Sunday, 28 June 2009

Spider Grip

My mini Darwin design does not have enough space to put the Z axis motor in-line with one of the treaded rods, so from the beginning I had been thinking of placing the motor along one of the side rods. I have been trying to think of a good way of mounting the motor for a while now, then a few days ago I had the idea of making this 'spider grip' (it looks a bit like a four legged spider).


The 'legs' arch up before going to the 'body' to give some elasticity, so that when the screws are tightened the rod is held very firmly against the motor.


Here it is fitted to the machine. It gives a very firm grip, however it can be twisted fairly easily around the axis, but is firm enough to keep it in place. The only forces that will be applied to the motor when in operation are a liner force along the length of the chain, and a rotary force around the motor spindle, so no force should be present in the one direction that the motor can twist.


I've just put a load of closeup pictures of the machine onto my flickr page.


Unfortunately I've just broken my extruder, but more about that next.

Thursday, 25 June 2009

Broken extruder

I broke my extruder!

I have used my extruder with CAPA before and it has been reasonably reliable, though I was never able to get any filament (I just rolled some bits). I gave up on trying to get any and so I recently purchased some ABS.

I put the ABS into the extruder, heated it up, and ran the last of the CAPA out. I turned the temperature up on the extruder, but was unable to get past 159 degrees. Eventually I decided that the temperature was not going to get any higher so I tried to run the ABS through anyway.

In the past the motor has stalled quite easily at low speeds when the extruder is not hot enough, but this time it didn't stall and instead pushed the heater barrel out of the PTFE rod. Presumably this is because I have never had the extruder this hot before.



I ordered some PTFE rod, some brass bolts, nichrome, thermistors, thicker cable (for connecting heater to board), drill bits and an M6 tap. This should be enough to make a few experimental barrels, although I'm not yet sure how I'm going to do this without a proper pillar drill or lathe.