LM8UU and LM8LUU Hybrid PTFE bearing

thingiverse

I've been experimenting with bearing designs lately, so I thought I'd share this latest hybrid 8mm bearing. The video below shows the finished product on an 8mm linear shaft: https://youtu.be/HjRh_Fa9G2I. This design combines PTFE tubing for contact with the linear shaft and a printable bearing housing. This has several advantages, including being lightweight, having an extremely low friction coefficient, and allowing the tube to be easily replaced if it wears out over time without needing to dismantle the linear shaft assembly. The PTFE tube only protrudes about 100-150 microns from the bearing wall, providing a glide surface with very little friction. The third image illustrates the overlap of the tubing from the bearing inner wall. Part Numbers and Variants I try to design things with high tolerances, so I've created 10 variants of each bearing size. Additionally, I've made 5mm test samples of each variant to allow for smaller test prototypes. The part numbers should help identify them and can be broken down as follows: * Part number: 24mm_Bearing_4xPTFE_8.2mmx2.2mm * Bearing length (2 variants): 24mm (LM8UU) or 45mm (LM8LUU) * Number of 2mm PTFE runners (2 variants): 4 or 6 * Inner diameter (3 variants): 8.2mm, 8.3mm, and 8.4mm * 2mm PTFE tube tolerance (3 variants): 2.2mm, 2.3mm, and 2.4mm Printing The 8.2mm ID will give the tightest fit, followed by the 8.3mm and then the 8.4mm I/D will be the loosest. There will also be a subtle variation in fit between, for example, an 8.4mm I/D with 2.2mm tube room and an 8.4mm I/D with 2.4mm diameter. The effect of this variation will depend on your printer's accuracy and the PTFE's actual O/D. I've made a few of these myself and found that the 8.2mm was a little too tight, especially since the 2mm PTFE tubing I'm using is approximately 2.1-2.25mm. For best results, I recommend measuring your PTFE tubing first and then starting with the 8.3mm ID version. The 5mm test samples should make the process less painful, but keep in mind that sliding 2mm PTFE tube into a 5mm sample is much easier than doing it on a 45mm length. I printed all my test prints in PLA at a layer height of 200 microns with a 50% infill. For final production bearings, I'll use 100 microns and slow everything down to get the best results. Future Pending on your response, I have some other ideas using this principle! Print Settings * Printer Brand: RepRap * Printer: Wanhao Di3 * Rafts: No * Supports: No * Resolution: 200 microns * Infill: 50% * Notes: Print for quality not speed! I slow down my settings for parts to improve the part quality, which ultimately improves future print quality. The aim of these bearings is to reduce the weight of moving parts and allow for greater print speeds. If you can print at 100 microns for even better results.