I have the Duet underneath my Kossel with the wifi antenna protruding slightly. If the wifi signal is reasonably strong in the room where the printer will be, then it should be OK to put the Duet underneath the bed, assuming it is not surrounded by a solid metal frame. There is no easy way of extending the antenna, and FCC/CE regulations make it impractical for us to offer a version with an external antenna.
The stall detection isn't reliable at low speeds and the stalled status is only updated once every full step. So the stalled status should be ignored unless the motor is moving at a reasonable speed, or trying to. Also, the stall detection really needs to be tuned to the type of motor you are using. I'll probably add some sort of auto tuning for it in a future release.
What about a silicone type heater rather than a PCB heater? They tend to be a bit better in my experience. Also, add some sort of insulation if you haven't already. Even a very thin reflective barrier can make a big difference.
Here's the start of the printer. It is mainly assembled from laser cut 1/8 inch thick 5052 aluminum (surprisingly affordable if you find a good supplier) and Misumi 2020 extrusion.
It is still very early in the assembly phase, but I need to get a start at configuring the firmware to test the Z axis before I get too far along in assembly (made that mistake before and had to tear everything apart to solve binding).
Thank you both for the suggestions. I've replaced the fan with a Nanoxia Deep Silent 60 - much better. It does transport less air, but since I've rather over-sized the power supply and won't be running it at full power, I hope this won't be a problem.
Ok, I found the bug. I don´t know why that is so, but never mind. I changed the wire orientation of the thermistor and that was it. Is there any diode in the thermistor or why the orientation matters? I thought that a thermistor is a restistor with a almost linear restistance dependency to the temperature.
I thought so too - it shouldn't matter which wire goes to which side of the thermistor. Maybe you have a bad connection somewhere which coincidentally got disturbed when you were swapping wires? I can't see anything obviously wrong with your configuration.
I just tested this 30mm 24V fan http://www.ebay.co.uk/itm/191458206299/. It works with PWM at the default frequency, right down to S0.1. But I can feel that at full PWM it is pushing less air than the E3D fan.
I used to have a fan shroud on my E3D hot end that took a 40mm fan, and I may return to that approach in future if the fan noise annoys me too much.
Would it be possible to upgrade a Duet Wifi to Duet Ethernet?
You might consider selling the Duet Wifi and buying a Duet Ethernet. The cost differential would likely be about what a Ethernet upgrade board would be, maybe less.
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