e^CNC

I ordered a Tiny-G motor controller a few days ago. It’s version 0.9, but considering I’ve been trying to get my hands on a pre-release for about a year I don’t mind.

New home for the 80/20 CNC. Broun Hall, Auburn University

An alternative to the physical limit switches on the RepStrap (US1881 Melexis, Hall Latch)
North Pole = Latch High, South Pole = Latch Low 

Extruder Side-view

The white spacer is a PTFE (Teflon) barrier that can easily be machined on a small lathe. The barrier is drilled through 3.5mm and threaded for a M6x1 brass heater barrel. The barrel is 50mm long and has been macined out of M6x1 threaded brass rod. The barrel has been drilled out to 3.0mm (with the ends turned down to 4.5mm. The nozzel is 14mm long and made of a 7/16” brass hex rod. Drilled and tapped to M6x1. The extruder hole is 0.5mm. These three items were ordered from eBay for $14.90.

The nichrome wire, thermistor, kapton tape, ceramic insulation tape, and Lasercut washer were ordered from the Makerstore.

The machine screws and aluminum mount were laying around the apartment. Now I need to build a proper drive mechanism.

Trouble with the extruder:

I’m trying to test out my heater barrel (using the codes M104 S90 \
M06 T0 \ M104 S0) and get nothing. No blinking LEDs on the A, B, or C
ports. I can see the temperature in ReplicatorG going up when I hold a
lighter near the nozzle so I know my thermistor is working. I’ve
measured the resistance of the heater terminals at 5.9~6.2 ohms
(depending on how I hold it) and I think that’s too narrow a range to
be a short.

My next step in debugging is going to be connecting six ohm power
resistors across the +/- of A, B (which I’ve been attempting to use),
and C and looking for voltages — but since the LEDs for the MOSFETs
aren’t blinking I don’t think this is going to make much of a
difference. I would try some spare nichrome wire but don’t have any.

I’ve tried ReplicatorG 17 and 18 and have a v1,2 Motherboard and v2.2 
extruder (running the 2.2 version firmware for both as the newest
firmware gives me the null extruder error mentioned elsewhere on this
forum)

Later that day…

I moved my extruder to A-/A+, set my machine driver to “CupCake w/
Headed Bed” and was able to use the control panel to set a target
temperature. I can now get the LEDs for A and B to blink (although B
tends to be more dull) when there is an open circuit between +/- of A
and B. I still cannot use B-/B+ to heat my extruder.

Is there any reason why one port would work over another? Could I have
damaged the B port in such a way that the MOSFET can no longer supply
enough current to heat the extruder? I didn’t think there was anything
inherently different between ports B and A.

5kg HDPE Plastic from eBay and a few things from MakerBot Industries (RepRap motherboard 1.2, extruder controller, bipolar stepper controllers, power supply, insulated nichrome wire, kapton tape, ceramic cloth, thermistors,extruder washer). The extruder nozzle and barrel (eBay) should be here shortly.

I still need to acquire four stepper motors (or three steppers and one geared DC motor) and decide on how exactly I want to build the frame.