Centering Spool Roller H2D/H2C TPU; H2Dual Compat.

This is a front-mount spool holder and roller compatible with the fantastic H2Dual AMS shelf and riser by Nothing Spectacular. This spool holder is designed to fit into the hexagonal holes on the front of the shelf and hold a roll of filament, and feed that filament through a centering arm directly into the print head. 

This is perfect for feeding TPU into the print head of an H-Series printer. I found some other solutions, but had problems when the print head would move quickly: The force from the move would drag the spool sideways and actually pulled it off the roller. By using the centering arm, this spool holder transfers the force of the print head into the arm itself, not pulling the spool off while allowing the print head to move quickly as well as feeding TPU into the print head on a low-friction path. Both a left and right-hand version are included. 

Additional Hardware Needed

1x Bambu PTFE Swivel Connector for P2S

This essential component is the lynchpin of the spool holder. This swiveling PTFE coupler mounts to a ball screw and swivels on that ball screw, allowing the filament to take any path and transfer force into the arm. It is available here on the Bambu Labs store for $4.99 and includes the ball screw. Note: There is a version of this PTFE tube coupler for the A1 (white). It does not include the ball screw. Be sure to purchase the variant for the P2S as it includes the ball screw.

4x 608ZZ Bearings

Four of these bearings are needed, two for each spool roller. These are available from Bambu Lab for $1.80 per 2-pack. Cheaper bearings are definitely usable, and you can even print simple 608ZZ bearings in place that will work fine. I have printed these with some success. 

Whatever extra PTFE Tube you have lying around

You've probably got some of this extra lying around; if not, you can find it from Bambu Labs here. I cut approximately 2 inches to guide the filament from the spool holder down toward the print head, and another ~3 inches in the print head itself to guide the filament around the other PTFE tubes. Use lengths that make sense for your personal setup. 

Print Materials

PLA-CF is my material of choice for this, but the rollers can be printed in PLA. I like the extra rigidity of the PLA-CF. If you are concerned about the heat from the print bed warping the PLA, it can be printed in PETG. If you would like to print this in ABS or ASA, make sure you scale up by about 0.5% to ensure proper tight fit, if your filament profile does not already account for that shrinkage. 

Assembly

1. Insert the ball screw through the hole at the top of the PTFE coupler and screw it into the hole on the arm. DO NOT OVERTIGHTEN, just screw it until it resistance builds. 
2. Insert about a 2" length of PTFE tube into the coupler. 
3. Insert the hexagonal pins into the hexagonal holes on the front of the H2Dual riser shelf, using the second and third from the center. The holder with the arm should hang over the inside of the printer, with the holder without the arm on the outside. 
4. Insert a spool roller bearing insert (the wider end) into the holes on each side of the roller and secure with some glue. 
5. Insert the roller bearing inserts (The narrower end) into the center of the roller bearings
6. Seat the bearings & spool rollers into the tracks in each holder.