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Subject: 
Re: LEGO meeting the engraver
Newsgroups: 
lugnet.trains
Date: 
Fri, 10 May 2002 19:55:56 GMT
Viewed: 
545 times
  
Erik,

As someone with a little molding experience (sand casting for metal, and
injection molding), I understand what you're saying.  I thought for a while
about how to do that, and you are right, you do need a moving cam inside the
mold so the part can be freed from the mold without.

I'm still curious if Lego uses hot runners or not when molding...

Scott Lyttle




Milling grooves into the parts can get you designs that would be impossible
or at least costly to mold into the part.

Molding a texture on the side of a brick is expensive. It requires more
moving parts in the mold, in particular a "split cavity" that expands around
the part instead of just moving away, or the part will not be able to slip
out of the mold.

The great example is the 1x2 corrugated brick. If you look at one you will
see the evidence for the mold's parting line going up the end faces of the
brick. This implies that there are two halves of the mold which move away
from this line--a split cavity. Producing a plastic part on this method has
many drawbacks versus a part with smooth walls. And there's a reason why the
corrugated brick is smooth on the two ends.

There are a lot of other techniques that bear on this but I'll leave it at that.

(I don't have any HP sets so I can't look at the textured arch.)

-Erik



Message is in Reply To:
  Re: LEGO meeting the engraver
 
(...) This is really cool, Steve. Milling grooves into the parts can get you designs that would be impossible or at least costly to mold into the part. Molding a texture on the side of a brick is expensive. It requires more moving parts in the mold, (...) (23 years ago, 10-May-02, to lugnet.trains)

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