Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes
  • B22C9/22—Moulds for peculiarly-shaped castings
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes

Definitions

• the invention relates to a method for manufacturing a mold.
• the term “molding” denotes the action of manufacturing an object using a mold.
• the term “molding” can also be used to designate the action of manufacturing a mold from a part called a model.
• the terms “molding material (s)” denote the material (s) used to make the mold; the terms “material (s) to be molded” denote the material (s) used to make the molded objects using the mold.
• the known mold manufacturing methods differ both by the molding materials they use, the various stages in the production of the mold, the shape of the mold obtained and its mode of use.
• Such a process is certainly relatively simple, but has an often long execution time due to the time necessary for drying or curing of the molding material, - dip molding, consisting in immersing the model in a liquid molding material for the hardening phase of the latter, repeat the operation until a gangue is deposited on the model, wait for the gangue to dry completely, detach it from the model.
• the molding material is chosen from wax, latex or other suitable thermosetting material.
• Plaster bands or a pasty molding material chosen from plaster and mastic in order to obtain a rigid mold, or a gelatinous material chosen from latex, silicone elastomers and alginate are used for this purpose. view of obtaining a flexible mold, in one or more parts, which is covered with a rigid support screed in plaster or plastered bands optionally fractionated to allow demolding.
• a material to be laminated and apply for example, on the surface of the model, pieces of glass cloth which one impregnates with polyester resin.
• the operations are numerous, moreover manual and for the most part impossible to automate, and the drying or hardening times of the molding material and / or of the screed material penalize the productivity of the process; - molding by casting under a screed, consisting in protecting the model with an insulating film (in aluminum foil for example), covering it with a uniform layer of a pasty material such as plastiline or clay, stamping a screed in plaster using the model thus covered, peel off said screed after setting the plaster and pierce it with a few tap holes, remove the pasty material and the insulating film from the model, replace the model in the plaster screed and close it tightly (with the exception of the tap holes), pour a silicone elastomer into the screed, which takes place between the model and the screed.
• a screed consisting in protecting the model with an insulating film (in aluminum foil for example), covering it with a uniform layer of a pasty material such as plastiline or clay, stamping a screed in plaster using the model thus
• the mold can be produced in one or more parts. This process is obviously particularly long and complex. Furthermore, among the molds and known mold manufacturing methods used in the foundry (such molds are intended to receive molten metal alloys), there may be mentioned: - sand molds (silica grains, etc.) or other non-siliceous refractory material (zircon, chromite, olivine, bauxite). Such a mold is constructed in two parts, each corresponding substantially to one half of the model, by compression of sand in a frame. The sand is thus clamped between the chassis and the model, then the model is removed.
• - sand molds silicon grains, etc.
• non-siliceous refractory material zircon, chromite, olivine, bauxite
• a binder in particular chosen from wet clay, silica gels, synthetic resins, cements, etc., or by ceramic type bonds which are created at high temperature. This process, however the most widespread, has multiple drawbacks:
• the sand mold being cold, solidification begins along the walls of the mold and must end in the weights (additional molding volume provided so that the volume of liquid metal poured is greater than the volume of solid metal of the finished part, due to the shrinkage of the metal when it solidifies); the cooling of the large object portions is very slow; conversely, the cooling of the thin object portions is rapid and makes filling difficult; the filling speed must be greater than the solidification speed, • the surface condition of the mold, and therefore of the object molded in such a mold, is coarse; finishing operations (polishing for example) on the object or mold are necessary,
• the molded object has a seam at the joint plane of the two parts of the mold; - the shells, forming a metal mold in two parts, made from a molding material chosen from cast irons, aluminum alloys, brasses, cupro-aluminums, steels, according to the metal alloy that the mold is intended to receive and the process for introducing said liquid alloy into the mold (alloy cast by gravity, cast under low pressure, cast under high pressure, cast centrifuged).
• the shells are molded in a frame containing the model and / or machined to the shapes of the model. Unlike the sand mold, the shells are reusable, have good dimensional accuracy and a good surface condition.
• the lost wax molding consisting in producing a destructible model (as opposed to the permanent models used in the other processes previously described) in wax by a conventional molding process, coating the wax model with a refractory product, after hardening of the refractory product forming the mold, melt the wax and extract it from the mold, bake the latter.
• This process makes it possible to obtain a precision mold making it possible to manufacture objects without stitching or surface defect.
• it is relatively complex and expensive, requires a model to be produced per mold produced, and provides a mold which can be used only once since it must be destroyed to release the molded object.
• the graphite used for the manufacture of such an ingot mold is an artificial graphite, produced from carbonaceous raw materials such as blacks (smoke or petroleum), cokes (metallurgical or petroleum), natural graphites, graphites industrial (from reground electro-graphite materials); after grinding, sieving and selection, the pulverulent raw materials are mixed with binders such as tars, pitches, phenolic and furfuryl resins; the doughs obtained are worked by grinding and wire drawing, then are cooked and regrind then remixed; they are then spun into hollow logs or blanks by extrusion; the logs or blanks are then baked with a view to obtaining the coking of the binder and the agglomeration of the basic carbon material, then graphitized by heating to more than 2000 ° C.
• carbonaceous raw materials such as blacks (smoke or petroleum), cokes (metallurgical or petroleum), natural graphites, graphites industrial (from reground electro-graphite materials)
• binders such as tars
• the logs or blanks undergo significant shrinkage during cooking and have a crusty surface which requires subsequent machining.
• the surface of the mold thus obtained is generally covered with a pyrocarbon deposit (obtained by pyrolysis of a hydrocarbon such as methane, at a temperature between 800 and 2000 ° C) or with a flexible graphite sheet known as Papyex ® (obtained by rolling flakes of expanded natural graphite).
• a pyrocarbon deposit obtained by pyrolysis of a hydrocarbon such as methane, at a temperature between 800 and 2000 ° C
• Papyex ® obtained by rolling flakes of expanded natural graphite
• the invention aims in particular to propose an extremely rapid mold manufacturing process, presenting a considerably limited number of operations which in addition can possibly be automated without using specific complex or expensive machines.
• Another objective of the invention is to provide a mold manufacturing process making it possible to obtain, without specific surfacing (finishing machining, polishing, depositing a finishing coating, etc.), a mold with high dimensional precision and excellent surface finish.
• the invention also aims to provide a mold for making molded objects devoid of seams.
• the invention also aims to propose a method devoid of machining operation and mold finishing operation.
• Another objective of the invention is to propose a process making it possible to obtain, without specific surface treatment (chemical or electrochemical treatment, protective coating, etc.), a mold resistant to corrosion and to oxidation.
• Another objective of the invention is to propose a process which can use a permanent model, capable of being used for the manufacture of several identical molds.
• Another objective of the invention is to propose a mold manufacturing process making it possible to obtain a refractory mold, suitable for the foundry field.
• the invention aims to provide a foundry mold in which the temperature of the molten alloy can be controlled.
• Another objective of the invention is to propose a mold manufacturing process which makes it possible to obtain a mold which can be used several times, and in particular a very large number of times, without significant deterioration of its surface condition, including when the material to be molded is corrosive and / or brought to a very high temperature (molten alloy for example).
• Another objective of the invention is to propose a process for manufacturing a mold which is simple to implement and without major risk for humans.
• the proposed method does not require any particular precaution (such as wearing a mask or a specific combination) for its implementation.
• Another object of the invention is to provide a recyclable mold.
• the invention relates to a method of manufacturing a mold for molding objects from a material called molding material, in which a model of the objects to be molded is used and the model is covered with a material , said molding material, characterized in that expanded graphite is used as molding material, the expanded graphite model is covered by forming a continuous thickness of expanded graphite or several separate thicknesses of expanded graphite distributed over the model, then compress the thickness (s) of expanded graphite against the model so as to obtain, for each thickness, a consolidated graphite block impermeable to the material to be molded.
• models called closed models whose external surface to be printed is a closed surface
• models called open models whose surface to be printed is an open surface.
• a closed model is an object that we want to reproduce in full, from all sides, while an open model is a part of an object, such as a face or a side (the rest of the object not to be molded).
• an open model it is often easier to form only one thickness of expanded graphite.
• a closed model if a single continuous thickness of expanded graphite is formed, this envelopes the model everywhere. It is then necessary either to cut the consolidated block obtained in order to remove the model, if the latter is a permanent model, or to destroy the model (by fusion or chemical reaction), if the latter is a destructible model (in wax or in polystyrene for example).
• a plurality of expanded graphite thicknesses are formed around the model; one can, in particular, form a first thickness on one side of the model and a second thickness on the other side of the model so as to completely wrap the model, in order to obtain a mold in two parts (that is i.e. in two blocks). It is not excluded, as a variant, to form more than two thicknesses around the model.
• the number of thicknesses is notably chosen according to the complexity of the shape to be molded (that is to say of the model). Note that two adjacent thicknesses are separated by a separation sheet for example, preferably planar and rigid to obtain a planar joint surface.
• the invention relates to a method of manufacturing a mold for molding objects from a material called molding material, in which a model of the objects to be molded is used and the model is covered with a material , said molding material, characterized in that expanded graphite is used as the molding material, at least one thickness is used, called preconsolidated thickness, formed of expanded graphite recompressed in at least one direction so as to present a density between 30 and 50 kg / m 3 , we have the pre-consolidated thickness (es) on the model, then we compress the so-called pre-consolidated thickness (es) against the model, so as to come cover the model and obtain, for each thickness, a consolidated graphite block impermeable to the material to be molded.
• preconsolidated thickness formed of expanded graphite recompressed in at least one direction so as to present a density between 30 and 50 kg / m 3
• the expanded graphite is not directly placed (in expanded form) on the model, but is supplied in the form of prefabricated thicknesses, in slightly recompressed expanded graphite, which can be handled - since they are consolidated - but are still malleable under low pressure.
• the invention therefore consists, on the one hand, in using expanded graphite as a molding material and in pressing against a model said material, in a still expanded form (non-cohesive) or in a pre-consolidated form ( weakly recompressed expanded graphite), and on the other hand, if several thicknesses of graphite (expanded or pre-consolidated) are formed, to simultaneously compress said thicknesses around the model.
• the invention proposes in particular a method of manufacturing a mold in two or more parts, in which all the parts of the mold are produced at the same time by common operations (the thicknesses being compressed together).
• the simplicity of the methods according to the invention contrasts with the known prior techniques mentioned in the introduction. These methods also surprise by their speed of execution: a simple instantaneous compression of the thickness (s) of expanded graphite or pre-consolidated (s) is enough to form the mold; the model can be immediately removed, without it being necessary to wait for the drying or hardening or baking of the molding material as is the case in the prior techniques.
• the methods according to the invention have multiple advantages: - they offer the possibility of making molds with complex shapes, - the mold obtained has excellent dimensional precision and surface condition, which allow to overcome the usual finishing operations (machining, polishing ...); the objects molded using such a mold are devoid of seams, - the release of molded objects using such a mold is facilitated by the lubricating nature of the recompressed expanded graphite, - the mold obtained exhibits a behavior mechanical (rigidity %), chemical (resistance to corrosion and oxidation %) and thermal (refractory, small dimensional variation in the face of significant thermal variations ...) interesting, which allows its use of many times and gives it a long service life.
• such a mold retains a good surface condition despite intensive use in a thermal environment (high temperature of the material to be molded, large variations in temperature between periods of non-use and the operations of casting the material to be molded. .) and chemical (corrosion, oxidation ...) often aggressive, - it is not necessary to make a frame for the mold, the thickness (s) of expanded graphite or pre-consolidated (s) can be compressed (s) directly between the model and the plate (s) ) of a press, - the process is harmless, the expanded graphite being neither toxic nor dangerous, - the model used can be permanent, which makes it possible to produce a plurality of molds from the same model, - the mold obtained is easily recyclable; it suffices to exfoliate again the graphite of the consolidated block (s), by means of an intercalation solution.
• expanded graphite a natural expanded graphite, optionally ground (but preferably as obtained after exfoliation) is used.
• the thickness (s) of expanded graphite or pre-consolidated (s) is compressed so as to obtain a consolidated block (s) having a density greater than 40 kg. / m 3 in the case of a mold intended for low temperature applications (plaster, elastomer, plastic type molding material), and preferably greater than 100 kg / m in the case of a mold intended for high temperature applications (mold foundry, molding material of the molten alloy type).
• a density greater than 100 kg / m indeed gives excellent thermal diffusivity to the consolidated block (s) of graphite, which makes it possible to regulate the temperature of the mold and therefore the rate of cooling of the material to be molded.
• a density greater than 40 kg / m guarantees perfect impermeability of the mold vis-à-vis the finest and most liquid molding materials, and a particularly fine surface finish of the mold.
• the thickness (s) of expanded or preconsolidated graphite is compressed in several directions, and in particular in three orthogonal directions. As a variant, the thickness (s) of expanded or preconsolidated graphite is compressed in a single direction.
• Uniaxial compression leads to the obtaining of consolidated block (s) of highly anisotropic graphite (the properties, thermal or otherwise, obtained according to the direction "c" of compression differ from those obtained in any direction "a" orthogonal to direction "c"), while compression in all directions (result obtained, for example, by compressing in three orthogonal directions) leads to the obtaining of consolidated block (s) (s) of weakly anisotropic graphite (s).
• By varying the compression stresses applied in each direction on each thickness of expanded or pre-consolidated graphite it is possible to adjust and control the properties, in particular thermal and mechanical, of the mold obtained.
• the thickness (s) of expanded or pre-consolidated graphite (s) is preferably subjected to a single compression operation in each direction.
• the thickness (s) of expanded or pre-consolidated graphite is compressed only once in each direction.
• the thickness (s) of expanded graphite or pre-consolidated (s) is subjected to a single compression operation, that this (these) thickness (es) is (are) compressed ( s) in a single direction or in several directions simultaneously.
• the molding of the model according to the invention is therefore reduced to only two steps: formation of one (or more) thickness (es) of graphite around the model then compression.
• the thickness (s) of expanded or pre-consolidated graphite (s), in at least one direction is subjected to a plurality of separate compression operations.
• This implementation can be advantageous in the first version of the invention. Indeed, for example, in this direction, a first compression is carried out adapted to consolidate the thickness (s) of expanded graphite with a view to allow its (their) manipulation, and, subsequently, a second compression adapted to impart a desired density to the consolidated block (s).
• the first version of the invention there is covered, at least partially, at least one thickness of expanded graphite with a thickness of expanded vermiculite, then all the thicknesses formed are compressed together so as to obtain, for each thickness of vermiculite formed, a block, known as a mixed block, of consolidated graphite / vermiculite, that is to say a block comprising a layer of consolidated vermiculite and a layer of consolidated graphite and moreover impermeable to the material to be molded.
• a block known as a mixed block, of consolidated graphite / vermiculite, that is to say a block comprising a layer of consolidated vermiculite and a layer of consolidated graphite and moreover impermeable to the material to be molded.
• at least one pre-consolidated thickness, called mixed thickness formed from at least two superimposed layers, one in expanded graphite and another in expanded vermiculite, compressed, is used.
• each mixed pre-consolidated thickness used is placed on the model so that its graphite layer is oriented towards the model.
• the compression of such a mixed pre-consolidated thickness against the model leads to the production of a mixed block as defined above. It is possible to use, for the manufacture of the same mold, at least one pre-consolidated thickness of graphite and at least one mixed pre-consolidated thickness.
• a mold comprising an "internal" portion of recompressed expanded graphite, intended to be in contact with the material to be molded, and an "external" portion of recompressed expanded vermiculite, at least partially enveloping the portion of graphite.
• the portion of vermiculite constitutes an insulating protection which proves useful in the case of a mold intended to receive a molding material brought to high temperature. It makes it possible in fact to be able to handle the mold during the operations of molding objects, without risk of burns. It should be noted that, in the case where the material to be molded is cast at high temperature (molten alloy for example), the thermal properties of the mold obtained by a process according to the invention are particularly advantageous: the good thermal conductivity and diffusivity recompressed expanded graphite makes the mold obtained a hot mold (as opposed to the sand mold).
• heating / cooling members such as part of an electrical (resistances) or hydraulic circuit, are placed in at least one thickness of expanded or pre-consolidated graphite during its formation (when graphite is in expanded form). Note that if a mixed pre-consolidated thickness is used, the heating / cooling elements are arranged in the graphite layer.
• the heating / cooling members are used to control the temperature of the mold and therefore the speed of cooling and consolidation of the material to be molded (molten alloy for example).
• the compression stresses applied to form the mold, in the presence of such heating / cooling members are chosen to be low enough not to damage said members, and in particular low enough to give the block (s) a density. (for graphite) less than 400 kg / m.
• At least one block is formed directly in the graphite mass, at least one pipe adapted to receive a heating / cooling fluid, by placing at least one destructible tube (by chemical reaction , by heating ...) or removable in the corresponding thickness of expanded or pre-consolidated graphite during its formation, the said tube (s) being destroyed or removed once said consolidated block.
• the compression stresses are chosen to be high enough to obtain a density of graphite which imparts tightness and mechanical strength to each pipe formed.
• the thickness (s) of expanded or pre-consolidated graphite is preferably compressed so that the consolidated block has a density greater than 150 kg / m 3 .
• the mold it is possible to heat the mold, or more generally to control the temperature, without contact, by exposing at least one face in graphite, called the outer face, of at least one consolidated mixed block or graphite, to a source of infrared radiation located outside and at a distance from the mold.
• the term "external face” means a graphite face of the thickness of graphite or of the mixed thickness, and therefore of the corresponding consolidated block, intended to be oriented towards the outside of the mold and to be visible during use. of the mold, so that it can be exposed to a source of infrared radiation.
• At least one outer face of at least one thickness of expanded or pre-consolidated graphite (mixed or not) is printed, shapes in open hollows, so-called capture forms, suitable for trapping infrared waves.
• the printed capture forms in particular have at least one front dimension (opening) of between 1 ⁇ m and 2 cm -and preferably between 100 ⁇ m and 1 cm-, and a depth of between 1 ⁇ m and 10 cm -and preferably between 5 mm and 5 cm-.
• the presence of the capture forms improves the supply of calories by such radiation heating: an incident wave penetrating inside a capture form undergoes multiple reflections on the faces facing the capture form; the energy of the wave is finally almost entirely absorbed by the graphite at the level of such a capture form (the proportion of the incident flux which is reflected towards the outside of the form - and therefore lost - is very low). Furthermore, by increasing the surface of the outer face, the presence of the capture forms also contributes to facilitating not only the supply of calories but also the removal of calories during cooling of the graphite block. Finally, the capture forms reduce the thermal inertia of the consolidated block of graphite, which is already weak due to the intrinsic properties of recompressed expanded graphite.
• the printed capture forms can be linear imprints such as slots, grooves, furrows ... straight or curved circular, square, triangular section ..., or point imprints of pyramidal, conical, hemispherical shape , cylindrical (square or circular section) ..., or much more complex shapes.
• the geometry of the printed shapes is chosen according to the wavelengths to be absorbed and the desired thermal response for the consolidated block of graphite. The invention thus makes it possible to provide a mold with means for regulating its temperature, without it being necessary to provide the mold with additional heating / cooling elements, or to provide for an additional step in the method of manufacturing the mold. for the implementation of these means.
• the Capture forms are in fact produced in the very mass of graphite, at the same time as the consolidated blocks of graphite are formed, during the compression of the thicknesses of expanded or pre-consolidated graphite. Furthermore, by virtue of the intrinsic properties of graphite, the capture forms are produced with extreme dimensional precision, so that an effective trapping of the waves is obtained as soon as the geometry and the dimensions of the capture forms are chosen. adequately depending on the nature of the waves to be trapped. The production of the capture forms is precisely controlled without requiring the use of specific and expensive complex precision tools.
• the method according to the invention can directly manufacture a graphite orthosis.
• the process can also prove useful for the cinema industry (making a hand mold, a face mask, etc.).
• the second version of the invention is preferred.
• a low compression is enough to obtain a precise and complete mold.
• the model is a face, it is an open model (only one face is to be reproduced) and only one pre-consolidated thickness is necessary.
• the invention extends to a mold obtained by a method according to the invention, and in particular to a foundry mold, a mold, called an orthopedic mold, for the molding of orthotics or prostheses, an art mold (for the reproduction of a work of art of the sculpture, statue, etc. type).
• the mold comprises at least a consolidated block, known as a mixed block, comprising at least two integral layers, including a layer of recompressed expanded graphite and a layer of recompressed expanded vermiculite covering at least partially the graphite layer.
• the mold comprises at least one consolidated composite or graphite block having at least one face, called the external face (visible from the outside when the mold is used), made of graphite, with open printed shapes in the hollow, so-called capture forms, suitable for trapping infrared waves.
• the capture forms have at least one frontal dimension of between 1 ⁇ m and 2 cm - and preferably between 100 ⁇ m and 1 cm - and a depth of between 1 ⁇ m and 10 cm - and preferably between 5 mm and 5 cm -.
• the invention also extends to a process for molding objects, characterized in that a mold according to the invention is used. It extends in particular to a foundry process for molding a molten alloy, in which a foundry mold is used according to the invention, as well as to a process for manufacturing an orthosis or a prosthesis, in which an orthopedic mold according to the invention is used, and also a method of reproducing a work of art of sculpture type, in which an art mold is used according to the invention.
• the invention also relates to a mold and to a mold manufacturing method characterized in combination by all or some of the characteristics mentioned above and below.
• FIG. 1 is a schematic sectional view of a press used according to the first version of the invention for manufacturing a mold
• - Figure 2 is a perspective view of a two-part mold according to the invention
• - Figure 2a is a perspective view cut from an outer face of the mold of Figure 2
• - Figure 3 is a view schematic in perspective, partially cut away, of another press used according to the first version of the invention to manufacture a mold
• - Figure 4 is a perspective view of another two-part mold according to the invention
• - the Figure 5 is a perspective view illustrating a method according to the second version of the invention.
• Figure 1 illustrates a mold manufacturing process according to the first version of the invention.
• a model 3 is placed in accordance with the objects which it is desired to reproduce using the mold, a transverse separation sheet 7 separating the press into two parts at level 'a median plane of the model 3, and a rigid removable or destructible tube, preferably full, extending between the model 3 and a wall of the press 1.
• a first thickness 5 of expanded graphite is then formed on one side of the separation sheet 7, that is to say around a first half of the model 3, as well as a second thickness 6 of expanded graphite on the other side of the separation sheet 7, that is to say ie around the other half of the model 3.
• the thicknesses 5 and 6 formed thus completely cover the model 3.
• the thicknesses of expanded graphite are then compressed by actuating at least one of the plates 2 of the press, until to obtain their consolidation.
• the compression ratio imposed is chosen according to the destination of the mold, and in particular of the material to be molded. In the case of a foundry mold, the thicknesses are compressed so as to obtain consolidated blocks of graphite with a density greater than 100 kg / m 3 .
• the two parallelepipedal graphite blocks 5a, 6a thus consolidated by compression are then removed from the press, then separated at their joint plane delimited by the separation sheet 7.
• the said separation sheet, the model 3 and the tube are removed 4.
• a mold is obtained in two parts 11, 10, each corresponding to a consolidated block.
• Part 11 includes an imprint 9 formed in the hollow in the consolidated block of graphite 6a, which corresponds substantially to one half of the model.
• Part 10 includes a cavity 8 formed in the hollow in the consolidated block of graphite 5a, which corresponds substantially to the other half of the model, as well as a pouring well 12 left by the tube 4, which extends between the footprint 8 and an outer face of the block.
• Each block 10, 11 also has linear capture forms 13 of the groove type and punctual capture forms 14 of the punch type, on its external face 15, 16, face against which the press plate has been applied.
• the plates of the press used are, for this purpose, each provided with a printing matrix having corresponding pins and ribs (not shown), having a depth (dimension according to the direction of compression) of between 1 cm and 5 cm.
• the compression of the thicknesses of expanded graphite 5, 6 results in the printing of the capture shapes on the faces 15, 16 of the blocks 10, 11.
• These shapes have dimensions and geometry suitable for trapping infrared waves.
• the linear shapes are for example straight (cylindrical) grooves or slots of semi-circular section (such as 13) or square or triangular or trapezoidal, or even curved grooves or slots, of any section ...
• the punctual shapes are by example of conical or pyramidal footprints of square or triangular section, or even hemispherical, etc.
• the geometry of the capture shapes can be even more complex and result from mathematical design calculations relating to a particular application and in particular to a radiation source. given wavelength.
• FIGS. 3 and 4 illustrate another mold manufacturing method according to the first version of the invention.
• a model 24 reproducing the objects to be produced with the mold, - a separating sheet 25 surrounding the model at the level of a median plane thereof, - a network 26 rigid tubes provided in the separation sheet and intended to form, within the mold, pipes for receiving a heating / cooling liquid, - a tube (not shown) extending at least between the model and a plane intersection of two columns of the press in order to form a pouring well within the mold.
• Expanded graphite 32 is added to each column 34, 35, 36 of the press on either side of the model, so as to form two thicknesses of expanded graphite separated, in the center of the press, by the separating sheet 25.
• Each part or half of the mold in fact comprises a consolidated internal thickness 32a of recompressed expanded graphite, which defines an imprint 29, and a consolidated external thickness 31a of recompressed expanded vermiculite, which envelops the thickness 32a and forms an insulating protection for the mold.
• the quantities of graphite and expanded vermiculite, introduced into the press to form the corresponding thicknesses, are chosen according to the dimensions of the press and the final density desired for the consolidated thicknesses 31a and 32a.
• Each mold half 21, 22 also includes grooves 27, 28 forming, with the combined grooves of the other mold half, pipes for the circulation of a heating / cooling liquid of the mold.
• At least one of the mold halves 21, 22 further comprises a taphole 30 extending between an exterior face of the mold and the cavity 29.
• the taphole is used for the introduction or injection of the molding material, preferably in liquid form.
• an independent circuit for circulating heating / cooling liquid can be produced in the thickness 32a of graphite of each of the mold halves. Such a process is preferred because it guarantees perfect sealing of the circuits.
• electrical resistances (cables) intended to be connected to a current generator for heating the mold by radiation. It is also possible, to obtain a mold according to the invention, to use a uniaxial press such as that illustrated in FIG.
• the operation can be repeated so as to compress the thicknesses in a third direction orthogonal to the first two.
• a parallelepipedic mold is then obtained (in two mixed blocks) of which four faces are isolated by a thickness of consolidated vermiculite if only two compressions are carried out, or whose six faces are isolated if three compressions are carried out.
• the temperature within the mold can also be controlled and adjusted by heating / cooling of said face (s), by contact of a heating body with said face (s) then by thermal conduction in the consolidated mass of graphite.
• a heating / cooling circuit it is not necessary to make or insert, within the graphite thickness, a heating / cooling circuit, in order to be able to control the temperature of the mold around the impression.
• Figure 5 illustrates a hand molding process according to the second version of the invention.
• two thicknesses 40, 41 are preconsolidated, formed from expanded graphite having been slightly recompressed in one direction in a uniaxial press such as that used in FIG. 1.
• the thicknesses have been pre-consolidated by compression in a direction parallel to direction D.
• pre-consolidated thicknesses ' formed from expanded graphite recompressed in several directions, and notably in three orthogonal directions.
• the thicknesses 40, 41 preferably have a density of between 30 and 35 kg / m 3 , i.e. just above the consolidation density of expanded graphite.
• Such pre-consolidated thicknesses are therefore still very malleable.
• the hand 42 to be molded is placed between the two thicknesses 40, 41, then said thicknesses are pressed against the hand, in the direction D.
• a compressive force is applied to the upper face of the thickness 41 , until the thicknesses completely cover the hand, that is to say until their opposite faces 44, 43 meet.
• the thicknesses being pre-consolidated they have a lamellar structure in parallel sheets which can slide together, which sheets are orthogonal to the direction of pre-consolidation of the thicknesses, and therefore, in the example, orthogonal to the direction D.
• the pressure exerted on the thicknesses 40, 41 to form the mold is reflected, on the parallel sheets forming the surfaces 43 and 44, by efforts orthogonal to said sheets, which are insufficient to cause their nesting.
• the invention makes it possible to manufacture not only two-part molds such as those illustrated, but also molds in one piece (such molds must be destroyed to allow the object to be removed from the mold) or molds made of it. three or more games.
• the presses used can be of any type and of any section.

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• Moulds For Moulding Plastics Or The Like (AREA)

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• 2003
  • 2003-10-06 FR FR0311682A patent/FR2860445B1/fr not_active Expired - Fee Related
• 2004
  • 2004-10-05 US US10/574,810 patent/US20070057402A1/en not_active Abandoned
  • 2004-10-05 JP JP2006530415A patent/JP2007507356A/ja active Pending
  • 2004-10-05 CN CNB2004800291232A patent/CN100376343C/zh not_active Expired - Fee Related
  • 2004-10-05 WO PCT/FR2004/002506 patent/WO2005035167A2/fr active Application Filing
  • 2004-10-05 CA CA002541401A patent/CA2541401A1/fr not_active Abandoned
  • 2004-10-05 EP EP04817149A patent/EP1680244A2/de not_active Withdrawn

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