PVC bends & stretches easily when heated with a heat gun, gas burner or charcoal fire. Get a coiled spring with an outside diameter slightly smaller than the pipe which you need to bend.
Tie a piece of cord to each end of the string then use this cord to position the spring inside the pipe. Heat the portion of the pipe you need to bend then bend to the appropriate angle. Cool the pipe with a wet rag then pull the spring out for the next bend. (this is much easier than the old method of packing the pipe with sand, then plugging the ends.)
Connect your custom bend with ordinary "Ts", "Els", and Couplings. Lowes & Home Depot also have 4-way crosses in some sizes. If you need 3-way corner fittings those probably will have to be ordered online.
Schedule 40 PVC in sizes from 1/2" through 1&1/2" can be heated and pushed inside/over the next larger/smaller size so you do not need reducers. Solvent weld as usual.
You can also make T's, El's etc at home.
I've done that with a propane burner, gently heating a PVC tube to get the correct bend. I did that for underground water piping for irrigating my garden. Connectors do add up to a lot when doing many connections.
I had a greenhouse a long time ago that fell apart so I tossed it out (rusted metal pieces). I figured that if people own 3-D printers, why not put them to use to make the connector pieces. For a structure, you're not concerned about making a watertight connection, just something strong enough to hold pieces together under load. Should be relatively easy to create designs that minimize amount of material printed that gets the job done.
I'm planning on buying a 3-D printer soon. Just trying to figure out what I'll create beforehand, in order to decide which model to buy. PLA is easier to print. But ABS is stronger, more flexible, doesn't break down as easily however it is more difficult to print (warp issues).
Thanks for the tips! I’m filing them away for later.
Unfortunately, with the trellis I’m working on, bends wouldn’t help much. I need a strong cage-style frame, but taller and wider than any of the ones I’ve found at the store, preferably in a block of 8, and strong enough to hold 100+ pounds of tomatoes and vines. The design I think would work best would require several 6-way, 5-way, and 4-way corner connectors. I found a place that sells all that but for more than I can afford. For now I’m still thinking that attaching caps to blocks of wood would still be the best alternative. It’ll look like a giant lego set, but it’ll work.
And hey, who doesn’t like legoes?