My solution was to order metal rodends from AliExpress. Along with this I redesigned the rodend mounts, and shortened the arms slightly (400 to 375) because the metal rodends have a bit more travel than the plastic igus ends.
Vitamins:
- 12* Metal Rod Ends - M5 female socket, M5 hole
- 6 * M5 Round cap screws, 20mm long
- 6 * M5 cap screws, 10mm long (leftover from v-rails)
- 6 * M5 washer
- 12* M5 nut
- 6 * 245mm Carbon Fiber Square Tube, 8mm OD, 6mm ID
RepRapped Parts :
- 12 * Rod End (https://github.com/paenian/bertha/blob/master/rod_end.stl)
Tools :
- 3mm Ball-end hex key
- Knife for part cleaning - exacto or similar
Note that the rods are short enough that you can cut the ends off of your old rods and re-use them. Also, if you buy the meter-long carbon fiber, you can now get 4 arms per meter instead of 3 - slightly more economical. Ideally, the rods should be as short as possible - in order to maximize build height. Using rod ends, this is about as good as it gets - to do better you'd need 12 universal joints. I've toyed with designing my own u-joints around M5 bearings, but the size is an issue. I might do more u-joint work in the future sized around M3 bore bearings, but this is as good as it gets for now.
Assembly:
- Glue the rod ends onto the rods. Note the cool 45 degree rotation... designed so that they'd print better, no other reason.
- Once rods are inserted into rodends, arrange hole side up between a clamping surface.
- Clamp 'em down. I'm using a cushion to insure that every rod is inserted all the way.
- Drip one drop of superglue into each rodend.
- Let dry.
Next is simply tightening nuts and bolts.- For the first end, the sequence is:
- M5 by 10mm bolt
- rodend plastic
- M5 washer
- metal rodend.
- Tighten it all down, keeping the rodend planar to the bolt insertion hole.
- For the second end, the sequence is:
- M5 by 20mm bolt
- M5 nut
- M5 nut
- Metal Rodend
- The reason for the two nuts is for fine length adjustment.
- The second nut locks against the metal rod end, holding it at a certain distance. This should be adjusted using a gauge to ensure that all rodends end up being 375mm long.
- Once the length is adjusted and locked in, tighten the first nut against the plastic to keep it from rotating/shaking.
- Repeat these steps for the other six rods.
Important:
Installing these rods is exactly like installing the other ones, but you should ensure that the bolt insertion holes are facing outwards - that way you can tighten the rodends or adjust their length without dismantling the entire bot.
