[hackspacebristol] Injection moulding machine

Jolyon Jenkins jolyonjenkins at googlemail.com
Tue Feb 23 11:02:45 UTC 2016


Yes I've done quite a bit of resin casting and found it hard to do
genuinely 3D parts because of problems with air bubbles which are only
partially solved by degassing. The main issue is that you have to have
quite a large pouring hole and an equally large hole for the air to come
out (sprue) and then you end up with large flashings that need to be
removed; and unless you can arrange for this to be in an inconspicuous part
of the piece, you then need to finish the part, and that all becomes hugely
time-consuming - you can't just crank them out. I partially solved this by
making a rotocasting machine (so the air bubbles end up inside the piece)
but it's a bit hit and miss.
I'm basically making dice which contain electronics.

On 23 February 2016 at 10:52, Richard Sewell <richard at jarkman.co.uk> wrote:

> I've got no experience of injection moulding, but I guess the obvious
> question in my mind is how it would compare to doing liquid resin casting
> to make the same parts. Probably needs very similar moulds, but less
> apparatus. Like this:
>
>
> http://makezine.com/2014/03/21/resin-casting-going-from-cad-to-engineering-grade-plastic-parts/
>
> I know that for grown-up injection moulding the mould CAD is terrifyingly
> complex, to account for shrinkage and warping and so on, but I presuem
> there are simple parts for which that's not an issue.
>
> Do you know what you want to make ?
>
> R.
>
>
> On 23/02/2016 10:31, Jolyon Jenkins wrote:
>
> I've been offered a small (benchtop) injection moulding machine for £200,
> which seems a good deal. It needs a little attention, but not much. It uses
> compressed air rather than a lever (and so I'd need to get a compressor
> too).
>
> Has anyone got experience of using such things? I don't really know about
> the moulds. I guess I could use my (Matt's old) CNC router to cut moulds
> from aluminium blocks (if I went very slowly) but I wouldn't be able to do
> any undercuts. When I look at places that produce moulds commercially the
> prices seem to be thousands of pounds, but maybe I'm looking in the wrong
> place. Any thoughts?
>
> J
>
>
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