Subject:
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Re: Technic's Dead (was: I need Technic)
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Newsgroups:
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lugnet.technic
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Date:
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Mon, 5 Aug 2002 19:30:45 GMT
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Viewed:
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2732 times
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Ralph Hempel wrote:
>[...]
> Steve,
>
> My Dad was one of the mold design and production managers at Husky Injection
> Molding way back when. I can tell you that LEGO bricks in general have a
> degree of mold complexity that is very high.
>
> There are a number of technical hurdles, not the least of which is that the
> parts are sprue-less, which means they don't have any obvious points at
> which the plastic "comes in" to the mold. This also means that the parts
> don't need to have sprues trimmed after production.
>
> On Technic parts, these injection points are typically inside the stud hole
> where they can't interfere with any close tolerances. LEGO parts also have
> almost invisible seams where the main mold halves join. These seams are
> usually along edges, which is the hardest kind of mold making.
>
> A Technic part such as a beam is molded in a two-cavity mold. One
> for the top, and another for the bottom. The holes are accomplished with
> what are called side-pulls. These are cam activated pins that retract so
> that the parts can be removed from the mold.
>
> If you look closely at a technic beam, there are recessed ridges that mate
> with the flanges on a pin. So you need a side pull from each side of the
> mold. More cost, more complexity.
>
> Take plastic shrinkage and mold life into account, and then realize that
> molds often have anywhere from 4 to 24 cavities, and pretty soon you have
> a big production problem. Incidentally, the part number is often molded
> into a brick followed by a dash and another number. The second number
> often indicates the cavity number of the part. If a part starts going
> bad, production can either fix the mold or seal off a cavity to prevent
> bad shots from getting into the finished goods.
>
> Oops, that's more than anyone probably wants to know. I'll stop now.
On the contrary, Ralph, that's fascinating! Thanks.
-Suz
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Message is in Reply To:
 | | RE: Technic's Dead (was: I need Technic)
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| (...) Steve, My Dad was one of the mold design and production managers at Husky Injection Molding way back when. I can tell you that LEGO bricks in general have a degree of mold complexity that is very high. There are a number of technical hurdles, (...) (22 years ago, 5-Aug-02, to lugnet.technic) !
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