WO2021052594A1 - Procédé de fabrication d'un motif de cire, motif de cire - Google Patents

Procédé de fabrication d'un motif de cire, motif de cire Download PDF

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Publication number
WO2021052594A1
WO2021052594A1 PCT/EP2019/075248 EP2019075248W WO2021052594A1 WO 2021052594 A1 WO2021052594 A1 WO 2021052594A1 EP 2019075248 W EP2019075248 W EP 2019075248W WO 2021052594 A1 WO2021052594 A1 WO 2021052594A1
Authority
WO
WIPO (PCT)
Prior art keywords
wax
mold
accordance
mold cavity
wax pattern
Prior art date
Application number
PCT/EP2019/075248
Other languages
English (en)
Inventor
Daniel Hüsler
Original Assignee
Adultimum Ag
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Adultimum Ag filed Critical Adultimum Ag
Priority to PCT/EP2019/075248 priority Critical patent/WO2021052594A1/fr
Priority to EP19773067.4A priority patent/EP4003622A1/fr
Publication of WO2021052594A1 publication Critical patent/WO2021052594A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C7/00—Patterns; Manufacture thereof so far as not provided for in other classes
    • B22C7/02—Lost patterns
    • 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
    • B29C33/44—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles
    • B29C33/52—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles soluble or fusible
    • 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
    • B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
    • B29C41/02—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor for making articles of definite length, i.e. discrete articles
    • B29C41/04—Rotational or centrifugal casting, i.e. coating the inside of a mould by rotating the mould
    • B29C41/042—Rotational or centrifugal casting, i.e. coating the inside of a mould by rotating the mould by rotating a mould around its axis of symmetry
    • 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
    • B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
    • B29C41/34—Component parts, details or accessories; Auxiliary operations
    • B29C41/36—Feeding the material on to the mould, core or other substrate
    • 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
    • B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
    • B29C41/34—Component parts, details or accessories; Auxiliary operations
    • B29C41/50—Shaping under special conditions, e.g. vacuum
    • 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
    • B29C67/00—Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00
    • B29C67/24—Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00 characterised by the choice of material
    • B29C67/241—Moulding wax
    • 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
    • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/28—Shaping operations therefor
    • B29C70/40—Shaping or impregnating by compression not applied
    • B29C70/42—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles
    • B29C70/46—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using matched moulds, e.g. for deforming sheet moulding compounds [SMC] or prepregs
    • B29C70/48—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using matched moulds, e.g. for deforming sheet moulding compounds [SMC] or prepregs and impregnating the reinforcements in the closed mould, e.g. resin transfer moulding [RTM], e.g. by vacuum

Definitions

  • the present invention relates to a method of making a wax pattern using a mold, for example for use in resin transfer molding or investment casting, by introducing wax in a molten, solid or flowable form into a mold cavity having a wall, the mold cavity having an internal shape corresponding to an outer shape of the wax pat tern.
  • the invention also relates to a wax pattern per se.
  • the investment casting or lost wax casting process has been in use for a very long time and has been used to make a highly diverse range of articles. Basically it in volves making a wax pattern of a desired article such as a piece of jewelry or a turbine blade, coating the wax pattern with a plurality of layers of a refractory coat ing, drying the coating to form a refractory shell and melting out the wax pattern to leave a hollow shell into which molten metal is then cast to form the desired article.
  • a wax pattern is made which forms a core around which at least one layer consisting of a mat or strands of rein forcing fibers is laid which is either in the form of a prepreg, meaning a layer of reinforcing fibers pre-impregnated with a resin, or into which a resin is subsequent ly permeated to form a fiber reinforced resin shell.
  • the fiber reinforced resin shell is cured chemically or thermally or by way of UV-light and the wax core is subse quently removed to leave a generally rigid shell.
  • the fibre covered wax pattern is placed in a mold which defines the outer shape of the fiber reinforced shell and impregnated with a resin in that mold known as resin transfer molding (RTM).
  • the present invention has the principle object of providing a novel and generally applicable technique for at least substantially mitigating and preferably completely overcoming the problems associated with wax shrinkage when making wax pat terns.
  • This method has the advantage that the pressurized fluid in the hollow interior of the wax pattern pushes the closed wall of the ax pattern outwardly during solidifi cation of the wax so that it fully conforms to the shape of the wall of the mold cavi ty, thereby maintaining the solidified removable wax in the shape of the pattern and at least substantially avoiding shrinkage effects at the outer surface of the wax pattern.
  • the shrinkage of the wax that occurs during cooling is thus compensated by an increase in the volume of the hollow interior of the wax pattern and this re- suits in the wax pattern having the desired external shape as determined by the mold.
  • said step of rotating said mold may be carried out, in particular continuously, during said step of cooling.
  • said step of rotating said mold may start before or after said step of cooling is initiated and may be conducted either during the complete cooling step or during the at least 50 to 90 % of the duration of said cooling step.
  • the volume of wax introduced into the mold cavity comprises 25 to 99%, in particular 40 to 95%, especially 50 to 90% of the volume of the mold cavity and the volume of wax in the mold cavity is prefera bly selected such that an average wall thickness of the wax pattern lies in the range from 1 5mm to 20mm, excluding any thickening which may occur at locally tapered regions of the mold cavity. Average wall thicknesses of these dimensions ensure that the wax can be adequately dilated by the internal pressure during shrinkage to compensate for the shrinkage.
  • the gas present in the mold cavity may be compressed during the introduction of the wax into the mold cavity. While the wax is cooled and rotated this increase in pressure may aid in urging the wax such that it covers the complete surface of the mold cavity, thereby improving the re sultant wax pattern.
  • the method may further comprise the step of filling the mold cavity with a pressur- izable fluid, preferably such that during said step of cooling, the hollow interior of the solidified pattern is subjected to the pressurized fluid during the solidification process.
  • a pressur- izable fluid preferably such that during said step of cooling, the hollow interior of the solidified pattern is subjected to the pressurized fluid during the solidification process.
  • the pressurizable fluid preferably comprises a gas such as air, CO2 or Nitrogen.
  • a gas such as air, CO2 or Nitrogen.
  • the use of a gas, particularly air or a constituent of air such as oxygen or nitrogen, means there is no contamination of the environment, it also allows bottled gas to be used instead of a compressor which can be advantageous as the quantity of gas required is not necessarily large for small to medium scale production of smaller articles.
  • the pressurizable fluid could comprises a liquid having a vapor phase with an adequate partial pressure at the solidification temperature of the wax.
  • the mold cavity is defined in at least one part of a mold having at least first and second parts and the wax is added to the mold when this is opened into at least one of the first and second parts, optionally only partially filling a cavity in at least one of the first and second parts and sub sequently closing the first and second parts by moving the cavities of the first and second parts towards one another and subsequently pressurizing a space of the mold not filled with wax, prior to rotating the mold to line the wall of the mold cavity with liquid wax.
  • a seal e.g. an elastic seal such as an O- ring or a seal made from an elastomer, may be present between the first and sec ond parts.
  • the use of such seals enables the gas present in the mold cavity to re main in the mold cavity as the wax is filled into the mold cavity.
  • a technique such as this makes it relatively easy to fill the open mold part with wax as it can be simply poured into the open mold part which is subsequently closed by at least one further mold part to form the mold cavity.
  • the open mold part can be selected in the design of the mold to have a volume greater than any other mold parts forming the total volume of the mold cavity in order to ensure that the desired total volume of wax can poured into one part of the mold. Also it is not es sential for the wax to be poured into the open mold part, it could be added in the form of wax granulate or pieces of solid wax and the mold can be heated to melt the wax prior to or during the rotation step.
  • the wax is preferably selected to be a wax molten at a higher temperature in range from 60 to 140°C, in particular to 70 to 120 ° C and to be solid at a lower temperature in a range from 30 to 100 ° C, in par ticular 60 to 90°C. It is particularly preferred if the higher temperature is only slight ly higher than the lower temperature. This reduces the amount of time and energy needed to cycle the mold over a range of temperatures and speeds up the rate of production of the individual wax patterns produced from the mold.
  • the temperature difference between the higher temperature and the lower temperature is selected to be less than 40°C, in particular less than 30 ° C, preferably less than 20 ° C and especially less than 10 ° C.
  • the pressure in the hollow interior of the wax pattern is preferably selected to lie in the range from 1.02 to 5bar, i.e. pressure difference between the interior of the wax pattern and an exterior of the mold or wax pattern is 0.02 to 4 bar, in the mol ten state of the wax. It has been found that pressures of this order of magnitude are sufficient to press the wax outwardly into contact with the wall of the wax cavity during solidification with the higher pressures up to about 4bar gage pressure be ing more appropriate for waxes having a higher temperature difference between the lower and higher temperatures as defined above or having more shrinkage.
  • the pressure in the hollow interior of the wax pattern may be less after the wax has solidified than before the wax has solid ified.
  • the gas such as air
  • the volume of the wax reduces enabling the gas, such as air, in the hollow cavity to expand and the pressure in the cavity to reduce.
  • the mold cavity may be heated to a temperature below a solidification tempera ture of the wax, in particular to a temperature selected in the range of 1 to 40°C, in particular 5 to 25°C, below the solidification temperature of the wax.
  • a temperature below a solidification tempera ture of the wax in particular to a temperature selected in the range of 1 to 40°C, in particular 5 to 25°C, below the solidification temperature of the wax.
  • the mold cavity When the mold cavity has a generally longitudinal direction it is preferably, but not necessarily, rotated about the longitudinal direction as axis. Alternatively the mold can be rotated about an axis orthogonal to the longitudinal direction. This has been found to facilitate the manufacture of the hollow wax pattern. It is also possi ble to rotate the mold about at least one further arbitrarily selected axis, particular ly if the mold cavity has a complicated shape which makes it difficult to ensure wax flows into all areas of the mold cavity.
  • the mold can be rotated about one axis but it can also be rotated about at least two preferably orthogonal axes. This may be convenient if molds for a variety of diverse articles are to be produced on the same piece of production machinery as this can then be laid out for rotation about the said two axes and be generally applicable to a wide range of diverse articles.
  • the step of cooling the wax pattern is preferably ef fected by cooling the mold, e.g. by means of fluid cooling, such as liquid cooling, said liquid optionally comprising at least one of water and a coolant or additive such as a wetting agent which ensures good heat transfer to and from the mold.
  • fluid cooling such as liquid cooling
  • said liquid optionally comprising at least one of water and a coolant or additive such as a wetting agent which ensures good heat transfer to and from the mold.
  • the methods of the invention preferably include the further step of forming the mold cavity to define at least one feature of shape by which the finished wax pat tern can be located in a further mold in a resin transfer molding process or inte grated into a wax tree in an investment casting process.
  • Such features of shape can for example include wax stubs which allow the wax pattern to be precisely located in a further mold during a resin transfer molding process. At least one of the stubs can be a hollow stub which facilitates pressuriz ing and/or venting the hollow interior of the wax pattern during its manufacture.
  • This the mold preferably has at least one passage for applying pressure to a liquid or gas present in the hollow interior of the wax pattern and/or for draining a liquid or gas from the hollow interior following solidification of the wax pattern.
  • the flowable wax that is used should be present at a temperature above the melt ing point of the wax and below a boiling point of said wax at standard tempera tures and pressures, i.e. wax may be introduced into the mold cavity in the liquid state.
  • the mold cavity may be evacuated to a pressure selected in the range of 0.02 to 0.95 bar, in particular to a pressure selected in the range of 0.05 to 0.5 bar prior to the introduction of the wax. Reducing the pressure in the chamber may aid select ing the pressure within the hollow cavity in a more controlled manner in depend ence on the amount of wax introduced into the mold cavity.
  • the wax may have a viscosity of greater than 2000 mPas for a temperature of less than 85°C and a viscosity of less than 800 mPas for a temperature greater than 105°C.
  • Such waxes have found to be particularly stable in shape up to their melt ing point and the transition between the liquid state and the solid state takes place over comparatively small temperature ranges making said waxes more cost effec tive in their use.
  • One or more inserts may be positioned at one or more predefined positions at said mold and said wax is solidified around said inserts at said one or more predefined positions.
  • the inserts may be functional elements such as elements having an outer thread, e.g. bolts, elements having inner threads, e.g. nuts, or supports for functional elements.
  • these inserts can be integrated into devices that are formed using the wax pat tern. For example if the wax pattern is used in a resin transfer molding process, the inserts can be integrated into the device by being adhesively bonded to the wall formed during the RTM process.
  • the present invention is also directed to a wax pattern obtainable by the method of any one of the preceding claims, the wax pattern having a hollow interior and an external surface substantially free of shrinkage effects.
  • a wax pattern can be used either in an investment casting process or in a resin transfer molding pro cess.
  • the wax pattern preferably has an average wall thick ness of the wax pattern between the outer surface of the wax pattern and the hol low interior thereof lies in the range from 1 5mm to 20mm excluding any thickening which may be present at locally tapered regions of the wax pattern.
  • the wax pattern may comprise one or more inserts present at an outer surface of said wax pattern at pre-definable positions.
  • the inserts may, for example be func tional elements which can be embedded in a device formed using said wax pat tern.
  • Devices formed using such wax patterns may for example be parts of hous ings of robots with integrated functional elements at pre-defined positions in order to mount components within the housings of said devices.
  • Fig. 1 a longitudinally sectioned schematic view of a opened mold having first and second parts defining a mold cavity for the formation of a wax pattern
  • Fig. 2 a schematic view of the closed mold of Fig. 1 illustrating preferred rotations thereof
  • Fig. 3 a perspective view of the finished wax pattern removed from mold cavity of mold of Figs 1 and 2,
  • Fig. 4 a schematic sectional view of a further mold similar to Fig. 2,
  • Fig. 5 a longitudinally sectioned view of the hollow wax pattern of Fig. 3 showing its hollow interior and illustrating the average wall thickness thereof.
  • Fig. 6 an alternative design of a mold for a wax pattern in which the wax is intro quizd via a port into the closed mold.
  • a mold 10 for forming a wax pattern The mold comprises upper and lower mold parts 12, 14 each of which defines in this embodiment a respective part 16, 18 of the mold cavity.
  • the lower mold part 14 defines a larger part 18 of the volume of the mold cavity and the upper part 12 a smaller part 16 of the volume of the mold cavity.
  • each mold part 12, 14 can define one half of the volume of the mold cavity or one part could define the entire volume of the mold cavity, the other part them being essentially flat at the side confronting the mold cavity.
  • the mold can be made of a metal such as aluminum or an aluminum alloy or can be made of a fiber reinforced plastic.
  • a release agent can be sprayed onto the wall of the mold cavity to stop the wax adhering to the wall of the mold cavity. It can be seen from Fig. 1 that the part 18 of mold cavity is partially filled with mol ten wax 20, although it could be filled with wax granulate or pieces of wax. An air space 22 is also present in the lower mold part 14 above the wax 20.
  • the mold cavity in the lower part 14 has a half cylindrical re cess 24 to form, together with a complementary half cylindrical recess 26 in the upper mold part 12, a first locating stub 28 (only shown in Figs 3 and 4) on the fin ished wax pattern.
  • the locating stub need not necessarily be cylindrical, it could have a conically tapering shape to facilitate the removal of the wax pattern from the mold or to form a tapering vent or in-gate in a lost wax casting process. Alter natively it could have a different shape such as a rectangular shape in cross sec tion to facilitate orientation of the wax pattern in a further mold in a resin transfer molding process.
  • the mold cavity in the lower part 14 has a half cylindrical re cess 30 to form, together with a complementary half cylindrical recess 32 in the upper mold part 12, a second locating stub 34 (only shown in Figs 3 and 4) on the finished wax pattern 36.
  • the locating stub 34 need not necessarily be cylindrical, it could have a conically tapering shape to facilitate the removal of the wax pattern from the mold or to form a tapering vent or in-gate in a lost wax casting process. Alternatively it could have a different shape such as a rectangular shape in cross section to facilitate orientation of the wax pattern in a further mold in a resin trans fer molding process. In this connection it should be noted that the wax pattern 36 does not require stubs to be provided for the subsequent handling of the wax pat tern 36.
  • a hollow needle 38 extending from a disc 40.
  • the disc 40 which fits in semicircular recesses 42, 44 formed in the mold parts 12 and 14 serves to close the half recesses 30 and 32 when the mold is closed and the needle 38 serves to pressurize the interior cavity 16, 18 of the mold.
  • the disc 40 prevents the hollow needle being blown out of the closed mold when pressure is applied to it to pressurize the cavity 16, 18 of the mold.
  • the disc 40 is connected to a rigid tubular extension 46 to the right of the disc 40 in Fig. 1.
  • the tubular extension 46 includes a manually operated shut-off valve 48 and a quick release coupling 50, similar to an air-line connection, which allows the tubu lar extension to be connected via a flexible line 52 and a pressure regulating valve 54 to a gas bottle 56.
  • the flexible line 52 could also be connected to a receiver of an air compressor or the like (not shown).
  • Fig. 2 now shows the situation when the mold is closed by placing the upper and lower mold parts 12, 14 together at the parting face 58 and clamping them togeth er.
  • Clamping can be effected in any desired manner, for example using cuffs (not shown) which fit around and apply pressure to the two mold parts 12, 14 or by the use of bolts (not shown) which pass through one mold part 12, 14 and engage in screw threads (also not shown) in the other mold part 14, 12 to hold the first and second mold parts 12, 14 together. Clamping of some form is necessary in order to prevent gas pressure applied vial the line 52, the quick release coupling 50, the shut-off valve 48, the tubular extension 46 and the hollow needle 38 to the mold cavity 16, 18 from forcing the mold parts 12 and 14 apart.
  • the aligned cylindrical recesses 24, 26 and 30, 32 define a longitudinal axis of the mold cavity 16, 18.
  • the wax 20 is present in a molten or flowable form in the mold cavity 16, 18 which has an internal shape corresponding to an outer shape of the wax pattern.
  • the method includes basically the steps of:
  • a pressurizable fluid is added to the mold cavity then this increases the pressure within the hollow interior 64 of the wax 20 used to form the solidified wax pattern 36 aiding in urging the wax 20 towards the surface of the mold cavity 16, 18, in order to avoid shrinkage effects at the surface of the solidified wax pattern 36.
  • the pressurizable fluid may be added if the outer surface of the wax pattern 36 has complex shapes present therein such as undercuts, recesses etc. with the pres surizable fluid then aiding in the flow of wax 20 into the regions of the wax pattern 36 having the complex shape.
  • the wax 20 can be added in liquid form into a part 18 of the mold cavity before the mold 10 is closed.
  • the mold is prefer ably preheated to a temperature corresponding to the melting point of the wax or to a temperature slightly above or below the melting point.
  • the mold is closed, the mold parts are clamped together and pressure is applied to the mold cavity from the gas bottle 50 via the pressure regulating valve 54, the flexible line 52, the quick release coupling 50, the opened shut-off valve 48, the tubular exten sion 46 and the hollow needle 38 so that the pressure determined by the pressure regulating valve 54 prevails in the mold cavity 16, 18.
  • shut-off valve 48 is then closed and the quick release coupling 50 disconnected from the flexible line 52 so that the closed mold can be rotated in the direction of the arrow 62 or in the oppo site direction to allow the molten wax to run around the wall of the mold cavity 16, 18 and wet this wall as well as into the space defined by the recesses 24, 26 and into the space defined by the recesses 30, 32 around the hollow needle 38.
  • the mold 10 is cooled so that the wax lining the wall of the mold cavity 16, 18 gradually solidifies.
  • the cooling can be done via a coolant flow ing through coolant passages in the mold or by full or partial immersion of the closed mold 10 in a liquid such as water.
  • the fact that the closed mold 10 is dis connected from the supply of pressurized gas means that the flexible line does not hinder the rotation.
  • the pressure prevailing in the hollow interior of the wax pattern presses the solidifying wax against the wall of the mold cavity 16, 18 and into the recesses 24, 26 and 3032 so that shrinkage effects do not occur at the surface of the wax pattern 36 but are compensated for by the pressure in the hollow interior 64 of the wax pattern 36.
  • the rotation of the closed mold about the longitudinal axis 60 should be carried out such that the molten wax 20 runs around the wall of the mold cavity until it is fully solidified but preferably not so fast that molten wax drips from one side of the mold cavity 16, 18 to the other.
  • the rotation can be a continuous rotation in one direc tion or can be alternately effected in opposite directions.
  • the mol ten wax wets the wall of the mold cavity and that excess molten wax not yet adher ing to the wall of the mold cavity runs around the mold cavity and progressively solidifies on the wax already solidifying at the cooled wall of the mold cavity. This ensures a relatively even thickness of the wax coating at the time of solidification.
  • the rotation can be effected manually and can be supplemented by rotation or oscillation or rocking about another axis, for example an axis orthogonal to the axis 60.
  • the rotation or movement of the closed mold to effect wetting of the wall of the mold cavity 16, 18 and a generally uniform thickness of the wall of the hol low wax pattern can also be effected by a machine or robot if desired (both not shown).
  • the finished wax pattern 36 is shown in a perspective view in Fig. 3 and in a longi tudinal section in Fig. 5.
  • Fig 5 shows that the wall thickness of the finished wax pattern 36 measured generally radially from the hollow interior 64 is relatively con stant in the middle section but greater at the tapered ends.
  • the method of the present invention is generally applicable to a wide variety of wax patterns, essentially without limitation.
  • wax patterns For very intricate patterns with many undercuts or internal structures it may be necessary to use more complicated motions of the closed mold to ensure all desired spaces are filled with wax and it may be necessary to use multipart molds or sliders to ensure the finished wax pattern can be released from the mold.
  • Another way of carrying out the basic method is to partially fill the mold cavity 16,18 with wax 20 in a solid form, for example with pieces of wax or in the form of a granulate. In this case after closing the mold it is necessary to heat the mold 10 to a higher temperature than the melting point of the wax to melt the wax and then to cool it during rotation of the mold 10. Otherwise the process is as described above.
  • the wax can be added to the mold cavity 16, 18 after the mold 10 has been closed.
  • Fig. 6 A further way of doing this is shown in Fig. 4.
  • Fig. 4 shows a schematic sectional view of a further mold 10 similar to the mold 10 shown in Fig. 2.
  • a hollow tube 66 is inserted from above the mold part 12 (or from any other direction) via a valve 76 and a shutter 78.
  • the hollow tube 66 is connected to a cylinder 70 containing, in this case molten wax 20.
  • Once the mold is closed pressure can be applied to the wax 20 via the piston 72 movable in the cylinder and the piston movement is used to control the volume of wax added to the mold cavity 16, 18.
  • the tube 66 is disconnected between the valve 76 and the shutter 78.
  • the supply of the wax 70 does not have to be designed in the manner described herein, but also other apparatus for the dosed provision of wax 70 can be used.
  • a gear pump can also be used.
  • the mold 10 Prior to filing the mold with the wax 20, the mold 10 can be evacuated using a vacuum pump 80, for example to pressures in the range of 0.02 to 0.95 bar.
  • the vacuum pump is connected to the mold cavity 16, 18 via a passage 82 a valve 84 and a shutter 86.
  • the passage 82 is disconnected between the valve 84 and the shutter 86 in a manner similar to the cylinder 70 for the supply of wax 20.
  • the seal 74 is provided between the mold parts 12, 14 if the mold 10 is to be evacuated, so that one can efficiently and expediently obtain the desired pres sures in comparison to if no seal were provided.
  • an insert 88 that is to be inte grated into the wax pattern 36 on solidification of the wax 20.
  • the insert 88 is held at the mold part 14 in the cavity 18 via a support 90.
  • the support can be a mag netic support, if the insert is magnetic, the support can be a holding apparatus or the support could be provided by a vacuum applied at the mold 10.
  • a vacuum may be applied using the vacu um pump 80.
  • the valve 84 and the shutter 86 are each closed.
  • the mold is filled with wax 20, e.g. 80% of the volume of the wax cavity is filled with wax 20.
  • the residual air in the mold 10 is compressed through the addition of the wax 20 in such a way that an overpressure is now achieved within the mold 10.
  • the pres sure in the mold may now be in the range of 1.02 to 4 bar depending on the initial vacuum pressure and the amount of wax added.
  • the mold 10 is then rotated about the axis of rotation 62 while the mold 10 is cooled, due to the pres surized gas in the mold 10 and the rotation of the mold 10, the initially liquid wax covers the complete surface of the cavities 16, 18 in contact with the mold parts 12, 14 such that a wax pattern 36 is formed having the outer shape resembling that of the inner shape of the mold 10, with the wax pattern 36 having the hollow interior 64.
  • the vacuum pump 80 may be discon nected and the mold 10 is partially filled with wax 20, once e.g. 60 to 70% of the desired volume of wax has been filled into the mold 10, the valve 84 is closed and the remaining wax is filled, also in this case the residual air present in the cavity is compressed to a pressure e.g. in the range of 1.4 to 2.5 bar in dependence on the volume of the wax filled and the amount of air that is permitted to leave the cavity 16, 18 prior to closing the valve 84.
  • a pressure e.g. in the range of 1.4 to 2.5 bar in dependence on the volume of the wax filled and the amount of air that is permitted to leave the cavity 16, 18 prior to closing the valve 84.
  • the hollow tube 66 is inserted into the left hand side of the recesses 24, 26 of the mold parts 12, 14 and is retained therein via a ring bead 68 engaging into a corresponding ring recess.
  • the hollow tube 66 is connected to the cylinder 70 con taining, in this case molten wax 20.
  • pressure can be ap plied to the wax 20 via the piston 72 movable in the cylinder and the piston move ment is used to control the volume of wax added to the mold cavity. Pressurization of the mold cavity can then take place, for example as previously described.
  • the valve 76 can be provided in the tube 66 or at the base of the cylinder 70 and the cylinder 70 and piston 72 can be discon nected from the valve as necessary to permit the required rotation of the mold.
  • the wax 20 in the cylinder 70 can be in a solid or softened but not molten state and a higher pressure can be applied in the cylinder 70 via the piston or ram 72 to cause the wax to flow into the mold cavity 16, 18 in a solid or softened state.
  • a higher pressure can be applied in the cylinder 70 via the piston or ram 72 to cause the wax to flow into the mold cavity 16, 18 in a solid or softened state.
  • the wax could be aerated rather like an aerated choco late so that the cavity 16, 18 is filled with the aerated wax and the air bubbles coa lesce during melting and separate from the wax.
  • the temperature increase during melting could then be sufficient to obtain the desired internal pressure and main tain it during solidification of the wax without the need for an external source of pressure.
  • at least the wax could be added to the cavity of the mold to gether with a liquid which has a suitable vapor pressure at the temperature of the molten and solidified wax to ensure sufficient pressurization of the mold cavity and that shrinkage effects are avoided.
  • Yet another possibility is to include a piston movable in a chamber forming an ex tension of the mold cavity.
  • the piston can then be moved to either pressurize or depressurize the hollow interior of the wax pattern.
  • connection between the mold and the source of pressurization includes a rotatable joint which permits rotation of the closed mold without the need for disconnection from the gas supply.
  • connection between the mold and the source of pressurization includes a rotatable joint which permits rotation of the closed mold without the need for disconnection from the gas supply.
  • the process can be highly au tomated and the resultant wax pattern 36 may be removed from the mold 10 using a robot, which could forward the wax pattern 36 to a different process stage where it is e.g. used in an RTM process to form a device having an interior space having the shape of the wax pattern 36.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)

Abstract

L'invention concerne un procédé de fabrication d'un motif de cire à l'aide d'un moule (10), par exemple destiné à être utilisé dans le moulage de résine par transfert ou le moulage à la cire perdue, par l'introduction de cire (20) sous forme fondue, solide ou fluide dans une cavité de moule (16, 18) ayant une paroi, la cavité de moule ayant une forme interne correspondant à une forme externe du motif de cire. Le procédé comprend les étapes de remplissage de la cavité de moule avec de la cire fluide, la rotation de la cavité de moule autour d'au moins un axe pour recouvrir la paroi de la cavité de moule avec de la cire, le refroidissement de la cire recouvrant la paroi de la cavité de moule pour solidifier la cire en un motif de cire présentant un intérieur creux, ce qui permet de conserver la cire sous forme du motif de cire pendant le processus de solidification ; et le retrait du motif de cire de la cavité de moule. L'invention concerne également un motif de cire.
PCT/EP2019/075248 2019-09-19 2019-09-19 Procédé de fabrication d'un motif de cire, motif de cire WO2021052594A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/EP2019/075248 WO2021052594A1 (fr) 2019-09-19 2019-09-19 Procédé de fabrication d'un motif de cire, motif de cire
EP19773067.4A EP4003622A1 (fr) 2019-09-19 2019-09-19 Procédé de fabrication d'un motif de cire, motif de cire

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2019/075248 WO2021052594A1 (fr) 2019-09-19 2019-09-19 Procédé de fabrication d'un motif de cire, motif de cire

Publications (1)

Publication Number Publication Date
WO2021052594A1 true WO2021052594A1 (fr) 2021-03-25

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Country Status (2)

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WO (1) WO2021052594A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114309474A (zh) * 2022-03-14 2022-04-12 成都航宇超合金技术有限公司 一种中小型单晶涡轮叶片的熔模铸造工艺
CN114570876A (zh) * 2022-03-09 2022-06-03 洪伟明 一种精密铸造用压蜡装置
CN114850398A (zh) * 2022-03-28 2022-08-05 洛阳双瑞精铸钛业有限公司 一种支承环熔模铸造用蜡模的制作方法
EP4268993A1 (fr) * 2022-04-27 2023-11-01 Ucosan BV Dispositif d'insertion, appareil et procédé de fabrication de pièce moulée

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2015923A (en) * 1978-03-09 1979-09-19 Trevelyans Birmingham Ltd Manufacturing Tanks and other Hollow Articles
US4601870A (en) * 1983-04-27 1986-07-22 M.C.L. Co., Ltd. Injection molding process
US20070158870A1 (en) * 2004-01-23 2007-07-12 Shonan Design Co., Ltd. Process for producing resin model and process of lost wax precision casting with the resin model
EP2509726A2 (fr) * 2009-12-08 2012-10-17 Siemens Energy, Inc. Procédé de coulée à la cire perdue pour la fabrication d'une composante creuse
CN106424587A (zh) * 2016-10-20 2017-02-22 苏州东吴黄金文化发展有限公司 一种素金空心路路通的制作方法

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2015923A (en) * 1978-03-09 1979-09-19 Trevelyans Birmingham Ltd Manufacturing Tanks and other Hollow Articles
US4601870A (en) * 1983-04-27 1986-07-22 M.C.L. Co., Ltd. Injection molding process
US20070158870A1 (en) * 2004-01-23 2007-07-12 Shonan Design Co., Ltd. Process for producing resin model and process of lost wax precision casting with the resin model
EP2509726A2 (fr) * 2009-12-08 2012-10-17 Siemens Energy, Inc. Procédé de coulée à la cire perdue pour la fabrication d'une composante creuse
CN106424587A (zh) * 2016-10-20 2017-02-22 苏州东吴黄金文化发展有限公司 一种素金空心路路通的制作方法

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114570876A (zh) * 2022-03-09 2022-06-03 洪伟明 一种精密铸造用压蜡装置
CN114570876B (zh) * 2022-03-09 2023-12-22 龙泉良固阀门有限公司 一种精密铸造用压蜡装置
CN114309474A (zh) * 2022-03-14 2022-04-12 成都航宇超合金技术有限公司 一种中小型单晶涡轮叶片的熔模铸造工艺
CN114850398A (zh) * 2022-03-28 2022-08-05 洛阳双瑞精铸钛业有限公司 一种支承环熔模铸造用蜡模的制作方法
CN114850398B (zh) * 2022-03-28 2023-08-11 洛阳双瑞精铸钛业有限公司 一种支承环熔模铸造用蜡模的制作方法
EP4268993A1 (fr) * 2022-04-27 2023-11-01 Ucosan BV Dispositif d'insertion, appareil et procédé de fabrication de pièce moulée

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