Thanks! I'm really happy with the Duet so far. Though I suspect there's a lot more to learn about configuring it. Stega Saurus will be working on reading the docs some more.
I'm glad the Duet connector kit included wire ferrules for the screw terminals. (3D printing has taught me to hate small screw terminals. Hate hate hate. They are never ever, ever what I want to see on a circuit board.) I wish I had a square crimp for the ferrules!
I was shocked that the RAMBo died, too. (Ouch, bad pun. I'll leave it.) I'm not sure what the ground path was, but it started from the external case of the LCD. I was wearing a wool shirt in Alaska winter, so a 1/2" arc would have been plausible for the static discharge. After replacing the LCD, the RAMBo actually still runs, I just can't reprogram it or re-flash the bootloader. That made me suspect the ground path was through an ICSP pin, since those are part of the LCD adapter, but it doesn't look like those pins are connected to anything. I might see if I can send it to SeeMeCNC to try to fix the bootloader, since I can't find anybody here who has an actual AVR programmer. I tried using an Arduino as ICSP with no luck.
I need to add grounding to the steppers still. One consequence of building up the Rostock iteratively over years is that there's a lot of Y-adapters in the wiring harnesses, so it's easy to pull one out and replace it with one that splices in extra wires for grounding. In this case, all five motors already have 12V DC fans cooling the steppers, so I'll probably use the ground line for the fan, which is on the 12V bus. Do you think I should also ground the extruder motor cases?
The Berd Air with the bigger pump moves a LOT of air on full speed, and with the little mosfet switch, responds well to PWM. With a normal unidirectional squirrel cage layer fan shroud, a PLA test print of a Bench had visible artifacts from the asymmetrical cooling. The Berd Air definitely addresses that concern, and there was plenty of room for a mount for it and the IR probe with the 713Maker effector platform. For someone like me, the minimal footprint of the Berd Air is really exciting. It broadens the range of answers to "hey, can I jam THIS combination of things onto the effector platform?" without having a big fan shroud sticking way out and bumping into the still-hypothetical printer enclosure. (And yes, the flyback diode is attached directly to the motor leads.)
Here's Stega installing the Berd Air + IR Probe mount that's currently in use. It turned out super simple! The next revision might have a little bit tighter and beefier part holding the Berd Air tube, but this has been solid for short test prints. I think an ideal solution would be to have the tube not be perfectly round so the holder can be keyed to prevent it from rotating during a print and coming into contact with the print head.
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http://gchristopher.net/3dprinting/berd ... _mount.jpg[/img]
The two criticisms I have of the Berd Air are:
- (minor complaint) Noise. With the duet-quiet motors, it's now the loudest part of the machine, but still quieter than the 1/16 microstepped motors. It's resting on a piece of packing foam right now, which helps a lot compared to having the whole case be an amplifying chamber. Maybe a nice rubber-damped mount will cut it down some more. But the machine as a whole is still quieter than before!
- Inconsistent placement of the holes. I'm actually fairly unhappy about this. One of the holes, in particular, is pointing away from the print head enough that there's a strong breeze noticeable in that direction.
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http://gchristopher.net/3dprinting/berdair_closeup.jpg[/img]
I think I'd actually be happier buying a Berd Air tube without the holes pre-drilled and sitting down with a drill press, clamps and a magnifying glass to really get the holes right. It would be fun to experiment with different aperture sizes and shapes, too, like slits instead of holes. There's plenty of air pressure to play with and the aluminum tube would let you get away a lot more than you could with a plastic printed fan shroud, both in terms of small size and being so close to the hot end and nozzle.