4-way coupler for connecting PVC pipe. This one is designed for a slip fit over 3/4 inch schedule 40 PVC pipe, but its parametric so it can be adjusted to join any size pipe. Though you can't see it in the preview, there's a little ledge inside that will stop the pipes from sliding through or colliding inside the coupler. Its chopped in half for easy printing. I've also added some pads to help the part stick to a cold platform, and counteract the tenancy for warping which makes gluing them together more difficult.
What's it for? Whatever! I made this to build a PVC scaffold around my rapidly growing tomato plants. You can buy a similar "Furniture Grade 4-Way Side Outlet Tee" where the coupling fits inside the pipe, like this one: http://www.pvcfittingsdirect.com/_e/4_way_Side_Outlet_Tees/product/4451-01/1_Furniture_Grade_4_way_Side_Outlet_Tee.htm ... but that would be less fun.
- If you'll need something other that a 3/4" Schedule 40 PVC slip fit coupling, edit the OpenSCAD file and modify the variables as desired. Grab the software from http://openscad.org if you don't have it. The variables to edit are at the top in the first few lines.
- pipe_od = the outer diameter of the pipe to fit in the coupler, in millimeters (26.67)
- gap = the clearance between the pipe outer diameter and coupler inner diameter (1.0)
- ledge = size of the ledge that stops the pipe from sliding through (2.0)
- wall = wall thickness of the coupler (3.0)
- pad_w = wall thickness of the anti-warping pads
- pad_r = radius of the anti-warping pads
- Save and compile the OpenSCAD file, and generate an STL file.
- Print two of them. I used Cura 12.07 default settings, PLA, with 50% infill. 190 degrees. Each half is about 1.5 hours to print.
- Clean out the strings if necessary. Use a hobby knife to trip off the anti-warping pads.
- Glue them together with cyanoacrylate. If they are a bit warped and don't fit perfectly, heat up the flat faces. I put them in a hot pan until they're just hot enough that they aren't quite sticky, then press them together, and wick the glue into the seams. This technique needs some improvement. Or a heated print bed to eliminate warping in the first place.