Dual Extrusion

[blah_59]

I've printed my raised dual j-head mount and the measurements look good, I have just about everything wired back up again and just need to knock a couple of bugs out. Which brings me to my question: Has anyone set up Marlin firmware for dual-extrusion yet? If so, what can you share to help me make it the process of setting it up go smoother?

I know there is a place to define the number of extruders, I need to change the motherboard from 33 to 34 and I think I need to invert the direction for the motor on the second extruder. But can anyone provide a list of specific changes you needed to do to make it work?

As always, any help is much appreciated.

[blah_59]

72 of you have read this and no one has done dual extrusion yet? You guys know that I rely 100% on your knowledge before I can make any progress, right?

Kidding aside, I have gotten a little closer. I took a Marlin branch from whosawhatsis (thingiverse minimal-extruder fame) that he uses for a bukobot that purportedly had dual extruder support. Well, it turns out it partially does.

I went through config.h and set up the thermistor, PID, axis steps, etc... Uploaded, then told Repetier host that I had 2 extruders. All motors move in the right direction (including the second extruder motor (which I did invert the direction in Marlin)). There are a couple of issues and I think Roy (of Panucatt fame) is going to once again be needed to be the hero, I have an X3 board.

Two majors and a minor:

Majors:
1) The second extruder thermistor is not being read (in pronterface or repetier host). The physical wiring path is good, I can unplug it from the 2nd extruder pins and plug it in to the 1st extruder pins and temps start showing up in software. Could it be a software pins.h setting?

2) The second heater is not pushing juice. When I heat up the 1st extruder, I measure just shy of 12v at the X3 board (and the board lights up telling me power is flowing). When I try to heat the 2nd extruder there is no light on the board and I measure 0v (and obviously the extruder doesn't get hot)

Minor:
1) I've been using the 12v side of D5 to full time power my extruder fan. I figured I would be able to use D4 or D6 to power the 2nd extruder fan but no joy. Is that a pins.h change?

Edited to add: I see that I can plug one in to D4 but then I would turn it on/off in Repetier...

If anyone knows answers to any of these questions, feel free to tell me. I don't have to wait for Roy......

[cvoinescu]

Marlin has code to prevent the extruder from heating if the thermistor reads either off-scale high or off-scale low. That way, if the thermistor gets accidentally disconnected, you won't have a glowing hot heater block fallen off the now molten PEEK slowly burning its way through your desk, in a misguided attempt by the firmware to run the heater cartridge at full blast to nudge the temperature a little above the current reading of -999.9 degrees Celsius.

So your (2) is likely caused by your (1), and you have only one major problem left.

[blah_59]

Thanks cvoinescu, that's the kind of brilliance I've been waiting for.

So, now I'm probably down to one big issue: anyone have ideas of things that would allow a thermistor to work on either the extruder 1 pins or the bed pins but not the extruder 2 pins?



**I'm hoping it's not the hardware answer that there is a problem with those pins on the board

[blah_59]

Ok, I moved one step closer thanks in full to cvoinescu......Thank You.

It appears that the pins are set up correctly in pins.h but for some reason the thermistor on pin 15 isn't being read. So I cheated a bit and set #define TEMP_1_PIN to 13 and #define TEMP_0_PIN was already set to 13 so basically the software thought both extruders were using the one thermistor. When I fired up repetier host I could switch back and forth between extruders and both spit out temperature readings. So then I heated extruder 2 and because it had a min temp above the threshold, power flowed from the X3 and, indeed, started heating the second hot end.

So, in conclusion, it appears that the only problem left is that pin 15 isn't working for the third thermistor. Does anyone know if I can use some generic, unused pins on the X3 for the thermistor and remap them in pins.h? If no one has tried it yet and can give me a solid response (Roy: wink, wink, nudge, nudge), I'll give it a shot and let everyone know how it goes.

[blah_59]

So, in Marlin it looks like the thermistor pins are marked as analog numbering scheme so I tried a couple of pairs of pins that weren't being used on the board that were marked in the wiring diagram as A_ (as opposed to most pins being labeled D_. Each of the pins that I told Marlin was my thermistor did come back with temperatures in the host software but they ranged from 65C to 245C at ambient temperature, so they were clearly not reading the thermistor and were picking up "junk" numbers from whatever happened to really be on those pins (like reading the wrong memory address, something is there but not what you wanted). I also, for fun, tried to map D6 to the thermistor and plug in there without luck. So for now it looks like I need to wait for some insight on the Azteeg X3 board from the man that built it. Sorry guys that it wasn't easier, but I have full confidence that Roy will have some magic up his sleeve.

[cvoinescu]

You need a 4.7k resistor between the analog pin and +5 V for a correct reading, in addition to the thermistor (which should be between the pin and ground). Make sure the pin isn't connected to anything else on the board. It also helps to connect a capacitor between the pin and ground, that is, in parallel with the thermistor. Any value between 1uF and 100uF will do just fine.

[blah_59]

Update: Roy is going to hook me up with one of his new shields with extra thermistor and heater pins. I didn't want to be lazy in the meantime so, I played around in Marlin and disabled my heated bed and remapped the bed pin to the second extruder and that let me move forward another step. I used the dual extrusion traffic cone thing featured on thingiverse a little while ago as a test print.

So the changes that were important just get dual extrusion to work are the thermistor type and motherboard 34 in config.h and the number of extruders in config_adv.h. The rest should be good but confirm that the thermistor and heater pins are configured in pins.h. The second heater should be on 9 and the second thermistor should be on 15.

The software tool chain took a little longer to figure out. I thought I had seen dual extrusion config stuff in repetier but now that I went looking for it I only found the physical setup stuff: number of extruders, offset, etc. but not importing two stl files for slicing. In slicer config there is a combine two stl function but the output can't be imported back in to repetier. So I used Cura to slice the files and then I tried printing in both Cura and repetier with the same results.

It would print the base of the cone in the first color and successfully change to the other color/nozzle where it would successfully print the first band in the second color. I got pretty close on the measurements for the nozzle offset so the second color stuck pretty well to the first color. The problem I ran into now is that when the printer switches nozzles, it fully retracts the filament that was just used. So after the second color change, the first color is no longer loaded in the hot end, it isn't even loaded in the cold end. The filament is resting on top of the gear. I turned retraction off completely with the same result.

So a couple of things to work on: Get rid of the full retracts, work on the temps (there seems to be wider temperature variations when using two extruders). I had to make the temperature limits more flexible in Marlin to allow the print to start.

But this is one step closer for those trying to get dual extrusion going.

For those that printed the dual j-head mount I posted on thingiverse, the offset I measured between nozzle tips is 35.5mm.

[blah_59]

Update 2: In Cura's Start/End-Gcode section of the settings there is an entry for switchExtruder.gcode.

Under there the default retract on extruder swaps is 36mm, which is huge for a direct drive extruder. I lowered it to 5mm, I'll let you know how it works.

The setting where you might want to replace numbers are (the F#### is the speed it retracts and extracts (in case you didn't already know)):

G1 E-36 F5000 to G1 E-5 F1000

and

G1 E36 F5000 to G1 E5 F1000

Update 3:

I just tried a test cube with the above retraction settings and I have a cube (now I need to fine tune the offsets a bit (it's pretty close), maybe add .05mm to X and .1mm to Y offsets):

[blah_59]

Update 4: After several test cubes, it looks like my offsets are: X = 35.2, and Y = 0.75.

I also modified a Dual-Extrude Yin Yang light knob into a pendant and it came out all right for a first "non-cube" print.