The need for large gates is to reduce pressure drops and consequently
the pressure needed to inject. Polypropylene runs very well at 400-500
psi and 350 degrees F. We use full round runners of 0.25 inch diameter.
To vent, use a pocket knife to scratch the parting surface at the
farthest points from the runner. Slowly increase pressure if you must
to get a complete fill. Try to keep the face temperatures (core and
cavity) below 110 degrees F for tool life.
A 5 gram shot is not much. You should be successful. When we do parts
of that size, we throw away more runner than the part we keep!
____________________________________________________
Steve Deak e-mail: sdeak@hasbro.com
Manager-Rapid Prototyping voice: (+1) 513-579-3270
Hasbro Toy Group fax: (+1) 513-579-3250
615 Elsinore Place
Cincinnati, Ohio 45202 USA "Our Business is Fun!"
> ----------
> From: NEIL HOPKINSON[SMTP:epxnmh@epn1.maneng.nottingham.ac.uk]
> Sent: Tuesday, September 30, 1997 11:25 AM
> To: rp-ml@ltk.hut.fi
> Subject: SL Injection moulding gate sizes
>
> I am planning to injection mould small shots (5g) from polypropylene
> using ACES moulds at ~14MPa (2000 psi). If I were using conventional
> steel moulds I would be able to get away with a gate size as small as
> 0.5mm in diameter. Does anyone know of any limitations on gate/sprue
> diameter when using ACES moulds as many pictures that I have seen
> seem to have very wide gates.
>
> Thanks
> Neil Hopkinson
>
>
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