Stepstruder MK6 Assembly 3 mm

If you are upgrading a MakerBot Plastruder MK5 to a MakerBot Stepstruder MK6 using the MakerBot Stepstruder MK6 Upgrade Kit, proceed to Stepstruder MK6 3MM Upgrade Instructions. Otherwise, continue below.

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
  • Two Pliers
  • Soldering Iron
  • Sharp Knife
  • Tape

Strongly suggested

Parts You'll Need

Nuts and Bolts


Custom Machined Parts


MK6 Nozzle


MK6 Thermal Core


MK6 Thermal Barrier


Laser-cut Parts


High Torque NEMA17 Stepper Motor


Hookup Wires


Power Resistors



This is not included in the extruder box. The Thermocouple comes packed in a white wax paper envelope that is included in the Gen4 electronics kit, in the ziplock bag with the 6 pin heads and rainbow cables.


PTFE Tubing


Anti-sieze Paste, Heat Sink, Ceramic Tape


Heat Shrink Tubing


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.

Attach thumb wheel.

Locate one thumb screw knob. Using two pliers press the knob onto the longest M5 bolt as shown below.

Filament Drive System

Add Plate A to stack.

Take Plate A and place it in front of you as shown in the picture.

Add Plate B to stack.

Find Plate B and place it over Plate A as shown.

Add Plate C to stack.

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.

Add nuts to Plate C.

Add four nuts to Plate C as shown. This is where you can mount a Magnetic Rotary Encoder if you choose to add one in the future.

Add Plate D to stack.

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

Bolt stack together.

Insert M3x25 bolts

Insert four M3x25 bolts into the holes as shown. These are for securing the motor. In this step they help keep the layers aligned.


Insert M3x22 bolts

Insert two M3x22 bolts as shown.


Hand tighten nuts onto the M3x22 bolts


Insert plunger.

Insert the plunger into the stack as shown.


Insert thumbscrew + nut

Prepare nut and bolt

Place a nut on the thumb screw as shown.


Insert nut and bolt

Insert the nut and bolt into the stack as shown.


Attach thumbscrew retainer bolts.

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

Tape nuts on filament drive housing.

Place an M3 nut into each of the four holes and tape into place as show.

Attach drive gear to motor shaft.

Bolt the gear onto the motor shaft as shown. The bottom of the drive gear should be 4.9 mm 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.

Fan mount assembly

Remove the fan connector

Using wire clippers clip off the fan connector as shown.

Strip the wires

Strip the ends of the fan wires and the black/red cable.

Add heat shrink

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 wires

Ensure the heat shrink is a few inches from the cable ends. Solder the fan wires to 24 inches of black/red wire as shown.

Shrink the heat shrink

Place the small heat shrink tube over the solder joint and heat as shown.
Place the large heat shrink over both solder joints and heat as shown.

Mount the fan to the bracket

Using two M3x16 bolts, two M3 nuts, and two M3 washers bolt the fan to the bracket as shown. Ensure the fan cable is oriented as shown. Ensure the fan label is facing the inside of the bracket.

Bolt motor to filament drive housing.

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.

Add drive housing

Place the filament drive housing as shown.

Tighten bolts

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.

Pre-load all the t-slots with nuts.

By doing this before the assembly, you will save yourself countless trips to the floor to find dropped nuts, and other headaches. We use a simple three-step process:

1: Tape to "top" side of the acrylic


2: Flip it, and insert nuts into the slots


3: Tape over the nut


Attach supports to one arch.

The supports are two of the same part. The tabs are asymmetrical though, so make sure the bottoms of the supports are flush with the bottoms of the tabs as shown. Tighten the bolts to finger tight for now.

Attach other side to supports.

Take the other support and attach it on the back side. Tighten the bolts to finger tight only.

Attach top to supports.

The top plate will bolt onto the arches as shown. Bolt it into plates and only finger tighten the bolts.

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 large circular cutout in the top plate. This is where the filament path goes, and we want it to be in-line with the mounting holes.

M3x40 bolts into top piece.

These bolts are how the hot end is attached to the filament drive mechanism. Drop them into place as shown.

1" spacers + nuts to bolts.

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

Attach filament drive to support.

The tabs on the filament drive ensure that you can only bolt the filament drive in the proper orientation. Insert it into the slots and then bolt it in place. Tighten the bolts to 1/4 turn past finger tight with the hex wrench. This is also a good time to tighten the rest of the bolts to 1/4 turn past finger tight as well.

Superglue spacer feet to support.

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.

Tape M5 nuts into spacer

Once the glue has dried, you'll want to insert the M5 nuts into the cutouts. I like to tape over these nuts to keep them from falling out during the rest of the assembly process and during usage.

Hot End Assembly

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 and trim 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.

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.

Using a razor knife trim the PTFE tube so that it's flush with the top of the thermal barrier tube as shown.
PTFE tubing must be inserted all the way
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

Bolt on power resistors.

The power resistors are the heating element for the hot end and should read 5 Ohm (5Ω). Pay extra attention to the markings on this element as customers who have accidentally grabbed a similar but incorrect power resistor have had a hard time discovering this issue after properly wrapping their hotend. Additionally, those who have sourced their own inexpensive 5 Ohm 25watt power resistors have reported their power resistors exploding. Please do not experiment with those!

Use the provided tiny M2 bolts to attach them to either side of the thermal core. Tighten them down with the hex wrench.

Connect Teflon Wires onto Power Resistors

Provided in the kit is a short length of PTFE insulated wire. This slippery bit of wire is capable of handling higher temperatures than your average bit of insulated wire. We'll be using it to wire the resistors together in a safe way.

The PTFE is rather difficult to strip with standard wire strippers, so get your sharp knife back out. Strip both ends of the wire Mark where the middle of the wire passes over one of the second resistor and then remove the PTFE covering the wire in that area.


Connect the new way!

Using your M2 hardware, insert the M2x5mm bolt through the tabs on the resistors from bottom to top(bolt head should face downward when hot end is standing up). Next comes the Teflon wire. Then the M2 washer, followed by the M2 nut.


The resistors themselves are 5 ohm resistors and we are going to wire them in parallel. The total resistance will be 2.5 ohms. This will be run at roughly 12v for a 57.6-watt heater. Since the new hot end has quite a bit more material to it, we need the higher heating capacity to make it operate. That is why you need a relay if you are using the Gen3 electronics.

Cut and add Heat Shrink tubing to teflon wires


Cut the black and red wire into two 24 inch pieces

One piece is for the extruder heater, one for the motor.

Solder red/black wire onto PTFE wires.

From the PTFE wire, we can use standard red/black wire to handle the rest of the path to the MOSFET or the relay. Simply solder one of each wire to one of the PTFE wires.

Insulate wires.

Starting January 1st, 2011, Stepstruder MK6 Kits will now include two sizes of heat shrink tubing. This will now be the preferred method for insulating soldered connections.

This picture shows the outer insulation — make sure that you've also insulated the two solder joints from each other so they don't short together.

Other options include Kapton or electrical tape.

Attach Thermocouple

Use the thermocouple included in your Extruder Controller v3.6 kit. 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.

First, wrap the tip of the thermocouple with a small piece of kapton tape to isolate it electrically.

Then, to attach it, take out your M2x5 bolt, and your M2 washer. Thread the bolt into the hole, and when you're about halfway down, put the metal end of the thermocouple between the washer and the heater core. Continue tightening the M2 bolt until the thermocouple is securely attached. You'll need to keep it in place as you tighten as it has a tendency to be pushed out before getting clamped down.

If the threaded hole is not quite deep enough for the M2 bolt, you can take an M3 nut and use it as an extra washer. This will give your bolt plenty of headroom.


Insulate the thermal core.

The video below was intended for the MK5, but is relevant to the MK6 as well.

Prepare the ceramic tape

Cut one length of ceramic tape 70 mm long.


Mark the center


Use the thermal tube to press a hole in the ceramic tape.


Your result should look like this


Mark the center of the longer piece of ceramic tape


Use the thermal tube to punch a hole through the longer piece.


You now have two pieces that look like this.


Slide the shorter strip around the thermal tube and under the wires on the sides with no resistors.

Slide the longer strip around the thermal tube and under the wires on the sides with resistors.

wrap it up with some tape.

Pierce the insulation with a razor blade to reveal all four bolt holes.


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


Place M3x22 into metal retainer plate.

Take the steel plate as shown and insert four M3x22mm bolts as shown. This will be the part that gets bolted to both the filament drive system and the thermal core.

Thread nuts onto bolts.

Thread four nuts onto the M3 bolts as shown. These nuts will keep the retainer plate firmly attached to the M3 bolts when they get tightened down in a later step. Put them pretty close to the top of the retainer plate.

Bolt retainer plate to thermal core.

Take the retainer plate and bolt the nuts into it using the provided hex wrench. Go ahead and tighten them down securely.

Tighten nuts against retainer plate.

Securely attach the retainer plate by tightening the nuts against it. This will lock it in place and become the mounting point.

Attach 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.

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.

Route wires through appropriate slots.

On either side of the supports are some conveniently placed gaps that are perfect for routing wires though. We prefer to route the heater wires through one slot and the thermocouple/thermistor wires out the other slot. This will keep things tidy and also help you remember what is what.


Tape on thermal cape under the motor

The thermal core can generate quite a bit of heat, so we've provided a thermal cape made from PET that should be taped on the back of the extruder as shown. This will prevent the vast majority of the heat from moving up and potentially overheating the motor.

NOTE: This part may be a silver color or clear; both work.

Completed Stepstruder MK6, 3 mm filament configuration


Next Step: Stepstruder MK6 Electronics Assembly

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