now I'm not so sure. The usual reason for failure was that some extra plastic occasionally leaked out of the block holding the extruder, and molten blobs of the plastic landed on top of the print and cooled, so that the extruder would eventually collide with it, knocking the print loose from the base, resulting in a failed mess.

So I just sent off the front and back pieces of the cage to 3DHubs. By not including any side pieces (I used a bunch of 2 mm diameter metal rods for this) I was able to save a lot on printing costs (cost was less than $100 vs. ~ $400 for printing the whole cage). Here is the finished result:

If you are determined to jam your hand in between the metal rods or between the plastic spokes you can still hurt yourself, but I think it offers a reasonable level of safety, while allowing good air flow.

I decided to make the air rudders (to be mounted behind the cage) out of thin aluminum sheets. Here is a video of one of them epoxied to the servo motor:

At first the servo wouldn't turn and I was worried that epoxy had gotten into the gears, but it was fortunately just some loose wiring. A second air rudder will run in parallel to this one, and be driven by a bit of coat hanger joining the two of them.

I also tried out a new inertial measurement unit this week (the AltIMU-10 v5 Gyro, Accelerometer, Compass, and Altimeter from Pololu Electronics www.polulu.com). So far I've been able to get temperature, magnetic, acceleration, and gyro data out of the thing in all 3 axes at about 50 Hz. I'm not sure yet whether or not it would be a good replacement for the electronic compass (without gyros) that I'm using now. The hope is that it might provide more reliable orientation data for AMOS in rough, dynamic water.