Replacement Piston Seals for Lubricant Suction Gun (SCAD)

This model is a half-seal for a suction gun. The piston assembly comprises two backing washers and two of of these half-seals positioned back-to-back. Suction guns go bad quickly, and the seals are not replaceable. They're effectively $30 single-use tools. After being exposed to fuels or certain lubricants, the seal lips absorb fluid and swell up. If it's immediate and severe, it can result in the piston sticking. If the material is shitty enough, it will stick to the tube so badly that it will tear, leaving rubber scum rings stuck to the tube, giving you with a seal that doesn't work well. Otherwise, exposure may result in the seal simply splitting or deforming such that it no longer seals once the swelling reduces. Is TPU the ideal material for these seals? No, but if you can't trust whether the new tool on the shelf has good NBR seals, crappy NBR seals, or completely worthless EPDM seals, then the relative performance proposition is moot. TPU is fairly tolerant of most things, but at least you actually know that it's a TPU blend, and that it's replaceable at negligible cost. Only time will tell what its defining weaknesses are. Is printing going to create a part with a good sealing surface? No. It's better than nothing, and nothing is the only other option. Designs and construction vary, but I threw out all the old suction guns a long time ago, so I can't give you a comprehensive survey of their dimensions and designs. This information applies only to the unlabeled, unknown brand thing I currently have. You may need to adjust dimensions or assembly procedures. The unit I have had the piston staked onto the rod. See the included images. Grind or file the staked spots down to remove the piston from the rod. Dress the rod with a file to make sure it's smooth. Use a threading die to thread the rod. The threads won't be perfect, but it should work. Sandwich the two half-seals between the two backing washers, and put them on the rod. You can use a nylon locknut to hold the new piston in place. Make sure the tube and seal is clean. Put some silicone grease on the seal, insert it sideways into the tube as far as the rod allows, and rotate it as you push it in. Printed in SUNLU 90A TPU, 3 walls, 4 top/bottom, 25% infill. I printed the two halves in separate runs, partly for testing, but also because I wanted to avoid creating burrs from stringing that would happen if there were multiple parts on the bed. You may have better luck dealing with TPU on your printer. With the material I used, the seal works fine, but it tends to chatter at times. For stretchier materials, it may be better to use a shorter lip height. I used 6mm (total 12mm seal height), but 5mm may have been better for the material properties. I'm including STL for 7mm through 4mm heights.