Double Extruder Assembly

Which Extruder Are You Building?

These instructions are for the Itty Bitty Double Extruder.  If you’re looking for the Itty Bitty Double FLEX Extruder (V1 or V2), you should start here:

 Itty Bitty Double FLEX Extruder

Before You Begin

Make sure you have everything you need:

• Printed parts:
  • Extruder block (3mm or 1.75mm)
  • Idler blocks (2)
  • Idler pins (2)
  • 2mm spacers (2)
  • 1mm spacers (2)
  • 80-tooth GT2 Pulleys (2)
  • Double groove mount
  • X carriage shelf
  • X carriage support bracket (right side)
  • X carriage servo support bracket (left side)
  • Z probe arm
  • Hexagon cooling fan shroud
  • Print cooling fan shroud
• Hardware kit:   Itty Bitty Double Extruder Hardware Kit
• Hobbed bolts with jam nuts (2):   Hobbed Extruder Bolt
• Hot ends
  • RRD Hexagon Hot ends (2) for 3mm or 1,75mm filament (NOTE: NOT Hexagon AO)
• NEMA 14 stepper motors (2)   NEMA 14 Stepper Motor
• 25x15x10mm fan
  • recommended:  Digi-Key
• 40x40x10mm fan
• HXT900 Servo:   HXT900 Servo
• Z probe snap switch
  • recommended:  Digi-Key
  • You can also use the snap switch that came with your MakerFarm printer.
•  Tools
  • Hex (Allen) wrenches: 2mm, 2.5mm
  • Needle-nose pliers
  • Scissors
  • (Optional) Taps: M3x0.5, M2.5×0.45

Printable Files

Download the printable files here:

Itty Bitty Double Extruder Printable Parts

All of the files are included for the entire extruder system for 1.75 and 3mm filament.  You can print all of the parts separately, or you can print the provided plate files, which contain multiple parts to be run as a single print job.  You will need to print:

• IttyBittyDoublePlate1.STL
• IttyBittyDoublePlate2-1.75mm.STL or IttyBittyDoublePlate2-3mm.STL
• Two copies of Parametric-Pulley-80-8-hex.STL (these will fit with Plate 1 if your printer can print a whole bed of parts cleanly without oozing or warping)

Printed Part Cleanup

	Remove support material from the filament channels in the main extruder block.
	Clean out the countersink holes in the bottom of the X carriage shelf. Make sure M3 flat-head screws will fit flush with the surface.
	(Optional) Tap two holes in the X carriage shelf with M3x0.5 threads.  If you don’t have an M3 tap, you may be able to form threads in the part by forcing in an M3 screw.  You may need to drill the holes out first, depending on your printer.
	(Optional) Tap two holes in each idler block with M3x0.5 threads.  If you don’t have an M3 tap, you may be able to form threads in the part by forcing in an M3 screw.  You may need to drill the holes out first, depending on your printer.  Be careful not to split the part, as the holes are parallel to the layers.
	(Optional) Tap four holes in the cooling fan shroud with M3x0.5 threads.  If you don’t have an M3 tap, you may be able to form threads in the part by forcing in an M3 screw.  You may need to drill the holes out first, depending on your printer.
	Clean out the two countersink holes in the bottom of the double groove mount.  Make sure M3 flat-head screws will fit flush with the surface.
	(Optional) Tap two holes in the Z probe arm with M2.5×0.45 threads.  If you don’t have an M2.5 tap, you may be able to form threads in the part by forcing in an M2.5 screw.  You may need to drill the holes out first, depending on your printer.
	Make sure the groove mount fits around the blocks on the X carriage shelf.  If it does not, remove plastic in the marked areas to make it fit.

Idler Blocks

	Insert an idler pin into a 688ZZ bearing and insert it into one of the idler blocks. You may need to round sharp edges on the pin, depending on how well your printer controls the first layer.
	Insert a sharp tool into one of the holes in the idler pin and rotate it to lock it into place. A scratch awl works well for this. Repeat for the other pin and idler block.
	Install two M3x12 flat head screws.  These are the anchor points for the extension springs.

Extruder Block

	Press two M4 nuts and two M3 nuts into the base of the extruder block.  These will serve as anchors for the mounting and groove mount tensioning screws.
	Press four 688ZZ bearings into the extruder block.  You may need to clean out the bearing seats, depending how well your printer prints overhangs.
	Install a 1mm spacer onto each hobbed bolt.  The beveled side goes toward the bolt head. Install the hobbed bolts into the extruder block. Install a 2mm spacer on the threaded end of each bolt after it is inserted.
	Press one of the jam nuts that came with each hobbed bolt into each pulley. Install the pulleys on the hobbed bolts. Adjust each pulley so the bolt turns freely but has no end play and lock it in place with a jam nut.
	Install the motors with six M3x8 screws and six M3 washers.  Leave the screws loose for now.
	Install a 20-tooth pulley on each motor. Slip a belt over the small pulley first, side the motor up and slip it onto the large pulley; repeat for the other side. Adjust the belt tension by moving the motor and tighten the motor screws.  The belt does not stretch, so it doesn’t need to be taut.  Just take out the slack.
	Install an idler block on each side of the extruder with an M3x25 screw and an M3 nut. Install the extension springs between the anchor screws at the top of the idlers.  A pair of needle-nose pliers or a hook can make this easier.

X Carriage

	Press four M3 hex nuts into the shelf using needle-nose pliers.
	Install a 25x25x10mm fan into the shelf with three M3x12 flat head screws.  Tap the holes in the fan or squeeze the plastic with pliers so the screw threads will grip.
	Install the hexagon fan shroud with two M3x6 button head screws.
	Press an M3 nut into each shelf bracket. Install an HXT900 servo into the left bracket using the screws that came with the servo.
	Press a servo arm into the Z probe. Install the probe onto the servo using the screw that came with the servo.
	Mount the snap switch to the Z probe with two M2.5×10 screws.
	Mount the shelf and brackets to the printer back plate using six M3x16 button head screws.

Final Assembly

	Install two hot ends into the double groove mount.
	Install the groove mount on the extruder block with two M3x12 flat-head screws. Do not tighten the screws.  Just install them for now.  You can tighten them later to bring the nozzles closer together if needed.
	Slide the extruder assembly with the hot ends onto the shelf and secure it with two M4x20 button head screws. If you cannot reach the left M4x20 bolt head to tighten it, you can temporarily remove the left support bracket, complete with the servo and arm and replace it after tightening the screw. If the tips of the hot ends are not exactly 20mm apart, you can adjust them by removing the assembly and adjusting the screws in the groove mount.  Tightening them will move the nozzles closer together.  Loosening them will move them further apart.  Reinstall the assembly to check your adjustment.
	Install a 40x40x10mm fan on the shroud using four M3x16 button head screws.
	Mount the print fan shroud on the extruder with an M3x25 screw and M3 nut.
	Make sure the heater blocks on your hot ends are oriented so the blocks and heater wires will not interfere with the Z probe. Use sharp scissors to cut slits and small round holes in the insulator so it will fit around the hot ends.  The slits should be 20mm apart.  Make sure the insulator will cover the tops of the heat blocks and will not interfere with the Z probe.
	Install the insulator between the fan shroud and the heater blocks.  Insert it from the rear so you can see the slits in the front and ensure that they are closed.

Wiring

A wiring channel is provided through the center of the extruder block.  All of the wires for the hot end heaters, thermistors, motors, fans, servo and limit switch should fit through this channel if they are bundled tightly and terminated after installation.  If you plan to rewire the extruder frequently, you may wish to route the wires elsewhere.

Calibration

Calibration instructions are available here:

 Double Extruder Calibration