MIM Technology
MIM Let Your Ideas Innovative components meeting technical challenges often require a complex design and superior material properties; high manufacturing costs often prevent them from being realised. The freedom of shape offered by MIM (metal injection molding) technology provides a universal platform for design engineers and product designers to develop creative solutions and at the same time observe tight target costs. Applications that used to be manufactured by more costly conventional processes can now take advantage of the cost savings of MIM technology. 2
Come True MIM components combine the outstanding material properties of metal and the complex design options of plastic technology. Shaping by the injection molding of metal powders (MIM) offers maximum freedom with respect to part geometry and material options far exceeding the design possibilities of machining and casting technologies. Undercuts, bores and blind holes can be formed in any direction. Wall thickness of 1 mm or less as well as bore diameters of just a few tenths of a millimetre can be realised. Relief-like structures and engravings such as company logos or identification marks can be produced in detail. Even the use of expensive high strength alloys, corrosion resistant and other premium steels is possible as no additional machining costs are incurred. MIM components achieve an excellent surface finish (usually surface roughness values Ra < 1 µm) without any subsequent operations. The microstructure of the sintered components allows electroplating and electro-polishing without any pretreatment. The depth of penetration after case hardening is comparable to the values of forged steels. MIM materials are usually weldable too. 3
MIM Enjoy the Benefits The benefits of MIM processing can best be exploited if MIM design concepts are employed in the development phase. Entirely new possibilities for dimensional and shape design are opened to the design engineer. High volume production of highly complex components is economical due to fully automatic MIM processing and yields process reliabilities conforming even to the strict requirements of the automotive industry The flexible geometric design can even be applied to high strength metals and premium steels Applications of plastics, aluminium, or zinc die castings whose loading conditions are at the limit can be replaced by high strength MIM parts Costly joining or assembling techniques can be avoided by designing complex MIM components that can replace two or even more assembled parts Threads can be produced in the primary shaping process (ie injection molding) Material and costs can be saved by optimising the part volume. Weight reduction leads to further savings for dynamically loaded components in the form of a reduced moment of inertia The most intricate geometries are exactly reproduced in detail Even innovative alloy materials according to specific customer requirements can be economically processed Metal injection molding technology offers virtually unlimited design freedom to the design engineer these are just a few examples of the possible variety of shapes. 4
MIM Its Strengths in Summary 3 dimensional complexity: The forming process of MIM technology is closely related to traditional plastic injection molding and thus allows the same level of complexity in a regard to the design geometries. Parts with bore holes, blind holes, slots, notches, inner and outer threads, recesses, undercuts, structured surfaces, and cavities are made by MIM without problems. Similarly sophisticated design elements are not feasible with alternative chipless shaping processes. Weight reduction: Optimum part design allows for weight reduction without losing functionality. Weight reduction has a positive effect on the cost of the finished product. High productivity: When large numbers of identical parts are required, the cost advantage of MIM technology is particularly evident. Depending on the application, even highly complex components can be made without costly finishing operations. This is why this technology is particularly suitable for high volume production. 5
MIM A Highly Technical Manu- facturing Process 1.) Feedstock preparation For the preparation of the feedstock, metal powders are first blended according to the desired alloy composition. Then thermoplastic polymers and additives are kneaded with the powder mix and heated to obtain a viscous mass. The mass is then cooled down and processed into granular pellets (feedstock). The metal powder alloy determines the mechanical and chemical properties achieved by the finished product. GKN engineers have excellent know-how for powder development as well as for controlling the feedstock properties achieved. 2.) Injection molding Thermoplastics injection molding machines with special modifications are used in MIM technology, similar process as applied in conventional plastics injection molding. After being dosed and fed into the injection unit the input material (feedstock) is molten and densified in front of the screwconveyor. By a forward movement of the screw the plasticized mass is injected with high pressure through a sprue and runner system into the individual cavities of the mold. Subsequently the mass is 'frozen' inside the mold cavities with their geometric design ('green compact'). After cooling down to the ejection temperature the mold is opened along the parting plane. The solidified parts, ie the green compacts, are ejected from their cavities by means of ejection pins and can then be removed by suitable handling systems. 6
MIM Metal Injection Molding Green compacts are characterised by: portions of approximately 10% binder and 90% metal powder strength similar to thermoplastic polymer parts homogeneous powder distribution without particle alignment 3.) Debinding and sintering Subsequent debinding serves to remove the polymer binder from the green compacts. At GKN Sinter Metals this first step is carried out in continuous sintering equipment. A catalyst is fed into the debinding muffle which is evaporated at temperature, thereby forming a reactive atmosphere by which the polymer is completely de-polymerised. The binder is continuously degraded during the reaction and escapes in a gaseous form from the compact. The resulting structure has an open porosity. This porous structure is known as the 'brown part'. The brown parts are directly transferred into the sintering muffle. Here the temperatures are increased almost to the melting point in a well-controlled process until the metal particles sinter. The furnace atmospheres applied may be inert or reducing. Processing conditions in the computer controlled equipment are precisely monitored. Only due to this effort is it possible to keep the 16 to 18 percent shrinkage of the parts under control in order to attain the final dimensions as specified by the customer. 7
MIM Secondary Processing MIM components can be further processed and enhanced in many ways. Among others, the following processes may be applied: Heat treatment Hardening, tempering, quenching and tempering, surface hardening, case hardening Physicochemical surface treatment Nitriding, carbonitriding, nitrocarburizing, boriding, siliciding Chemical surface treatment Pickling, chemical deburring, burnishing, etching Mechanical surface treatment Engraving, barrel finishing, grinding, polishing, deburring, shot peening Applying nonmetallic anorganic coatings Chromatising, phosphating, anodizing, enamelling Applying metallic coatings Electroplating, chemical metal coating, melt dip coating, metal spraying, chromizing Applying organic coatings Printing, adhesive bonding, varnishing Applying wear resistant coatings CVD coating, PVD coating 8
MIM - Dimensional Tolerances MIM dimensional tolerances* [mm] Nominal dimension X [mm] Standard tolerance [mm] Up to 3 +/- 0,05 3 <x> 6 +/- 0,06 6 <x> 15 +/- 0,075 15 <x> 30 +/- 0,15 30 <x> 60 +/- 0,25 Typical tolerances of sintered MIM components The standard dimensional tolerances given in the adjoining table are generally achieved after sintering with consideration of the 16 to 18 percent shrinkage. These standard values are just guidelines since the real dimensional tolerances depend on the geometry and material composition and therefore can easily vary. If even closer dimensional tolerances are required, these can sometimes be achieved by re-designing the MIM component. In addition to that, GKN offers a variety of chipless and chipping finishing operations in order to conform to the highest requirements. (* Given tolerances serve as guidelines) MIM compared to competing technologies Parts / Year presssinter machining die casting investment casting low average high Part Complexity If the strengths and benefits of MIM technology are employed at the design stage, substantial advantages can be achieved over almost all conventional technologies. These are usually reflected as improved function and enormous cost savings. MIM paves the way to simplify entire component assemblies by reducing the number of individual parts. This helps to reduce the sources of error in the manufacturing process, enhance process reliability and thus guarantee higher quality. Résumé: MIM technology proves economical where complex shaped components with close dimensional tolerances, demanding mechanical properties and excellent surface finish are required. 9
MIM - Guidelines for Part Design In order to fully exploit the inherent potential of MIM technology, these guidelines for part design should be observed at the earliest possible design stage. We have compiled the most important design principles in the following graphics for optimum MIM design from the beginning! Example: fixture Flat bottom face MIM components exhibit about 16 to 18 percent shrinkage during the debinding and sintering process and therefore require a sliding bottom surface. Ideally a flat bottom face should be designed for sufficient part stablility. This can help to avoid distortion and resulting subsequent leveling costs. Threads Inner threads that are planned in the design stage can be shaped by MIM in the primary shaping process, provided they are designed adequately and can be realised by so-called spinning cores. 10
Example: shaft guide Radii The use of radii on edges, for example, has several positive effects on the overall picture of the MIM component. Not only are handling and aesthetic appearance of the finished parts improved, but also the material costs can be reduced. Rounded edges improve the strength, too, as the load is better distributed. Weight reduction Weight reduction can best be realised by creating free space in the MIM component. Besides reducing the weight of the component, the reduction of material cost also leads to a lower sales price of the part. Further the dynamic properties of the component can also be improved. Example: linking block Constant wall thickness If possible, the wall thickness should be constant all over the part and abrupt wall changes should be avoided. This guarantees a uniform mold fill during injection molding. Ribs and links Ribs and links serve to stiffen the part and mainly improve the strength of the MIM component. These design elements can also be used to improve the dimensional accuracy. 11
About GKN Sinter Metals GKN Sinter Metals a wholly owned subsidiary of U.K.-based GKN plc, a global industrial company is the world s largest producer of precision powder metal products. With a focus on superior delivery, quality and total solutions, the company offers extensive technical expertise in design, testing and various process technologies. GKN Sinter Metals offers a full range of more than 10,000 complex shape, highstrength products for the automotive, commercial vehicle, home appliance, lawn and garden, office equipment, power tool, recreational vehicle and process industry markets. The company s global footprint spans more than 13 countries across five continents. GKN Sinter Metals is in close proximity to its customers with more than 30 global locations and a workforce of approximately 5,500 employees. For more information about GKN s world of solutions visit www.gknsintermetals.com Production Plants Argentina GKN Sinter Metals de Argentina S.A. Ruta Nac. 5 Km. 159,5 (B6622GKA) Chivilcoy Bs. As. Argentina Phone: *54-11-5368-3700 E-mail: infoargentina@gknsintermetals.com Brazil GKN Sinter Metals Ltda. Av. Emancipacão, 4.500 - Santa Esmeralada CEP 13186-542 Hortolandia SP Brazil Phone: *55-19-2118-9400 E-Mail: infobrazil@gknsintermetals.com Canada GKN Sinter Metals St. Thomas Ltd. 7 Michigan Boulevard St. Thomas, Ontario Canada N5P 1H1 Phone: *1-519-631-4880 E-mail: infona@gknsintermetals.com China GKN Sinter Metals Danyang Number 7 Mechanical Industry Park Danyang Development Zone Danyang, China Phone: *86-511-86-885-556 E-mail: infochina@gknsintermetals.com Germany GKN Sinter Metals Engineering GmbH Krebsöge 10 42 477 Radevormwald Germany Phone : *49 2191-693-0 E-mail : infogermany@gknsintermetals.com GKN Sinter Metals Filters GmbH Dahlienstraße 43 P.O.Box 1520 42 477 Radevormwald Germany Phone: *49 2195-609-27 E-Mail: feedback@gkn-filters.com India GKN Sinter Metals Ltd. 146, Mumbai Pune Road Pimpri, Pune 411 018 Maharashtra, India Phone: *91-20-2742-6261, 6262, 6263 E-mail: infoindia@gknsintermetals.com Italy GKN Sinter Metals SpA Fabrikstraße 5 39 031 Bruneck (BZ) Italy Phone. *39-0474-570211 E-mail: infoitaly@gknsintermetals.com North America GKN Sinter Metals 3300 University Drive Auburn Hills, Michigan 48326-2362 USA Phone: *1-248-371-0800 E-mail: infona@gknsintermetals.com South Africa GKN Sinter Metals Cape Town P.O.Box 156 Sacks Circle Bellville, 7530 South Africa Phone: *27-21-950-6200 E-mail: infoafrica@gknsintermetals.com GKN Sinter Metals Sales Offices Worldwide China E-mail: France E-mail: Japan E-mail: Korea E-mail: Spain E-mail: Sweden E-mail: infochina@gknsintermetals.com infofrance@gknsintermetals.com infojapan@gknsintermetals.com infokorea@gknsintermetals.com infospain@gknsintermetals.com infosweden@gknsintermetals.com United Kingdom E-mail: infouk@gknsintermetals.com Copyright by GKN Sinter Metals - Rev. 1.0