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https://github.com/cscott/3d-multimaterial

Direct-drive multi-material printing using Printrbot extruders
https://github.com/cscott/3d-multimaterial

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Direct-drive multi-material printing using Printrbot extruders

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# Direct-drive multimaterial printing using Printrbot extruders



Thing tracker at

https://cscott.github.io/thing-tracker/#/thing/3367036c-9556-4aa5-b3d4-02ff7dc592d1



## Description



This repository contains a collection of parts used to implement

direct-drive multimaterial printing on a [Printrbot] Simple Metal.

It should be generalizable to other Printrbot models, and other

3d printers, but we generally use Printrbot extruder designs

and [Marlin]'s [Printrboard]/[Extrudrboard] support.  The basic

direct-drive multimaterial concept is due to [Brian Roe](http://roemotion.com)

([@MakerBrian](https://twitter.com/MakerBrian)).



The direct-drive design uses the standard extruder directly above the

hot end for precise no-lag filament control and compatibility with

flexible filaments.  It is wired up to the extruder output on the

[Printrboard] and controlled by Marlin as "Extruder 0".



We use a Printrbot [Gear Head Extruder] for direct drive, using the

fact that this extruder is self-loading: once filament is introduced

above the drive gears, the extruder will grab it and feed it through

without manual intervention.  (We're actually using the [beta version

of the gear head extruder](https://www.youmagine.com/designs/printrbot-gear-head-extruder) which used a printed housing.)



Above this direct-drive gear head extruder is a V-shaped merge adapter

which accepts 1-4 bowden tubes containing different filament

materials.  This is integrated with the housing of the gear head

extruder to place the merge as close to the extruder input as

possible.  This minimizes the distance that unsupported filament must

travel during filament changes, and thus (hopefully) prevents jams.






At the moment I've designed the merge as a single printed piece which

fits into an 8mm hole on direct-drive extruder handle or body.  The

idea is to make it easy to retrofit an existing gear-head extruder

by simply drilling an 8mm pocket in the handle, although I don't

own one of the newer Aluminum Gear Head Extruders to fully test this.



The bowden tubes from the merge piece run to individual bowden drives

mounted on filament spools.  I'm using SPANNERHANDS' excellent

[spool design](https://www.thingiverse.com/thing:2119644) with a

slight remix to move the PFTE coupler and mount an extruder where

the PFTE coupler used to attach.  The extruders connect to an

[Extrudrboard] or [Extrudrboard2] and feed the filament from the

spool into the bowden tube to direct it to the merge piece.

Two extruders are always driven simultaneously to move filament,

one on the spool and one at the print head, although during

filament change operations there may be times when no filament

is actually in contact with the direct drive, and thus the

spool extruders are working alone.



The [Marlin] firmware is modified to support this style of operation,

building on the `MK2_MULTIPLEXER` support upstreamed to support Prusa's

[Super Switch](https://github.com/prusa3d/Original-Prusa-i3/issues/29).







## Instructions



### Step 1: Build spools






Start by printing out a [SPANNERHANDS spool] for each filament bowden

extruder you are going to use. I'm using the "v5 1kg" variant, but

with a little effort you could adapt these instructions to one of the

other spool variants.  Use [`spool-remix-lid2.stl`] instead of the

stock `LID2` part.  Mount the SPANNERHANDS `PTFE_COUPLER_v2_0.stl`

part to [`spool-remix-lid2.stl`].  We are going to mount our

bowden extruder on `LID1`, where the `PTFE_COUPLER` part would

normally go.  Assemble the `LID_Bracket`, `BASE_Bracket`,

and two `CLASP_BRACKET_v2_0` parts; I printed these in a contrasting

color.



Use two `Glue_Joint` parts to assemble the lid and base halves;

I recommend gluing both at once with the parts assembled into a complete

circle so you can ensure that the gap between top and bottom is not

too large as you glue them up.  Otherwise you tend to get top and bottom

halves which are ~178° of arc instead of 180°, and when you finally put

top and bottom together you get a pacman which won't close completely.

You can scale up the Z axis of the SPANNERHANDS `Flex_Seal` parts and

then trim them into a wedge to kludge around the problem if this happens.



I found the stock spool bearing mounts a little too tight, so I printed

the 50mm spool at 102% to fit my 52mm-core diameter spools with the right

fit for the bearings.  I use the remix at

[thing:2372633](https://www.thingiverse.com/thing:2372633) to fit my

32mm core diameter spools; I didn't need to scale that in any way.







### Step 2: Mount bowden extruders






Now print out [`mount-1kg.stl`] and attach it to the LID1 part of the

spool, with four M3x10mm screws like all of the other SPANNERHANDS

spool parts.  After it is attached to the spool you can mount the

extruder, placing the mount between the extruder body and the stepper.

I recommend M3x25mm screws here; some models of Printrbot extruder

might need some extra length to account for the mounting plate between

the extruder and stepper.



You can optionally use three M3x8mm screws to secure the bottom of

the extruder.  Some models of Printrbot extruder (for example, the

injection-molded plastic extruder) don't have these mounting holes.

They are probably overkill for this use anyway.









Insert a

[Groove mount 1.75mm Bowden coupler](https://www.filastruder.com/collections/e3d-spare-parts-and-accessories/products/bowden-couplings-all-types)

where the hotend would usually mount on the extruder.









You can route the wires for the stepper down the back of the spool and

through the hinge.  You'll probably need [servo extension cables] to

reach your Extrudrboard/Extrudrboard2 from wherever you decide to

mount your spools.  You can use [`spool-remix-hanger.stl`] to mount

the spool to the wall while leaving room for the stepper motor cable.







### Step 3: Assemble gear head direct-drive extruder






Print out [`gearhead-remix-base.stl`], [`gearhead-remix-clamp.stl`],

and [`gearhead-remix-gearbox.stl`]. (The photo also shows an early

version of [`bowden-block-4.stl`], the bowden merge piece.)









You'll also need (4) [5x8x2.5mm ball bearings] (or just three; see

note 2 below).









First, install a pair of bearings into the `base` piece, and then install

the Printrbot Gear Head Extruder Gear Set into the bearings.



**NOTE 1:**

Printrbot [sells these](https://printrbot.com/shop/gear-head-extruder-gear-set/),

but the pair that I have came from the Beta program for the Gear Head Extruder.

It's possible the production gear set differs from the beta gears.



**NOTE 2:**

Printrbot's original instructions stated that the rear stepper motor

bearing (the bearing behind the hollow gear you just installed) is

optional.  But if you're buying bearings, no reason to pinch pennies.



**NOTE 3:**

You may want to try [walter](https://www.thingiverse.com/walter/about)'s

[remix of the gear head extruder](https://www.thingiverse.com/thing:1052966).

It appears to use the same Printrbot gear set and bearings---but again,

I'm not certain whether production gears differ from beta gears, and if so

which walter used.  Some modifications will be necessary to adapt his

remix to Printrbot bottom-mounting holes, but maybe you don't need those.









Now install the other pair of bearings into the `gearbox` piece, and

bolt it to the base using (2) M3x20mm screws and (2) M3 nuts, sandwiching

the gears between them.  Before closing things up, align the set screw in

the left-hand gear with the channel in the base; this will allow you to

insert an allen wrench to tighten this gear onto the stepper shaft.









Attach the assembled gear box to the stepper.  Ensure the flat on the stepper

shaft is aligned with the allen wrench channel.  Use (2) M3x10mm screws in

the top holes to attach the gear box to the stepper, and then tighten the

set screw to secure the drive gear to the stepper shaft.



You probably want to use `M302 P1` to allow cold extrudes, then hook up

your stepper at this point and do a test extrusion w/o filament or hot end

in order to check that the gears turn smoothly without slipping or grinding.









Now attach the extruder to the Y-axis of your printer using (2) M3x10mm

screws through the bottom mounting holes into (2) M3 nuts in the slots

provided.  (I'm using M3x12mm screws because I have an extra 3mm aluminum

plate mounted to my Y-axis, to support a previous dual-extruder

experiment [similar to this one](https://www.thingiverse.com/thing:1539380).)



Insert your hot end, and ensure it is snug and flush to the bottom surface

fof the extruder as shown in the picture.  Any gap here will allow flexible

coil to kink and coil into the gap, eventually pushing your hot end off in

the middle of a print.  (This is the voice of experience speaking.)









Install the `clamp` piece using two M3x22mm screws into the stepper.

There is a ridge on the clamp piece that should fit into the ring at

the top of your hot end and keep it from slipping downward.  Be

careful of the screw length here: if the screw is too long it will

bottom out in the blind mounting hole on the stepper and not bend the

PLA clamp piece enough to properly grip the hotend.  (Again, the voice

of experience.)  The `clamp` is secured to the Y-axis using another

M3x10mm screw and M3 nut into its bottom.



You can do a test print, feeding filament through the hole in

the top of the remixed gear head extruder, to make sure everything

is working correctly to this point.  Be sure to use `M92 E127` to

reset your extruder steps/mm if you weren't previously using a

gear head extruder.







### Step 4: Install bowden merge piece






Print out [`bowden-block-4.stl`] and install (4)

[Filastruder/E3D "Embedded for plastic" 1.75mm Bowden Couplers](https://www.filastruder.com/collections/e3d-spare-parts-and-accessories/products/bowden-couplings-all-types).  (You could also use the 2-way or 3-way merge piece if

you prefer.)



To be continued...







### Step 5: Wire up the bowden extruder steppers

### Step 6: Update Printrboard firmware

### Step 7: Test 'er out!



## Related



* The [Extrudrboard2] design allows connecting up to four multiplexed

  steppers to a Printrboard.

* [SPANNERHANDS spool] system.

* Printrbot [Gear Head Extruder].

* [Multimaterial community forum](http://forum.monstercafe.net/topic6.html)



## License



These designs are licensed under the [GPLv2+].



[Printrbot]: http://printrbot.com

[Printrboard]: http://reprap.org/wiki/Printrboard

[Extrudrboard]: http://reprap.org/wiki/Adding_more_extruders#RAMPS_using_ExtrudrBoard

[Extrudrboard2]: https://github.com/cscott/extrudrboard2

[Marlin]: http://www.marlinfw.org/

[Gear Head Extruder]: https://printrbot.com/shop/gear-head-extruder-v2/

[SPANNERHANDS spool]: https://www.thingiverse.com/thing:2119644

[servo extension cables]: http://www.ebay.com/itm/2-3-foot-XH2-54-Long-Stepper-Motor-Extension-Cables-for-3D-Printers-5-Pieces/272523242942

[5x8x2.5mm ball bearings]: https://amazon.com/gp/product/B00ZHST8NU/

[`spool-remix-lid2.stl`]: ./spool-remix-stl/spool-remix-lid2.stl

[`spool-remix-hanger.stl`]: ./spool-remix-stl/spool-remix-hanger.stl

[`mount-1kg.stl`]: ./mount-stl/mount-1kg.stl

[`gearhead-remix-base.stl`]: ./gearhead-remix-stl/gearhead-remix-base.stl

[`gearhead-remix-clamp.stl`]: ./gearhead-remix-stl/gearhead-remix-clamp.stl

[`gearhead-remix-gearbox.stl`]: ./gearhead-remix-stl/gearhead-remix-gearbox.stl

[`bowden-block-4.stl`]: ./bowden-stl/bowden-block-4.stl

[GPLv2+]: https://spdx.org/licenses/GPL-2.0+.html