Why have I decided to manufacture my own pulleys myself?
I) Not finished
The stock pulleys have only conical indentation at the end of the pulley, which acts as a starting point for drilling.
Also no M3 grubscrew either.
So basically you need to drill it on a lathe if you want precise work, and this directly affects the precision of the machine.
(Imagine an eccentric pulley).
If you make the pulley first, then you drill it even on a lathe, there is no way you can drill an absolutely concentric hole in the middle.
I tried to use a 32 teeth pulley once, we drilled on a lathe, and it was a tiny bit of eccentric hole, destroying the print quality immensely.
But if you drill the hole first, and you machine the outside while putting the workpiece onto a shaft, then it will be concentric, and now if you cut the teeth on the outside, then the endresult will be absolutely concentric.
In general, you always loose precision if you have to remove the workpiece and put back onto the lathe. There are solutions (4-jaw chuck, collet chuck) for the issue, but you start to tool yourself against this specific problem, which is expensive.
III) Low quality tooth profile
If you want to cut the teeth right, ie. within the tolerance specified in the DIN7721 standard,
then you need different cutting tool for the most popular teeth counts.
Some cheap sources, definietly save on cutting tools, having lower quality tooth profile.
IV) New possibilities
No more flipping the belts on the bearing end!
V) Less mechanical stress on the belts
With bigger diameter the belt turns on a bigger radius, that means less stress on the belt.
Also with toothed bearing (read below), you can forget about belt flipping.
The problem with belt flipping:
- unnecessary stress on the belt, especially the steel cords inside. It may break, or delaminates over time.
- aesthetically unpleasant
- limited by the belt width (you can not flip a 20mm wide belt).
VI) Different (out of standard) width pulleys
It is just an idea now, but the possibility is there.
We can have 20mm wide pulley, if you are thinking in a really big (above 500mm) machine,
and you are affraid of belt stretch.
Let's see what we have here.
I) T2.5@32 pulley
III) 608@T2.5 bearing
IV) 624@T2.5 bearing
V) High quality belt
Maybe you can source elsewhere, but this one is steel reinforced, and known to be working high quality belt.
Tolerance and precision
There is no backlash, if you have
- good enough tooth profile (minimal clearance between the pulley's teeth and belt's one)
- low weight carriage (under 1.5kg or 3 pounds for american readers:)
- numerous teeth contact (16 teeth pulleys or more)
- high enough tension, so the belt does not slip between the belt
Notice the non-existant or minimal clearance between the belt and pulley's teeth.
(For closeup picture, please refer to the bearing section.
This one could is not easily photographed because of the metal skirt)
High quality belts
You can get it here(TODO)
Bearings example assembly
In case of toothed 608 bearing:
I have been working on the planet furiously during the whole week.
"It has to start somewhere
It has to start sometime
What better place than here
What better time than now"
-- Rage Against The Machine
Guerrilla Radio (1999)
This is an upcoming blog about adventures of a reprap enthusiast.