Re: [Emc-users] Toothed belt pulleys [Was: Re: G2 moves, puzzle ]

[Erik Christiansen]

On Sun, Nov 08, 2009 at 07:19:02PM +, Andy Pugh wrote:
> 2009/11/8 Ian W. Wright :
> >
> > One thing you could try is the way I have just made a set of
> > toothed belt pulleys for my new little gantry mill. I used
> > 'Polymorph' (Jett Sett) and the way I did it was ...
> 
> I confess I don't really understand this thread. Are you making
> especially big pulleys where cost is a problem? For the usual sizes
> (30 teeth or so) that only cost £7 or so, I can't see the point.

Pretty much anything can be bought, but where's the fun in that?

Sometimes I need to think of something that would be useful, after
making it with EMC. It helps with motivation to get back to finishing
the CNC conversion. (The motor power supply is nearly finished. Yay!)

Erik

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Re: [Emc-users] Toothed belt pulleys [Was: Re: G2 moves,, puzzle ]

[Andy Pugh]

[Offlist]

2009/11/9 Ian W. Wright :

> One of the main reasons I did it this way was that I wanted
> 24 tooth pulleys which aren't part of the standard range
> here.

Are you sure? HPC have them in at least 5mm and 2.5mm pitch:
http://www.hpcgears.com/newpdf/timing_pulleys_2.5mod.pdf

RS also have them for about the same price
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2864553

Fish4Parts are slightly cheaper, but have much longer URLs so this
might not work:
http://www.fish4parts.co.uk/advanced_search_result.php?exact=on&16=Pilot+Bore&17=24&18=&19=&categories_id=1601&inc_subcat=1&cPath=80_1094_16_1601&x=41&y=10

(Finding component suppliers was one of the bits of a previous job
that I liked the most)

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Re: [Emc-users] Toothed belt pulleys [Was: Re: G2 moves,, puzzle ]

[Andy Pugh]

2009/11/9 Andy Pugh :

> [Offlist]

That want well :-/

Sorry everyone.

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Re: [Emc-users] Toothed belt pulleys [Was: Re: G2 moves,, puzzle ]

[Ian W. Wright]

 >>> One thing you could try is the way I have just made a 
set of
 >>> > toothed belt pulleys for my new little gantry mill. I 
used
 >>> > 'Polymorph' (Jett Sett) and the way I did it was ...

 >>I confess I don't really understand this thread. Are you 
making
 >>especially big pulleys where cost is a problem? For the 
usual sizes
 >>(30 teeth or so) that only cost ?7 or so, I can't see the 
point.

Andy,

One of the main reasons I did it this way was that I wanted 
24 tooth pulleys which aren't part of the standard range 
here. The other reason was that I already had the Polymorph 
and didn't have a spare 95UKP for the set

Ian

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Re: [Emc-users] Toothed belt pulleys [Was: Re: G2 moves, puzzle ]

[Steve Blackmore]

On Sun, 8 Nov 2009 19:19:02 +, you wrote:

>2009/11/8 Ian W. Wright :
>>
>> One thing you could try is the way I have just made a set of
>> toothed belt pulleys for my new little gantry mill. I used
>> 'Polymorph' (Jett Sett) and the way I did it was ...
>
>I confess I don't really understand this thread. Are you making
>especially big pulleys where cost is a problem? For the usual sizes
>(30 teeth or so) that only cost £7 or so, I can't see the point.

I only make pulleys where the price is extortionate due to size, bizarre
tooth numbers or custom boss types. As you say, for small stock sizes
it's cheaper to buy ready made.

Steve Blackmore
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Re: [Emc-users] Toothed belt pulleys [Was: Re: G2 moves, puzzle ]

[Andy Pugh]

2009/11/8 Ian W. Wright :
>
> One thing you could try is the way I have just made a set of
> toothed belt pulleys for my new little gantry mill. I used
> 'Polymorph' (Jett Sett) and the way I did it was ...

I confess I don't really understand this thread. Are you making
especially big pulleys where cost is a problem? For the usual sizes
(30 teeth or so) that only cost £7 or so, I can't see the point.

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Re: [Emc-users] Toothed belt pulleys [Was: Re: G2 moves, puzzle ]

[Gene Heskett]

On Sunday 08 November 2009, Ian W. Wright wrote:
>One thing you could try is the way I have just made a set of
>toothed belt pulleys for my new little gantry mill. I used
>'Polymorph' (Jett Sett) and the way I did it was to get a
>long belt of the pitch I wanted and a bit wider than I
>intended to use. I chopped a length off htis of the right
>number of teeth for the pulley being careful to cut it at
>the root of one of the teeth so that, when I put the ends
>together, the pitch was maintained. Now I turned a recess in
>a piece of metal or acrylic ( I used scrap bits of both for
>different pulleys) so that the belt would just fit into the
>recess with its ends tightly butting - that was the plan
>anyway but I actually ended up with the recess a bit larger
>in diameter and shimmed it down to size with paper strips. I
>drilled the centre of this mold and put a peg in of the
>diameter of the shaft the pulley was to fit and then turned
>a brass hub for the pulley with securing screws and a
>knurled section which would be inside the pulley.. Now it
>was just a case of filling the recess with the thermoplastic
>- dunk the plastic beads in very hot water until they turn
>transparent and coagulate into a lump - fish the lump out
>and knead it in your fingers to get the trapped water out,
>then press it into the mold like plasticene forcing it first
>into the teeth of the belt with something like a screwdriver
>blade, then filling the centre. This is much easier to do
>than to describe!! I didn't bother with cheeks on my pulleys
>and they run fine without shedding the belts but, if you
>need cheeks, you can just turn up a couple of disks if thin
>metal and bolt them right through the pulley - warming them
>a bit first will set them flush against the sides of the
>pulley. The finished thing is an exact fit to the drive belt
>and is of a tough nylon consistency. This is the easiest way
>I have found to make the pulleys but, if you really want a
>metal one, this would also be a good first step as you could
>measure from this the exact OD required and use it to gauge
>a formed flycutter while you make it..
>
More of that thinking outside the box.  Love it, Ian.
How about just pouring it full of epoxy if a release agent could be found?

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Re: [Emc-users] Toothed belt pulleys [Was: Re: G2 moves, puzzle ]

[Ian W. Wright]

One thing you could try is the way I have just made a set of 
toothed belt pulleys for my new little gantry mill. I used 
'Polymorph' (Jett Sett) and the way I did it was to get a 
long belt of the pitch I wanted and a bit wider than I 
intended to use. I chopped a length off htis of the right 
number of teeth for the pulley being careful to cut it at 
the root of one of the teeth so that, when I put the ends 
together, the pitch was maintained. Now I turned a recess in 
a piece of metal or acrylic ( I used scrap bits of both for 
different pulleys) so that the belt would just fit into the 
recess with its ends tightly butting - that was the plan 
anyway but I actually ended up with the recess a bit larger 
in diameter and shimmed it down to size with paper strips. I 
drilled the centre of this mold and put a peg in of the 
diameter of the shaft the pulley was to fit and then turned 
a brass hub for the pulley with securing screws and a 
knurled section which would be inside the pulley.. Now it 
was just a case of filling the recess with the thermoplastic 
- dunk the plastic beads in very hot water until they turn 
transparent and coagulate into a lump - fish the lump out 
and knead it in your fingers to get the trapped water out, 
then press it into the mold like plasticene forcing it first 
into the teeth of the belt with something like a screwdriver 
blade, then filling the centre. This is much easier to do 
than to describe!! I didn't bother with cheeks on my pulleys 
and they run fine without shedding the belts but, if you 
need cheeks, you can just turn up a couple of disks if thin 
metal and bolt them right through the pulley - warming them 
a bit first will set them flush against the sides of the 
pulley. The finished thing is an exact fit to the drive belt 
and is of a tough nylon consistency. This is the easiest way 
I have found to make the pulleys but, if you really want a 
metal one, this would also be a good first step as you could 
measure from this the exact OD required and use it to gauge 
a formed flycutter while you make it..

Ian
_
Ian W. Wright
Sheffield  UK

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Re: [Emc-users] Toothed belt pulleys [Was: Re: G2 moves puzzle ]

[Erik Christiansen]

On Sat, Nov 07, 2009 at 08:13:56PM +0200, Roland Jollivet wrote:
> I watched milling of aluminium toothed pulleys at a company once. They had
> put a whole lot of 2" discs on a shaft, maybe 10" long, tightened up, and
> had the whole thing in a dividing head, then just milling grooves with an
> end mill. If there are buyers for the pulleys, you could do the same. The
> effort is almost the same, and you get to recoup your time costs.

Ah, yes, that is more economical than doing them individually, yet
better quality than cheapo extruded pulley centres.

> While discussing pulley shapes, I thought this is quite interesting. See
> picture (not the best though). One might expect the belt to jam, but it
> obviously does not. Notice the flanges are on alternate sides. This allows a
> pulley, with walls, to be moulded in a simple two part mould. Completely
> irrelevant here, of course.

Now that's even more interesting, because I'm not willing to give up (at
least one) integral cheek. For HTD pulleys, milled from the side,
alternating flanges are a definite possibility, if angular registration
is restored after flipping the half-done blank. Thank you for that one,
too. :-)

Erik

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Re: [Emc-users] Toothed belt pulleys [Was: Re: G2 moves puzzle ]

[Erik Christiansen]

On Sat, Nov 07, 2009 at 05:47:34PM +, Leslie Newell wrote:
> Most cad packages will open dxf files. A quick Google search popped up 
> LinuxCad . It says it opens dxf files.

Many thanks. It looks like good bang for the buck, judging by the
screenshots and self-recommendation on the site.

Erik

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Re: [Emc-users] Toothed belt pulleys [Was: Re: G2 moves puzzle ]

[Andy Pugh]

2009/11/7 Roland Jollivet :

> I watched milling of aluminium toothed pulleys at a company once. They had
> put a whole lot of 2" discs on a shaft, maybe 10" long, tightened up, and
> had the whole thing in a dividing head, then just milling grooves with an
> end mill.

The pulleys I am currently using look to have been cut with a profiled
milling cutter on a horizontal mill or possibly hobbed. That surprised
me as I would have expected them to be broached in a pot-broach.

Most of the profiles don't look to lend themselves to DIY milling.

> Notice the flanges are on alternate sides.

Cunning, though I have seen at least two designs of flangeless belts.

http://www.goodyearep.com/productsdetail.aspx?id=3400 and another with
staggered teeth but no helix


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Re: [Emc-users] Toothed belt pulleys [Was: Re: G2 moves puzzle ]

[Roland Jollivet]

I watched milling of aluminium toothed pulleys at a company once. They had
put a whole lot of 2" discs on a shaft, maybe 10" long, tightened up, and
had the whole thing in a dividing head, then just milling grooves with an
end mill. If there are buyers for the pulleys, you could do the same. The
effort is almost the same, and you get to recoup your time costs.

While discussing pulley shapes, I thought this is quite interesting. See
picture (not the best though). One might expect the belt to jam, but it
obviously does not. Notice the flanges are on alternate sides. This allows a
pulley, with walls, to be moulded in a simple two part mould. Completely
irrelevant here, of course.

http://www.fotothing.com/photos/9bf/9bf00269f5f6d51b810f9d2b2cc1d602.jpg

Roland



2009/11/7 Erik Christiansen 

> On Sat, Nov 07, 2009 at 12:47:44PM +, Leslie Newell wrote:
> > You don't need two cheeks on both pulleys. It is quite common to have two
> > cheeks on the smaller pulley and none on the larger one. Another common
> > setup is one cheek on each pulley, on opposite sides. As long as the
> shafts
> > are reasonably well aligned both arrangements work very well.
>
> The latter is _most_ interesting, because the gullets can then freely be
> plunged with a slot drill from the side, and the tooth tips could be
> chamfered quickly with a larger diameter cutter. (Assuming that a
> chamfer is an adequate approximation of rounded corners.)
>
> > I have uploaded a 2D dxf of a 48T HTD pulley to filebin
> > . This was extracted from a
> > 3D model from the SDP/SI website 
>
> Asking wikipedia about "dxf file", I've found a long list of
> applications which can display that stuff. I'll see if I can find one of
> them on linux. (I see that it's a text file, but looking at that only
> tells me that there are lots of arcs in the pulley. :-)
>
> Erik
>
> --
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>-- The Mahabharata
>
>
>
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Re: [Emc-users] Toothed belt pulleys [Was: Re: G2 moves puzzle ]

[Leslie Newell]

Most cad packages will open dxf files. A quick Google search popped up 
LinuxCad . It says it opens dxf files.

Les

Erik Christiansen wrote:

> 
> Asking wikipedia about "dxf file", I've found a long list of
> applications which can display that stuff. I'll see if I can find one of
> them on linux. (I see that it's a text file, but looking at that only
> tells me that there are lots of arcs in the pulley. :-)
> 
> Erik
> 

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Re: [Emc-users] Toothed belt pulleys [Was: Re: G2 moves puzzle ]

[Erik Christiansen]

On Sat, Nov 07, 2009 at 12:47:44PM +, Leslie Newell wrote:
> You don't need two cheeks on both pulleys. It is quite common to have two 
> cheeks on the smaller pulley and none on the larger one. Another common 
> setup is one cheek on each pulley, on opposite sides. As long as the shafts 
> are reasonably well aligned both arrangements work very well.

The latter is _most_ interesting, because the gullets can then freely be
plunged with a slot drill from the side, and the tooth tips could be
chamfered quickly with a larger diameter cutter. (Assuming that a
chamfer is an adequate approximation of rounded corners.)

> I have uploaded a 2D dxf of a 48T HTD pulley to filebin
> . This was extracted from a
> 3D model from the SDP/SI website 

Asking wikipedia about "dxf file", I've found a long list of
applications which can display that stuff. I'll see if I can find one of
them on linux. (I see that it's a text file, but looking at that only
tells me that there are lots of arcs in the pulley. :-)

Erik

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[Emc-users] Toothed belt pulleys [Was: Re: G2 moves puzzle ]

[Erik Christiansen]

On Sat, Nov 07, 2009 at 10:15:39PM +1100, Frank Tkalcevic wrote:
> I was thinking of installing a blank in the 4th axis vertically, then using
> a small ballnose endmill across the top of the pulley to shape each tooth.
> I'm not sure of the profile; if it is a simple semicircle, then it would be
> simple case of cutting across the pulley for each tooth, and maybe a clean
> up pass or two to get rid of the burs.

But then you have to make and attach two cheeks, to keep the belt on,
unless the cheeks are thicker than the pulley gullet radius, so there's
something left after the teeth are cut.

For the small number that I'd do, a narrow abrasive belt running around
the end of a finger the width of the belt, and somewhat thicker than the
gullet, could fit between the integral cheeks, to chamfer both gullet
lips in one go.

But abrasives should stay in another room, so that looks like hand work.
:-(

Erik

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