Multi-component injection molding offers new possibilities for plastics processing, combining different materials or colors in a single molding. Production can be done in one process without the need for additional assembly or post-machine processing steps. Multi-component injection molding is a fully automated process with a high degree of flexibility, making it ideal for high volume production. As early as 1961, aRBURG successfully used this technology.
The ultimate molded part has many functions and features. Using this process, colored parts with high pressure resistance, heat resistance or chemical resistance can be produced. Parts that can be manufactured with aRBURG aLLROUNDER are technically soft and hard material combinations, sandwiches and composite components that can be used to create reproducible color parts using alternating injection molding processes.
The multi-component injection molding concept covers multiple independent processes. Common to these processes is the simultaneous injection of a corresponding number of different materials into the mold using two or more injection molding devices to produce the ultimate product in a series of steps. The ultimate part can be used directly without subsequent processing.
According to the number of gates, it can be divided into two groups of systems using single gates, including sandwich and alternating injection molding processes. The multi-gate system can be initially divided according to the core pulling and transfer process. The transfer process involves the transfer of the robot system between two standard machines, which is transferred by the rotation of the robot system and the mold in a particular multi-component machine. The mold rotation includes rotation of the movable mold half by the rotating device, rotation of the mold inner member, and rotation about the vertical axis (GRaMTM process).
Advantages of applying multi-component injection molding: In multi-component injection molding, the components of the molded part are completely separated. All components are visible on the surface, reflecting the appearance and function of the part. For example, keyboard buttons, labeled switches, or handles with soft areas for added comfort. In addition to the ability to produce injection molded parts of multiple colors or materials in one process, the need for precision in forming technology can also deliver continued growth benefits without the need for additional assembly or subsequent processing. Injection molded parts are resistant to external influences such as mechanical, thermal or chemical effects, and are achieved by a suitable combination of materials and high bond strength. The adhesion of the two component bonding surface can be achieved by chemical bonding or mechanical linking. If chemically compatible materials are used, permanent molecular bonding can also be achieved by melting or welding processes. The types of mechanical links range from fiberglass that can be fixed on the surface to solid connecting elements (such as holes and undercuts) on the part. In terms of processing technology, the aRBURG aLLROUNDER modular design enables a relatively wide range of manufacturing processes. Includes soft and hard composite parts with TPE or LSR, sandwich or composite parts, or surface color repeatable parts made with an alternating injection molding process.
The two-component injection molding automatic two-component injection molding mold has two-stop type, and the molded parts are pre-filled and the parts are produced through another injection molding stage. Prefabricated parts are produced in the first cavity. The mold is then opened and the entire movable mold half is rotated 180° to rotate the preform cavity to the final injection position. The prefabricated part is then manufactured as the ultimate part by adding a second material. The mold cavity can be rotated in the same direction or alternately in different ways. After the final part is demolded, the empty cavity can be pre-prepared.
The three-stop mold for simultaneous release molded parts integrates a stripping station into a two-component molding in order to demold the part independently of the production process. The mold is then rotated clockwise in steps of 120°. There is an opening on the side of the third station from which the gripper gripper can reach the closed mold, demold the part and its gate, and place it on the conveyor for further processing. aRBURG's patented molding technology enables the simultaneous manufacture and removal of molded parts, greatly reducing cycle times and increasing productivity.
The molding process for injection molding three or more components of three or more components can be achieved by various methods. The following describes two possible methods.
The two-station mold can be set up in a manner similar to the three-component mold described above to complete the two-stop mold setting. In the first process step, three or more (up to five) components are simultaneously injection molded to produce prefabricated parts. Then, the entire half mold is rotated 180 and moved to the second position. At this time, the preform is injection molded using other materials to produce the final part. Alternatively, in a correspondingly configured mold, the part can be combined with up to five surface elements composed of other materials/colors in one production step. Thus, the insert in the mold can be rotated between the three stations by the rotating template and the electrically driven rotating device. Station 1 injects all cavities through hot runners and needle nozzles. Station 2 performs up to five injection molding processes on a specified number of cavities. The third station can then be used to demold parts from the closed mold. Part demoulding during the production process greatly shortens the overall cycle time, further improving the productivity of multi-component injection molding.
Four-stop molds For example, multi-layer plastic parts can be produced using a four-station mold. This method is easy to implement when using recycled materials and barrier layers. The schematic depicts the forming steps of a four-layer molded part. The innermost layer is produced at the first station. Then, the mold is rotated 90° to the next station. At this time, the first component was injection molded using the second component. Then, the mold half continues to rotate to the third station, and finally rotates to the fourth station for the final stage of production.
At this time, a protective outer layer or a surface layer of the molded part is injection molded on the part. After the cooling phase, the final multi-layer part is released from the cavity. In a continuous cycle, each time the mold is opened, an ultimate molded part is produced.
Alternate injection molding, alternating injection molding alternately injects the same plastic component of two different colors into the same cavity.
Both colors are placed in a special mixing nozzle before entering the mold. The two-color components are mixed to form a color effect. The two colors can be purposefully mixed to configure. In the alternate injection molding process, the two injection units are joined together by a special alternating injection unit with a mixing nozzle. The unit is mounted on a fixed installation of the machine and is therefore in front of the mold. Factors that affect the ultimate color include the cycle sequence, the design of the molded part, the location of the gate, and the activity characteristics of the material. In addition to the injection rate, simultaneous injection molding or alternating injection molding is also one of the decisive parameters. There is a special alternating injection molding program in the SELOGICa controller that manages the cycle sequence and material control. The same machine can be used for two-component injection molding as long as the alternating injection unit is removed.
The sandwich injection molding sandwich injection process injects a core material into the outer skin. The process takes place in two or three steps in one cavity. First, the material of the surface layer is injected into the cavity portion. The core component is then injection molded through its first material into its internal center. Finally, the first component is sealed at the gate location. In this way, the core material can be prevented from appearing on the surface, and at the same time, the second component in the gate system can be removed for the first injection of the first component.
A common application situation is that the molded part needs a beautiful appearance, and the core needs to use recycled materials, or the technical parts need a hard core, and the surface layer needs to be improved to obtain a better part feel. It is also possible to produce molded parts with stylish features such as a colored core with a transparent surface. Composite injection molding and core retraction process: In the core retraction production process, the hollow portion of the mold is first closed and later re-opened using a sliding core or slider in the cycle. When producing a part with two components, the first injection molding stage first injects the prefabricated component and then opens the second hollow part in the same cavity (for example, by dragging the sliding core). Finally, the second component is injection molded into the prefabricated part, so that the complete part is produced and the final part is taken out of the mold. When injection molding, you can also rotate the template to open the cavity and then inject the second component into the first component. If there are two or more components, composite injection molding can be used, but as the number of components increases, the complexity of the mold increases dramatically. Since all the required actions can be done in the mold, no external machine parts are required. However, the machine must have a sufficient number of programmable cores to control the slider. If only one mold is needed to complete the production, and there is no need to open the mold in the middle, and there is no need to transfer the prefabricated parts, the composite injection molding has obvious advantages. However, compared to multi-component injection molding, this production method is carried out in a strict phase sequence rather than in parallel. Application examples have improved the productivity of mobile phone casings. Mobile phone housings are typically manufactured in two-component molds in conventional two-station molds. However, this example integrates the third station, which separates the parts independently of the production process, significantly shortening the cycle time. The mold is rotated clockwise by 120 steps. The mold at the third station has an opening at the rear of the mold through which the gripper gripper can advance into the mold, thereby demolding the part and its gate and placing it on the conveyor for further processing. aRBURG's patented molding technology can be manufactured and processed into parts at the same time to further increase productivity.
A five-component machine for making toothbrushes. This special machine configuration is aLLROUNDER 630S2500-350/100/100/100/100. A horizontal injection molding unit of size 350 was inserted into the mold in a conventional manner by means of a fixed template. The other four units are mounted vertically on a common base and are perpendicular to the machine axis along the parting line for manual adjustment. The substrate is mounted on a fixed template. All machine processes are fully integrated into the SELOGICa control software. The MULTILIFT robot system ensures fast and reliable handling of parts. With the eight-cavity three-station hot runner mold, the demolding of the finished part can be done by rotating the rotating arm bundle mold on the rotating template. The part is sent to the corresponding conveyor that has been color coded. A toothbrush that has been subjected to color soft contact polishing is produced in a soft and hard combination using soft components of four colors. A toothbrush body made of PP can be combined with four different TPE color surfaces in one production step. The eight-cavity mold is rotated by a rotating mirror and an electrically driven rotating device. In the first station, injection molding is carried out in all eight cavities through hot runners and needle-shaped closed nozzles, and in the second station, injection molding is performed four times in units of two cavities.
The molded parts are then further processed and packaged in a pre-arranged order according to color. The two-color briefcase case is designed to accommodate a4 size and is manufactured in two components. Samples of briefcases produced by aRBURG are used for demonstrations and training, as well as for trade shows. The machine used in this process is the aLLROUNDER 820S400-3200/150. The mold uses a composite injection molding method and the so-called “core pulling technology, the aRBURG logo is pulled back by the shaft core. The outer casing is asymmetrically designed to facilitate the assembly of the parts in a single cavity for easy assembly. The part thickness is 2.5mm, two half shells It is assembled by a purely mechanical method of injection molding the hinge.
The briefcase is closed with two sliding buckles that are injection molded together with the half casing. For the aRBURG logo, you need to consider the letter spacing and the letters can't be made too small. The configuration of the mold is: aBS/PP is the first component, and aBS/PP/TPE is the second component. Professional application of injection molding envelopes. Depending on the configuration of the aLLROUNDER machine, a variety of inserts can be overmolded with up to two components. This is the easiest way to combine multiple functions into a unit injection molding process without the need for part processing. The insert can be a contact to be injection molded or a bearing or sleeve (with core). The insert can be fed manually or continuously. The insert can be placed in place and the finished part is demolded by the robotic system, which means the production process is highly automated.
Assembled injection molding uses a rotating mold, and components that need to be assembled after injection molding can be separately molded on a two-component machine and then assembled in a mold. An example of a seal assembled in a cable conduit illustrates how the assembly process can be implemented in a mold. Two separate components are first formed simultaneously at the respective mold stations. Then, after opening the mold, insert it by rotation
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