Overview
The sliding section consists of three UHMWPE angle pads placed in three corners of the tube. The pads completely cover the outer side of the rail. The pad overhangs are pushed towards the rail by 6-32 screws, which regulates the friction.
2 out of 4 sides of the sliding section can be mounted to the perforated angle or to another sliding element.
The mounting section has a pattern of holes on each side of the tube to mount the lead nut, perforated angle or another sliding element.
There are 3 sizes of the sliding element:
3.5": sliding section / mounting section / sliding section
2.5": sliding section / mounting section
1": sliding section
Materials
- Aluminium square tube, 1.5", 1/8" thick
- UHMWPE channel, 1¼"x¾", 1/8" thick
- Nylon screws, 6-32, 1/4"
Cheaper and more widely available machine screws can be used instead of Nylon screws, but it's a matter of convenience - steel screws need to be worked with hacksaw and file instead of the knife.
Source Files
Making
Make the tube piece from SVG or PDF template, according to the instructions in Howto section
1. Using knife or hacksaw, cut off a couple of 1/2" pieces of UHMWPE channel. UHMWPE is hard to cut with a knife, so be careful and don't place body parts in the way of the blade. Cut the pieces in half in the middle of the base, this will make four angles 3/4" x ~5/8"
2. Make one 5/8" x 5/8" angle piece by cutting off about 1/8" from the longer side. You can use another angle piece as a guide, but cut off a tad more than 1/8". The result should be three pads that will wrap around the outer surface of aluminum angle rail, plus one extra pad. The extra pad can be used for the limit switch or for another sliding section.
3. Enclose one side of a small aluminum angle with two UHMWPE pads and insert it into the sliding element tube. Insert third UHMWPE pad into the sliding element tube at an angle and force it inside
4. Align the UHMWPE pads to be flush with the sliding element tube. Clamp the sliding element in the vise and drill shallow pilot holes in the pads through the mounting holes for 6-32 screws.
5. Mark sides with Sharpie to know which pad goes into which corner. Remove the pads and drill 1/4" holes where the pilot holes are. Use file to remove burrs from the holes in UHMWPE pads. Cut off the far corner facing inside the sliding element in those sides that have the hole. Cut at 45 deg within 1/16" from the hole. This is needed for 10-24 screw head to fit inside the sliding section.
6. In the same sides, cut the edges so they are slanted and form a "V" when UHMWPE pads are put together (see picture). This is needed for the center punched angle rails to slide.
7. Tap the mounting holes for 6-32 screws in the sliding element tube with 6-32 tap (or with 6-32 steel screw). Install a pair of nylon 6-32 screws from inside on one side of the tube, using small screwdriver. Don't tighten the screws all the way, leave ~1/32" gap. Snap the 5/8"x5/8" UHMWPE pad in place and install the third nylon 6-32 screw. Install remaining nylon 6-32 screw (leave ~1/32" gap) and test-snap the 3/4"x5/8" pads in place.
8. Remove and clamp the 3/4"x5/8" pad in the vise and using hacksaw (or Dremel), remove material where the rail edge touches the pad. Approximately 1/3rd of the thickness needs to be removed. This is what the result might look like. Repeat this step for the other 3/4"x5/8" pad.
9. When the pads are installed back into the sliding element, the rail should move freely. Using knife, cut off the ends of the nylon screws that are sticking out. Tap the holes for the friction adjustment screws with 6-32 tap or with 6-32 steel screw. Install friction adjustment screws. The sliding section is now complete.
10. If there is more than one sliding section, repeat the above steps. Test the sliding element with a rail and adjust friction as needed.
Link: Contraptor
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