Dual Extruders

How do dual extruders work? Does each extruder have its own axis letter? Or do they both use E and you have to do a tool change to get from one to the other.

Is there a wiki page that talks about this? I searched for dual extruders and found nothing.

I use RAMPS and it has a second (currently un populated) driver socket to work a 2nd extruder. I think they get referred to as E1 and E2. Your firmware has to support multiple extruders. OK that tapped me out, that's all I know about dual extruders. If you don't get enough info here try the #reprap IRC channel on freenode.net.

I am running dual extruders. They share an axis letter, and are selected with a tool change, at least in current firmwares such as Marlin.

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Thank you - that was what I thought. So from host software, there only needs to be one section to control the extruder using axis E, and perhaps a way to do a tool change.

What about for hot end temperature. Do we only turn one on or off at a time, and monitor the temperature of only one, with the necessary tool changes in between, or is there G code to address the heaters independently.

I have a post or two on my WordPress site with the link below if you are interested in learning a lil more about dual extruders. Im participating in Printrbots dual extruder beta.

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My printer can either use the E parameter and do tool changes to select which extruder to use or alternatively just use A and B parameters instead without any need for toolchange. With the latter one has to add the x and y offsets to compensate for the different locations of the extruders. With the E and toolchange the offsets are taken care of by one of the commands in the toolchange procedure.

From what I understand the E and toolchange method is the 'standard' way of doing things but for me it caused a lot of problems. I put it down to bugs in the firmware as after thoroughly checking the gCode I never found any problem with it, and in any case the exact same gCode would result in different problems. It seems the firmware sometimes loses track of the absolute extrusion amount of each extruder during a tool change.

I am running the Makerbot 7.3 firmware on a Chinese Makerbot clone. I had seen the exact same problems even in previous firmware versions.

Quote
lister6520
It seems the firmware sometimes loses track of the absolute extrusion amount of each extruder during a tool change.

You could switch to relative extrusion and avoid the problem completely.

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rhmorrison Wrote:
-------------------------------------------------------
>

Quote
lister6520
> It seems the firmware sometimes loses track of the
> absolute extrusion amount of each extruder during
> a tool change.
>

>
> You could switch to relative extrusion and avoid
> the problem completely.


That was actually the first thing I did but it just made things worse.

Well perhaps not exactly worse but wrong in a different way - whenever there were gentle curves it would extrude in fits and starts

I guessed it would be a quantization problem that would be fixed by increasing the number of decimals in the g-code but this then caused the machine to stall after a few layers and require a power cycle to bring it back to life. (Increasing the decimals beyond 4 cause me this problem even with single extrusion)

What I eventually did was to use the A and B parameters (with absolute extrusion and three decimals) instead of the E parameter and that finally solved the problem. I have had no issues since then.

Maybe there are other/better solutions but the A/B thing worked for me so I didn't look further.

What is the toolchain that everybody is using for multi-material printing. I know slic3r supports dual extruders, but I'm not sure how to produce the equivalent of STL files for multiple extruders.

Obviously I can figure out how to use one extruder for support and the other for object printing. I was wondering about using both extruders for object printing.

Thanks

jbernardis Wrote:
-------------------------------------------------------
> What is the toolchain that everybody is using for
> multi-material printing. I know slic3r supports
> dual extruders, but I'm not sure how to produce
> the equivalent of STL files for multiple
> extruders.
>
> Obviously I can figure out how to use one extruder
> for support and the other for object printing. I
> was wondering about using both extruders for
> object printing.
>
> Thanks

I use Skeinforge 50 to generate the gCode for each extruder separately. (So for instance from ObjectA.STL I generate ObjectA.gcode and from ObjectB.STL I generate ObjectB.gcode.)
Then I use a home made program to combine the two gCode files into a single one, interleaving the layers from each source gCode. I use the A and B parameters for the right and left extruders respectively rather than using the common E and doing a toolchange.

Initially I had used ReplicatorG to do the combining but I had various issues and found it easier to write my own combiner.

Create two STL files, one for each color. Read through this on how to combine them: [forums.reprap.org]

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Thanks for this!