Mk4/4S Spool Roller with 608s

This Spool Roller fits the standard Mk3/4/4S Holder Mount Arm. It uses printed or metal 608 bearings to provide a much smoother rolling action for better filament feeding and more consistent printing.

Filament spools went from plastic to cardboard, which has a pretty high friction on the stock spool holder. It can result in uneven filament tension, especially when printing Flex/TPU filament.

This design solves that, with all printed parts (no hardware required).

608 Bearings

The Spool Roller should fit any metal 608 bearing; it also works very well with either of my Printed Assembled 608 Bearings to make it all printed parts:

- My favorite bearing for this: https://www.printables.com/model/1642789-608-roller-bearing

- Also good: https://www.printables.com/model/1715172-a-better-608-bearing

Details

- Fits standard 1 kg filament rolls, up to 70 mm wide.

- Similar size as the original spool holder.

- Fits any 608 bearing (printed or metal).

- Fits the bayonet joint of the Mk3/4/4S Holder Mount Arm.

- The design is optimized for good shaft stiffness without metal hardware, with a wide inner section and a center bearing to minimize shaft deflection under the 1 kg spool load.

Printing Instructions

- Printed layout files are included as examples.

- Material: PLA works well.

- Shaft:

- Print it laying down with supports; set the overhang threshold angle at 29 degrees.

- At least 4 perimeters (w. 0.4 mm nozzle)

- Roller:

- Print with random seam & scarf joint.

- Orient on the thicker flange with the tapered flange up, no supports required.

- Clip:

- No supports required

Post Processing

Check the fit of the bearings on the shaft, the surface at the supports might be a bit rough. File/sand the bearing seats if necessary.

Check the bayonet fit in the standard mount, file the bayonet flanges/hooks to fit if needed.

Assembly Steps

- Slide the Center Bearing (Purple) into the Roller (Blue) on the tapered flange side; it should slide halfway into the Roller.

- Push the Shaft (Yellow) in.

- Slide the Outer Bearing (Green) into the Roller.

- place and slide the Clip (Orange) in place to lock in the Outer Bearing.

All parts Step 1 Step 3 & 4

Cross section view of the full assembly: