Stepstruder MK6 Assembly 3 mm

If these instructions don’t seem to match what you received in your kit, please see the Stepstruder MK7 assembly instructions instead.

A stepper motor extruder allows control over flowrate as well as the ability to retract filament during a build to virtually eliminate unwanted ooze and strings. The MK6 stepper motor measures in at a whopping 100 oz-in of torque enabling the use of a direct drive setup. Direct drive extrusion means there is no gearbox on the motor so there is no need to account for backlash (extra play in the system when reversing directions), and it also enables very fast filament retraction speeds at an instant.

The MakerBot StepStruder™ MK6 contains certain parts that can be dangerous if used in an improper manner. The extruder tip can become hot (>250 celsius). There is also a powerful motor that can pinch fingers. Make sure you always run the extruder fully assembled and that you never touch the hot metal end. Always keep the extruder away from flammable objects and never leave it unattended while heated up.

Tools You’ll Need

The Stepstruder MK6 goes together pretty easily, but you’ll need a few tools to speed the process along:

• Scissors
• 1.5mm Hex Wrench
• 2.5mm Hex Wrench
• 13mm Wrench
• Adjustable Wrench
• Soldering Iron
• Sharp Knife
• Tape
• Vise
• Superglue / Acrylic cement
• Kapton Tape

Part List

Prep Work

Peel off protective coverings

The acrylic parts come with a protective paper film that covers the surface. Use your fingernail or a small screwdriver to remove this film.

Remove the fan connector

Using wire clippers clip off the fan connector as shown.

Attach drive gear to motor shaft

Bolt the gear onto the motor shaft as shown. The bottom of the drive gear should be 4.9mm from the top of the motor. Use an M5 bolt to set the height of the drive gear as shown. Ensure the set screw contacts the flat part of the shaft.

Mount the fan to the bracket

parts needed:

• fan
• bracket
• 2 M3x16 bolts
• 2 M3 nuts
• M3 washers

Bolt the fan to the bracket as shown. Ensure the fan cable is oriented as shown— the fan label should be facing the inside of the bracket.

You may need to change the angle of the bracket to make it more square. You can use the table for leverage.

Add the motor

Place the motor on a flat surface. Ensure the wires are to your left when facing the motor.

Add the fan mount.

Place the fan mount on the motor as shown.

Add Cork Gasket

Place the cork gasket as shown.

Filament Drive System

Plate A

Add Plate A to stack on top of gasket. Add an M3 nut to the left side of Plate A

Plate B

Add Plate B to stack.

Plate C

Plate C is three pieces of Black Delrin. Place plate C onto the stack as shown. Pay careful attention to the orientation of the parts.

Plate D

Plate D is the top of the sandwich. Place it on the stack as shown.

Insert thumbscrew + nut

Place an M5 nut on the M5 nut with thumb screw as shown.

Bolt Stack Together

Insert 4 M3x25 bolts.

Insert two M3x22 bolts into the holes as shown. These are for securing the motor. In this step they help keep the layers aligned.

Insert the nut and bolt into the stack as shown.

Insert two M3x22 bolts as shown. Hand tighten nuts onto the M3x22 bolts.

Check Alignment

Tighten the bolts evenly. The cork gasket should be evenly compressed on all sides as shown.

Tighten the bolts such that the drive gear is symmetric in the filament slot as shown.

1″ Spacers + Nuts to Bolts

These spacers will ensure that the hot end is separated properly from the filament drive mechanism.

Insert the M3x40 bolts through the acrylic plate. Put one spacer on each bolt and then thread a nut onto it. Feel free to tighten the nut to 1/4 turn past finger tight.

Hot Assembly

Assemble the hot assembly

Heater Cartridge

Put the Heater Cartridge in place.
* Be careful handling the cartridge heater, the leads can be broken off if stressed *
The fiberglass sleeves are for thermal protection and not intended for strain relief.

The heater cartridge should slide easily into the hole we’ve had precision-milled into the aluminum hot end. Put it right in the middle like this; the ends will stick out a bit.

Now lock in in place with the M3 x 4mm set screw. It will be the shorter of the two bolts in the MK6+ kit. Tighten down about a third to half turn past finger-tight.

Do not tighten too tight and distort the heater cartridge body as this will damage it.

Attach Thermocouple

Use the thermocouple included in the Extruder Controller v3.6 kit for a MakerBot Thing-O-Matic. (Or purchased separately in our store.) This is the long, brownish wire with a metal tip on one end, and red/yellow wires on the other end. Attaching it to your hot end is very easy: we will be bolting it to the side of the MK6 thermal core.

Ensure that you use a layer or two of Kapton tape wrapped around the thermocouple end to electrically isolate the thermocouple from the metal extruder body (Picture does not show the Kapton tape isolation).

To attach it, use the M3 x 6mm bolt included in the MK6+ kit, along with a M3 washer. Thread the bolt into the tapped hole and tighten the thermocouple under the washer. You’ll need to keep it in place as you tighten as it has a tendency to be pushed out before getting clamped down. It’s a good idea to wrap the thermocouple lead around the block as we’ve done here, so both leads come off the same side of the heater block.

Prepare Ceramic Tape

Cut Shorter Piece of Ceramic Tape

Cut one length of ceramic tape 47.6 millimeters long (1 7/8 inches long).

You can also get the proper length if you wrap the tape around the width of the heater element.

Cut Longer Piece of Ceramic Tape

Cut another piece 60.3 millimeters long (2 3/8 inches).

You can also get the proper length if you wrap the tape around the width of the heater element.

Mark Centers

Fold each piece of ceramic tape in half and mark the centers.

Make Holes

Use the thermal tube to press a hole in each piece of ceramic tape at the marked centers

Trim Shorter Piece of Ceramic Tape

Trim the shorter piece of tape like the image below. You want to make room for the heater

Apply Anti-sieze to Threads.

If you ever plan on disassembling your hot end, it’s imperative to apply the included anti-sieze compound to the threads. This stuff will protect against rust, corrosion, seizing, and galling that can happen at high temperatures. Simply smear a bit on your finger or a swab and apply it to the external threads. It should be applied to the nozzle threads and the thermal barrier tube threads.

Bolt Nozzle Into Thermal Core

To bolt the nozzle in all the way, get an adjustable wrench and your 13mm wrench. Screw the nozzle all the way into the thermal core by hand. Tighten them against each other with the wrenches. Use the 13mm wrench on the nozzle, and the adjustable wrench on the flat parts of the heater core.

Thread In Thermal Barrier Tube

The thermal barrier tube is what provides the structural support for the PTFE as well as keeps the heat from travelling all the way up to the filament drive mechanism. Apply the anti-sieze and screw it all the way into the heater core. There isn’t much to grip on, so just make sure you tighten it as much as possible with your fingers.

Insert the PTFE Tubing

Insert the PTFE tube into the thermal barrier tube with the pointed end at the nozzle. Ensure the PTFE tube is pushed all the way into the nozzle.

This cutaway drawing shows the full insertion of the PTFE tube. Note that it extends all the way into the nozzle. You can check this by pulling it out and measuring it (should be roughly 80mm) or by unscrewing the nozzle with the PTFE tube in place.

If you’re having trouble fitting the PTFE insert into the tube, put your PTFE barrel into the freezer for 15 minutes or so. The PTFE will shrink and slip in easily.

Trim the PTFE Tubing

Using a razor knife trim the PTFE tube so that it’s flush with the top of the thermal barrier tube as shown.

Wrap Ceramic Tape Around Thermal Core

Slide the two strips onto the thermal tube.

Wrap Thermal Core

Using kapton tape, carefully wrap the thermal core to hold the ceramic tape in place and to further insulate.

Take your time during this step.

Make Holes In Insulation

Pierce the insulationwith a razor blade to reveal all four bolt holes. Be careful as the thermal core is aluminum and you risk stripping the threads!

Clear Holes

Clear the bolt holes of any insulation. Insert four bolts in the bolts holes to make sure they can all screw in.

Metal Retainer Plate

Thread the four remaining M3 x 25 bolts through the central holes in the plate, then screw them into the holes in the thermal core.

There are nuts on these bolts; the retainer plate will be held firmly in place after we attach it to the assembly.

Heat Sink

Provided in the kit is a circular heat sink. It is slightly oversized for the thermal barrier tube, so get your pliers and gently compress it a bit to reduce the diameter. Once you do that, it should have a nice friction fit over the thermal barrier tube. The heat sink is not strictly necessary, but it does help with keeping excess heat in the hot end and not the filament drive.

Add Heat Sink to Thermal Barrier

Attach Thermostat to the Stack

Attach the Hot End to Acrylic assembly

Attach the hot end to the filament drive system. The four bolts sticking down should fit into the corresponding holes on the metal retainer plate. The top of the thermal barrier tube should also fit into the hole in the bottom of the filament drive mechanism; sand or use a file to enlarge it if necessary. Pop it into place as shown.

Put some nuts on the end of the retaining bolts and tighten them down with the pliers.

Make Adjustments

Arrange wires and tighten bolts

Attach One Arch

Using 2 M3x16 bolts and 2 M3 nuts, attach the arch to the stack.

Locate the 2 Supports

The supports are two of the same part. The tabs are asymmetrical though. Using 2 M3x16 bolts and 2 M3 nuts, attach the arch to the arch.

The Second Arch

Using 4 M3x16 bolts and 4 M3 nuts, attach the second arch to the stack.

Attach Bottom to Supports

The bottom parts bolt onto the arches as shown. The hex nut cutouts are slightly off-center for mounting purposes. Make sure you keep them on the same side. You will also want to ensure that a line drawn through the hex cutouts will pass through the where the filament goes.

Superglue Spacer Feet

Using superglue, or ideally acrylic cement, you’ll want to attach the spacer feet to the bottom of the supports. Make sure the hole in the spacer lines up with the hex cutout or you’ll be in for a grumpy surprise. If you’re using superglue, its a good idea to scratch up the surfaces to be glued for better adhesion.

Add Bearing

Slide the 606 bearing over the shaft of the stepper motor. It should just fit into the round opening in the acrylic plate. It will stick out of the acrylic but should be flush with the tip of the stepper’s shaft. This will allow you to apply more pressure to the filament against the hobbed pulley and prevent slippage.

Heat Shrink Tubing

Place 1 inch of large heat shrink around both fan wires and 1 inch of small heat shrink around the black fan wire as shown.

Solder Fan Wires

Locate your hookup wire. Cut in half. Strip the ends.
Twist and fold ends into loops before soldering.

Shrink the Heat Shrink

Place the small heat shrink tube over the solder joints. Then place the large heat shrink over both solder joints.

M5 Nuts

Insert the M5 nuts into the cutouts of the support. You can tape over these nuts to keep them from falling out during the rest of the assembly process.

Congratulations! You’ve completed the stepstruder.