Re: [CAD_CAM_EDM_DRO] Re: Making Stepper Pullys

Hi Bill,

I suspect that you can't find generalised formulas for designing these
pulleys because each belt manufacturer seems to have their own 'standards'.
When I started messing about with initial designs for my machine I looked
around for sources of belts generally available - old photocopiers,
lawnmowers etc.. and gathered together a selection of half a dozen
apparently identical belts - same pitch, width, length etc - and set to to
'design' the form tool to slot the pulleys. Every belt was different!!! Out
of the 6 I didn't have two with the same 'mark-space' ratio of tooth / space
and all the teeth had different flank angles. Also there were differences in
the thickness of the belt which I initially dismissed but then found has a
real effect when you are trying to run the belt round a small pulley.
So, especially in our case where we need to keep the backlash down and
therefore need the belt to fit the pulley quite closely, you need to choose
a particular product from one supplier and, if necessary, copy what they
have done.(see my post to John Stevenson)
Related to this, of course, is the need for careful choice in replacing a
broken belt on an existing machine - if you don't replace it with EXACTLY
the same as the original (and the one which is currently fitted may not, of
course, be the original), you are likely to build in errors.

Ian
--
Ian W. Wright
Sheffield UK
www.iw63.freeserve.co.uk

----- Original Message -----
From: <wanliker@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: 24 November 2001 23:29
Subject: Re: [CAD_CAM_EDM_DRO] Re: Making Stepper Pullys


> In a message dated 11/24/2001 3:23:44 PM Mountain Standard Time,
> machines@... writes:
>
>
> > It's just a simple machining job to index the blank round and use a
> > form tool.
> >
>
>
>
>
>
>
>
>
>
>
> The computations for stepper pulleys is somewhat like gears, and the OD,
must
> be computed as well as the depth of cut, and this is different for
different
> number of teeth.
> So it would be nice to input number of teeth, belt pitch, and have
everything
> printed out, just like magic...........
>
> I have posted before several times asking for the information to do this,
and
> never got even one answer, this is why I posted the scource of the
formulas.
>
> Notw: The correct year is 1988, I made a mistake on the post.
> bill
>
>
> [Non-text portions of this message have been removed]
>
>
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