MendelMax 1.5 Extruder not heating up

I have a MendelMax 1.5 ordered from Blomker Industries and am having issues with the extruder not heating up. The heater for my print bed and the motors all work fine. I have checked the connections to the heating resistor in the nozzle and they are all fine, thermistors are also working and reading on the computer.

One question I have is the wiring diagram shown in the picture that is attached. The wiring from the heating resistor branches off before connecting to the motherboard, and I don't understand the purpose of doing that instead of a single wire in and out. I changed the wiring to single wires, but still nothing.

I also tried running a print and used a multimeter to read current across the wires going to the heating resistor and got nothing.

The reason I ask is I don't know where to start troubleshooting the problem before tearing things apart. I have this idea that the software just isn't telling the extruder to turn on? I got my software from this site: [blomker.com]

Please let me know if you have any suggestions/ideas.

Thanks!

1. You can't read current "across" wires, only voltage.
2. To read current you have to be "in the circuit", i.e. detach a wire and put the probe tips between the wire and where it was connected - then and only then can you measure current.

Start at the beginning, detach the heater resistor wires and measure the resistance.
If it is zero then you have a short! It should be around 6.8 ohms.
If the resistance is correct then instead of connecting the resistor connect your multimeter probe tips to + and - and then activate the heater. Do you see 12 volts (or not)?

If not it is either a pin configuration problem or your MOSFTET.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

... to 'measure' a current without ripping up the circuit you can measure the drop voltage across a known resistor.

With 'Ohms law' I=U/R and e.g. a resistor value of 12 Ohms and a measured voltage of 1.5 Volts 'across' the resistor the current would be 1.5 / 12 = 0,125 Amps or 125mA ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Thanks for the help, I found out there was a bad connection at the resistor and fixed it. I am now test extruding plastic and have a problem. I started printing ABS and it was coming out relatively slow- even at 280C. I switched to PLA to run at a lower temperature. I extruded the rest of the ABS out of the reservoir and now the PLA is not extruding. I then turned the heat to 200C and the nozzle has plastic bubbling at the end, but nothing coming out. I increased the temperature but there are just bubbles coming out then too. When I lower the temperature, nothing happens when I try to extrude. Any ideas?

Thanks in advance,

Jack

Hi Jack,

switching between ABS and PLA 'on the fly' is most a bad idea, as you can (or have already done) clogg the nozzle with the mixture that behaves sometimes totally different than any of the plastics ... seems to form some crystal-like phases that won't melt anymore or you start carbonizing it, what's result in hard particles/residues blocking the nozzle ...

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Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

I don't think the nozzle is clogged because the PLA is slowing coming out. But it is not a constant flow and it looks discolored yellow so maybe it is slightly clogged and overheating? The extrusion rate is sporadic so maybe I should clean the nozzle anyways. If so, any suggestions on how to tackle that? What would happen if I switched back to ABS? I'm still working on my first print and hear that PLA is better for learning

Thanks!