How to determine the parting surface, the factors that need to be
considered are more complex. Because the parting surface is
affected by the plastic parts in the mold
Molding position, gating system design, structural
manufacturability and precision of plastic parts, insert position
and shape and pushing method,
Die manufacturing, exhaust, operating process and other factors, so
the selection of parting surface should be comprehensively analyzed
By comparison, a more reasonable scheme is selected from several
schemes. The following rules should be followed when selecting
parting surfaces
Then:
a) Ensure that plastic products can be demoulded
This is a first principle, because we set up the parting surface in
order to be able to smoothly exit the cavity
Out of the product. According to this principle, the parting
surface should be preferred on the largest contour line of the
plastic product, preferably in one
And the plane is perpendicular to the mold opening direction. The
overall profile of the parting should show a shrinking trend and
should not have any influence
Release the concave and convex shape, so as not to affect the
release.
b) Make the cavity depth the shallowest
The depth of the mold cavity has the following three effects on the
mold structure and manufacturing:
1) At present, the processing of the mold cavity is mostly made of
EDM molding, and the deeper the cavity is, the longer the
processing time will be
Mold production cycle, while increasing production costs.
2) The depth of the mold cavity affects the thickness of the mold.
The deeper the cavity, the thicker the moving and setting die. One
aspect ratio
More difficult; On the other hand, various injection machines have
certain restrictions on the maximum thickness of the mold, so the
depth of the cavity is not appropriate
It's too big.
3) The deeper the cavity depth, the greater the actual size
difference between the upper and lower ends of the same size when
the drawing inclination is the same.
Figure 2. In order to control the specified dimensional tolerance,
it is necessary to reduce the demoulding inclination, which leads
to the difficulty of demoulding of plastic parts. Due to the
In this way, the parting surface should be selected to make the
cavity depth as shallow as possible.
c) Make the plastic parts beautiful in appearance and easy to clean
Although the plastic mold is very precise, the plastic part will
leave a ring of hair on the parting surface after it is demoulded
Edge. We call it a flash. Even if these rough edges are removed
immediately after stripping, they will still leave traces on the
plastic parts,
The appearance of the plastic parts is affected, so the parting
surface should be avoided on the smooth surface of the plastic
parts, and the parting surface a position in Figure 3 is molded
After cutting the raw edge, leaving traces on the smooth surface of
the plastic parts; Parting surface b in FIG. 3 is in the position
of cross-section change.
Although there are still traces after cutting off the raw edge, it
does not look obvious, so the latter should be chosen.
d) Try to avoid lateral core-pulling
For plastic injection molds, lateral core-pulling should be avoided
as much as possible, because the lateral core-pulling mold has a
complex structure, and
And directly affect the size of the plastic parts, the accuracy of
the match, and time and money, manufacturing costs significantly
increased, so in all
You can only use it when you have it.
e) Make the parting surface easy to process
The accuracy of parting surface is an important part of the
accuracy of the whole die, and strive to parallel the flatness and
the matching surface of the moving and fixed die
The degree is within the tolerance. Therefore, the parting surface
should be flat and perpendicular to the stripping direction, so
that the machining accuracy can be obtained
A guarantee. If the parting surface is inclined or curved, the
difficulty of processing increases, and the accuracy is not
guaranteed, and it is easy to make
Flash phenomenon of overflow material.
g) Keep the lateral core-pulling as short as possible
The shorter the core pulling, the shorter the distance of the
oblique pumping, on the one hand, the thickness of the moving and
fixed die can be reduced, and the plastic parts can be reduced
Inch error; On the other hand, it is conducive to demoulding and
ensuring the accuracy of plastic parts.
h) Conducive to exhaust
For medium and small plastic parts, because the cavity is small and
the air amount is not much, the exhaust can be used by the gap of
the parting surface. Therefore,
Selection of parting surface should be conducive to exhaust.
According to this principle, the parting surface should be located
at the last arrival of the molten plastic during injection
Position, and do not close the cavity
In summary, there are many factors affecting the selection of
injection mold parting surface, and the general requirement is to
smoothly release the mold and ensure the plastic
The mold structure is simple and easy to manufacture. After
selecting a parting surface scheme, there may be some
Shortcomings, and then take other measures to compensate for the
existing problems, in order to choose close to the ideal parting
surface.
