Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/22—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip
  • B22F3/225—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip by injection molding
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
  • A61C13/00—Dental prostheses; Making same
  • A61C13/20—Methods or devices for soldering, casting, moulding or melting
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/12—Both compacting and sintering
  • B22F3/1208—Containers or coating used therefor
  • B22F3/1258—Container manufacturing
  • B22F3/1275—Container manufacturing by coating a model and eliminating the model before consolidation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
  • B22F5/007—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of moulds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28B1/00—Producing shaped prefabricated articles from the material
  • B28B1/24—Producing shaped prefabricated articles from the material by injection moulding
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28B7/00—Moulds; Cores; Mandrels
  • B28B7/34—Moulds, cores, or mandrels of special material, e.g. destructible materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28B7/00—Moulds; Cores; Mandrels
  • B28B7/34—Moulds, cores, or mandrels of special material, e.g. destructible materials
  • B28B7/346—Manufacture of moulds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C33/00—Moulds or cores; Details thereof or accessories therefor
  • B29C33/38—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
  • B29C33/3814—Porous moulds
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
  • A61C13/00—Dental prostheses; Making same
  • A61C13/20—Methods or devices for soldering, casting, moulding or melting
  • A61C13/206—Injection moulding
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/3094—Designing or manufacturing processes
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/3094—Designing or manufacturing processes
  • A61F2/30942—Designing or manufacturing processes for designing or making customized prostheses, e.g. using templates, CT or NMR scans, finite-element analysis or CAD-CAM techniques
  • A61F2002/30957—Designing or manufacturing processes for designing or making customized prostheses, e.g. using templates, CT or NMR scans, finite-element analysis or CAD-CAM techniques using a positive or a negative model, e.g. moulds
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/3094—Designing or manufacturing processes
  • A61F2002/30968—Sintering
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2310/00—Prostheses classified in A61F2/28 or A61F2/30 - A61F2/44 being constructed from or coated with a particular material
  • A61F2310/00005—The prosthesis being constructed from a particular material
  • A61F2310/00011—Metals or alloys
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2310/00—Prostheses classified in A61F2/28 or A61F2/30 - A61F2/44 being constructed from or coated with a particular material
  • A61F2310/00005—The prosthesis being constructed from a particular material
  • A61F2310/00179—Ceramics or ceramic-like structures
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2310/00—Prostheses classified in A61F2/28 or A61F2/30 - A61F2/44 being constructed from or coated with a particular material
  • A61F2310/00005—The prosthesis being constructed from a particular material
  • A61F2310/00179—Ceramics or ceramic-like structures
  • A61F2310/00185—Ceramics or ceramic-like structures based on metal oxides
  • A61F2310/00203—Ceramics or ceramic-like structures based on metal oxides containing alumina or aluminium oxide
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy

Definitions

• the present invention relates, inter alia, to a proces ⁇ for producing a sinterable ceramic or metallic body which can also have an individual and distinctive shape and, for example, consists of a dental bridge shell.
• the production is executed using a tool/moulding tool which can be assembled from two or more tool parts and whose moulding space corresponds to the shape of the body.
• the invention also relates to a device or tool for producing the said sinterable ceramic or metallic product or ceramic prosthesis (metallic prosthesis) .
• the inven- tion also relates to a process for producing a shell for a metallic or ceramic product or a ceramic prosthesis (metallic prosthesis) which is designed to be anchorable to a base which has been prepared in the human body and which can, for example, include or consist of an implant, tooth remnant(s), etc.
• the invention also relates to an injection moulding tool for the said product or prosthesis.
• the invention also relates to a process for producing an injection moulding composition which comprises a polymer melt and/or wax melt (binding agent) and powder particles which are mixed into this melt.
• the composition is intended to be squeezed or pressed, in the melted state, into one or more spaces in an injection moulding tool in order to achieve a sinterable body which i ⁇ formed when the composition is in solidified form and which preferably has an individual and/or complex shape.
• the invention relates to a powder for an injection moulding composition which, in the melted state, can be squeezed or injected under low or medium pressure, by which in this case is meant 1-200 bar, into one or more moulding spaces in an injection moulding tool for the purpose of forming a sinterable solidified body which preferably has an individual and/or complex shape.
• the invention relates to an injection moulding composition for forming, in a tool, a sinterable body which preferably has an individual and/or complex shape.
• the composition comprises a sinterable powder which has been treated with a hydrophobic agent and which can be mixed into a melt of binding agent, for example paraffin wax and/or polyethylene.
• the invention can also be used for producing products in metal/hard metal, with use being made of metal powder, for example titanium powder, which is moulded and sintered to the desired density.
• the body/product/prosthesis which i ⁇ referred to above and which is produced using the present invention must be sinterable.
• the sintering confers the desired hardness on the body during the course of a certain degree of shrinkage. Such sintering is well known per se and is not part of the subject-matter of the present inventio .
• TECHNICAL PROBLEM In connection with production of the said product, there is a marked need to be able to produce a technically simple tool for producing one or a few products, for example when making dental product ⁇ , manufacturing prototypes, making products in small series, etc.
• the tool mu ⁇ t have a technical construction which permits economic use.
• the sole product, or the few products, must themselves carry the tool cost ⁇ , which, in the case of dental bridge production, for example, implies a tool cost of only 20- 30 SEK/product, calculated at present-day prices.
• the production of dental products having individual and often complicated shapes for example dental bridge shells
• a ⁇ ingle treatment step for example, it is difficult, when casting ceramic bodies, to prevent these bodies buckling, result ⁇ ing in poor fitting shape.
• the ⁇ e problem ⁇ are solved by ⁇ pecifying special tool construction, tool production and a specially indicated injection moulding composition.
• the invention al ⁇ o provide ⁇ solutions to this problem and makes it possible to create, in one and the same tool assembly, the underside and external contours of a body/dental bridge, which can extend between two or more teeth/attachment points in the dentine. In doing this, it is possible to avoid previous problems involved in creating bodies in several manufacturing steps, in which the external shape is transferred via a copying function and the internal shape is produced by means of spark machining using (a) tool(s) to which the internal shape has previously been transferred by means of copying.
• a wet composition is used whose solvent (water) is driven off by drying under ambient conditions or at an elevated temperature.
• the demand placed on the material in the tool part which is produced using the wet composition is that it exhibits the properties which are required as regards the injection moulding and other aspects of the produc ⁇ tion.
• the composition must be easy to shape or pour and, in the solidified state, exhibit shape-stability properties within given areas. It must be pos ⁇ ible for the chemical reaction to take place at room temperature and it must be possible to regulate the porosity by means of pre ⁇ ure and temperature.
• the invention al ⁇ o solves these problems and recommends, as an example, that the modulus of elasticity should be > 1 GPa in the solidified material. There is a marked need, in thi ⁇ connection, to obtain a coherent, sinterable body as the result of the injection moulding.
• SOLUTION That which can principally be regarded as being characteristic of a process according to the invention is, inter alia, that at least one tool part is produced from a wet composition which comprise ⁇ solvent, heat- conducting particles and material which is easy to work and whose shape is stable in solidified form.
• the material is caused to solidify in a binding function (for example chemical reaction) , after which the solvent is driven off by drying and a pore channel system is thereby formed in the solidified material.
• a part of the shape of the body is transferred to the said tool part or the solidified material.
• the remaining shape or shapes of the body is/are transferred to the other tool part(s).
• Sinterable injection moulding composition is injected or squeezed into the moulding space using a low or medium compression moulding pressure, by which, in this case, is meant a compres ⁇ ion moulding pre ⁇ sure of between 1-200 bar.
• Heat which arises due to the injection moulding composition which has been injected into the moulding space is conducted away by means of the said heat-conducting particles in the solidified material. Gas or air which is trapped in the moulding space during the injection or the squeezing-in is conducted away through the pores in the solidified material.
• That which characterizes an injection moulding tool for carrying out the said process is that it is arranged with at lea ⁇ t one tool part made of material which i ⁇ readily worked and form-stable, examples of such material which may be mentioned in this context being plaster, cement, aluminium phosphate-bound or sol-bound
• the material must contain pores and admixed heat-conducting particles which are to form a heat-removal network for the heat.
• the ⁇ aid tool part can be combined with one or more other tool part ⁇ in order to form one or more moulding spaces for the said product(s) /prosthesis(prosthese ⁇ ) .
• the injectionmoulding tool is arranged, in association with the formation of the sinterable product or prosthesis, to receive an injection moulding composition which is squeezed in using a low pressure or a medium pressure and which contains a sinterable ceramic powder or metallic powder. Heat which is generated during the moulding, and gas or air which is trapped in the moulding space, can be conducted away with the aid of the said heat-conducting particles and the said pores, respectively.
• the latter is caused to solidify and the solidified material is allocated the function of a second tool part which can cooperate with the first tool part, in which second tool part the second delimitation surface of the moulding space is formed by the outer shape or upper surface of the second model.
• the first and second tool parts are separated and the second model is removed.
• the tool parts are brought together once again and means for forming the shell are injected or squeezed into the moulding space which is thereby formed, with heat removal being effected by way of the said heat-removing particles.
• An injection moulding tool for the said process can principally be regarded as being characterized in that the first tool part is arranged to support a first model of the base (the jaw) which is to support the shell or equivalent dental product.
• the base forms, by means of its upper parts, a first delimitation surface for the moulding space.
• a second model which corresponds to the shape of the shell or the dental product, can be applied to the first model.
• the second tool part is formed out of or with solidified wet composition which is applied at least around and enclosing the second model when the latter assumes its position on the first model.
• the second model can then be removed from the first model in order to form the moulding space.
• the shell can be produced by means of injection moulding composition which is injected or squeezing into the moulding space which has thus been established. Heat removal during the injection or squeezing-in is arranged to take place by way of the heat-conducting particles which are admixed with the solidified wet composition.
• the powder particle surfaces are coated with one or more agents, for example stearic acid, by means of which agent or agents the particle surface ⁇ are hydrophobicized while, at the same time, deagglomerating and lubricating functions are implemented in the injection moulding composition both for the mutual separation (and better admixture) of the powder particles and for facilitating the introduction of the composition into the respective moulding space using squeezing-in or injection members.
• agents for example stearic acid
• That which can principally be regarded as characterizing a powder for the said injection moulding composition is that the powder particles are dried in order to obtain particle surfaces which are free from physically adsorbed water, in particular, and that the particle surfaces are coated with one or more agents, for example stearic acid.
• the agent has a hydrophobicizing effect and brings about deagglomeration and lubricating functions which keep the particles apart and, respectively, facilitate injection and/or squeezing into each space of the said space ⁇ .
• the powder can be mixed with polymer and/or wax (for example paraffin wax) which contains binding-agent melt.
• Hydrophobicization of the particle surfaces is preferably brought about mechanically by, for example, mixing the said powder and hydrophobicizing additives in a vessel in the presence of milling media on a drum bench.
• the size, quantity, hardness and form of the milling media can be cho ⁇ en such that the milling effect is avoided.
• the task of the milling media is to effect abrasion of the particle surfaces, thereby creating reactive surfaces for binding between the particles and the hydrophobicizing medium which has been supplied. This binding is important for keeping the particles apart during the mixing process.
• milling media having a high degree of hardness and increased ⁇ ize and quantity are chosen in order, apart from bringing about the abovementioned effect, also to bring about a simultaneou ⁇ milling effect, i.e. decrea ⁇ e in the size of particles.
• An injection moulding composition according to the invention can also be regarded as being characterized in that the proportion of wax in the solidified body substantially exceeds the proportion of polyethylene, and in that the latter proportion is only 1-10 percent by volume of the former proportion.
• ADVANTAGES By mean ⁇ of that which has been proposed above, technically efficient manufacture of dental products (dental bridge shells) and prototypes can be achieved employing tools which are used only once or just a few times. The costs of producing the tools are minimal and very attractive from the industrial point of view. The processes involved in producing the product can also be considerably simplified and do not require any additional mea ⁇ ures arising from the use of the new type of tool.
• the injection moulding composition can be arranged to be technically easy to prepare, using elements of conventional production processe ⁇ in which the preparation i ⁇ characterized by technical ⁇ implicity and good economy.
• the production of wet compositions for one or more tool parts is effected using techniques and material with which the dental technician or equivalent is thoroughly familiar per se. The removal of injection-moulded, sinterable products from each tool part is simplified and ensured in a reliable and effective manner.
• FIGURE LIST A presently proposed embodiment of the proce ⁇ , device ⁇ and joint filler ⁇ /powder ⁇ will be de ⁇ cribed below while at the same time referring to the attached drawings in whichj
• Figure 1 shows, in vertical section, an example of the principles of a tool
• Figure 2 shows the tool according to Figure 1 in horizontal section
• Figure 3 shows the tool according to Figures 1 and 2 in perspective obliquely from above
• Figure 4 shows a second embodiment of the tool in vertical section.
• An injection moulding tool designated by 1, is shown diagrammatically in Figure 1.
• the tool comprises a lower tool part 2 and an upper tool part 3.
• the tool parts can be acted on towards and away from each other, in the directions of arrows 4, 5.
• the tool represent ⁇ the injection moulding of a body 6 having a simple shape, for example a cylindrical body (body shape) which i ⁇ provided with a bottom part, which body (body ⁇ hape) is produced in the mould 7 of the tool which is formed by the tool surfaces 8, 9.
• a channel for injection moulding composition is shown by 10.
• the tool part 3, and, where appropriate, the part 2 as well contain, in their material, baked-in heat-conduction particles which can consi ⁇ t of aluminium particle ⁇ , alloy particle ⁇ , bronze particles, etc.
• the particles form a network in the material for the purpose of effecting heat removal for heat which arises in the injection composition 11 during the injection moulding event.
• a tube system 12 of a substantial nature can be included as a supplement, with it being po ⁇ sible to circulate coolant in the directions of arrows 13, 14 in accordance with Figure 2.
• Figure 4 shows an example of a complicated shape which can be injection moulded, consi ⁇ ting, for example, of a dental bridge ⁇ hell 15 which ha ⁇ to be applied to a base which is arranged in the human body and which is formed from tooth remnants (implants, etc.), which tooth remnants are represented by 16 and 17 in Figure 4.
• the dental bridge has to be attached to two tooth remnants 16 and 17 and extend over the space 18 for a tooth which has been removed.
• the said tooth remnants are symbolized or reproduced by a first model 19 which constitutes a copy of the said tooth remnants (or equivalent) .
• the shapes of the tooth remnants have been transferred to the fir ⁇ t model using a copying process which can be of a type which is known per se.
• the first model is anchored in a known manner to a first tool part
• a second model 21 is applied to the first model.
• the shape of the second model is produced in a known manner.
• a member 22, which can have the shape of a cylinder, is applied to the tool part 20.
• the inner space of the member forms a space 23 for a wet composition 24, which is applied to the space 23 in viscous form.
• the wet composition can be subjected to mechanical pressure using a compressing member 25 (disc) .
• the wet composition contains 50 percent by weight of a metallic or alloy powder for constituting the said heat-removal function.
• the wet composition is caused to solidify in the space by means of a chemical reaction. During the latter reaction, the solvent (water) in the wet composition is driven off and forms pores (a porous wall) in tool part 24.
• a moulding space F is formed in which a first delimitation surface is constituted by the upper surface 26' of the base 19 and a second delimitation surface 27 is constituted by the upper surface 27' of the second model.
• the tool part is returned to the position ⁇ hown in Figure 4 and the injection moulding compo ⁇ ition 28 i ⁇ pressed or injected into the moulding space F using an injection member 29, which can be of a known type.
• the injection pressure T can be between 1-200 bar.
• Compres ⁇ ion of the wet compo ⁇ ition 24 is effected using a tool part 29.
• the tool parts 20 and 29, and the member 22, are arranged to absorb lateral displacement forces f' , f' ' which can arise due to the injection moulding composition 28 being injected, thereby guaranteeing precision in the injection-moulded product.
• Heat removal takes place, as described above, by means of the heat-removing particle ⁇ 24a which are included in the solidified wet composition. Air (gas) which is trapped in the moulding space is conducted away via the porosity in the tool part 22 in the directions of the arrows 30.
• Example I of an injection moulding composition containing H 2 0 3 powder.
• the powder was hydrophobicized in a HD-polyethylene container, with 3 g (1.96% by weight) of finely powdered stearic acid (KEBO) being added, on a drum bench for 3 hours using 1 kg of aluminium oxide milling media.
• KEBO finely powdered stearic acid
• a melt wa ⁇ prepared from 30.0 g of paraffin wax (KEBO, melting point: 62-64°C) and 2.0 g of stearic acid, of identical quality to that described above, at a temperature of 120°C.
• An injection-mouldable composition which was obtained by mixing this melt and the hydrophobicized ceramic powder had a dry matter content of 81.2% by weight, which corresponds to 50.1% by volume of aluminium oxide.
• a corre ⁇ ponding test was carried out using an identical Alcoa SG 16 ceramic powder which was neither heat-treated nor hydrophobicized. In this case, all the stearic acid was added to the paraffin wax melt so that the paraffin wax/stearic acid ratio corresponded to that in the above case, i.e. approximately 6:1.
• An injection- mouldable composition which was obtained by mixing this melt and the untreated ceramic powder had a dry matter content of 78.0% by weight, which corresponds to 45.2% by volume of aluminium oxide.
• Example II of an injection moulding composition containing Al 2 0 3 powder.
• An injection moulding composition was prepared having an Al 2 0 3 /MgO powder content of 48% by volume: a mixture of 405 grams of A1 2 0 3 powder (A16SG, ALCOA, USA) and 2 grams of MgO as ⁇ intering aid (MERCK, GERMANY) was heat-treated in a heating chamber at 300°C for one hour, after which the powder wa ⁇ hydrophobicized with 10 gram ⁇ of stearic acid by being treated in an HD-polyethylene container together with Si 3 N 4 spheres on a drum bench. The stearic [lacuna] at a temperature of 70°C. The composi ⁇ tion was homogenized at 70°C for two hours by means of propeller stirring.
• composition was poured into the filling trough, which had been preheated to 70°C, of a medium- pres ⁇ ure injection moulder (MPIM) (GO CERAM HB, Sweden) .
• MPIM medium- pres ⁇ ure injection moulder
• Component ⁇ were injection-moulded u ⁇ ing moulding tool ⁇ as described in the examples below.
• the components were then placed on a powder bed of coarse-grained A1 2 0 3 for controlled elimination of the organic additives in an RCE (Rate-Controlled Extraction) Binding Agent Remover (GO CERAM HB, Sweden) in air.
• the components were then sintered (baked) to dense bodies at 1650°C for one hour, and in an atmosphere of air, in a super kanthal kiln.
• Example III of an injection moulding composition containing stainles ⁇ 316 ⁇ teel powder.
• the stearic acid-coated steel powder was ⁇ tirred into a melt of 80 gram ⁇ of paraffin and 5 grams of polyethylene, containing 17% by weight of ethylenebutyl acrylate, at a temperature of 75°C.
• the composition was homogenized at 75°C for two hours by means of propeller stirring. Sedimentation experiments showed that the steel powder did not sediment, or sedimented much more slowly, and had a considerably lower tendency to separate out from the paraffin than in experiments without the addition of polyethylene.
• the composition was poured into the filling trough, which had been preheated to 75°C, of a medium- pressure injection moulder (MPIM) (GO CERAM HB, Sweden) .
• MPIM medium- pressure injection moulder
• Components were injection-moulded using moulding tools which were made as de ⁇ cribed below.
• the components were then placed in a powder bed of coarse-grained A1 2 0 3 for controlled elimination of the organic additives in an RCE (Rate-Controlled Extraction) Binding Agent Remover (GO CERAM HB, Sweden) in hydrogen.
• the components were then sintered (burnt) to dense bodies at 1350°C for two hours, in vacuo, in a graphite resi ⁇ tance kiln.
• Example ⁇ of injection moulding tool ⁇ (comparison with state of the art) .
• Three injection moulding tools were manufactured in different materials, with all the tools being of the ⁇ ame design as depicted above.
• One tool was produced, by milling, entirely from black steel.
• a plate was cast in acrylate plastic, with a metal cylinder being applied to the middle of the plate.
• the cylinder part, projecting up from the plastic, was covered with wax, thereby constituting the mould cavity.
• a slurry containing 70% by volume of hard plaster and 30% by volume of fine-grained aluminium powder was poured over the plastic plate together with the wax-covered metal cylinder. After solidification, the plaster was shaped and an inlet hole for the injection moulding composition wa ⁇ bored in it.
• a moulding tool half was produced from a slurry containing 70% by volume of cement and 30% by volume of aluminium powder.
• the steel tool turned out to be ten times more expensive and took three times as long to manufacture as compared with the other two tools.
• the tool part which is produced from a wet composition can also be prepared from ceramic/metallic powder mixtures containing a temporary binding agent.
• the required properties are obtained by driving off the temporary binding agent after the embedment and then baking the tool part at a high temperature. This temperature is chosen so that the metal melts and forms a network for efficient heat removal.
• the co-sintered ceramic structure retains it ⁇ shape and porous structure.
• the metal and the ceramic can preferably be selected such that the ceramic is bound at contact points (by means of so-called neck formation) at the same time as the metal begins to melt and thus form a heat-conducting network through the pore channel structure.

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• 1995
  • 1995-06-28 SE SE9502338A patent/SE514696C2/sv not_active IP Right Cessation
• 1996
  • 1996-06-24 US US08/981,706 patent/US6066274A/en not_active Expired - Lifetime
  • 1996-06-24 AU AU63230/96A patent/AU6323096A/en not_active Abandoned
  • 1996-06-24 WO PCT/SE1996/000819 patent/WO1997001408A1/en active IP Right Grant
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  • 1996-06-24 DE DE69616087T patent/DE69616087T2/de not_active Expired - Lifetime
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