Re: Alternative to ABS rails? A weed-trimmer line!
Love the idea of extruding or moulding the plastic for the rails. No waste at all and means you can 'repurpose' plastic from other sources ('repurposing' is my favourite made up word at the moment).
For a mould you might also be able to use square aluminium tube cut in half lengthwise or c-section. Melt the plastic and squeeze it into the mould. I have read somewhere (once and in a place that I can't remember where now but I believe the ABS pellets are used in injection moulding processes ( same idea, melt it down and squeeze it in).
With weed-trimmer line, I've only ever seen nylon used. Not that I've ever paid too much attention. Have you come across some ones made from more glue friendly plastics?