GUS Simpson Build Manual

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GUS Simpson Documentation


Bottom exploded view

Parts Needed:

  • Basalt Bed
  • Top Plate
  • Bottom Plate
  • Heated Bed
  • 3 Shoulders
  • 3 Plastic Washers
  • 3 M8x100 Screws
  • 3 M8 Nuts (or M8 Nylock Nuts)
  • 6 M8 Washers
  • 12 608 Bearings


  1. Place 4(four) 608 bearings into each of the Shoulders. These bearings should slide right in if your parts have printed accurately. If they don't slide in easily, these can be carefully tapped in with a rubber mallet. If they still not fitting you should not force the bearings into place. Try heating up the parts in the oven on the lowest temperature and attempt to insert the bearings.
  2. Slide one Plastic washer onto each of the the M8x100 bolts and insert the bolt/washer sub assemblies into the holes in the corners of the bed.
  3. Place the heated bed (not illustrated) on the top plate, making sure that it fits flat in place without any bumps. Guide the wires for the heated bed through the hole in the top plate(not pictured).
  4. Now carefully slide the top plate up the bolts that are threaded through the basalt bed, aligning the bolts by hand to fit the holes. You should be able to get the basalt bed, heated bed and top plate to stack with no gaps. If you ended up with gaps check to make sure that the heated bed is in place correctly and that it is flat against the top plate.
  5. Slide an M8 washer onto each of the bolts.
  6. Slide shoulders onto the bolts.
  7. Slide an M8 washer onto each of the bolts.
  8. Slide the Bottom Plate onto the bolts and attach a M8 Nut (or Nylock Nut) ontoto each bolt. The Shoulders should move freely, so don't tighten the base assembly too much.


Hub exploded view, missing hub screw

Parts Needed:

  • Bowden Nut
  • Lock Nut
  • Hub Top
  • Hub Washer
  • Hub Center
  • Hub Bottom
  •  ? M3 Bolts
  •  ? M3 Nuts
  • 4 6702 Bearings
  • 3 608 Bearings
  • Ubis Hotend


  1. Insert 608 and 6702 bearings in each hub part (Hub Bottom, Hub Center, Hub Top).
  2. Screw the Hub Screw into the Hub Bottom.
  3. Slide the Hub Center, Hub Washer, Hub Top onto the Hub Screw in this order.
  4. Screw the Lock Nut onto the Hub Screw making sure that the ring on the Lock Nut is oriented towards the Hub Top.
  5. Screw the Bowden Nut onto the top of the Hub assembly.
  6. Push the Ubis Hotend into the Hub Bottom and secure it with M3 Nuts and M3 Bolts.


ToDo: Install eccentric stops and endstops now?
Define approximate fishing line length. Define length of M3 Bolts for Pulleys]

Motor arm exploded view
Motor arm exploded view from behind
Slave arm exploded view
Stringing illustration

Parts Needed:

  • 3 Motor Arm
  • 3 Slave Arm
  • 3 Pulley
  • 6 608 Bearings
  • [LENGTH NEEDED] 80lb+ Fishing Line
  • 6 M8x60 Bolt
  • 3 M3x16 Bolt
  • 12 M3x6 SHCS
  • 6 M3 Bolts for Pulley (LENGTH NEEDED)
  • 6 M3 Nut
  • 6 M8 Nut
  • M8 Nylock Nut
  • 6 M8 Washers
  • 3 Machine Head Guitar Tuner
  • 3 NEMA 17 Motor

Before assembling arms you should carefully check all the corners of the gears and edges of the holes near the string path. These should be smooth with no sharp edges that could cut into the Fishing Line. It is recommended to sand all inner corners should also be sanded.

  1. Insert 608 Bearings on the arms.
  2. Motor Arm Assembly:
    1. Insert 2 M8 Nuts into the slots inside the arm.
    2. Screw a M8x60 bolt through the M8 Nuts from the inside of the Motor Arm and make sure that there are no gap between non-threaded parts of the bolts and nuts.
    3. Secure these bolts firmly with M8 Nylock Nuts from the other side of the Motor Arm. Do not over tighten as this may cause the motor arm to break.
    4. Secure the spring to the of the Motor Arm with a M3x16 Bolt. This bolt should thread well into the plastic.
    5. Install the Guitar Tuner with the hardware that came with it.
    6. Screw NEMA 17 Motor onto the Motor Arm with M3x6 SHCSs. Do not install pulley at this time.
    7. Repeat for the two remaining Motor Arms.
  3. Assemble the slave arm by inserting M8 Nuts screwing in two M8x60 Bolts in the same way that as the Motor Arm.
  4. Insert two M3 nuts into each Pulley.
  5. Just barely slide the pulley onto the tip of the motor shaft.
  6. Tie a length (how long?) of Fishing Line to the spring and string the arms using this illustration as a guide
  7. Cut the string and tie it to the Guitar Tuner. Do not tighten the Guitar Tuner at this time.
  8. Push the pulley onto the NEMA 17 Motor shaft until holes on the Motor Arm match the holes on Pulley. Thread 2 M3 Bolts (MUST DEFINE LENGTH) into the Pulley in order to secure the Pulley to the NEMA 17 Motor shaft.
  9. Tighten the Guitar Tuner so the arm will stay together.
  10. Repeat for the two remaining arms.



Parts Needed:

  • Hub Assembly
  • 3 Arm Assemblies
  • 3 Eccentric Stops
  • 3 Limit Switches
    Bowden Tube
  • M8 Washers
  • 3 M8x55 Bolts
  • 3 M8 Nylock Nuts
  • 6 M8 Washers
  • 2 M4 Nuts


  1. Slide a M8 Washer onto each M8x55 Bolts.
  2. Attach the Hub Assembly to each of the Arm Assemblies with M8x55 Bolt/Washer assemblies.
    1. Note that the parts should be aligned so the motor arms are on top.
  3. Slide another M8 Washer onto then end of each Bolt and secure them with M8 Nylock Nuts.
  4. Screw the Eccentric Stops and Limit Switches on the arms using M3 and M2 Bolts.
  5. Unscrew the Bowden Nut from Hub Assembly, insert the Bowden Tube through the hole on the Bowden Nut.
  6. Screw two M4 Nuts on the ends of Bowden Tube and widen the inside of both ends of the tube using a 2mm drill bit.
  7. Place one end of this Bowden Tube/Nut Assembly into the nut slot in the Hub Screw and secure it with Bowden Nut.
  8. Slide the second end of the into the Bowden Tube/Nut Assembly into the nut slot in the Extruder.

Filament Drive and Bowden Tube


Parts Needed:

  • Filament Drive – Block
  • Filament Drive – Arm
  • Filament Drive – Bearing Insert
  • Filament Drive – GUS Shoulder Mount
  • 608 Bearing
  • M3x20 bolt
  • 4 M3x25 Bolt
  • 2 M3x35 Bolt
  • 3 M3 Nyloc Nut
  • 2 Filament Drive Spring
  • Hobbed Pulley
  • Nema 17 Stepper Motor
  • Bowden Tube
  • 2 M4 flat nut
  • Bowden Nut (Plastic)
  • Base Assembly


  1. Fit the bearing insert into the 608 bearing.
  2. Bolt the assembly into the arm with the M3x20 and a Nyloc nut.
  3. Bolt the block to the motor with the four M3x25 bolts.
  4. Two of the bolts go through the shoulder mount first, one of the bolts goes through the block and then the arm before screwing in to the motor while the last one simply goes through the block and into the motor.
  5. Press the hobbed pulley onto the motor shaft so that the groove lines up with the filament holes and tighten the set screw.
  6. Hang the result on one of the shoulders.
  7. Take the Bowden tube and whittle at it to make the ends a little thinner. The goal is to be able to screw an M4 nut on each end. Once you have the first nut screwed on as far as it will go, trim the end of the tube flush with the nut.
  8. Add the Bowden nut to the end of the hub screw that does NOT have the nut trap and then feed the tube through the hub screw until the nut seats in the nut trap.
  9. Now you can add the M4 nut to the other end of the Bowden tube, again trimming the tube flush with the nut.
  10. Fit this end into the nut trap on the top of the filament drive. You can feed a scrap of filament through the block, around the pulley and into the tube to check for fit.
  11. Add the tensioning bolts to the arm.
  12. Check the fit and tension. The bolt heads should be secure in the block and the idler should force the filament against the pulley so that pulling or pushing the filament moves the motor.
  13. You should find tooth marks on the filament but it should move freely in the tube.