Patent Application
20060073235
The present invention relates generally to injection molding, and more particularly to a convertible injection molding system, apparatus, and method.
In a typical injection molding system, one or more materials (such as molten plastic or metal) are injected into a mold in order to form a molded part. The mold includes one or more molding chambers for receiving the injected material(s). After a material is injected, the material is typically allowed to set for some period of time, after which another material may be injected. When the molded part is complete, the molded part is ejected from the mold, for example, by externally actuating various ejector components that are built into the mold.
Thus, an injection molding machine typically includes at least an injection mechanism for causing injection of one or more materials into a mold and an ejection mechanism for ejecting the molded part (e.g., by activating the ejector components in the mold). Conceptually, the mold fits into the injection molding machine between the injection mechanism and the ejection mechanism.
The mold typically includes two separate halves, each half defining a portion of each molding chamber. One of the mold halves is mounted onto the injection side of the injection molding machine, while the other mold section is mounted onto the moveable ejector side of the injection molding machine. During molding, the two sections are typically forced into contact with one another to form the molding chamber(s), for example, by forcing the movably mounted mold section against the fixedly mounted mold section. After the mold sections are in contact, the material(s) can be injected into the molding chamber(s).
As known in the art, each of the mold sections may be composed of multiple interconnected modules. For example, as described in published PCT application number WO 03/031141 A1 (hereinafter referred to as the “Person PCT application”), a first mold section may include a first mold module, a drive module, and a distributing module, while a second mold section may include a second mold module, an ejector module, an engaging module, and a guide module. The first mold section may be fixedly mounted within the injection molding machine and the second mold section may be movably mounted in the injection molding machine, in which case the second mold section may be moved into contact with the first mold section in order to form one or more mold chamber(s) for the injection molding process. The engaging module, together with an outer locking means, locks the second mold module against the first mold module and absorbs the forces which act to separate the first and the second mold modules from each other during the injection molding process. The guide module supports the second mold module, the ejector module, and the engaging module to ensure that they move in a suitable fashion in relation to the first mold section. Multiple-part molds are also discussed in U.S. Pat. Nos. 4,274,617; 5,837,086; and 6,652,263.
The ejection mechanism may include a replaceable ejector plate packet. Published German patent application number DE10059045 describes an injection molding machine having a replaceable ejector plate packet that is attached to a base ejector plate packet by a bolt with a flange that cooperates with a curved recess at the base of a cross-bar fitted into a slot in the base packet.
The ejection mechanism in the injection molding machine may include an actuator that is directly or indirectly coupled to the ejector components of the mold and can be hydraulically or electrically operated to actuate the ejector components of the mold. In injection molding machines that do not include a hydraulically-operated actuator, the ejector components of the mold may be actuated in other ways. For example, a portion of the mold may be moved within the injection molding machine so as to engage the ejector components of the mold with an ejection actuator that is fixedly attached to the injection molding machine. Such an injection mechanism can be implemented using a HASCO® guided ejector pull back device (part number Z165) that is incorporated into the movable portion of the mold and a HASCO® ejector rod (part number Z166) that is fixedly attached to the injection molding machine. In order to eject the molded part from the mold, the movable portion of the mold may be moved so that the guided ejector pull back device engages with the ejector rod, thereby actuating the ejector components of the mold.
All of the above-referenced patents and patent applications are hereby incorporated herein by reference in their entireties.
A convertible injection molding system uses a standardized, reusable mold frame (base) and modular inserts formed from various combinations of standardized components and when combined are known as a stack. The mold base can support one or more stacks. A stack is the combination of the standardized blank mold components which include, but are not limited to, a cavity block, a core block, a primary support insert, a secondary support insert, an ejector retainer plate, an ejector plate insert, and a clamp plate insert. These components can be assembled into four different configurations with three different opening/closing sequences. Specifically, the mold components can be assembled into a two plate configuration utilizing the cavity block, the core block, the primary support insert, the ejector retainer plate, and the ejector plate insert; a two plate configuration with sleeves utilizing the cavity block, the core block, the primary support insert, the ejector retainer plate, the ejector plate insert, and the clamp plate insert; a floating core plate configuration utilizing the cavity block, the core block, the primary support insert, the secondary support insert, the ejector retainer plate, and the ejector plate insert; and a floating core plate configuration with sleeves utilizing the cavity block, the core block, the primary support insert, the secondary support insert, the ejector retainer plate, the ejector plate insert, and the clamp plate insert. All of these configurations, combined with additional alignment components and other incendiary components, make up what is referred to as a “blank stack” and are used in the manufacture of the final assembly which will fulfill the expected geometry requirements and is now referred to as the “stack”.
Thus, in accordance with one aspect of the invention there is provided injection molding apparatus comprising a plurality of stack components including at least a cavity block, a core block, a primary support insert, a secondary support insert, an ejector retainer plate, an ejector plate insert, and a clamp plate insert. The stack components can be assembled into at least four mold configurations including a two plate configuration utilizing the cavity block, the core block, the primary support insert, the ejector retainer plate, and the ejector plate insert; a two plate configuration with sleeves utilizing the cavity block, the core block, the primary support insert, the ejector retainer plate, the ejector plate insert, and the clamp plate insert; a floating core plate configuration utilizing the cavity block, the core block, the primary support insert, the secondary support insert, the ejector retainer plate, and the ejector plate insert; and a floating core plate configuration with sleeves utilizing the cavity block, the core block, the primary support insert, the secondary support insert, the ejector retainer plate, the ejector plate insert, and the clamp plate insert.
The stacks fit into one of many standard mold base configurations having standard interfaces for supporting interchangeability within the different mold bases. The mold base typically includes a standard hot runner that interfaces with a standard gate position in the cavity block. The mold base typically includes a standard ejector interface that interfaces with ejector components located within a predetermined area of the ejector plate insert. The mold base typically includes multiple fluid circuits for interfacing with standard inlets and outlets on the stack. The fluid circuit can be a water circuit for cooling. The fluid circuit can also be used for a fluid circuit for actuating any mechanisms within the confines of the stack.
The two plate configurations typically support an opening sequence involving one parting line with no latch locks or early return mechanisms. The floating core plate configurations are typically capable of supporting two opening sequences utilizing the same floating core plate, specifically a first opening sequence involves the use of latch locks with delayed pull bar and early return mechanisms to open a main parting line before opening a second parting line and a second opening sequence involves the use of latch locks with no delay pull bar and no early return mechanisms to open a second parting line before opening a main parting line.
The molds typically include a so-called “floating core” in which the core block is coupled to the primary support insert in the assembled mold base in such a way that the combined core block and primary support insert are able to move relative to a floating core plate (if a floating core plate option is used) or ejector housing plate of the mold base. The floating core allows the core block to automatically align with the fixed cavity block when the mold base is closed. A plurality of spring packs may be operatively coupled between the floating core plate or ejector housing plate and the primary support insert for holding the core block in a semi-fixed position relative to the primary support insert while allowing sufficient movement of the assembled core block and primary support insert for automatic alignment. Each spring pack may include a stripper bolt, a number of spring washers arranged on the stripper bolt, and a cap, in which case each stripper bolt may include a proximal end coupled to the floating core plate or ejector housing plate and a distal end onto which the cap is mounted for making contact with the primary support insert to apply sufficient pressure to the face to hold the assembled unit in place but still allow enough movement for proper alignment with the cavity block.
The primary support insert, the floating core plate support insert, the ejector retainer plate, the ejector plate insert, and the clamp plate insert may be formed from stainless steel for corrosion resistance and there is no hardening requirement. The cavity block and the core block, however, are typically formed from a tool steel material that usually requires hardening. Guide lock pin holes, assembly guide pin holes, and gate detail are typically formed in the cavity block after hardening. Similarly, guide lock pin holes and dowel pin holes are typically formed in the core block after hardening.
Both the blank cavity block and the blank core block may include extra material so that a sufficient amount of material, required for a particular application, can be removed from each block to result in a predetermined combined thickness of the two blocks.
The mold base typically includes standard interfaces for interfacing with the at least one stack. Each stack is interchangeable with the different mold bases.
In accordance with another aspect of the invention there is provided an injection molding kit having component parts capable of being pre-assembled for use in an injection molding system, the kit comprising the combination of a cavity block; a core block; a primary support insert; an optional floating core plate support insert; an ejector retainer plate; an ejector plate insert; and an optional clamp plate insert. The blank mold components can be assembled into at least four mold configurations including a two plate configuration utilizing the cavity block, the core block, the primary support insert, the ejector retainer plate, and the ejector plate insert; a two plate configuration with sleeves utilizing the cavity block, the core block, the primary support insert, the ejector retainer plate, the ejector plate insert, and the clamp plate insert; a floating core plate configuration utilizing the cavity block, the core block, the primary support insert, the secondary support insert, the ejector retainer plate, and the ejector plate insert; and a floating core plate configuration with sleeves utilizing the cavity block, the core block, the primary support insert, the secondary support insert, the ejector retainer plate, the ejector plate insert, and the clamp plate insert.
The kit may also include latch locks which, when used with the floating core plate configurations, allows for opening a second parting line before opening a main parting line. The kit may include latch locks with delayed pull bar and early return mechanisms which, when used with the floating core plate configurations, allows for opening a main parting line before opening a second parting line.
The foregoing features of the invention will be more readily understood by reference to the following detailed description, taken with reference to the accompanying drawings, in which:
A convertible injection molding system uses a standardized, reusable mold frame (base) and modular molds formed from various combinations of standardized mold components. As opposed to prior art systems, which generally require custom mold frame components for each mold that are usable only for that mold, a standardized, reusable mold frame has standardized interfaces for use with molds having different internal geometries and features. Substantial functionality may be incorporated into the mold frame components in order to simplify the mold components.
In an exemplary embodiment of the present invention, an injection molding system includes a standardized mold base that receives, or is outfitted to receive, one or more stacks. The injection molding machine typically includes, among other things, an injection mechanism for injecting one or more materials into the mold(s) and an ejection mechanism for ejecting a molded part from the mold(s). The stacks interface with the injection mechanism of the injection molding machine through a runner clamp plate of the mold base and with the ejection mechanism of the injection molding machine through an ejector clamp plate of the mold base. The runner clamp plate includes a hot runner system for conveying injection molding material to the stacks. The runner clamp plate and the ejector clamp plate can be integral components of the injection molding machine or can be separate components that are attached or otherwise installed in the injection molding machine. The runner clamp plate and the ejector clamp plate include standard runner and ejection interfaces, respectively, and are “universal” in that they can interface with machines having different internal geometries.
In an exemplary embodiment of the present invention, a universal mold base, including the runner clamp plate and the ejector clamp plate, is installed into the injection molding machine for receiving one or more stacks. The runner clamp plate is typically attached to a fixed machine plate of the injection molding machine, and the ejector clamp plate is typically attached to a movable machine plate of the injection molding machine. The mold base can be configured to support one or more stacks at a time. For example, the mold base can be configured to support one, two, or four stacks simultaneously. When installed into the injection molding machine, the mold base can be considered part of the machine as opposed to part of the mold.
In an exemplary embodiment of the present invention, the stacks are modular, and include a series of interconnected modules or plates. The modules or plates are standardized and can be arranged in various combinations to meet specific user requirements. Standardized “blank” mold components can be produced in quantity and provided to a toolmaker, who designs tools around the standardized components. The use of standardized components typically reduces the overall toolmaking cost and time.
Stacks (including the mold base) are typically pre-assembled so that the unitary stack can be shipped or stored as a single unit and help to reduce the likelihood of damage or loss of the stack components. The stacks include standard runner and ejection interfaces as well as standard water and air interfaces.
If the floating core plate option is not used, then the floating core plate 14 is not installed in the mold base, and the corresponding support insert is not used in the stack. In this situation, the support insert associated with the ejector housing plate 16 is considered to be the primary support insert (as it would then be the only support insert used in the stack), the core block 15 is attached to the support insert so that the core block 15 and support insert are movably coupled to the ejector housing plate 16, and the ejector clamp plate system 2 excludes the floating core plate 14.
In an exemplary embodiment of the present invention, the various mold components can be arranged into four configurations, namely a standard two-plate configuration with no sleeves (referred to hereinafter as the “2P” configuration), a standard two-plate version with sleeves (referred to hereinafter as the “2P-S” configuration), a floating core plate option with no sleeves (referred to hereinafter as the “FCP” configuration), and a floating core plate option with sleeves (referred to hereinafter as the “FCP-S” configuration).
The FCP-S configuration includes a cavity block 302 with cycle counter 316, a core block 304 with guide/lock pins 318, a primary support insert 306, a secondary support insert 308, an ejector retainer plate 310 with stroke limiters 320, an ejector plate insert 312, and a clamp plate insert 314.
Thus, only one support insert is required unless the floating core plate option is used, in which case two support inserts are required. Also, the clamp plate insert only requires machining if sleeves are required.
The floating core plate option is typically used when a secondary movement is needed within the mold. For example, the floating core plate option may be used to remove steel from the product before the main parting line opens using a collapsible core, to pull a side action on the cavity side of the tool, to remove the core from the plastic before opening the parting line, or to strip the molded part off of the core. The floating core plate option may also be used to perform a secondary movement when the part geometry has a large undercut.
In exemplary embodiments of the present invention, the floating core plate option supports two opening and closing sequences, specifically a first sequence in which the main parting line opens before the second parting line and a second sequence in which the second parting line opens before the first parting line. For the first sequence, latch locks with delayed pull bar and early return mechanisms are used. For the second sequence, latch locks with no delay pull bar and no early return mechanisms are used. It should be noted that the same floating core plate is used for both sequences. It should also be noted that the opening/closing sequence for the 2P embodiments opens and closes one parting line with no parting line lock or early return mechanisms.
The floating core plate option should not be confused with a so-called “floating core,” which is also included in an exemplary embodiment of the present invention. As opposed to a floating core plate option, which allows for a secondary movement in the mold, a “floating core” allows for self-alignment between the cavity block and the core block, for example, to compensate for shifting of plates during assembly or shipment or to compensate for heat expansion. In an exemplary embodiment of the present invention, the core block 304 is allowed to “float” with respect to primary support insert 306 by plus-or-minus 0.2 millimeter. Guide lock pins in the core block 304 align with holes in the cavity block 302 to permit self-alignment of the core block 304 with the cavity block 302.
In an exemplary embodiment of the present invention, the mold base includes four spring packs, arranged substantially at the four corners of the floating core plate 14 (if floating core plate option is used) or the ejector housing plate 2, which push against the primary support insert 306. The pressure of the spring packs against the primary support insert 306 normally holds the core block 304 in a substantially fixed location relative to the cavity block 4, but still allows for movement of the core block 304 relative to the floating core plate or ejector housing plate specifically for the purpose of enabling self-alignment (although such play also allows for unwanted movement, such as during shipping, that can cause misalignment). The first time the mold is closed, the core block 304 self-aligns with the cavity block 302, and the spring packs normally hold the core block 304 in the aligned position unless and until something causes movement of the core block 304.
It should be noted that the spring packs are not required for “floating core,” although without spring packs or some other securing mechanism, the core block 304 would move about freely and would likely have to re-align each time the mold is closed. Such frequent re-alignment would likely cause premature wearing of the guide lock pins and holes.
In an exemplary embodiment of the present invention, the combined height of the finished cavity block 302 and core block 304 is 85 millimeters. The rough height of the blank cavity block 302 is approximately 55 millimeters, while the rough height of the blank core block 304 is approximately 65 millimeters. Thus, there is an overlapping material height of approximately 35 millimeters.
In an exemplary embodiment of the present invention, the Husky VG 750 nozzle with plunger style gate is the standard configuration. The cavity block 302 is configured for a standard gate diameter of 1.80 millimeters to match the standard valve stem and is configured with an “L” dimension of 36.00 millimeters. The user configures the part geometry in the cavity block 302 to achieve this “L” dimension.
Gate position and shrinkage is typically defined through preliminary ESI work, which typically includes moldflow analysis. The position of the gate will determine the location of the part in the cavity block 302 as well as the overall thickness of the cavity block 302. The parting line on the core block 304 is adjusted to achieve the overall 85 millimeter standard height. The gate location in the blind stack is always in the same position in the stack. Among other things, this makes it possible to have a standardized hot runner. The gate detail and gate diameter are completed after hardening of the cavity block 302.
In an exemplary embodiment of the present invention, the mold components are designed such that all ejector components must fit within a predetermined area of the stack.
If a pneumatic slide unit is to be used (e.g., to activate underground sliders in the cavity side before the mold opens), air lines are typically added to the cavity block 302 to actuate the toggle side action. One of the water circuit inlet and outlet locations in the hot runner manifold can be used for air if only one water circuit is required in the cavity block 302. In an exemplary embodiment of the present invention, two types of pneumatic slide units can be employed, one having a stroke of 2.18 millimeters and one having a stroke of 3.95 millimeters.
In an exemplary embodiment of the present invention, lifter design is standardized using a standard lifter rod.
In embodiments of the present invention in which side action sliders are used, it may be necessary to providing cooling for the slider, particularly for large sliders. Cooling of the slider can be done in the slide support with the O-rings placed in the cavity half.
As discussed above, in an exemplary embodiment of the present invention, the cavity block 302 must be hardened. Certain machining is performed after hardening of the cavity block 302. This typically includes machining the guide lock pin holes (e.g., by hard machining, jig grinding, or wire electrical discharge machining (EDM)), machining the assembly guide pin holes (e.g., by hard machining, jig grinding, or wire electrical discharge machining (EDM)) and machining the gate detail. Machining of the guide lock pin holes and the assembly guide pin holes must be in the correct relation to the gate detail location. The assembly guide pin holes are typically machined for a loose fit with the hot runner manifold for ease of assembly. The gate detail must be machined for the standard nozzle (e.g., for Husky VG 750 nozzle with plunger style gate, the gate detail must be machined with an “L” dimension of 36.00 millimeters and a gate diameter of 1.80 millimeters).
Also as discussed above, in an exemplary embodiment of the present invention, the cavity block 304 must be hardened. Certain machining is performed after hardening of the cavity block 304. This typically includes machining the guide lock pin holes (e.g., by hard machining, jig grinding, or wire electrical discharge machining (EDM)) and machining the dowel pin holes (e.g., by hard machining or jig grinding). Machining of the guide lock pin holes must be in the correct relation to the gate detail location. The c'bore of the guide lock pin holes should not need to be machined but should be checked to confirm the fit of the head of the guide pin. The dowel pin holes are used to align the primary support insert 306 with the core block 304 during assembly, and must be in the correct relation to the corresponding holes in the primary support insert 306.
It should be noted that the blank stacks will be approximately 35 millimeters thicker than shown in
The present invention may be embodied in other specific forms without departing from the true scope of the invention. The described embodiments are to be considered in all respects only as illustrative and not restrictive.
This application claims priority from U.S. Provisional Patent Application No. 60/606,936, which was filed on Sep. 3, 2004, and which is hereby incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60606936 | Sep 2004 | US |
