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2 Starting New in the Mold DesignField
The only prerequisite for the beginner is some knowledge of
mechanical
drawing delineation, whether it is done electronically on a
computer (with
programs like Autocad) or on the drawing board with pencil. Of
course, the
designer must also be familiar with some areas of basic
arithmetic and
trigonometry; both are required to put dimensions on the mold
parts so they can
be machined. Some of the advantages of electronic drafting are
the following:
(1) Designs of entire, or portions, of earlier built molds can
be easily usedagain by simply copying or modifying some existing
design features
from the program's memory, without the need for tedious
redrawing.
(2) An up-to-date library of standard mold components and
hardware can
be established, which can be easily and quickly accessed and
reproduced in new designs without the need for redrawing them
every
time they are needed.
(3) The quality of the drawings produced by a computer printout
does notdepend on the skilled hand of the designer.
(4) The computer permits easy transmission of designs to other
locations,
such as in-house manufacturing centers or manufacturers at
other
addresses.
Note the computer is only a tool to the designer; ultimately,
the quality of a
design depends entirely on how well the designer understands
what is required
and what can be made. Also be aware that even the most
experienced designer
will not always come up with the best design on the rst attempt,
but will try out
different ideas in the course of the design job. This often
necessitates sketching,
erasing, and redrawing part or all of the picture, which is much
easier to do
electronically. There is a saying about the difference between a
draftsman and a
designer: ``the draftsman uses the pencil, the designer uses the
eraser.'' In the old
days, the designer made his drawings on paper without much care
for the
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appearance of the resulting picture; it was then usually left to
draftpersons to
produce a good, readable drawing.
The important thing is the thought that goes into the design of
the mold, to
ensure the best possible design. Different solutions are always
possible toachieve the same end; in fact, all mold designers have
their own ideas on how to
solve certain design problems. To take advantage of various
ideas, and to arrive
at the best mold, it is good practice for the designer, after
creating a mold layout,
to consult with a colleague, or to arrange a design meeting of
peers to discuss
the proposed design. In many cases it is even better to provide
two or more
different layouts. These alternatives should then be discussed,
and the best
design or a composite of the various ideas should then be agreed
upon.
This procedure is standard practice in all major design ofces
around the
world. It may appear to be time-consuming, but the time (and
emotions) invested
in such peer critique are usually outweighed by the benets of
arriving at a better
mold. Since, in general, mold designers (especially beginners)
may not be
familiar with machining and assembly practices, someone who is
familiar in
these areas should be included at such design meetings; this
prevents a design of
mold parts that may be difcult (or even impossible) to produce
economically or
to put together at assembly. It is also benecial to have someone
who knows theactual molding process look at a new layout. It is
much less expensive to catch
an error while it is still in the designing stage, than to nd
out about it later when
steel has been cut or, even worse, when the mold is
completed.
Time and money can be saved by spending more time during the
design
stage to consider alternatives and to get the designer involved
in the
manufacturing process of the mold, than by rushing a job through
the design
ofce to save a few hours there. When estimating the total time
to build a mold,allocate approximately 1520% of the total time for
designing and detailing,
about 6070% for machining, and 1520% for assembling the mold.
(This, of
course, depends on the shape of the product and the complexity
of the mold.)
And remember that the better the drawings are when given to the
shop (or an
outside source), the less time is wasted during machining and
assembly of the
mold.
6 Starting New in the Mold Design Field
