Here is a video of my RepRap printing a new part. Click the image to download the video. You will need the DivX codec to play this. The video runs at 10x speed and I’ve removed the audio. My memory card filled up before the part finished printing.
I will be at the Ann Arbor Maker Fair on Saturday 29th August with this machine if anyone wants to check it out and see it running.
There are a few quality issues I have to address still. The bottom few layers don’t lie down right and so the bottom of the part has all sorts of strange loops. In the video, I attempted to print 10 foundation layers instead of the normal 4. This didn’t help at all. I also have a lot of play in the carriage, which means the the nozzel sometimes rocks back and forth. Finally, I think there might be some backlash in the x axis, but it is hard to get to the pulley that is loose.
I spent a lot of time trying to get an extruder kit I got from Bits-From-Bytes working, but it never worked for more than an hour or two. The biggest problem was that one of the gears was off-center. This meant the amount of force seen by the motor was highly variable and I was never able to get it to run in the sweet spot.
While I was working on that, the good people at reprap.org developed a new pinchwheel extruder. This thing is much simpler and I was able to build one using MDF, like everything else. The new extruder runs off a stepper motor, and the shaft runs right against the plastic rod, no gears to mess with.
I’ve also had a lot of trouble with the stepper controllers overheating. I decided to over-solve this problem so that I don’t have to worry about it any more. I connected the 4 heatsinks with a piece of aluminum and mounted an old graphics card cooler to it.
I used thermal compound to make a good connection and I used the old heatsinks to provide a rigid clamp and prevent the thin aluminum from warping. The first time I did this, the heatsink was parallel to the plywood. This made it difficult to get to the connectors and the potentiometer. I also spent a lot of time filing the edges so they were not so sharp.
The second time I did it, I orientated the heatsink perpendicular to the plywood and the accessibility has improved. To avoid sharp edges I just folded the metal over and clamped it tight. This was faster and ended up with a less sharp edge. I also orientated the factory edge away from the board, where my hands are more likely to be.
