Quote Originally Posted by curious aardvark View Post
I get the rails slide up and down - but you still need rods to connect the rails to the effector.
The sliding up and down is not a real issue with a delta (got 2). And good wheels tend to be smoother than rails.
Don't really see what you gain and why you don't need to connect the effector to the sliding part with rods.
The effector and print head still need to be able to move around, so you still need play in the rod ends.
I like the magnetic ball and cup connectors.
All I see - with deltas and rails, is a more complicated setup with a lot more places things might stick or lose glide.
Thanks for the input, I don't really mind the side track on the thread it just helps me understand what other people use and have success with or not. I will take it all in and come up with what i think will work best for my needs.

Linear rails are used on most industrial CNC machines, I know a printer isn't the same as far as forces etc. That being said, as long as they are properly maintained and of decent quality they are extremely smooth and have little slack/play in the mechanism. Less play is always better ;-)

Also, because my printer will not be constructed with vertical extrusions, the expense of the rails is minimal as buying extrusions and pulleys and maybe carriages would probably not be that much cheaper than Hiwin rails.

While ebay/Chinese rails may have a little grit and could have snagging issues, I seriously doubt Hiwin or Bosch or any other high quality rail would have these issues. I have personally worked on 15-20yr old wire EDM machines with linear rails and they were still incredibly smooth and had little play. Wire EDM creates a lot of fine carbon dust and metal dust, as long as the rails are properly maintained they have a very long life span with no drag, snags or slop. Especially on a printer where there is almost no processing contaminants.

The only thing better is Linear motors. Basically a mag lev train sort of system but extremely accurate. I worked on a large CNC machine with those once and it was pretty amazing to see how smooth and friction free it was. Unfortunately they are insanely expensive. the mechanisms are minimum $1000 and then you need special drivers for the motors etc. A little overkill for our purposes as well lol.

I like the idea of 2 smaller steppers Vs one larger one. I might do that but I will see what the difference is.

I was thinking of trying to make a different belt system but I'm not sure its a good idea. I had a sea-flea once that had cable steering. the steering wheel (IE stepper) had a spool on it that allowed for a stainless steel braided cable to be wound around it about twice. on the motor side (IE carriage) there were hooks where the cable ended. at any corners the cable had to make there was a pulley on a spring. This automatically tensions the entire system and made for extremely smooth and accurate steering system. I know they use this same system on F1 Tunnel race boats because of the precise steering control. The "wings" off the back of the motor you see in pictures is where the cable is attached to the motor. This also allows the amount of mechanical advantage to be adjustable by changing the size and amount of pulleys in the system. You can also buy wire that is coated with plastic to stop any vibrations the braids may cause.

What do you think?