Re: [CAD_CAM_EDM_DRO] Toothed pully design information needed.

Hi,

I have made the timing belt pulleys for my mill using a flycutter - quite a
robust one in my horizontal mill. The supplier I got the belts from was
happy to photocopy the relevant page out of the catalogue which gave the
tooth geometry but I actually measured up the belts and worked from that
info. The problem as I saw it is that usually, the pulleys have some
'freedom' built into the tooth widths - i.e. the belt teeth do not
completely fill the pulley spaces, presumably to allow for any inaccuracies.
I saw this as a possible source of inaccuracy in the system in the form of
backlash and so made my pulleys to fit the chosen belts exactly. Notice I
said 'chosen belts' - I actually measured up several supposedly identical
belts from different sources and found that no two of them actually had the
same 'mark/space ratio' of tooth to space distance - something to look out
for if you ever have to replace these belts! Making a fly cutter isn't too
difficult as the belt tooth shape doesn't vary much as it passes round the
pulleys - its the bit in between that bends, so the cutter really just has
straight sides tapered at the same angle as the belt teeth. When the pulleys
are finished, a rub with a file over the edges of the tooth tips will round
the corners enough to stop them cutting the belts.

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

----- Original Message -----
From: <ptengin@...>
To: <CAD_CAM_EDM_DRO@egroups.com>
Sent: 11 November 2000 05:39
Subject: Re: [CAD_CAM_EDM_DRO] Toothed pully design information needed.


> In a message dated 11/10/00 9:38:42 AM Hawaiian Standard Time,
KM6VV@...
> writes:
>
> << Bill,
>
> Yes, it would be nice to be able to cut timing belt pulleys. But don't
> you use a flycutter for someting like that? I guess it would be useful
> to have a program to calculate the pitch dia, blank sizes and all that
> stuff. Please advise when you get it working!
>
> Alan
> >>
> Bill and Alan,
>
> If you folks get the tooth form information needed, you're all set. Just
> need a CNC mill to cut the form cutter :) My two cents is to cut the
> sprockets from steel, cast iron or maybe brass. I have aluminum sprockets
on
> my FB-2 and they already show signs of wear since I did not fully enclose
the
> belt drive.
>
> BTW, see if information on HTD profile belts can be found as I believe
the
> profile is easier to cut. The teeth are deeper so the sprocket is probably
> more forgiving of imperfections of the cut profile etc. Also, since the
teeth
> are deeper, the belts are less prone to skipping under load.
>
> Peter
> THRD, Inc.
>
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