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[OM] Re: Motor Drive Caps

Subject: [OM] Re: Motor Drive Caps
From: drchrisbarrett <drchrisbarrett@xxxxxxxxxxxxxxxxxxxx>
Date: Fri, 08 Dec 2000 10:14:00 -0800
I think strength will be a problem with the stereolith technique as well.

Also, if the cap is removed/replaced a lot then the plastic will tend to be
eroded. Then we'd have plastic dust kicking around in the shutter.

Perhaps a hybrid solution with a plastic disc (with the coin slot moulded in)
and an attached metal bayonet might work.

We'd need a couple of dies, one to cut out thin steel sheet, and one to press
it into shape.

Then the problem would be getting a strong bond between the plastic disc and
metal bayonet.

I'm thinking as I type here.

I'm concluding that an all metal solution would be best.

Chris

Giles wrote:

> As it happens, I have heard of the technique - uses a UV laser, steered by
> a computer to scan the surface of bath of UV sensitive resin.  Where the
> laser touches the resin hardens.  When a layer is completed a platform in
> the liquid bath lowes a fraction, resin flows over the top of the hardened
> part and the laser does another run -  and so on.
>
> I have managed to successfully make a near exact copy of an MD cap using
> silicon moulding rubber to form a mould.  The rubber is flexible enough to
> mould even the severe undercut involved and to then pull out from beneath
> it, though there is a high risk of tearing each time the mould is used.  I
> used carbon fibres for added strength which worked for the large scale
> parts of the cap but the fibres did not find their way into the bayonet
> lugs, only the epoxy resin did.  So I have a nice strong carbon fibre copy
> of a cap with very weak bayonet lugs.  One might be able to use such a cap
> as a permanent fixture - install once and leave it in place - but removing
> it might break off the lugs.
>
> A pretty result but not very useful.
>
> Giles
>
> drchrisbarrett wrote:
>
> > Date:          Wed, 06 Dec 2000 16:27:20 -0800
> > From:          drchrisbarrett <drchrisbarrett@xxxxxxxxxxxxxxxxxxxx>
> > Organization:  Netscape Online member
> > To:            chenriks@xxxxxxxxxxxx, cnocbui@xxxxxxxxxxxxx,
> >                Olympus List <olympus@xxxxxxxxxxxxxxx>
> > Subject:       Motor Drive Caps
>
> > Some time ago I contemplated seeing if our Stereolithography kit at work
> > could do it. You've probably not heard of this, but it is a laser system
> > which "writes" on the surface of a bath of resin. Where the resin has
> > been exposed, it solidifies. The system gradually builds up the layers to
> > make a three dimensional object.
> >
> > The problem with it is it is quite expensive, and I don't think we can
> > get quite the resolution needed for the fine detail on the cap. They
> > would also need some further work to finish them off.


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