This is a LM12UU PTFE linear bearing based on romanz' LM10UU linear bearing.
I.D. with PTFE Tubing: 12mm (nominal)
I.D. without PTFE Tubing; 14mm
O.D: 21mm at 4mm each end and 20.5mm in middle
Need 4mm O.D. x 2mm I.D. PTFE tubing; 6pcs at 25mm long. Helpful if you chamfer the ends.
Part has nominal 4.10mm dia. for PTFE tubing and there is a 0.08mm per side clearance from PTFE to linear rod.
As with any bearing, there is a break-in period. After inserting the PTFE tubes into the housing, slide over guide rod and work in the tubes into the printing housing by pressing in all directions. Make sure you slide the PTFE bearing back and fourth over the linear rod to break in the PTFE tubing.
PTFE tubing at 4.0mm: https://www.amazon.com/gp/product/B073RF7777
Suggestions from other PTFE Linear Bearing users and designers:
- Make sure belts are not too tight. If belts are too tight, then the PTFE will break down and sloth off.
- Confirm your bearings are aligned and carriage slides free and smooth
- Insert 1.75mm filament inside the PTFE tube before assembling into housing. This reduces the compression of the PTFE tubes
- Use a little 3in1 lubricant or Super Lube on linear rods
3D Solutech PLA
PLA can be used, since the PTFE tubing is only contacting the linear rod.
PETG offers a bit of flexibility and should not snap as easily as PLA can during the inserting of the PTFE tubing.