U.S. patent application number 13/399947 was filed with the patent office on 2013-08-22 for method and apparatus for molding parts.
This patent application is currently assigned to Apple Inc.. The applicant listed for this patent is Daniel W. JARVIS, Bryan P. KIPLE, Dhaval N. SHAH, Michael B. WITTENBERG. Invention is credited to Daniel W. JARVIS, Bryan P. KIPLE, Dhaval N. SHAH, Michael B. WITTENBERG.
Application Number | 20130214450 13/399947 |
Document ID | / |
Family ID | 48981677 |
Filed Date | 2013-08-22 |
United States Patent
Application |
20130214450 |
Kind Code |
A1 |
KIPLE; Bryan P. ; et
al. |
August 22, 2013 |
METHOD AND APPARATUS FOR MOLDING PARTS
Abstract
A method and apparatus for injection molding plastic parts is
described. In one embodiment, at least two materials are
simultaneously injected into a mold. The resulting molded part can
include at least two different regions. Each region can have
distinct physical properties. Positions of the regions within the
molded part can be at least partially controlled by controlling
flow fronts of the at least two materials within the mold.
Inventors: |
KIPLE; Bryan P.; (Los Gatos,
CA) ; WITTENBERG; Michael B.; (Sunnyvale, CA)
; SHAH; Dhaval N.; (Fremont, CA) ; JARVIS; Daniel
W.; (Sunnyvale, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KIPLE; Bryan P.
WITTENBERG; Michael B.
SHAH; Dhaval N.
JARVIS; Daniel W. |
Los Gatos
Sunnyvale
Fremont
Sunnyvale |
CA
CA
CA
CA |
US
US
US
US |
|
|
Assignee: |
Apple Inc.
Cupertino
CA
|
Family ID: |
48981677 |
Appl. No.: |
13/399947 |
Filed: |
February 17, 2012 |
Current U.S.
Class: |
264/250 ;
425/130 |
Current CPC
Class: |
B29K 2105/16 20130101;
Y10T 428/24926 20150115; Y10T 428/24802 20150115; H05K 7/18
20130101; B29C 70/62 20130101; Y10T 428/24909 20150115; B29C
45/0013 20130101; B29C 45/164 20130101 |
Class at
Publication: |
264/250 ;
425/130 |
International
Class: |
B29C 45/16 20060101
B29C045/16 |
Claims
1. A method for molding a uniform part with non-uniform physical
properties, the method comprising: selecting a first material;
selecting a second material, wherein the second material has at
least one different physical property than the first material;
simultaneously injecting the first and second materials into a
mold; and controlling flow fronts of the first and second materials
in the mold.
2. The method of claim 1, further comprising: producing a uniform
molded part with a first region having a first physical property
and a second region having a second physical property different
from the first physical property.
3. The method of claim 1, wherein the first material is injected
through a first gate and the second material is injected through a
second gate.
4. The method of claim 1, wherein the first and second materials
are plastic resins.
5. The method of claim 4, wherein the first material includes a
glass filler.
6. The method of claim 1, wherein the flow fronts determine
positions of the physical properties on the part
7. The method of claim 1, the controlling flow fronts comprising:
controlling positions of the first gate and the second gate on the
mold; controlling injection pressure of the first and second
materials; and controlling temperatures of the first and second
materials.
8. The method of claim 2, wherein the first region has a different
stiffness from the second region.
9. The method of claim 2, wherein the first region has a different
hardness from the second region.
10. The method of claim 2, wherein the first region has a different
flexural strength from the second region.
11. An apparatus for injection molding a part with non-uniform
material properties, the apparatus comprising: a first hopper
configured to hold a first material; a second hopper configured to
hold a second material; a mold including a first gate and a second
gate; a first barrel, coupled to the first hopper and coupled to
the first gate, the first barrel disposed between the first hopper
and the first gate, the first barrel melting the first material; a
second barrel, coupled to the second hopper and coupled to the
second gate, the second barrel disposed between the second hopper
and the second gate, the second barrel melting the second material;
and, an injector controller coupled to the first and the second
barrels, configured to coordinate the injection of the melted first
and the second materials simultaneously into the mold.
12. The apparatus of claim 11, wherein the first material has a
different physical property than the second material.
13. The apparatus of claim 11, wherein the first and second
materials are plastic resins and the first material includes a
glass filler.
14. The apparatus of claim 11, wherein the molded part produced by
the mold has a first region and a second region.
15. The apparatus of claim 14, wherein the first region has at
least one physical property different from the second region.
16. An apparatus for injection molding a part with non-uniform
material properties, the apparatus comprising: means for holding a
first material; means for holding a second material; means for
melting the first and second materials; means for simultaneously
injecting the first and second melted materials; and means for
receiving the injected first and second materials;
17. The apparatus of claim 16 wherein the simultaneously injecting
the first and second melted materials comprises: means for
controlling the injection of the first material through a first
gate; and means for controlling the injection of the second
material through a second gate.
18. The apparatus of claim 16, further comprising: means for
controlling a flow front of the first melted material; and means
for controlling a flow front of the second melted material.
Description
FIELD OF THE DESCRIBED EMBODIMENTS
[0001] The described embodiments relate generally injection molding
and more particularly to injection molding plastic parts with
non-homogenous material properties.
BACKGROUND
[0002] Injection molding, and injection molding plastic parts in
particular, has become a very cost effective method for quickly
manufacturing parts. Typically, a single plastic resin is selected
and prepared for injection into the mold. The result is a plastic
part with uniform physical properties.
[0003] Sometimes a part may be formed from two different plastic
resins. In this scenario, a first material is injected, then after
a predetermined time period (usually determined by the amount of
time needed for the melted resin to set), a second material is
injected. A common term of art used to describe this method is the
"two shot" method. In this method, the first material is shot into
the mold. The mold can be repositioned and then can receive the
second material. The two shot method can have associated
disadvantages. First of all, there is an increased cycle time to
produce molded part. That is, in order for a complete part to be
produced, it takes one cycle of for the first material, and then
one cycle for the second material. Secondly, there is often a
perceptible line at the interface of the two different materials.
Oftentimes, this visible line may be undesirable.
[0004] There can be some designs when it is desirous for a single
part to have varying physical properties. For example, a designer
may want a first section or region of a part to have a first amount
of stiffness, and a second section of the part to have a second
amount of stiffness. Single shot injection molding typically only
provides uniform physical properties throughout the entire part. On
the other hand, a two shot process can introduce a second material
(providing a second physical property) but with added cycle time,
and therefore, added cost. Further, the resulting product may no
longer be visually acceptable due to visible interface lines
between the first and second materials.
[0005] Therefore, what is desired is a cost effective way to
produce an injection molded part with non-uniform material
characteristics in a short process.
SUMMARY OF THE DESCRIBED EMBODIMENTS
[0006] This paper describes various embodiments that relate to an
injection molding method and apparatus. The methods and apparatus
disclosed can produce plastic parts with non-uniform physical
properties while appearing smooth and uniform.
[0007] In one embodiment, a method for molding a part includes
selecting a first and a second material, simultaneously injecting
the first and second materials and controlling the flow fronts of
the first and second materials within the mold. In another
embodiment, the molded part can include a first region having a
first physical property and a second region having a second
material property.
[0008] In one embodiment, an apparatus for injection molding a part
includes a first hopper to hold a first material, a second hopper
to hold a second material, a mold including a first gate and a
second gate, a first barrel coupled to the first hopper and
positioned between the first hopper and the first gate, a second
barrel coupled to the second hopper and positioned between the
second hopper and the second gate and an injector controller,
coupled to both barrels and configured to coordinate the injection
of materials from the first and second barrels into the mold.
[0009] Other aspects and advantages of the invention will become
apparent from the following detailed description taken in
conjunction with the accompanying drawings which illustrate, by way
of example, the principles of the described embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The described embodiments and the advantages thereof may
best be understood by reference to the following description taken
in conjunction with the accompanying drawings. These drawings in no
way limit any changes in form and detail that may be made to the
described embodiments by one skilled in the art without departing
from the spirit and scope of the described embodiments.
[0011] FIG. 1 shows one embodiment of an injection molding system
in accordance with the specification;
[0012] FIGS. 2A and 2B show a simplified view of a portion of an
injection molding system, in accordance with the specification;
[0013] FIG. 3 shows another embodiment of an injection molding
system in accordance with the specification;
[0014] FIG. 4 shows an exemplary injection molded part 400 made in
accordance with the specification; and,
[0015] FIG. 5 is a flowchart of method steps for molding a part
with non-uniform physical properties in accordance with the
specification.
DETAILED DESCRIPTION OF SELECTED EMBODIMENTS
[0016] Representative applications of methods and apparatus
according to the present application are described in this section.
These examples are being provided solely to add context and aid in
the understanding of the described embodiments. It will thus be
apparent to one skilled in the art that the described embodiments
may be practiced without some or all of these specific details. In
other instances, well known process steps have not been described
in detail in order to avoid unnecessarily obscuring the described
embodiments. Other applications are possible, such that the
following examples should not be taken as limiting.
[0017] The various aspects, embodiments, implementations or
features of the described embodiments can be used separately or in
any combination.
[0018] In the following detailed description, references are made
to the accompanying drawings, which form a part of the description
and in which are shown, by way of illustration, specific
embodiments in accordance with the described embodiments. Although
these embodiments are described in sufficient detail to enable one
skilled in the art to practice the described embodiments, it is
understood that these examples are not limiting; such that other
embodiments may be used, and changes may be made without departing
from the spirit and scope of the described embodiments.
[0019] A method and apparatus is described for injection molding.
The process can produce a molded part using at least two materials.
In one embodiment, the materials can be plastic resins. The two
materials can also have different physical properties from each
other, especially after the materials have been used for making
injection molded parts. For example a first material, although
similar to second, can produce a stiffer molded part through the
addition of an effective amount of glass filler.
[0020] An apparatus is provided that enables the simultaneous
injection of a first and a second material into a mold. The first
and second materials can have associated flow fronts within the
injection mold. Through controlling the flow fronts, the position
of the first and second materials can at least be partially
controlled within the mold. Controlling the position of the
materials can allow a designer to control at least partially the
position of the different material, and hence the position of
different physical properties in the final molded product. In other
words, controlling the position of the materials within the final
product can enable the designer to create a product with area
specific physical properties.
[0021] FIG. 1 shows one embodiment of an injection molding system
100 in accordance with the specification. Injection mold 101 can
include two pieces. The mold 101 pieces are commonly referred to as
a cavity 104 and a core 102. Other embodiments may include more
than two mold pieces. Typically, the cavity 104 and core 102 are
brought together before material for molding is heated and
injected. The cavity 104 and core 102 can later separate, after the
molding material cools, enabling the finished part to be ejected
from the mold. Hopper 110 can hold a first material and hopper 112
can hold a second material. In one embodiment, first and second
materials can be gravity fed from hoppers 110 and 112 into
appropriate barrels. Barrels can be used to process the injection
molding material by mixing, heating and finally injecting material
into the mold 101. Returning to FIG. 1, a first barrel 120 can mix,
heat and inject material from hopper 110 into the injection mold
while a second barrel 122 can mix, heat and inject the material
from hopper 112 into the mold 101.
[0022] In one embodiment, the first and second materials can be
injected relatively simultaneously. That is, both barrels can heat,
mix and inject both materials at substantially the same time. In
one embodiment, an injection controller 150 can be coupled to the
first barrel 120 and the second barrel 122. The injection
controller 150 can be used to coordinate the injection of the
materials from the first 120 and second 122 barrels. For example,
the injection controller 150 can cause the first barrel 120 and the
second barrel 122 to simultaneously inject molding material into
the mold 101. Simultaneously injecting two materials advantageously
produces a single, homogenous part with comprised of two different
materials. In one embodiment, each material can possess unique
physical properties. In one embodiment, there is no visual
difference between the first material and the second material in
the injection molded part. In other words, although two different
materials are used, the resulting part can have no visible
delineation between the two materials (no break lines), the final
part appearing as a smooth, continuous part. This is achievable,
for example, when the both the first and second materials are
plastic resins, but one of the two materials can have an additional
filler. The introduction of the filler can affect the physical
properties of the molded part, particularly in the region in the
molded part including the filler material.
[0023] Injection molded material is typically introduced through
"gates" in an injection mold. FIG. 2A shows a simplified view of a
portion of an injection molding system 200, in accordance with the
specification. In this illustration, the cavity/core mold 101 from
FIG. 1 unit is shown in a simplified manner as mold 210. FIG. 2A is
further simplified by showing only two gates 230 and 232. Other
embodiments and systems can include more than two gates. A first
barrel 220 is coupled to the first gate 230 and a second barrel is
coupled to the second gate 232. The first barrel 220 can convey the
first material and the second barrel 222 can convey the second
material to the mold 210. In other words, material is injected from
barrels 220 and 222 through respective gates 230 and 232 into the
mold 210.
[0024] Positioning of the gates 230 and 232 with respect to the
mold 210 can aid in controlling the position of the first and
second material within the mold. As material is injected through
the gates, the material moves through the mold by pushing forward
"flow fronts". Flow front 240 illustrates the position of material
from gate 230 and flow front 242 illustrates the position of
material from gate 232. As shown in FIG. 2a, the flow fronts are
relatively close to the gates. This condition (position of flow
fronts 240 and 242) can occur when the first and second materials
are initially injected into the mold 210.
[0025] FIG. 2B shows the progress of the flow fronts 240, 242 in
the mold 210. As more material is injected, the flow fronts 240,
242 progress further into the mold 210. Eventually, the flow fronts
240, 242 from the gates 230 and 232 will contact each other and
form an interface region 250.
[0026] When the first material and the second material are similar
resins, there may be no visible delineation at or near the
interface region 250. In one embodiment, the first material can be
a plastic resin with a glass filler and the second material can be
a substantially similar polymer resin to the first material, but
without a glass filler. A molded part that can be produced with
these first and second materials and molding system 200 can appear
as a smooth and uniform part, but can be comprised by two different
materials, each material having physical properties. The first
material can have at least one physical property different from the
second material.
[0027] A plastic part can have physical properties, typically
related to the particular plastic resin used for molding. One
common method to change the physical properties of a molded part is
to add certain compounds to the plastic resins, prior to melting
and molding (for example, the glass filler mentioned above). Thus,
the physical properties of a plastic part can generally be
controlled by selecting and adding compounds to the plastic resin
used for the molding process. Although only one characteristic has
been discussed (increasing stiffness though the addition of a glass
filler to the plastic resin), other characteristics may be changed
in a similar manner. By way of example and not limitation, other
filler examples are wood flour, calcium carbonate and aluminum
powder. Also, other physical characteristics may be characterized
other than strength. Other physical properties of interest can be
tensile strength, flexural strength, hardness, compressive
strength, impact strength among many others.
[0028] Thus, by selecting two materials (such as two different
compounds of plastic resins), and simultaneously injecting both
materials into a mold, a visually continuous part can be made, with
separate regions, each having different physical properties.
[0029] FIG. 3 shows another embodiment of an injection molding
system 300 in accordance with the specification. The system 300
includes a mold 310, a first gate 320, a second gate 322 and a
third gate 324. A first material 330 is injected into the mold 310
through gate 320 and 324. A second material 332 is injected into
the mold 310 through gate 322. As shown, the first material 330 is
positioned in regions near the gates 320 and 324 while the second
material 332 is positioned near the gate 322. Other embodiments can
have more gates and can use more than two materials.
[0030] The position of the gates 320, 322 and 324 with respect to
the mold 310 as well as injection characteristics such as injection
pressure, material temperature and working viscosity can determine
how the flow fronts of the material form, propagate, and,
ultimately form interface regions 340 and 341. Position of the
interface regions 340 and 341 in the mold 310 can determine the
final position of the materials 330 and 332 in the injection molded
part. Thus, by controlling the flow fronts of the injected
material, a designer can control the position of the materials in
the final injection molded part. If the first material 330 has
different physical properties than the second material 332, then
different regions (related to the first material 330 and the second
material 332) of the injection molded part can possess the physical
properties related to the injected material.
[0031] FIG. 4 shows an exemplary injection molded part 400 made in
accordance with the specification. Although the mold that produces
part 400 is not shown for clarity, exemplary sprues 410, 412 and
414 are shown (sprues can be coupled to gates on the mold and may
be disposed between barrels such as barrel 220 and gates such as
gate 230). Furthermore, the sprues 410, 412 and 414 are illustrated
as they may be positioned relative to each other and with respect
to the mold. The dashed lines 430 from the sprues 410, 412 and 414
to the part 400 illustrate the relationship between regions on the
part 400 and the sprues 410, 412 and 414. Thus, region 420 can be
related to material from sprues 410 and 412, while the region 422
within the dashed line can be attributed to material from sprue
414.
[0032] For example, if the bulk of part 400, requires stiffness,
while a section of the part requires relatively more flexibility
than the bulk, then the material comprising region 420 can be made
relatively stiffer than region 422. In one embodiment, if a plastic
resin is used for both regions 420, 422, a glass filler can be
added to the polymer used in region 420 to add stiffness.
[0033] Continuing this example, by using similar materials with
different physical properties (at least one physical property
differs between the similar materials), a molded part can be
produced with at least two regions, each region with a different
physical property. Furthermore, since the two materials are
injected into the mold relatively simultaneously, the resulting
molded part can appear smooth, uniform and continuous, even across
interface region 440. Through the positioning of gates with respect
to the mold and controlling the flow fronts of the materials
injected into the mold, the position of multiple regions within the
final molded part can be determined.
[0034] Injection molded parts produced as described herein can have
several advantages. Regions of different physical properties can be
positioned to enhance the performance of molded parts. For example,
if a corner of a molded part can be subject to impacts, the
designer may want that corner to be composed of a relatively
ductile material. However, the same molded part may require a
relatively stiff (and perhaps less ductile) material in other
regions. Using the methods described above, a single molded part
can be injection molded with a ductile region (such as region 422
in FIG. 4) and a relatively stiffer region (such as region 420 in
FIG. 4). The stiffness and/or ductility of the regions can be
controlled by adding effective amounts of filler to plastic resins
that can be selected for the injection molded part. Also, since the
two materials are injected substantially simultaneously into the
mold, the resulting molded part can have a uniform, smooth
appearance with no delineation between materials.
[0035] FIG. 5 is a flowchart of method steps 500 for molding a part
with non-uniform material properties in accordance with the
specification. Persons skilled in the art will understand that any
system configured to perform the method steps in any order is
within the scope of this description.
[0036] The method begins in step 502 where a first material is
selected. In step 504, a second material is selected. Often times,
the first material and the second material can both be plastic
resins. The first material can differ from the second material by
the addition of a component meant to change at least one physical
property after the material has melted and cooled (i.e., after
molding). For example, a glass filler can be added to the first
material to affect the stiffness of the molded part where the first
material is disposed.
[0037] In step 506, the first and second materials are prepared for
injection. In one embodiment, the materials are mixed, placed in
hoppers, fed from hopper and heated. Often, the materials are
heated in the barrels such as barrels 120 and 122 shown in FIG. 1.
In Step 508, the first and second materials are relatively
simultaneously injected into the mold 101. The term relatively
simultaneously is used to indicate that both materials are injected
into the mold at substantially the same time. In step 510, the flow
fronts of the first material and the second material are
controlled. Controlling the flow fronts allows the designer to
control the position of the first and second materials with respect
to the molded part. After the heated material cools, in step 512,
the molded part is ejected from the mold. Since two different
materials with two different physical properties are selected, the
resulting part can have two or more regions, each region with a
characteristic physical property related to the material selected
in steps 502 and 504. The method then ends.
[0038] The foregoing description, for purposes of explanation, used
specific nomenclature to provide a thorough understanding of the
described embodiments. However, it will be apparent to one skilled
in the art that the specific details are not required in order to
practice the described embodiments. Thus, the foregoing
descriptions of specific embodiments are presented for purposes of
illustration and description. They are not intended to be
exhaustive or to limit the described embodiments to the precise
forms disclosed. It will be apparent to one of ordinary skill in
the art that many modifications and variations are possible in view
of the above teachings.
* * * * *