Tải bản đầy đủ - 0trang
10 16-Cavity Hot-Runner Mold for Cover Caps with Segmented Internal Contours Made from Polypropylene (PP) or Polyethylene (PE)
Example 10: 16-Cavity Hot-Runner Mold for Cover Caps with
Figure 2 16-cavity hot-runner mold with needle-shutoff nozzles
1: cavity plate FS, 2: needle-shutoff nozzles, 3: mold insert FS, 4: hot-runner manifold, 5: distributor bush, heated, 6: nozzle heater band, 7:
support disk, 8: thermal insulation sheet, 9: pneumatic cylinder, 10: clamping plate DS, 11: collapsible core, 12: mold insert BS, 13: mounting
elements, 14: core retainer plate, 15: clamping plate BS, 16: internal core retainer plate, 17: stripper plate, 18: latch lock, 19: ejector rod, 20: core
(Courtesy: Hasco, Liidenscheid)
locks (18). This stroke motion is performed via
the ejector rod (19) that is connected to the ejector
system. During this sequence, the V-guided profile
cores and V-ledges (in 11) leave their injection
position and collapse over the inside core taper.
After approx. 15mm stroke, the undercuts have been
demolded. In the second demolding sequence,
the latch locks release the block on both platens so
that the stripper plate can remove the article.
The small tolerances permitted for the molded part
and the 10 s cycle time are made possible by very
intense circulation cooling in the mould platens
and the separation of insert cooling into several
circuits. This has been contributed to by dividing
the serial core head cooling of the collapsible cores
into four groups (20).
Example 11, Four-Cavity Injection Mold for a Housing Made from
The four-cavity mold is used to produce two each of
the upper and lower halves of a cosmetic device
housing. The two halves of the housing are joined
together by means of snap fits. These hook-shaped
connections form internal and external undercuts on
both parts that are released by lifters.
The four cavities are arranged in a rectangle at the
mold parting line (Fig. 3). The mold inserts (1 1, 14)
are made of hardened steel; the lifters (7, 8, 20) are
The lifters move sideways in the ejector plates (9,
10) and are attached to slide blocks (12) that run in
corresponding guide grooves. The four leader pins
for the two mold halves as well as the guide pins for
the ejector plates are not shown in the drawing.
Mold dimensions are 296mm x 547 mm, with a
mold height of 290mm. The mold weighs approximately 280 kg.
The melt flows from a heated sprue bushing (13)
through an H-shaped runner system to the four
submarine gates feeding into the cavities (Figs. 1, 3).
Mold Temperature Control
The cavity inserts are provided with cooling channels for temperature control, while the cores contain
bubblers in which baffles (19) ensure that the cooling water is directed to the tip of the bubbler well.
The temperature in the cavity inserts is monitored
with the aid of thermocouples (1 6).
Upon opening of the mold, the molded parts and
runner system are retained on the core half. As soon
as the machine ejector actuates the ejector plates (9,
lo), the runner system and molded parts are released
and pushed off the cores by the lifters (7, 8,20) and
ejectors (17). The submarine gates shear off, while
the lifters release the undercuts formed by them.
Inside the housing halves (H) there is an undercut
boss formed by the end of a core pin (18) and the
surrounding hole in the core insert. The core pin
(18) is fitted into the core insert with a certain play
(V). As the parts are ejected, this pin is carried along
by the molded part until the boss is clear of the hole
in the core insert. The core pin (18) now stops and
the boss is stripped off the end of the core pin by the
remaining ejector motion. Before the mold closes,
the ejectors must be pulled back.
Figures 1 to 3 Four-cavity injection mold to produce a housing
with integrated snap fits
1: mold plate; 2: bar; 3: mold plate; 4, 5: bars; 6: clamping plate; 7, 8:
lifters; 9, 10: ejector plates; 11: mold insert; 12: sliding block; 13:
heated spme bushing; 14: mold insert; 15: O-ring; 16: thermocouple;
17: ejector; 18: core pin; 19: baffle; 20: lifter
Example 11: Four-Cavity Injection Mold for a Housing Made from Acrylonitrile-Butadiene-Styrene (ABsj
Examples example 12
Example 12, Four-Cavity Injection Mold for a Nozzle Housing Made from
The nozzle housing for a windshield washer system
has three interconnected channels and two external
mounting clips. Core pulls and slides are required to
release the molded parts.
The nozzle housing (Fig. 1) is used to distribute the
water coming from the water pump to the two spray
nozzles of an automobile windshield washer
system. The hose from the pump is slipped over the
conical tip on the end of a tubular extension A. The
channel in this extension divides inside the housing
into two channels D that lead to the spray nozzles. A
hook H and a snap spring F are used to attach the
housing. The ribs R serve to stiffen the tubular
The mold (Figs. 2 to 4) contains four cavities. To
release the hook and snap springs, four pairs of
slides (12, 13) actuated by cam pins (28) are used.
The cavity surface is formed by the slide inserts
(32). The slides are held in place in the closed mold
by the heel blocks (9) and wear plates (10).
The channels D are formed by core pins that are
attached to a total of eight slides (22). The cam pins
(18) are employed to actuate the slides, while the
pins (26) hold the slide (22) in place when the mold
The channel in the tubular extension A is formed by
the core pin (19), the conical tip of the extension by
the bushing (23). The adjacent core pins (19) and
bushings (23) on one side of the mold are attached
to a bridge (15, 16). The base of the cylinder (24) is
also bolted to the center of the bridge between the
two core pins. The rod of cylinder (24) is attached to
the backup plate (4). To pull the core pins (19) the
piston in the cylinder is pressurized and the cylinder,
along with the bridge and core pins, moves away
from the mold. The bushing (23) are held in place by
the pins (25).
The cavity insert (21) is made of through-hardened
steel, while the slide inserts (32) and slides (22)
utilize case-hardened steel.
The drawings were produced on a CAD system;
Figs. 2 to 4 two dimensionally (2D), Fig. 1 three
The melt flows from the sprue bushing (1 1) into the
mold via an H-shaped runner system through the
cavity insert (21) to a pinpoint gate at the parting
line associated with each pair of slides and enters the
cavity at the hook H of the molded part (Fig. 3).
Mold Temperature Control
Cooling channels in the plates (1, 3 and 4) are
provided for mold temperature control.
The ejector pin (3 1) is located in the cavity where air
entrapment may occur. It thus also aids in venting.
Part Release/Ej ection
Part release and ejection are accomplished by means
of a latch mechanism (17) and stripper bolt (27) not
described in M h e r detail.
The mold first opens at parting line I, at which point
the gates shear off the molded parts and are pulled
out of the cavity insert (21). The runner system is
held on the sucker pins (30). The cam pins (18)
Figure 1 Nozzle body for an automobile windshield washer system,
A tubular extension; D: channels; F: snap spring; H: hook; R: rib
Example 12: Four-Cavity Injection Mold for a Nozzle Housing Made from Polyamide
actuate the slides (22), which withdraw the short
core pins from the molded parts.
As the mold opens at parting line 11, the slides (12,
13) on mold plate (4) are spread apart by the cam
pins (28). At the same time, the undercuts on the
hooks and the snap springs are released along with
the pins (25) blocking the hydraulic side cores. so
that the core pins (19) can now be withdrawn. The
parts are now ejected by ejectors (29) and (31).
Finally, the runner stripper plate (2) is actuated by
the stripper bolts (27) (parting line 111) and the
runner system is stripped off the sucker pins (30).
Before the mold closes, the ejectors must first be
retracted and then the hydraulic cores set.
Figures 2 to 4 Four-cavity injection mold for a nozzle housing of
1: clamping plate; 2: m n e r stripper plate; 3: mold plate; 4: backup
plate; 5: bar; 6: clamping plate; 7, 8: ejector plates; 9: heel block; 10:
wear plate; 11: sprue bushing; 12, 13: slides; 14: slide guides; 15, 16:
bridge; 17: latch mechanism; 18: cam pin; 19: core pin; 20: runner
plate; 21: cavity insert; 22: slide; 23: bushing; 24: hydraulic cylinder;
25, 26: locking pins; 27: stripper bolt; 28: cam pin; 29: ejector; 30:
sucker pin; 31: ejector pin; 32: slide insert
Examples example 13
Example 13, Single Split Cavity Mold for a Threaded Plug Made from
The threaded plug is a cylindrical body 65mm in
diameter and 23 mm high with a trapezoidal thread
having a pitch of 3.5mm. A split cavity is used to
form the threads. The necessary number of split
cavity segments depends on the thread pitch and its
profile as well as on the material used to mold the
Figure 1 shows the plan view of a thread with a
trapezoidal profile. If one attempted to form this
thread in a split cavity with two halves, i.e. the
parting line lay in the plane of the figure, the mold
would damage the thread upon opening, because of
the undercuts at the positions H.
The present mold (Figs. 2, 3) has four cavity
segments (1) each of which is actuated by two cam
pins (2). The cavity segments are guided on the
mold plate (3) and when closed are held in position
by means of wear plates (4) attached to the mold
plate (5). The mold is constructed of standard mold
The part is gated centrally via a pneumatic
Operation of the nozzle is described in Example 97
The spme (8) in the nozzle tip (7) is attached to the
molded parts via 2 pinpoint gates next to the central
Before the mold opens, the spme (8) is separated
from the molded part and ejected by actuating the
pneumatic nozzle (6).
Figure 1 Thread with rectangular profile (plan view)
The more pronounced the flanks of the thread profile
are inclined (trapezoidal/triangular thread) and the
smaller the thread pitch and depth, the smaller are
the undercuts. With injection molding, the size of
the undercut is decreased by the shrinkage of the
resin up to the moment of ejection. In addition,
many resins are still elastic enough to withstand
minor deformation without damage. If in spite of all
these factors the undercut is still too large, the
number of segments forming the split cavity must be
The investigation of the situation with regard to
undercuts and the determination of the necessary
number of cavity segments is best carried out with
the aid of a computer which can be used to search
out the regions endangered by the undercuts on the
basis of the thread geometry.
Part Release/Ej ection
As the mold opens, the four cavity segments (1) are
spread apart by the eight cam pins (2) and the
threads are released. Now the ejectors (9) can strip
the molded part off the core.
Ejection takes place hydraulically via the molding
machine. The molded part is blown off the ejectors
(9) by a blast of air.
Mold Temperature Control
The mold plates (3) and (5) as well as the cavity
segments (1) are provided with cooling channels.
The hollow core (10) contains a cooling insert (1 1)
with grooves to guide the cooling water.
Example 13: Single Split Cavity Mold for a Threaded Plug Made from Polyacetal (POM)
Threaded plug with sprue
Figures 2 and 3 Single split cavity mold for a threaded plug of
1 : cavity segments; 2: cam pin; 3: mold plate; 4: wear plate; 5 : mold
plate; 6: pneumatic nozzle; 7: nozzle tip; 8: spme; 9: ejector; 10:
hollow core; 1 1: cooling insert
Example 14 / Example 15
Example 14, Demolding a Polyethylene Container with External Undercuts
The twenty-liter container (US Patent 4648834)
shown in the mold drawing (Fig. 1) has several
external rims that normally require side action in the
mold to be released.
Such side action significantly increases the cost of a
mold. This example shows that with clever use of
the shrinkage of the molded part and for moderate
undercut depth mold costs and manufacturing time
can be saved while simplifying mold handling
(weight, volume, mechanics).
The mold consists of a cavity half (1) and a core half
(2) which are guided by means of leader pins (3) and
aligned with respect to one another by means of a
taper lock (4).
A ring (5) that forms the underside of the rim on the
outside of the container is attached to the cavity half
Stripper rings (7, 8) that give the shape of the
external undercuts move on guide pins (6) attached
to the core (2) and passing through the tapered
alignment section (4). Stripper ring (7) is actuated
by ejector rods (9), while stripper ring (8) is attached
to stop bolts (10) that limit its motion.
Part release and ejection are described in Fig. 2 in
The mold has opened. The molded part and core
have separated from the cavity.
The stripper ring (7) is pushed forward by the ejector
rod (9). The molded part is pushed off the core,
while the undercuts continue to pull stripper ring (8)
along. The taper of the core now releases the inner
surface of the molded part, the diameter of which
decreases as the result of shrinkage, so that the rim
formed in the ring (8) can now be snapped out of the
recess. The ring (8) now stops.
Stripper ring (7) now completely pulls the rim on the
molded part out of the ring (8).
Ring (7) comes to a stop. The molded part is ejected
The air used to eject the part is directed to the inside
through the valve insert (1 1). Before the mold opens,
compressed air is forced under the bottom edge of
the container through the cavity half in order to
facilitate removal from the cavity.
Example 15, Injection Mold with Reduced Opening Stroke for Milk Crates
Beverage crates (US Patent 4731014) usually have a
grid-like structure on their exterior surfaces as a
result of the stacking rim, reinforcing ribs and
handles, the release of which requires the injection
mold to have external slides (side action). If the
slides are located in the stationary cavity half of
the mold, the opening stroke required equals twice
the crate height plus the axial stroke of these slides
in order to be able to eject the molded part.
The ejection principle described here needs a shorter
opening stroke. It is thus well suited for especially
deep parts or for stack molds.
The milk crate shown in Fig. 1 has dimensions
of 300mm x 300mm and a height of 280mm. Its
grid-like structure forms external undercuts.
Figures 2 to 4 illustrate the ejection principle along
with the additional possibility of releasing internal
undercuts (on the core).
The mold (Fig. 2) consists of the core (1) with core
lifters (2), cavity bottom plate (3) with spme bushing
(4) and the cavity frame (5) with movable external
slides (6). The cavity frame (5) can be moved in the
direction of mold opening by means of hydraulic
During opening (Fig. 3), the cylinders (7) hold the
bottom plate of the cavity (3) and cavity frame (5)
together. The molded part (8) is held in the cavity by
virtue of its external undercuts; the core (1) is
withdrawn. Any undercuts on the inside of the
molded part are released by the displacement of the
Example 15: Injection Mold with Reduced Opening Stroke for M i k Crates from Polyethylene
Figure 1 Mold for a 20-liter container with external undercuts
1: cavity half; 2: core half; 3: leader pin; 4: taper lock; 5 : ring; 6: leader pin; 7:
stripper ring; 8: stripper ring; 9: ejector rod; 10: stripper bolt; 11: valve insert
Figure 1 Milk crate
Figure 2 Single-cavity mold for a milk crate
1: core; 2: core lifters; 3: bottom plate of cavity; 4: sprue bushing; 5 :
cavity frame; 6: external slides; 7: hydraulic cylinders; 8: molded part
Example 15/Example 16
Figures 3 and 4 Single-cavity mold for a milk crate
1 : core; 2: core lifters; 3: bottom plate of cavity; 4: spme bushing; 5 :
cavity frame; 6: external slides; 7: hydraulic cylinders; 8: molded part
core lifters (2) on the core (1). The molded part can
now shrink freely and becomes smaller than the
cross-section of the core. The cylinders (7) then
push the cavity frame (5) toward the core (Fig. 4).
The rim of the molded part which is now smaller
pushes against the core lifters (2) or core (1) in
which case the core lifters (2) if present are
The external slides (6) located in the cavity frame (5)
do not follow the axial movement of the frame until
they are far enough apart to release the external
contour of the molded part (8). The molded part can
now drop free.
The opening stroke of the mold is thus only somewhat larger than the crate height H plus the distance
B required for the side action.
Example 16, Two-Cavity Injection Mold for Recessed Refrigerator
Handles Made from Polyamide
A two-cavity injection mold had to be made for
injection molding recessed handles for refrigerators
of polyamide reinforced with 35wt.% glass
fibres. The recessed handles (Fig. 1) have a grooved
internal structure, three flat channels from the
outside to the inside, two metal inserts to be
encapsulated, and recesses, into which the case of
the refrigerator door engages when the handle is
Construction of the Mold (Figs. 2 to 5)
Because of the hnction of the molded part the main
axis of the handle indentation is set at an angle of
45" to the recesses which engage with the case walls.
Since the recesses and the attached and encapsulated
metal inserts are to demold on opening the mold
(Fig. 2), an ejection motion with an angle of less
than 45" to the handle must release the molding
Figure 1 Recessed refrigerators handles of
polyamide reinforced with 35 wt.% glass
fibers and two metal inserts
top: front; bottom: rear
Example 16: Two-Cavity Injection Mold for Recessed Refrigerator Handles Made from Polyamide
[rum the core (1 1). Further, a mechanical slide (13)
is required for releasing the flat channels and the
beaded edge of the mold.
The handles must be pushed away from cores (1 1)
without any tilting; thus, hydraulically operated
ejectors are not acceptible since, because of possible
differences in forward motion, they do not guarantee
exactly parallel guidance. It was decided to operate
the ejector by means of rack and pinion mechanisms
(23), which are dnven through pinions (19), shaft
(25), external geai-wheel (21), and racks (24), by the
opening movement of the mold. In order to ensure
the necessary delay in the ejector motion until
release of the molding by the mechanical slide (13),
the block (39) in the top half of the mold, which
encloses the outer racks (24), runs freely along a
distance of 24 mm in the recess in the mold plate on
the nozzle side, until meeting the stop. The loosely
inserted spring (42), which is tensioned by mounting
the mold on the machine, acts as support. Only when
the block (39) is stopped by the spring (42) on the
opposite side does the relative movement of the
outer rack (24) begin, rotating the outer gear wheels
(21), which again operate the internal rack drive.
The block (39), outer racks (24), outer gear wheels
(21), and spring (42) were economically mounted in
milled grooves on the top side of the mold, partially
enclosed by the cover plate (41). The shafts (25)
were mounted in bearings (36) under the outer gear
wheels (21) to maintain a low bending moment in
the spindles. Their exact position is achieved by
bearings, fitting the inner racks (23) to the actual
ejector (32), as well as by mutual displacement of
the outer racks (24) made possible by means of
slotted holes in these. The racks are finally
connected to the block (39) by pins (40). Subsequently, the outer racks are finally calibrated along
their length in order to ensure a precisely defined
ejector position in the case of a closed mold.
The slides (13) are made of steel with material no.
1.2541, while the mold components (10, 11, 12)
utilize steel no. 1.2343.
The spme opens into an S-shaped runner formed in
the cavity block (12). The S-shape provides a central
spme for both cavities, which are displaced because
of the rack and pinion ejector mechanism. An
overlapping gate connects with a central lug of the
respective molded part, which is concealed when the
handle is mounted, so that the mark caused by this is
As the opening motion begins, the mechanical slides
(13) are moved outward by the cam pins (15) and
release the three flat channels. Simultaneously, the
spme begins to be released from the spme bushing
(31). After an opening distance of 24mm the open
recesses of the molded part and the metal inserts are
withdrawn from their cores. Then the motion of the
outer racks (24) begins relative to the ejector-side
mold half. The ejectors (32) are advanced, effecting
a movement of the molded part at an angle of 45" to
the mold axis. The resulting movement vertical to
the mold axis pulls off the overlapping gate. The
axial component of the ejection movement carries
with it the strip (lo), such that after a distance of
14 mm the recesses formed by the strip (10) are also
released. The moldings are now pushed hrther until
they fall from the core (1 1). Finally, the spme, which
in the meantime has also been hlly released, is also
ejected by the machine ejector through the spme
On closing the mold, the spring (42) ensures that the
ejectors (32) have returned before the mold finally
closes. The return pins (28) for the spme ejector
have the same effect, but in this case synchronously
with the closing action.