Belt drive question

[satguy]

please forgive the stupidity of this question but i have searched this forum with no luck.
I am keen on the idea of a belt drive to drive my short linear rail system. I know the first pulley is attached to the shaft of the stepper motor which drives the belt. Now my question is how do you attach the second (non powered) pulley on the other end? i.e do i use a shaft of some sort to attach it to the frame? most places sell the pulley's alone with no shaft. or is there some other system i dont know about.

can someone please guide me in the right direction please

thanks

[harryn]

Hi - almost everything I know about belts I learned from reading info from these guys. http://brecoflex.com They have more examples and parts than you can imagine.

I personally have been focusing on the AT-10 -25mm wide belt profile, but there are of course different opinions on what is optimum.

To answer you question - I don't think that you should attach one end of the belt to the pulley or shaft.

In the setups I have seen with a pully on each end, the belt can be imagined as a continuous rubber band which goes around both pulleys (powered and idle). The belt is attached to the moving "object" and sort of goes along for the ride with the belt motion.

You can imagine that the belt might be continuous for this arrangement, but more commonly, it is not, so you attach it to each end of your "moving object" with a sort of clamp that grabs the end of the belt and allows for adjustment / tightening.

Reading you question again, I realize that I might have answered a differenent question than you asked. The "idler" pulley is mounted on a shaft which is supported by bearings from your frame.

[harryn]

Hi - one example - see post 17 of this thread

http://cnczone.com/forums/showthread...858#post532858


The forum can be tricky to search. I searched each section, especially the build logs using "belt" as the search word.

[ger21]

Originally Posted by harryn The forum can be tricky to search. I searched each section, especially the build logs using "belt" as the search word.

Use the Google search at the top right.

[satguy]

where can i buy the shaft to install the idler pulley on a flat metal plate? i can only find the pulley itself but no one seem to sell the shaft for them? is this something that is expected to be fabricated by myself?

[ger21]

How about using these?
http://www.mcmaster.com/#allen-shoulder-screws/=23tzq1

[satguy]

looks good thank you gerry. if theres any other options please let me know

[harryn]

Hi, I am not sure if they are better or not, but I have also seen standard and precision shaft sold on McMaster and also at bearing supply places.

I am not sure about Australia, but in the US, this is a common supplier for bearings and shafts:

http://web.applied.com/

Maybe there is a more local supplier near you.

[handlewanker]

Hi, I take it you will be driving the Table? with a screw? Then the second pulley is attached to the end of the screw and coupled together with a toothed flat belt to the stepper motor.
Does this help?

You could attach the stepper motor directly to the screw, but it depends on the resolution per step that you want.

BTW, I'm in Melbourne, where are you?
Ian.

[satguy]

thanks for your suggestions. what i am doing is not a CNC router but something similar.
I have a linear rail which i want to move up and down using a belt system and a stepper motor.
on the one end of the linear rail i have the stepper motor and its shaft connected a XL pulley. the belt spans the length of the linear shaft and connects to the second pulley on the other end. The second pulley serves no purpose but to act as a point for the belt to go around and keep it tentioned.

I guess im after the best way to do this so the second pulley is free rotating and does not cause too much friction for the motor to handel.

Im in Sydney by the way.

[handlewanker]

Hi Satguy, it sounds like you are having a toothed belt going round two pulleys one at each end of the framework, and the belt is cut through one side and attached to each side of the gantry with a tension device, and one pulley is driven by stepper motor the other is a return idler pulley to hook the belt over.

In which case all you need for the second "idler" pulley attachment is two angle brackets to sandwich the pulley between, with a pin for the pulley to run on, and be attached to the framework end face.

The belt ends are clamped with a cable clamp to the side of the gantry, and the other end of the belt has a turnbuckle attached to the other side of the gantry to make the belt tight.
A sketch if required.
Ian.

[satguy]

thank you ian.
thats pretty much what i had in mind. question is though do you think that the idler pulley should be the type with a bearing in it to make it run smooth or should a non bearing one work just as well