WO2017107132A1

WO2017107132A1 - System and method for injection molding multi-material components

Info

Publication number: WO2017107132A1
Application number: PCT/CN2015/098667
Authority: WO
Inventors: Wai Kee HUI
Original assignee: Hui Wai Kee
Priority date: 2015-12-24
Filing date: 2015-12-24
Publication date: 2017-06-29

Abstract

An injection molding system comprises: a base stage configured to receive a base material and defining: a base component chamber for forming a base component; a primary base frame chamber communicating with the base component chamber, for forming a base frame; and a secondary base frame chamber communicating with the primary base frame chamber. The system includes an overmold injection stage configured to receive an overmold material, and defining: an overmold frame chamber for receiving a portion of the base frame; and an overmold component chamber for receiving the base component and forming a multi-material component, coupled to the base frame. The system also includes an indexer configured to engage and move the portion of the base frame into the overmold frame chamber such that a remainder of the base frame extends into the secondary base frame chamber for coupling to a further base frame formed in the primary base frame chamber.

Description

SYSTEM AND METHOD FOR INJECTION MOLDING MULTI-MATERIAL COMPONENTS

FIELD

The specification relates generally to injection molding, and specifically to a system and method for injection molding multi-material components.

BACKGROUND

Various techniques exist for the manufacture of multi-colour injection molded articles such as miniatures for tabletop games. For example, an entire article may be molded in a single injection shot, and the article may then be painted. This process, however, requires the deployment of additional equipment (e.g. paint spray booths) , as well as staff to operate and maintain the additional equipment. Further, the use of paint may have undesirable environmental consequences, and may also render highly detailed colouring of the finished part difficult or impossible.

An alternative process involves the use of multiple molding steps to produce a multi-colour article. Specifically, a first portion of the article is produced in a first injection shot with plastic of the desired colour； that portion is then transferred to a second mold as an insert, and a further portion of the article is overmolded with the first portion using a differently-coloured plastic. This process can be repeated as necessary to produce a multi-coloured finished article that requires no painting. The above process nevertheless suffers from certain disadvantages. For example, the removal of intermediate portions of the article and the placement of those portions in subsequent molding stages is generally performed manually, rendering the process labour-intensive and prone to error.

SUMMARY

According to an aspect of the specification, an injection molding system is provided, comprising: a base injection stage configured to receive a base material and defining a set of base injection chambers, including: a base component chamber for forming a base component from the base material； a primary base frame chamber in communication with the base component chamber, for forming a base frame coupled to the base component from the base material； and a secondary base frame chamber in communication with the primary base frame chamber； an overmold injection stage configured to receive an overmold material, and defining a set of overmold injection chambers, including: an overmold frame chamber for receiving a portion of the base frame； and an overmold component chamber for receiving the base component and forming a multi-material component, coupled to the base frame, from the base component and the overmold material； an indexer configured to engage the base frame and move the portion of the base frame from the primary base frame chamber to the overmold frame chamber such that a remainder of the base frame extends to and is received in the secondary base frame chamber for coupling to a further base frame formed in the primary base frame chamber.

BRIEF DESCRIPTIONS OF THE DRAWINGS

Embodiments are described with reference to the following figures, in which:

FIGS. 1A and 1B depict an injection molding system, according to a non-limiting embodiment；

FIGS. 2A and 2B depict the system of FIG. 1B in example operational states, according to a non-limiting embodiment；

FIG. 3 depicts a base frame and base component formed by the syste of FIG. 1B, according to a non-limiting embodiment；

FIGS. 4A and 4B depict the system of FIG. 1B in additional example operational states, according to a non-limiting embodiment；

FIG. 5 depicts an injection molding system, according to another non-limiting embodiment；

FIG. 6 depicts an example mold stage in the systems of FIGS. 1 and 5, according to a non-limiting embodiment； and

FIG. 7 depicts a method of injection molding multi-material components, according to a non-limiting embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1A depicts an injection molding system 100. The injection molding system 100 includes at least two distinct molds. In particular, as illustrated in FIG. 1A, the system 100 includes a first mold in the form of a base injection stage 104, and a second mold in the form of an overmold injection stage 108.

In general, the system 100 is configured to produce a multi-material component consisting of a base part molded in an injection molding operation within the base stage 104, and a further part overmolded on the base part in another injection molding operation within the overmold stage 108. As will now be apparent to those skilled in the art, the overmolding of the further part onto the base part to complete the multi-material component requires the base part to be relocated from the base stage 104 to a specific location within the overmold stage 108 (i.e. as an insert within the overmold stage 108) . As will be discussed in greater detail below, the system 100 includes several features enabling the above-mentioned relocation of parts between stages to be performed at least partially automatically. Among those features is an indexer 112 (two indexers 112 are illustrated in FIG. 1A, arranged between the base stage 104 and the overmold stage 108) . A variety of indexer mechanisms are contemplated； in the present embodiment, indexers 112 include members rotatable about an axis A, for engaging the molded parts and moving the parts from the base stage 104 to the overmold stage 108 (i.e. in a direction perpendicular to axis A) .

Turning to FIG. 1B, a top view of the

stages

104 and 108 is shown. Each of the injection molding stages defines a plurality of chambers. As will now be apparent, each of the

stages

104 and 108 can include lids or covers defining some portion of the chambers. Such lids or covers are configured to be closed prior to injecting material (e.g. flowable polymer) into the

stages

104 and 108, and to be opened following the completion of an injection operation in order to release the parts formed by the operation. Thus, each of the

stages

104 and 108 can have a closed position (for injecting material and forming parts) , and an open position (for releasing parts and receiving parts as inserts) . In the drawings, the lids or covers are omitted for simplicity of illustration.

The base stage 104 defines a base component chamber 116, a primary base frame chamber 120 -which in the present embodiment surrounds the base component chamber 116 -as well as a secondary base frame chamber 124. As seen in FIG. 1B, the

chambers

116, 120 and 124 are all in communication with each other (that is, connected in such a way that injected material can flow between the chambers) . More specifically, the base component chamber 116 is in communication with the primary base frame chamber, and the secondary base frame chamber is also in communication with the primary base frame chamber.

The base stage 104 also includes at least one inlet (not shown) for receiving a base material in at least one of the above-mentioned chambers. Typically, a plurality of inlets are provided at least into the primary base frame chamber 120, although it will be apparent to those skilled in the art that a wide variety of inlet arrangements may be employed. Preferably, no inlets are provided to the secondary base frame chamber. Upon injection of the base material (e.g. a flowable polymer) into the base stage 104, the primary base frame chamber 120 forms a base frame, and the base component chamber 116 forms a base component coupled to the base frame. In an initial injection shot (i.e. at the start-up of the system 100, before any parts have been molded in the base stage 104 and placed in the overmold stage 108) , some base material may also flow into the secondary base frame chamber 124； in some embodiments the base stage 104 may include one or more valves to prevent this. As will become apparent below, however, in subsequent injection shots the base material will be substantially prevented from flowing into the secondary base frame chamber 124.

The overmold stage 108 defines an overmold frame chamber 128, and an overmold component chamber 132. The overmold frame chamber 128 is configured to receive a base frame fabricated within the primary base frame chamber 120 of the base stage 104. In other words, the overmold frame chamber 128 is not configured to receive any injection material itself. The overmold component chamber is configured to receive the base component formed in the base component chamber 116 of the base stage 104, and also (after receiving the base component) to receive an overmold material via one or more inlets (not shown) . The receipt of the overmold material forms a multi-material component (that is, comprising the base material and the overmold material) , coupled to the base frame.

Further, as mentioned earlier, the system 100 includes at least one indexer 112. The indexer 112 is configured to engage a base frame molded in the base stage 104 and move the base frame. In particular, the indexer 112 is configured to move a portion of the base frame from the primary base frame chamber 120 (where the base frame was formed) into the overmold frame chamber 128. Once the base frame's movement is complete, the remainder of the base frame (that is, the portion not received within the overmold frame chamber 128) extends between the overmold stage 108 and the base stage 104, and is received in the secondary base frame chamber 124. So received, the base frame can be coupled to another base frame formed in the (now vacant) primary base frame chamber 120. The fluid communication provided between the primary and secondary

base frame chambers

120 and 124 results in injection material flowing into the primary chamber 120 not only forming a new base frame, but also bonding the new base frame to the already-formed base frame, a portion of which is placed within the secondary chamber 124.

An example fabrication process using the system 100 will now be described in order to illustrate the discussion of the elements of the system 100 introduced above. Referring to FIG. 1B, the system 100 is shown in a start-up state, in which neither stage 104 nor 108 contains any injection material. Referring now to FIG. 2A, the system 100 is shown following the injection of a base material into the base stage 104. No material has been injected in the overmold stage 108 at this point, as the overmold stage 108 requires the presence of components molded in the base stage 104.

Following the fabrication of a base frame 200 and a base component 204 in the base stage 104, the coupled base frame 200 and base component 204 are displaced from the base stage. In the present embodiment, in which the indexers 112 are disposed between the

stages

104 and 108, the initial displacement of the base frame 200 and the base component 204 may be performed manually, to engage the base frame 200 with the indexers 112.

As seen in FIG. 2B, the coupled base frame 200 and base component 204 are shown following their displacement from the first stage 104 and into engagement with the indexers 112. It is contemplated that in other embodiments, this first displacement need not be performed manually. Instead, base stage 104 can include a lifting mechanism (not shown) that not only raises the base frame 200 and base component 204 from the base stage 104, but also moves the base frame 200 and base component 204 towards the indexers 112. In still other embodiments, the indexers 112 may be integrated within the base stage 104, or with the above-mentioned lifting mechanism.

Referring now to FIG. 3, the engagement between the base frame 200 and the indexers 112 will be discussed. In general, the base frame 200 includes at least one (and in the present embodiment, a pair) longitudinal member oriented substantially in parallel to the direction of movement of the base frame 200 between the base stage 104 and the overmold stage 108. The longitudinal member includes a plurality of interlocking structures for engaging with the indexer 112, which in the present embodiment is a rotatable member such as a gear. The indexer 112 can include a motor (e.g. a servo motor) to drive the gear. The nature of the interlocking structures is not particularly limited. In the embodiment shown in FIG. 3, the interlocking structures include a plurality of apertures 300 through the base frame 200 on each of the longitudinal members. The indexers 112 each include at least one rotatable gear with teeth configured to fit into the apertures 300. Other interlocking structures are also contemplated, such as teeth formed on one or both sides of the longitudinal members, and castellations formed along the edges of the longitudinal members.

Also noted in FIG. 3 (and also visible in the previous drawings) is a pair of tabs 304 formed in the base frame 200 at one end thereof. As will be discussed in greater detail below, the tabs 304 enable the base frame 200 to be connected to a subsequently formed base frame.

As a result of the mechanical engagement between the base frame 200 and the indexers 112, the position of the base frame 200 (and thus, the distance travelled by the base frame 200 and the base component 204) can be controlled by controlling the number of rotations undergone by the indexers 112. Turning now to FIG. 4A, the base frame 200 has been moved by the indexers 112 such that the base component 204 is received within the overmold component chamber 132, and a portion of the base frame 200 is received within the overmold frame chamber 128. Further, the remaining portion of the base frame 200 extends from the overmold stage 108 to the base stage 104 and is received within the secondary base frame chamber 124. As seen in FIG. 4A, the tabs 304, once received in the secondary base frame chamber 124, are disposed in close proximity to the primary base frame chamber 120, to permit the base frame 200 to be bonded to a subsequently-formed base frame.

Upon receipt of the base frame 200 and base component 204 within the overmold stage 108, the overmold stage 108 is injected with the overmold material to form a multi-material component in the overmold component chamber 132. The result of the overmolding injection shot is shown in FIG. 4B, in which the base component 204 has been combined with overmold material to form a multi-material component 400. Also of note, the base stage 104 has also been injected with an additional shot of base material. The base stage 104 and the overmold stage 108 can be injected with their respective materials substantially simultaneously. Thus, in addition to the component 400 being formed, a new base frame 200a and a new base component 204a are formed. The new base frame 200a is coupled not only to the new base component 204a, but also to the previous base frame 200 (specifically, to the tabs 304) .

As will now be apparent to those skilled in the art, the above process can be repeated as desired to form additional base and multi-material components. Further, from the arrangement shown in FIG. 4B, no manual intervention is required, as the base frame 200 is already engaged with the indexers 112. Therefore, the indexers 112 can be activated to move the base frame 200 and the component 400 out of the overmold stage 108 (e.g. to downstream processing for the removal of the component 400 from the base frame 200) , and to simultaneously (because the base frame 200 and the base frame 200a are coupled) move the base frame 200a and the base component 204a into the overmold stage 108.

The system 100 and the operation thereof as described above can readily be modified to produce multi-material components with a greater number of materials. In particular, other systems can have a base stage and a plurality of sequential overmold stages, with indexers between at least the base stage and the first overmold stage (but preferably between every adjacent pair of stages) .

Although the embodiments described above and shown in the drawings contemplated that an assembly of a base frame and base component move immediately into the overmold stage 108, in other embodiments the distance between stages may be greater, and thus the spacing between "active" frame and component assemblies (i.e. those engaged in a mold stage) may be greater. For example, in some embodiments, there may be an inactive frame and component assembly in between each pair of active assemblies. That is, every second assembly in a chain of coupled base frames and components may be received in a mold stage.

In some embodiments, additional stages may follow the final overmold stage. For example, a disassembly apparatus may follow the final overmold stage, having a chamber for receiving the multi-material component, and including a treatment device (e.g. an ultrasound emitter) for detaching the multi-material component from the base frame.

Referring now to FIG. 5, a system 500 according to a further embodiment is shown. The system 500 includes a base stage 504, a plurality of sequential overmold stages 508 and 512, and a finishing stage 516 (e.g. an ultrasonic chamber for disintegrating a portion of the base frame) for detaching completed components 520 from the base frames to which they are coupled. Each overmold stage bonds an additional injection material to the base component formed in the base stage 504. Also of note in system 500 is that, as noted earlier, intermediate base frames (and associated components) such as base frame 524 extend between each stage； that is, only every second base frame is operated on in each injection operation.

Referring now to FIG. 6, an example of an injection molding base stage 600 is shown. The base stage 600 can be followed by any suitable number of overmold stages. The base stage 600 includes a primary base frame chamber, currently shown containing a base frame 604, the longitudinal members of which are configured to engage indexers (not shown) . The base stage 600 also includes a plurality of base component chambers, currently shown containing respective base components 608. Further, the base stage 600 includes a secondary base frame chamber, currently shown containing a part of a previously formed base frame 612.

The base stage 600 also includes a lifting mechanism 616 which can be activated once the mold is open to raise the base frames 604 and 612 (which are coupled to each other via the tabs 620) in order to permit the chain of base frames to be advanced to the next mold stages. In some embodiments, each mold stage can include a lifting mechanism, while in other embodiments, only a subset of the series of mold stages need include a lifting mechanism.

Turning now to FIG. 7, the operation of the system 100 as described above is illustrated as a method 700 of injection molding multi-material components. At block 705, any active stages of the system are closed (that is, made ready for injection) . When the system has not been started, the only active stage is the base stage. Otherwise, the active stages include the base stated and any subsequent stages containing base frames. It is also contemplated that in order to wind production down, the base stage may be rendered inactive, such that the chain of base frames ceases to be elongated.

At block 710, the active stages receive a shot of their respective materials, substantially simultaneously. At block 715, following the requisite cooling or curing periods, the active stages are opened to release the newly formed components therein. At

blocks

720 and 725, the chain of base frames and coupled components (whether base components or multi-material components) are raised from the injection chambers and indexed ahead to the next stage. From block 725, the performance of the method 700 can repeat, beginning again at block 705. In addition, for the components exiting the final stage of the system, block 730 can be performed instead, to detach the finished multi-material components from their base frame.

In some embodiments, the system includes a controller (e.g. a computing device, PLC or the like) connected to each mold stage and to the indexers. Upon detection that every mold stage has completed a shot, the controller can send signals to the mold stages, lifting mechanisms and indexers to implement the method 700 substantially automatically.

The nature of the materials contemplated for use in the system 100 as discussed above is not particularly limited. For example, the base and overmold materials may be similar (or identical) polymers having different colouring compounds therein (as shown in FIG. 4B) . In other embodiments, the materials can include different polymers, with or without distinct colouring compounds.

Although the discussion above involves rotatable indexers, a wide variety of other indexers are also contemplated. For example, the indexers 112 shown in FIG. 1 can be replaced or supplemented with linear actuators such as hydraulic or pneumatic pistons. Any given embodiment of the system 100 can also include a plurality of different types of indexer (e.g. a different indexer per injection stage) .

The scope of the claims should not be limited by the embodiments set forth in the above examples, but should be given the broadest interpretation consistent with the description as a whole.

Claims

An injection molding system, comprising:

a base injection stage configured to receive a base material and defining a set of base injection chambers, including:

a base component chamber for forming a base component from the base material；

a primary base frame chamber in communication with the base component chamber, for forming a base frame coupled to the base component from the base material； and

a secondary base frame chamber in communication with the primary base frame chamber；

an overmold injection stage configured to receive an overmold material, and defining a set of overmold injection chambers, including:

an overmold frame chamber for receiving a portion of the base frame； and

an overmold component chamber for receiving the base component and forming a multi-material component, coupled to the base frame, from the base component and the overmold material；

an indexer configured to engage the base frame and move the portion of the base frame from the primary base frame chamber to the overmold frame chamber such that a remainder of the base frame extends to and is received in the secondary base frame chamber for coupling to a further base frame formed in the primary base frame chamber.
The injection molding system of claim 1, the base injection stage and the overmold injection stage each having a closed position for receiving the base material and the overmold material, respectively, and an open position for releasing the base component and the multi-material component, respectively.
The injection molding system of claim 1, the primary base frame chamber having first and second ends； the first end defining a plurality of tab cavities for forming tabs in a corresponding end of the base frame； the secondary base frame chamber defining spaces to receive the tabs and place the tabs in contact with the second end of the primary base frame chamber.
The injection molding system of claim 1, the primary base frame chamber having a longitudinal cavity for forming a longitudinal member of the base frame； the indexer including at least one rotatable member for engaging the longitudinal member and rotating to move the primary base frame.
The injection molding system of claim 4, the longitudinal cavity configured to form a plurality of interlocking structures in the longitudinal member for engaging with the rotatable member.
The injection molding system of claim 5, wherein the interlocking structures include at least one of teeth, castellations, and apertures.
The injection molding system of claim 1, further comprising a lifting mechanism configured to lift the base frame from the base injection stage prior to movement of the base frame by the indexer.
The injection molding system of claim 1, further comprising a controller connected to the base injection stage and the overmold injection stage, and to the indexer.
An injection molding process, comprising:

injecting a flowable base material into at least a base stage of a plurality of sequential injection stages, for forming a first base frame coupled to a first base component；

responsive to the injection, activating an indexer to move the first base component and a portion of the first base frame from the base stage to an overmold stage of the plurality of injection stages； a remainder of the first base frame remaining in the base stage；

responsive to the moving, injecting the flowable base material into the base stage for forming a second base frame coupled to a second base component and to the remainder of the first base frame； and

injecting a flowable overmold material into the overmold stage for forming a multi-material component from the first base component and the overmold material.