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Dual Motor Extruder Firmware/Hardware Qusetion

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Hallo Everybody,

I do have underextusion Problems and Robetl's Fedder is grate but in may case not enough. I still have underextusion problems so I was thinking about a more radical Solution. Using two drive wheels and two stepper motors. From the harware side I do have a solution. But I am by far not the software/electronic expert. So dose anyone know a easy solution to power the second motor?

I thought of 2 possibilities:

1. use the E2 stepper in the UM2 and make some intelligent Firmware change to send it the same pulses as E1

2. make the driver E1 somehow stronger to power 2 motors in parallel (About 3A)

(transitors?? ore a second pollulu ??)

For anyone interested in the concept hire are some pictures:


Filamentguides and a spring mechanism will be added




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I started having underextrusion and its clearly not due to the feeder. I've been using Roberts feeder for months and it works great.

In my case the nozzle was having trouble dealing with PLA/PHA filaments even at low speed and higher temp while Ultimaker PLA was doing great even at high speed. Something to do with viscosity I guess. In the end my nozzle was a mess even if atomic pull was coming out clean most of the time.

Even the change filament procedure was causing the feeder to skip backward on those filament.

You might just not have nailed the good tension with the feeder.


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I agree your feeder is probably not the issue, with roberts feeder (I use my own version but basically the same) I can put more pressure than I'll ever need, up to the point fillaments start leaking out at the top of the heater ...

Did you try manualy feeding fillament ? just push it by hand, maybe you should check the PTFE coupler (the white part) above your heaterblock, if this thing is deformed it will cause to much friction.


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I ordered a new Teflon insulator some time ago but Ultimaker support can take a while...

my hotend is looking quite ok and manual extrusion has a resistance (i wood guess around 200-300g or so) and this resistance was from day one. I do not think that it is unusual. Im priting with blue Ultimaker PLA beside that I have printed with Inofill PLA. In my case both are quite similar in underextusion.


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I never printed with Infill. So the nozzle shouldn't be the problem with only that amount of time used.

Did you ever try printing with Pronterface connected to the printer? Connect to the printer before starting the print because it reset the printer.

I see a lot of color change in your print. Maybe the PID of the nozzle need to be tuned to be more stable at 220C.

You can monitor the bed and nozzle temp with pronterface. If after 5 minute into the print the nozzle temp is still changing more than ~2-3C you can try tuning the PID.


M303 C8 S220 command will trigger 8 cycles around 220C and will output the P I D values

use M301 command and set the P I D values.


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Yes, looks like underextrusion. There are many causes. The most common is printing too cold and too fast so lets check that first.

.06mm 50mm/sec at 220C? Is that right? Please confirm. That's the equivalent of 15mm/sec at .2mm layers and according to this graph (stay slower than half the blue line) the top speed at 220 .2mm layer is about 35mm/sec. So you are printing half of top recommended speed for 220Cwhich should be fine.


Other likely problems - filament tangles. Check your filament every 15 minutes for tangles. Even better put the filament on the floor. It goes into the feeder at such as severe angle that it makes it tough for the feeder. Maybe this isn't a problem for Roberts's feeder. Still it's a trivial thing to do.

This is how we roll...

Red spool

Next thing is isolator and nozzle. These both require 10 minutes of taking the head apart. It's really not hard. I can link to a video if you want. Just start by removing the side fans and then the 4 longs screws. Be very gentle with the nut with the holes in it that holds the nozzle itself - in fact you should probably heat it to 160C while unscrewing the nozzle to melt any "pla glue". Also be very gentle with the temp probe and heater probe.

Check the white isolator - put filament through it. Especially slightly bent filament. If resistance is high consider drilliing it out until your new one arrives.

Also burn out the nozzle - there may be something on the walls of the nozzle causing a partial clog.

Have you tried the "atomic method" aka cold pull?


Your feeder should be able to put out about 5kg of force. If it's skipping you can increase that force by about 20% by increasing the current. You can add this command anywhere near the top of your gcode except to 1.5 amps. Don't go higher. And don't do this if it isn't skipping backwards as it won't help and will just make the extruder hotter which can melt the pla and cause the filament to grind.

M907 E1250 sets extruder current to 1.25 amps which is the default


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