Testing out the spectra line drive system that I’m going to use on the delta 3D printer I’m working on. The system is derived from Rob Poveys system with the main difference being how the grooves are made in the pulley/drum. The groves in this system is V shaped from being made with a tap in a lathe.
I can’t get the line to slip on the pulley at all even with very slack line, the motors will skip steps instead.
In theory the pulleys should grip the line even harder when tension is increased but the downside might then be that the line might deform and go deeper into the groove causing mm/step to be off by some amount.
I guess only time will tell when the printer is up and running.
BTW, you might want to turn the sound down, I have some really bad resonance issues in this test system.
http://www.youtube.com/watch?v=pKerL-opsj4
I hope it does hold. My experience is spectra can slip when you think it’s impossible. I’m using sand paper for grip now. Everything else slipped or eroded and then slipped.
We need a 3d printable version of this 
I have another idea for it.
@Aaron_Kartash
I exported the pulley and drum to stl format if you would like to try printing them. I do not have a printer yet so I can’t really test myself. The hole for the grub screw I made 2.5mm for M3 screw but it needs to be tapped ofcourse.
The drum is made for 2x 693zz bearings.
I dont know if this will work printed, I guess its not optimal since it will need loads of support and could probably split from the line tension but have a go if you’d like :).
https://drive.google.com/file/d/0B-xBE70A26rWR1NadDhTZE5TRzg/edit?usp=sharing
https://drive.google.com/file/d/0B-xBE70A26rWazA2cE5UYU1Sb28/edit?usp=sharing