SI22747A - Injection moulding of multimaterial components - Google Patents

Abstract

The problem the invention is solving lies in that multimaterial injection moulding enables in most cases, even without a robot, the inclusion also of other materials, e.g. silicones, vulcanised elastomers, and in the case of additional thermal treatment, also ceramic and metallic materials. It enables, as well, the manufacture of products assembled from several mutually movable or rotatable parts. A traditional one-component injector is applied, featuring a software capable of activation of subsequent injections from additional dosators. A static stirrer heated up simultaneously with the tool is mounted on the tool. The flow to the stirrer takes place from a two-component dosator, whereas the outflow into a tool cavity through a hot nozzle. After the standard injection of a thermoplast or high-filler compound - preceded by previous installation of inserts made of metals, ceramics or composites, if needed - a slide is pulled out from the tool and two mixed components are injected into the newly created room. Vulcanisation takes place in the tool at the same temperature as in the case of crystallisation of a thermoplast. The essence of the invention lies in the combination of simultaneous application of new materials and integrated injection with the application of additional injection units directly on the tool. As an essential element of the invention there is a heated static stirrer mounted directly on the tool, with a dosing cylinder attached, which allows vulcanisation of elastomers and silicones in the tool with simultaneous application of crosslinking agents just before the injection. Application of high crystalline engineering plasts enables the injection of thermoplasts and elastomers of smaller volumes without carrying out a two-temperature regime.

Description

INJECTION OF MULTIMATERIAL COMPONENTS

The object of the invention is a complete process that enables the fastest, cheapest and most environmentally friendly production of components consisting of several materials with combined equipment and tools, which can also spray a component of thermoplastic or vulcanized rubber and silicones, as well as metal and ceramic materials with powder injection molding. Thus, components with multiple components and materials do not need to be assembled by manual or robotic assembly, but are injected in one cycle.

Description of the invention:

A: The field of the invention relates to the processing of plastics, since injection molding techniques, including combinations with powder materials, are typical plastics processing technologies.

B: Demonstration of a problem solved by the invention

The problem solved by the invention is that multimaterial injection molding allows in most cases, even without a robot, the integration of other materials, e.g. silicones, vulcanized elastomers, and with the additional heat treatment of ceramic and metal materials. It also enables the production of composite products from several mutually moving or rotating parts. Selected technology with a suitable tool enables modern automatic production of all these variants without the use of a two-temperature regime in tool cavities.

C: Description of the new solution

We use a classic one-component syringe, with software that allows you to trigger further syringes from added dispensers. A static mixer, heated at the same time as the tool, is installed on the tool. The flow to the mixer is from a two-component dispenser and the outflow into the tool cavity via a hot nozzle. After a classic thermoplastic syringe or a high-fill compound, if necessary by pre-inserting inserts of metal, ceramics or composites, pull out the slider in the tool and inject the mixed components into the newly formed space. Vulcanization takes place in the tool at the same temperature as the thermoplastic crystallization. The most suitable material combinations are polyamides with liquid crystalline silicone or thermoplastic polyurethane, which, with the addition of the crosslinker, vulcanize into silicone or polyurethane rubber. Depending on the needs and complexities of the component, another thermoplastic injection molding group is attached to the tool, e.g. for high-fill compounds. Below, we describe the individual examples that can be implemented with the technology described.

New multimaterial injection molding technology also enables injection molded products. In this process, a part of the component, either metal, ceramic, composite or also more thermally resistant plastic, is inserted into the injection molding tool, and then the product is sprayed with other plastic, either over the entire surface or only one part. A classic syringe, a fairly sophisticated tool and a worker or worker is sufficient. the robot. Another option is two-component injection molding, in which another injection group sprays another material into the same tool, usually softer.

With two-component micro-injection of metals, e.g. magnetic and non-magnetic steels are simultaneously sprayed, e.g. for position sensors and actuators, flowmeters. At the same time, molded memory alloys, printed cartridges and sensor elements can also be sprayed.

We use a fine metal powder with particles of 2 to 5 μm in size, bound with a mixture of waxes and polymers, so that part of the binder remains in the brown piece after evaporation and thus binds the powder to sintering. Then sinter the residue and redistribute the volume to 99% of theoretical density.

One of the most promising uses of dust spray is plastomagnets. Mostly, these are rare earth ceramics, NdFeB, bound with PA12 or PPS according to temperature requirements. With this type of binder, we do not burn or sinter, so avoiding the usual shrinkage of 12 to 25%. We can therefore achieve high accuracy. For sintering and sintering technologies, any sinterable material can be used, e.g. steels, Ti, carbide solids, Ni, Co- and Alz alloys, and metal matrix composites, and for ceramic injection, the oxides Al and Zr, carbides and nitrides, e.g. S13N4. Carbides and oxides have particles below microns in size, silicates slightly above microns and metals up to 10 μs, and magnets above 300 μs. We reach up to 65% density, with a mixture of different sizes up to 72%. Waxes and polymers of PE, PA, PP, as well as resins and aqueous polymers, e.g. alcohols. During removal, part of the binder is broken or broken. evaporate, the smaller part remaining until sintering. Products of 0.2 to 20 mm thickness, 1 m length and weight of several kg are known, but typical products are measured in grams and centimeters.

Plastic / ceramic hybrids obtained by injection molded ceramic injection molding are becoming a rapidly growing automated high-speed technology. Until now, it has been used primarily for textile guides, tools, but the combination of high hardness, strength and corrosion resistance with low cost and the flexibility of molding plastics penetrates into the most important industries. The technology was developed with ZrO ₂ and Si ₃ N ₄ ceramics. Dust is bonded to up to 50% of polyolefin and wax binders. The contraction is compensated by experiential excesses. They evaporate a portion of the binder and sinter, yielding ceramic densities up to 99. Highly tolerant sites, e.g. bush openings, sanded subsequently.

Multi-pole permanent magnets produced by multi-component injection molding are ideal for establishing precise magnetic control in sensors and actuators. They developed a single-syringe engine rotor. The directional magnets in the rotor create three magnetic fields, two for speed measurement and switching, and the third for rotor drive in the brushless motor. Two SrFeO and NdFeB compounds are used to achieve precision and high magnetic flux. In the compounds, the magnetic particles must orient themselves before solidifying the melt.

For the sensors and actuators, they have the unattainable advantage of being able to combine many different magnetic functions in the same compact product, including precisely separated polar fields, which serve as laptops in tachometers, engines, brakes and medical apparatus. The magnetization can already take place in the tool.

Powder injection molding is increasingly used for the production of metal components made of stainless steel, magnetic alloys, titanium and ceramics, mainly Al- and Zr-oxide. High thermal, mechanical, chemical and friction properties, as well as high-gloss surfaces, unlimited three-dimensional design, two-component design, are advantages that win over mechatronic assemblies.

Until recently, soft magnets, good enough for coils, failed to develop, so they mainly used iron alloy sheets and sintered or sintered. pressed soft ferrite, more recently with powder spray. New polymer-bonded soft-magnetic composites are now being developed that are penetrating the industry.

Thermoconducting compounds, e.g. PA12-filled ceramics accelerate the penetration of ever smaller, including polymer electronics, and especially diode lamps. The diodes convert 30% of the energy into light, the rest into heat, not the infrared rays but the heat remaining in the material. If not removed, it shortens the duration and affects the color of the light. The classic production of diode lamps is the pouring of the circuit into silicone and the assembly together with the diodes on the Al-housing, which dissipates heat. Due to the freedom of design and faster production at a lower cost, the new solution is electronics injection molding for thermally conductive plastics that integrates sealing, protection, installation and cooling functions.

D: Advantages of the invention

The innovative system, which has been tested in the laboratory, enables the production of small multimaterial components with segments of thermoplastics, thermoplastic elastomers, vulcanized elastomers, silicones, metals and ceramics. The essence of the invention is in the combination of the simultaneous use of new materials and integrated injection molding, using additional injection units directly on the tool. As an essential element of the invention is a heated, direct-tool mounted static mixer with a connected dosing cylinder, which allows the vulcanization of elastomers and silicones in the tool, with the simultaneous use of crosslinkers just before injection. The use of high-crystalline engineering layers allows the injection of thermoplastics and elastomers in smaller volumes without performing a two-temperature regime. So far, two-component thermoplastic / elastomer injection has required cooling of one and heating of the other part of the tool, which is especially demanding and expensive, especially for multi-tool multimaterial tools, or even exceeds the state of the art.

Advantages of the invention:

- simultaneous use of thermoplastics, elastomers, silicones, metals and ceramics, in a compound or as an insert

- single-temperature tool

- flexibility, possibility of changing dosage units

Claims (1)

PATENT APPLICATIONS 1. A process for injection molding multimaterial components, characterized in that - that part of the tool is a static mixer, heated to the melt temperature and connected directly to the heated nozzle, - the dosing of the two components is carried out directly on the mixer on the tool, allowing the use of crosslinkers and crosslinking - the vulcanization of thermoplastic elastomers or silicones directly in the tool - the use of a high crystalline thermoplastic or a high-density compound at the same time as the first and low-temperature crosslinking as the second component, allowing simultaneous cooling and vulcanization and use of the unit-temperature regime in tool cavities, - that a second thermoplastic injection unit is mounted on the tool and injects a highly charged metal magnetic or ceramic compound directly into the tool plane of the tool, tearing off when ejected.