A method and mold for preparing a coiled ceramic spring

Abstract

The present invention provides a method and a mold for preparing a parallel-coil ceramic spring, belonging to the field of parallel-coil ceramic springs. The method for preparing a parallel-coil ceramic spring consists of the following steps: preparing a winding mold assembly by 3D printing, preparing a ceramic winding wire, and preparing a parallel-coil ceramic spring. The method and mold for preparing a parallel-coil ceramic spring of the present invention do not need to adopt a reverse demolding and pressure-sintering process to prepare a parallel-coil ceramic spring, and the parallel-coil ceramic spring prepared has good consistency in parallelism and verticality, which effectively improves the stability, load-bearing capacity, reliability and service life of the parallel-coil ceramic spring; and improves the dimensional stability of the prepared parallel-coil ceramic spring, and improves the preparation reliability.

Description

Technical Field

[0001] The invention relates to the field of parallel coil ceramic springs, and in particular to a method and a mould for preparing a parallel coil ceramic spring. Background Art

[0002] As one of the commonly used mechanical parts, springs are used to mitigate vibration impact, store energy, control movement, measure force, etc., and are widely used in various mechanical equipment and sealing devices. Among them, ceramic springs have excellent performance far exceeding traditional metal springs in terms of high temperature resistance, low conductivity, corrosion resistance, and wear resistance. Ceramic springs can be used as high-temperature sealing components of supersonic aircraft, electrode materials in SOFC, piezoelectric materials and micro sensors, as well as gas separation device components and catalyst carriers, etc., and have broad application prospects.

[0003] Since ceramics are brittle materials, their preparation process has always been a difficult problem in related research fields at home and abroad. Early springs were mainly prepared by mechanical processing. Later, gel injection molding, extrusion winding, chemical vapor deposition, melt spinning and other processes were used to prepare ceramic springs. Among them, extrusion winding molding has the advantages of low cost, simple process, low environmental requirements and short production cycle. It is the optimal process for mass production of ceramic springs.

[0004] However, the existing extrusion molding ceramic spring preparation process requires that the ceramic wire extruded by the extruder be wound on a spiral tooling mold in the direction of the thread, and after the wire is dried and hardened, the mold is removed in the opposite direction; in order to facilitate the demolding operation, the spring prepared by this method (such as Figure 3 (As shown in the left figure) The lines all have a certain spiral angle, and there is a lack of tightening lines at both ends, which cannot ensure the parallelism, verticality and compression force of the ceramic spring. This not only leads to poor consistency of batch springs, but also affects the stability, load-bearing capacity, reliability and service life of the spring.

[0005] In addition, since the coiled ceramic spring has the problem of shrinkage deformation during the sintering process, which leads to the problem of excessive tightening of the spring, it is limited by the aforementioned reverse demolding operation requirements and can only be pressed by the method of press-firing. A silicon nitride pressing sheet is used at the middle and bottom end of the spring blank to press the spring section, and the spring is contracted and tightened by relying on gravity and sintering shrinkage. However, the press-firing method is greatly affected by the placement of the pressing sheet and changes in process parameters, resulting in poor consistency of the final coiled ceramic spring, large randomness of shrinkage, inability to stably control the size, and poor reliability. Summary of the invention

[0006] In order to solve the technical problems existing in the prior art, the present invention provides a method and a mold for preparing a parallel coil ceramic spring, which does not require the use of a reverse demolding and press-sintering process to prepare the parallel coil ceramic spring. The parallelism and verticality of the prepared parallel coil ceramic spring are consistent, thereby improving the stability, load-bearing capacity, reliability and service life of the parallel coil ceramic spring; and improving the dimensional stability of the prepared parallel coil ceramic spring, thereby improving the preparation reliability.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a parallel-coil ceramic spring comprises the following steps: preparing a winding mold assembly by 3D printing, preparing a ceramic winding wire, and preparing a parallel-coil ceramic spring.

[0009] The method for preparing a winding mold assembly by 3D printing is as follows: α-silicon nitride powder and a sintering aid are added into a ball mill at a weight ratio of 88-95:5-12, anhydrous ethanol is continuously added, the ball milling speed is controlled to be 200-300 rpm, mixed and ball milled for 22-24 hours, and then transferred into an oven, dried at 60-70° C. for 22-24 hours, and passed through a 60-mesh sieve to obtain silicon nitride abrasive; silicon nitride abrasive, a light-curing resin, and a 3D printing aid are added into a homogenizer, the homogenizing speed is controlled to be 600-650 rpm, homogenized at room temperature for 4-6 minutes, and then transferred into a three-roll grinder, the grinding speed is controlled to be 130-160 rpm, the grinding output particle size is controlled to be within the range of 5-8 μm, and after grinding treatment, vacuum degassing is performed to obtain silicon nitride ceramic slurry; the winding mold assembly model is introduced into a 3D printing machine, and the 3D printing machine is used to prepare a winding mold assembly by 3D printing. After slicing by the supporting software of the 3D printer, 3D printing is performed using silicon nitride ceramic slurry to obtain a mold assembly blank; the mold assembly blank is degreased and sintered, first at a heating rate of 0.4-0.6℃ / min, the temperature is increased to 330-350℃, and the temperature is kept for 2-2.5h for a primary degreasing, and then the temperature is continued to be increased to 600-620℃ at a heating rate of 0.4-0.6℃ / min, and the temperature is kept for a secondary degreasing for 1-1.5h; then in an inert atmosphere environment, the temperature is increased to 1500-1550℃ at a heating rate of 20-22℃ / min, and then the temperature is increased to 1850-1880℃ at a heating rate of 4-5℃ / min, and the temperature is kept for sintering for 2.5-3h, and then naturally cooled to room temperature, and polished with diamond abrasive to a surface roughness of ≤0.6μm to obtain a winding mold assembly.

[0010] Preferably, the sintering aid is at least one of the following: aluminum oxide, yttrium oxide, lanthanum oxide, magnesium oxide, cerium oxide, erbium oxide, zirconium oxide;

[0011] The 3D printing additives include: a dispersant, a photoinitiator, a pH adjuster, and a defoamer; the weight ratio of silicon nitride abrasive, photocurable resin, dispersant, photoinitiator, pH adjuster, and defoamer is 60-70:19-25:0.5-2.5:0.1-1.5:0.1-1.5:0.02-0.15.

[0012] The photocurable resin may be a conventional 3D printing photocurable resin, preferably one of the following: hydroxyethyl methacrylate, hydroxypropyl methacrylate, 2-phenoxyethyl acrylate, polyurethane acrylate.

[0013] The photoinitiator may be a conventional photoinitiator, preferably one of the following: TPO, BPO, 819, 184, IGM.

[0014] The dispersant is preferably hexadecyltrimethylammonium chloride or polyacrylate; the pH adjuster is preferably 2-phenoxyethyl acrylate; and the defoamer is preferably a polyether defoamer.

[0015] The method for preparing the ceramic winding wire comprises: weighing silicon nitride abrasive, deionized water, a binder, a plasticizer, and an organic solvent by weight, respectively, putting them into an internal mixer, controlling the internal mixer temperature to be 10-20° C., and mixing and mixing to obtain silicon nitride ceramic mud; transferring the silicon nitride ceramic mud into a vacuum mud refiner, controlling the vacuum degree to be 0.05-0.1 MPa, the mud refinement temperature to be 16-18° C., the mud refinement relative humidity to be 55-70%, the single mud refinement time to be 5-8 min, and after continuously performing mud refinement for 2-4 times, controlling the extrusion diameter to be 0.5-3 mm, and extruding to obtain the ceramic winding wire.

[0016] In the preparation of the ceramic winding wire, the weight ratio of silicon nitride abrasive, deionized water, binder, plasticizer and organic solvent is 95-100:15-30:10-30:5-10:10-40.

[0017] In the preparation of the ceramic winding wire, the silicon nitride abrasive is the same as the silicon nitride abrasive used in the step of preparing the winding mold assembly by 3D printing; the binder is polyvinyl butyral and / or polymethyl methacrylate; the plasticizer is butyl stearate and / or polyethylene glycol-600; and the organic solvent is anhydrous methanol or anhydrous ethanol.

[0018] The method for preparing a coiled ceramic spring comprises the following steps: assembling a winding mold assembly into a winding mold; then winding and fixing the ceramic winding wire in the direction of the thread groove of the winding mold, covering the surface with a plastic wrap, and then placing the wire in an oven and drying it at 50-70° C. for 5-8 hours; extracting a core rod 4 from one end of the winding mold, removing a fixing cover 5, and then pressing the first thread component 1, the second thread component 2, and the third thread component 3 originally fixed on the core rod inwardly (i.e., pressing them in the direction of the spring center) to separate them from the dried and formed coiled ceramic spring blank, thereby obtaining a coiled ceramic spring blank; inserting a silicon nitride spacer in the middle of the tightening ring of the coiled ceramic spring blank to prevent possible excessive tightening during the sintering process, and then performing degreasing sintering. The spring is first heated to 330-350°C at a heating rate of 0.4-0.6°C / min, and is kept warm for a degreasing operation for 2-2.5 hours. The spring is then heated to 600-620°C at a heating rate of 0.4-0.6°C / min, and is kept warm for a secondary degreasing operation for 1-1.5 hours. The spring is then heated to 1500-1550°C at a heating rate of 20-22°C / min in an inert atmosphere. The spring is then heated to 1760-1800°C at a heating rate of 4-5°C / min, and is kept warm for sintering for 2.5-3 hours. The spring is then cooled to 950-1000°C at a cooling rate of 14-15°C / min, and is naturally cooled to room temperature. The spacer is removed to obtain a parallel coil ceramic spring.

[0019] A mold used in the aforementioned method for preparing a coiled ceramic spring comprises: a first thread component, a second thread component, a third thread component, and a core rod;

[0020] The mandrel is provided with a rod body, and the vertical cross section of the rod body in the length direction is a triangle;

[0021] One end of the rod body is fixedly connected to an end cover;

[0022] Positioning grooves are provided on three planes in the length direction of the rod body;

[0023] The first thread assembly, the second thread assembly, and the third thread assembly are all arc-shaped sheet structures, and each of the arc-shaped sheet structures is provided with slide rails on both sides along the length direction; the slide rails can be slidably fixed in the positioning slide groove, so that the first thread assembly, the second thread assembly, and the third thread assembly are fixed to the outer surface of the rod of the mandrel;

[0024] The arcuate surface of each arcuate sheet structure of the first thread assembly, the second thread assembly and the third thread assembly is provided with a thread groove;

[0025] After the first threaded component, the second threaded component, the third threaded component and the core rod are fixed together, a cylinder is formed; and the outer surface of the cylinder has a spring thread groove formed by continuous splicing.

[0026] Furthermore, the mold further comprises: a fixed cover;

[0027] The fixing cover is connected to the end of the cylinder formed by the first threaded assembly, the second threaded assembly, the third threaded assembly and the core rod away from the end cover, and is used to fix the first threaded assembly, the second threaded assembly and the third threaded assembly to the outer surface of the core rod.

[0028] Preferably, a groove is provided around the rod body at the connection surface between the end cap of the mandrel and the rod body, so that the first threaded component, the second threaded component and the third threaded component can be inserted and fixed to the outer surface of the mandrel.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The method for preparing a parallel coil ceramic spring of the present invention comprises the following steps: using α-silicon nitride powder and a sintering aid to prepare silicon nitride abrasive, and then combining it with a photocurable resin and an additive to prepare silicon nitride ceramic slurry; using the silicon nitride ceramic slurry for 3D printing to prepare a winding mold assembly; then using the silicon nitride abrasive and an additive to prepare a ceramic winding wire, after the winding mold assembly is assembled into a winding mold, the ceramic winding wire is wound and fixed in the direction of the thread groove of the winding mold, and then dried and formed, and then the winding mold is disassembled to remove the assembly to prepare a parallel coil ceramic spring blank; and then degreasing and sintering are performed to prepare a parallel coil ceramic spring; the aforementioned technical means cooperate with each other and work synergistically, and there is no need to use a reverse direction demolding and press-sintering process to prepare the parallel coil ceramic spring, and the parallel coil ceramic spring prepared has good consistency in parallelism and verticality, which effectively improves the stability, load-bearing capacity, reliability and service life of the parallel coil ceramic spring; and the dimensional stability of the prepared parallel coil ceramic spring is improved, and the preparation reliability is improved.

[0031] (2) The method for preparing parallel coil ceramic springs of the present invention effectively solves the problem of poor consistency in parallelism, verticality, etc. of extruded ceramic springs. The spring image LED measuring instrument detects that the parallelism (the degree of parallelism between the spring axis and the mounting surface) of the parallel coil ceramic springs prepared by the method of the present invention is less than 0.1, and the verticality (the degree of verticality between the spring axis and the mounting surface) is less than 0.1. The dimensional stability of the parallel coil ceramic springs is high, and the preparation reliability is high.

[0032] (3) The method for preparing a parallel coil ceramic spring of the present invention effectively improves the force structure of the spring, and increases the load-bearing capacity, reliability and service life of the parallel coil ceramic spring; the stiffness of the parallel coil ceramic spring prepared by the method of the present invention is 10-15N / mm, the fatigue life (number of cycles at room temperature) exceeds 1000 times, the maximum load is 38-60N, and the maximum compression is 3.8-4.0mm.

[0033] (4) The winding mold used in the method for preparing the parallel coil ceramic spring of the present invention does not need to adopt the reverse demolding and pressure firing process compared with the existing conventional resin mold. The winding mold can theoretically withstand the winding-drying-disassembly cycle process. In addition, combined with the self-lubricating properties of silicon nitride ceramics, the winding mold has a long effective service life. At the same time, the surface quality of the parallel coil ceramic spring blank is significantly improved during the preparation process. The surface roughness of the fired parallel coil ceramic spring is less than 1μm, which effectively improves the surface quality of the parallel coil ceramic spring.

[0034] (5) The method for preparing parallel coil ceramic springs of the present invention effectively reduces the difficulty of processing parallel coil ceramic springs, improves the preparation stability, and facilitates large-scale batch preparation of parallel coil ceramic springs. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of a winding mold assembly used in the method for preparing a coiled ceramic spring of the present invention; in the figure, 1 is a first spiral component; 2 is a second spiral component; 3 is a third spiral component; 4 is a core rod; and 5 is a fixed cover.

[0036] Figure 2 It is a schematic diagram of a winding mold; in the figure, the left figure is a schematic diagram of a winding mold used in the present invention; the right figure is a schematic diagram of a winding mold used in the present invention to prepare and coil a ceramic spring blank.

[0037] Figure 3 It is a schematic diagram of a parallel coil ceramic spring; in the figure, the left figure is a schematic diagram of a parallel coil ceramic spring prepared by using an existing resin winding mold through reverse demolding and pressure sintering; the right figure is a schematic diagram of a parallel coil ceramic spring prepared by the method and mold of the present invention. DETAILED DESCRIPTION

[0038] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described.

[0039] Example 1

[0040] A method for preparing a coiled ceramic spring, specifically comprising:

[0041] 1. 3D printing to prepare winding mold assembly

[0042] According to the weight ratio of 92:8, α-silicon nitride powder and sintering aid were added to the ball mill, and anhydrous ethanol was continuously added. The ball mill speed was controlled to 250rpm. After mixed ball milling for 23h, the mixture was transferred to an oven and dried at 65℃ for 23h. The mixture was sieved through a 60-mesh sieve to obtain silicon nitride abrasive. The silicon nitride abrasive, photocurable resin, dispersant, photoinitiator, pH adjuster and defoamer were added to a homogenizer, and the homogenization speed was controlled to 630rpm. After homogenization at room temperature for 5min, the mixture was transferred to a three-roll grinder, and the grinding speed was controlled to 150rpm. The particle size of the ground material was controlled within the range of 5-8μm. After grinding and vacuum degassing, silicon nitride ceramic slurry was obtained. The winding mold assembly model was imported into the 3D After slicing by the printer's supporting software, 3D printing was performed using silicon nitride ceramic slurry to obtain a mold assembly blank; the mold assembly blank was degreased and sintered, first at a heating rate of 0.5°C / min, the temperature was increased to 340°C, and the temperature was kept warm for 2.2 hours for a primary degreasing, and then the temperature was increased to 610°C at a heating rate of 0.5°C / min, and the temperature was kept warm for a secondary degreasing for 1.2 hours; then in an inert atmosphere environment, the temperature was increased to 1530°C at a heating rate of 21°C / min, and then the temperature was increased to 1850°C at a heating rate of 4.5°C / min, and the temperature was kept warm for sintering for 2.75 hours, and then naturally cooled to room temperature, and polished with diamond abrasives to a surface roughness of ≤0.6μm to obtain a winding mold assembly.

[0043] Among them, the sintering aids are yttrium oxide, lanthanum oxide and zirconium oxide; the weight ratio of yttrium oxide, lanthanum oxide and zirconium oxide is 1:1:2.

[0044] The weight ratio of silicon nitride abrasive, photocurable resin, dispersant, photoinitiator, pH regulator and defoaming agent is 65:22:1.5:0.8:0.7:0.09.

[0045] In this embodiment, the photocurable resin is hydroxyethyl methacrylate; the photoinitiator is TPO; the dispersant is hexadecyltrimethylammonium chloride; the pH adjuster is 2-phenoxyethyl acrylate; and the defoamer is a polyether defoamer.

[0046] like Figure 1 As shown, the winding mold assembly includes: a first thread component 1, a second thread component 2, a third thread component 3, a core rod 4, and a fixed cover 5.

[0047] The mandrel 4 is provided with a rod body, one end of which is fixedly connected to an end cap; a groove is provided around the rod body at the connection surface between the end cap and the rod body, so that the first thread assembly 1, the second thread assembly 2, and the third thread assembly 3 are inserted and fixed on the outer surface of the rod of the mandrel 4. The vertical section of the rod body in the length direction is a triangle; positioning grooves are provided on three planes in the length direction of the rod body.

[0048] The first thread assembly 1, the second thread assembly 2, and the third thread assembly 3 are all arc-shaped sheet structures, and each of the arc-shaped sheet structures is provided with slide rails on both sides along the length direction; the slide rails can be slidably fixed in the positioning slide grooves so that the first thread assembly 1, the second thread assembly 2, and the third thread assembly 3 are fixed to the outer surface of the rod of the mandrel 4. The arc surface of each arc-shaped sheet structure of the first thread assembly 1, the second thread assembly 2, and the third thread assembly 3 is provided with a thread groove.

[0049] The first threaded component 1, the second threaded component 2, and the third threaded component 3 can all slide in cooperation in the positioning groove of the core rod 4 through the slide rail, and are used to fix the first threaded component 1, the second threaded component 2, and the third threaded component 3 to the outer surface of the rod body of the core rod 4; after the first threaded component 1, the second threaded component 2, and the third threaded component 3 are fixed with the core rod 4, a seamless cylinder is formed (that is, the vertical cross-section in the length direction is circular); and the threads outside the first threaded component 1, the second threaded component 2, and the third threaded component 3 are continuously spliced ​​on the outer surface of the cylinder to form a complete spring thread groove.

[0050] The fixing cover 5 is connected to the end of the cylinder formed by the first threaded assembly 1, the second threaded assembly 2, the third threaded assembly 3 and the core rod 4, which is away from the end cover, and is used to fix the first threaded assembly 1, the second threaded assembly 2 and the third threaded assembly 3 to the outer surface of the core rod 4.

[0051] 2. Preparation of ceramic winding wire

[0052] Silicon nitride abrasive, deionized water, binder, plasticizer and organic solvent were weighed by weight respectively, put into an internal mixer, controlled the internal mixing temperature at 15°C, and mixed by internal mixing to obtain silicon nitride ceramic mud; the silicon nitride ceramic mud was transferred into a vacuum mud refiner, controlled the vacuum degree at 0.09MPa, the mud refining temperature at 17°C, the mud refining relative humidity at 65%, the single mud refining time at 7min, after 3 consecutive mud refinings, controlled the extrusion diameter at 2mm, and extruded to obtain ceramic winding wire.

[0053] Among them, the weight ratio of silicon nitride abrasive, deionized water, binder, plasticizer and organic solvent is 98:22:20:7:25.

[0054] The silicon nitride abrasive is the same as the silicon nitride abrasive used in the step of preparing the winding mold assembly by 3D printing. The binder is polyvinyl butyral; the plasticizer is butyl stearate; and the organic solvent is anhydrous ethanol.

[0055] 3. Preparation of coiled ceramic springs

[0056] like Figure 2As shown in the left figure, the winding mold assembly is assembled into a winding mold: the first thread component 1, the second thread component 2, and the third thread component 3 are slid and inserted into the fixed outer slide groove of the mandrel 4 rod body respectively, and inserted into the end cover groove of the mandrel 4 to be fixed, so as to obtain a cylinder with a continuous splicing on the outer surface to form a complete spring thread groove; then the fixing cover 5 is inserted into the end of the cylinder away from the end cover and fixed, and the winding mold is assembled; as shown in FIG. Figure 2 As shown in the right figure, after the ceramic winding wire is wound and fixed in the direction of the thread groove of the winding mold, the surface is covered with plastic wrap, and then placed in an oven and dried at 60°C for 7 hours; the core rod 4 is pulled out from one end of the winding mold, and the fixing cover 5 is removed, and the first thread component 1, the second thread component 2, and the third thread component 3 originally fixed on the core rod are pressed inward (that is, pressed toward the center of the spring circle) to separate them from the dried and formed parallel coil ceramic spring blank, and a parallel coil ceramic spring blank is obtained; a silicon nitride spacer is inserted in the middle of the tightening ring of the parallel coil ceramic spring blank to prevent excessive tightening during the sintering process, and then Degreasing sintering, first at a heating rate of 0.5 ° C / min, the temperature was raised to 340 ° C, and the temperature was kept for 2.2 hours for primary degreasing, and then at a heating rate of 0.5 ° C / min, the temperature was raised to 610 ° C, and the temperature was kept for 1.2 hours for secondary degreasing; then in an inert atmosphere, the temperature was raised to 1530 ° C at a heating rate of 21 ° C / min, and then at a heating rate of 4.5 ° C / min, the temperature was raised to 1760 ° C, and the temperature was kept for 2.75 hours. After cooling to 980 ° C at a cooling rate of 14.5 ° C / min, it was naturally cooled to room temperature, and the spacer was removed to obtain a parallel coil ceramic spring (such as Figure 3 as shown on the right).

[0057] The stiffness of the parallel coil ceramic spring prepared in this embodiment is 15N / mm, the fatigue life (number of cycles at room temperature) exceeds 1000 times, the maximum load is 60N, and the maximum compression is 4.0mm; using a spring image LED measuring instrument to detect, the parallelism of the parallel coil ceramic spring (the degree of parallelism between the spring axis and the mounting surface) is <0.1, and the verticality (the degree of verticality between the spring axis and the mounting surface) is <0.1.

[0058] Compared with the prior art using a resin winding mold, the parallel coil ceramic spring (such as Figure 3 As shown in the left figure), the maximum load of the parallel coil ceramic spring of the present invention is increased from 50N to 60N; the fatigue life (number of cycles at room temperature) is increased from no more than 800 times to more than 1000 times; the surface roughness of the parallel coil ceramic spring is reduced from 2μm to <1μm.

[0059] At the same time, the resin winding mold used in the prior art will be worn and deformed after 5-10 uses due to the reverse demolding operation, and the mold cannot be used any longer, and has a short service life; the assembled winding mold used in the present invention does not require reverse demolding operation and press-firing process, and combined with the self-lubricating properties of silicon nitride ceramics, it can withstand the winding-drying-disassembly cycle process.

[0060] Example 2

[0061] A method for preparing a coiled ceramic spring, specifically comprising:

[0062] 1. 3D printing to prepare winding mold assembly

[0063] According to the weight ratio of 88:12, α-silicon nitride powder and sintering aid are put into a ball mill, and anhydrous ethanol is continuously added, and the ball mill speed is controlled to be 200rpm. After mixed ball milling for 22 hours, the mixture is transferred into an oven, dried at 60°C for 22 hours, and sieved through a 60-mesh sieve to obtain silicon nitride abrasive; silicon nitride abrasive, photocurable resin, dispersant, photoinitiator, pH adjuster, and defoamer are put into a homogenizer, and the homogenization speed is controlled to be 600rpm. After homogenization at room temperature for 4 minutes, the mixture is transferred into a three-roll grinder, and the grinding speed is controlled to be 130rpm. The particle size of the ground material is controlled within the range of 5-8μm. After grinding treatment and vacuum degassing, silicon nitride ceramic slurry is obtained; the winding mold assembly model guide After being sliced ​​in the supporting software of the 3D printer, 3D printing is performed using silicon nitride ceramic slurry to obtain a mold assembly blank; the mold assembly blank is degreased and sintered, firstly heated to 330°C at a heating rate of 0.4°C / min, and kept warm for a degreasing process for 2 hours, then heated to 600°C at a heating rate of 0.4°C / min, and kept warm for a second degreasing process for 1 hour; then, in an inert atmosphere environment, the temperature is increased to 1500°C at a heating rate of 20°C / min, and then the temperature is increased to 1860°C at a heating rate of 4°C / min, and kept warm for sintering for 2.5 hours, and then naturally cooled to room temperature, and polished with diamond abrasives to a surface roughness of ≤0.6μm to obtain a winding mold assembly.

[0064] Among them, the sintering aids are aluminum oxide, yttrium oxide and cerium oxide; the weight ratio of aluminum oxide, yttrium oxide and cerium oxide is 1:2:2.

[0065] The weight ratio of silicon nitride abrasive, photocurable resin, dispersant, photoinitiator, pH regulator and defoaming agent is 60:19:0.5:0.1:0.1:0.02.

[0066] In this embodiment, the photocurable resin is hydroxyethyl methacrylate; the photoinitiator is BPO; the dispersant is polyacrylate; the pH adjuster is 2-phenoxyethyl acrylate; and the defoamer is a polyether defoamer.

[0067] The winding mold assembly used in this embodiment is the same as that in Embodiment 1.

[0068] 2. Preparation of ceramic winding wire

[0069] Silicon nitride abrasive, deionized water, binder, plasticizer and organic solvent were weighed by weight respectively, put into an internal mixer, controlled the internal mixing temperature at 10°C, and mixed by internal mixing to obtain silicon nitride ceramic mud; the silicon nitride ceramic mud was transferred into a vacuum mud refiner, controlled the vacuum degree at 0.05MPa, the mud refining temperature at 16°C, the mud refining relative humidity at 55%, the single mud refining time at 5min, after 4 consecutive mud refinings, controlled the extrusion diameter at 2mm, and extruded to obtain ceramic winding wire.

[0070] Wherein, the weight ratio of silicon nitride abrasive, deionized water, binder, plasticizer and organic solvent is 95:15:10:5:10.

[0071] The silicon nitride abrasive is the same as the silicon nitride abrasive used in the step of preparing the winding mold assembly by 3D printing. The binder is polymethyl methacrylate; the plasticizer is polyethylene glycol-600; and the organic solvent is anhydrous methanol.

[0072] 3. Preparation of coiled ceramic springs

[0073] Assemble the winding mold assembly into a winding mold: slide the first thread component 1, the second thread component 2, and the third thread component 3 into the fixed outer slide groove of the core rod 4 respectively, and insert them into the end cover groove of the core rod 4 to fix them, so as to obtain a cylinder with a continuous splicing on the outer surface to form a complete spring thread groove; then insert the fixing cover 5 into the end of the cylinder away from the end cover and fix it to assemble the winding mold; then wind the ceramic winding wire in the direction of the thread groove of the winding mold, cover the surface with plastic wrap, and then place it in an oven and dry it at 50℃ for 7h; pull out the core rod 4 from one end of the winding mold, remove the fixing cover 5, and press the first thread component 1, the second thread component 2, and the third thread component 3 originally fixed on the core rod inward (that is, press them towards the center of the spring) to make them aligned with the core rod. The dried and formed parallel coil ceramic spring blank is separated to obtain a parallel coil ceramic spring blank; a silicon nitride spacer is inserted in the middle of the tightening ring of the parallel coil ceramic spring blank to prevent excessive tightening during the sintering process, and then degreasing and sintering are carried out, first at a heating rate of 0.4°C / min, the temperature is increased to 330°C, and the temperature is kept for 2 hours for a degreasing process, and then the temperature is continued to be increased to 600°C at a heating rate of 0.4°C / min, and the temperature is kept for a second degreasing process for 1 hour; then in an inert atmosphere environment, the temperature is increased to 1500°C at a heating rate of 20°C / min, and then the temperature is increased to 1780°C at a heating rate of 4°C / min, and the temperature is kept for sintering for 2.5 hours, and then the temperature is reduced to 950°C at a cooling rate of 14°C / min, and then naturally cooled to room temperature, and the spacer is removed to obtain a parallel coil ceramic spring.

[0074] The stiffness of the parallel coil ceramic spring prepared in this embodiment is 10N / mm, the fatigue life (number of cycles at room temperature) exceeds 1000 times, the maximum load is 38N, and the maximum compression is 3.8mm; using a spring image LED measuring instrument to detect, the parallelism of the parallel coil ceramic spring (the degree of parallelism between the spring axis and the mounting surface) is <0.1, and the verticality (the degree of verticality between the spring axis and the mounting surface) is <0.1.

[0075] Example 3

[0076] A method for preparing a coiled ceramic spring, specifically comprising:

[0077] 1. 3D printing to prepare winding mold assembly

[0078] According to the weight ratio of 95:5, α-silicon nitride powder and sintering aid are put into a ball mill, and anhydrous ethanol is continuously added, and the ball mill speed is controlled to 300rpm. After mixed ball milling for 24 hours, the mixture is transferred to an oven, dried at 70°C for 24 hours, and sieved through a 60-mesh sieve to obtain silicon nitride abrasive; silicon nitride abrasive, photocurable resin, dispersant, photoinitiator, pH adjuster, and defoamer are put into a homogenizer, and the homogenization speed is controlled to 650rpm. After homogenization at room temperature for 6 minutes, the mixture is transferred to a three-roll grinder, and the grinding speed is controlled to 160rpm. The particle size of the ground material is controlled within the range of 5-8μm. After grinding treatment and vacuum degassing, silicon nitride ceramic slurry is obtained; the winding mold assembly model is introduced into After slicing by the supporting software of the 3D printer, 3D printing was carried out using silicon nitride ceramic slurry to obtain a mold assembly blank; the mold assembly blank was degreased and sintered, firstly heated to 350°C at a heating rate of 0.6°C / min, and kept warm for 2.5 hours for a first degreasing, then heated to 620°C at a heating rate of 0.6°C / min, and kept warm for a second degreasing for 1.5 hours; then in an inert atmosphere environment, the temperature was increased to 1550°C at a heating rate of 22°C / min, and then increased to 1880°C at a heating rate of 5°C / min, and kept warm for sintering for 3 hours, and then naturally cooled to room temperature, and polished with diamond abrasives to a surface roughness of ≤0.6μm to obtain a winding mold assembly.

[0079] The sintering aids are yttrium oxide, magnesium oxide and erbium oxide; the weight ratio of yttrium oxide, magnesium oxide and erbium oxide is 1:3:1.

[0080] The weight ratio of silicon nitride abrasive, photocurable resin, dispersant, photoinitiator, pH regulator and defoaming agent is 70:25:2.5:1.5:1.5:0.15.

[0081] In this embodiment, the photocurable resin is hydroxyethyl methacrylate; the photoinitiator is IGM; the dispersant is hexadecyltrimethylammonium chloride; the pH adjuster is 2-phenoxyethyl acrylate; and the defoamer is a polyether defoamer.

[0082] The winding mold assembly used in this embodiment is the same as that in Embodiment 1.

[0083] 2. Preparation of ceramic winding wire

[0084] Silicon nitride abrasive, deionized water, binder, plasticizer and organic solvent were weighed by weight respectively, put into an internal mixer, controlled the internal mixing temperature to be 20°C, and internal mixing was performed to obtain silicon nitride ceramic mud; the silicon nitride ceramic mud was transferred into a vacuum mud refiner, controlled the vacuum degree to be 0.1MPa, the mud refining temperature to be 18°C, the mud refining relative humidity to be 70%, the single mud refining time to be 8min, after two consecutive mud refinings, controlled the extrusion diameter to be 2mm, and extruded to obtain ceramic winding wire.

[0085] Wherein, the weight ratio of silicon nitride abrasive, deionized water, binder, plasticizer and organic solvent is 100:30:30:10:40.

[0086] The silicon nitride abrasive is the same as the silicon nitride abrasive used in the step of preparing the winding mold assembly by 3D printing. The binder is polyvinyl butyral and polymethyl methacrylate; the weight ratio of polyvinyl butyral to polymethyl methacrylate is 1:1. The plasticizer is polyethylene glycol-600; and the organic solvent is anhydrous ethanol.

[0087] 3. Preparation of coiled ceramic springs

[0088] Assemble the winding mold assembly into a winding mold: slide the first thread component 1, the second thread component 2, and the third thread component 3 into the fixed outer slide groove of the core rod 4 respectively, and insert them into the end cover groove of the core rod 4 to fix them, so as to obtain a cylinder with a continuous splicing on the outer surface to form a complete spring thread groove; then insert the fixing cover 5 into the end of the cylinder away from the end cover and fix it to assemble the winding mold; then wind the ceramic winding wire in the direction of the thread groove of the winding mold and fix it, cover the surface with plastic wrap, and then place it in an oven and dry it at 70℃ for 8h; pull out the core rod 4 from one end of the winding mold, remove the fixing cover 5, and press the first thread component 1, the second thread component 2, and the third thread component 3 originally fixed on the core rod inward (that is, press them towards the center of the spring) to make them contact with the dry The dry-formed parallel coil ceramic spring blank is separated to obtain a parallel coil ceramic spring blank; a silicon nitride spacer is inserted in the middle of the tightening ring of the parallel coil ceramic spring blank to prevent excessive tightening during the sintering process, and then degreasing and sintering are carried out, firstly, the temperature is increased to 350°C at a heating rate of 0.6°C / min, and the temperature is kept for 2.5 hours for a degreasing operation, and then the temperature is increased to 620°C at a heating rate of 0.6°C / min, and the temperature is kept for a second degreasing operation for 1.5 hours; then, in an inert atmosphere environment, the temperature is increased to 1550°C at a heating rate of 22°C / min, and then the temperature is increased to 1800°C at a heating rate of 5°C / min, and the temperature is kept for sintering for 3 hours, and then the temperature is reduced to 1000°C at a cooling rate of 15°C / min, and then naturally cooled to room temperature, and the spacer is removed to obtain a parallel coil ceramic spring.

[0089] The stiffness of the parallel coil ceramic spring prepared in this embodiment is 12N / mm, the fatigue life (number of cycles at room temperature) exceeds 1000 times, the maximum load is 46.8N, and the maximum compression is 3.9mm; using a spring image LED measuring instrument to detect, the parallelism of the parallel coil ceramic spring (the degree of parallelism between the spring axis and the mounting surface) is <0.1, and the verticality (the degree of verticality between the spring axis and the mounting surface) is <0.1.

[0090] It can be seen that the method for preparing a coiled ceramic spring of the present invention adopts α-silicon nitride powder and a sintering aid to prepare silicon nitride abrasive, and then combines it with a photocurable resin and an additive to prepare silicon nitride ceramic slurry; the silicon nitride ceramic slurry is used for 3D printing to prepare a winding mold assembly; then the silicon nitride abrasive and the additive are used to prepare the ceramic winding wire, and after the winding mold assembly is assembled into a winding mold, the ceramic winding wire is wound and fixed in the direction of the thread groove of the winding mold, and then dried and formed, and then the winding mold is disassembled to remove the assembly to obtain a coiled ceramic spring blank; and then degreasing and sintering are performed to obtain a coiled ceramic spring; the aforementioned technical means cooperate with each other and work synergistically, and there is no need to adopt the reverse direction demolding and press-firing process to prepare the coiled ceramic spring. The parallelism and verticality of the prepared coiled ceramic spring are consistent, which effectively improves the stability, load-bearing capacity, reliability and service life of the coiled ceramic spring; and the dimensional stability of the prepared coiled ceramic spring is improved, and the preparation reliability is improved.

[0091] Unless otherwise specified, all percentages used in the present invention are by mass.

[0092] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a coiled ceramic spring, characterized in that: The method comprises the following steps: preparing winding mold assembly by 3D printing, preparing ceramic winding wire, and preparing parallel coil ceramic spring; The method for preparing a winding mold assembly by 3D printing comprises the following steps: uniformly mixing α-silicon nitride powder, a sintering aid, and anhydrous ethanol by ball milling, drying, and sieving to obtain silicon nitride abrasive; homogenizing and grinding the silicon nitride abrasive, a light-curing resin, and a 3D printing aid to remove bubbles to obtain silicon nitride ceramic slurry; importing a winding mold assembly model into a 3D printer supporting software slice, and performing 3D printing using silicon nitride ceramic slurry to obtain a mold assembly blank; degreasing, sintering, and polishing the mold assembly blank to obtain a winding mold assembly; The method for preparing the ceramic winding wire comprises: kneading the silicon nitride abrasive with deionized water, a binder, a plasticizer, and an organic solvent to obtain a silicon nitride ceramic mud; and extruding the silicon nitride ceramic mud after mud refining to obtain the ceramic winding wire; The method for preparing a parallel-coil ceramic spring comprises the following steps: assembling a winding mold assembly into a winding mold, winding a ceramic winding wire and fixing it on the winding mold, coating and drying the winding mold, and then disassembling the winding mold to obtain a parallel-coil ceramic spring blank; and degreasing and sintering the parallel-coil ceramic spring blank to obtain a parallel-coil ceramic spring. The winding mold comprises: a first thread component (1), a second thread component (2), a third thread component (3), a core rod (4), and a fixing cover (5); The core rod (4) is provided with a rod body, and the vertical cross-section of the rod body in the length direction is a triangle; One end of the rod body is fixedly connected to an end cover; Positioning grooves are provided on three planes in the length direction of the rod body; The first threaded component (1), the second threaded component (2), and the third threaded component (3) are all arc-shaped sheet structures, and each of the arc-shaped sheet structures is provided with slide rails on both sides along the length direction; the slide rails can be slidably fixed in the positioning slide grooves so that the first threaded component (1), the second threaded component (2), and the third threaded component (3) are fixed to the outer surface of the rod body of the core rod (4); The arcuate surfaces of the arcuate sheet structures of the first threaded component (1), the second threaded component (2) and the third threaded component (3) are provided with threaded grooves; The first threaded component (1), the second threaded component (2), the third threaded component (3) and the core rod (4) are fixed together to form a cylinder; and the outer surface of the cylinder has a spring thread groove formed by continuous splicing; The fixing cover (5) is connected to an end of a cylinder formed by the first threaded component (1), the second threaded component (2), the third threaded component (3) and the core rod (4) which is away from the end cover, and is used to fix the first threaded component (1), the second threaded component (2) and the third threaded component (3) to the outer surface of the rod body of the core rod (4); A groove is provided around the rod body at the connection surface between the end cap of the mandrel (4) and the rod body, so that the first threaded component (1), the second threaded component (2) and the third threaded component (3) can be inserted and fixed to the outer surface of the rod body of the mandrel (4).

2. The method for preparing a parallel coil ceramic spring according to claim 1, characterized in that: In the 3D printing method for preparing the winding mold assembly, the weight ratio of α-silicon nitride powder to sintering aid is 88-95:5-12; The sintering aid is at least one of the following: aluminum oxide, yttrium oxide, lanthanum oxide, magnesium oxide, cerium oxide, erbium oxide, and zirconium oxide.

3. The method for preparing a parallel coil ceramic spring according to claim 1, characterized in that: In the 3D printing preparation of the winding mold assembly, the homogenization speed is 600-650 rpm, the homogenization temperature is room temperature, and the homogenization time is 4-6 min; The grinding speed is 130-160rpm, and the particle size of the grinding output is controlled in the range of 5-8μm.

4. The method for preparing a parallel coil ceramic spring according to claim 1, characterized in that: In the 3D printing preparation of the winding mold assembly, the degreasing and sintering is first heated to 330-350°C at a heating rate of 0.4-0.6°C / min, and then heated to 600-620°C at a heating rate of 0.4-0.6°C / min, and then heated to perform a second degreasing; then, in an inert atmosphere environment, the temperature is increased to 1500-1550°C at a heating rate of 20-22°C / min, and then the temperature is increased to 1850-1880°C at a heating rate of 4-5°C / min, and after heat preservation and sintering, it is naturally cooled to room temperature to obtain the winding mold assembly.

5. The method for preparing a parallel coil ceramic spring according to claim 1, characterized in that: In the preparation of the ceramic winding wire, the binder is polyvinyl butyral and / or polymethyl methacrylate; The plasticizer is butyl stearate and / or polyethylene glycol-600; The organic solvent is anhydrous methanol or anhydrous ethanol; The weight ratio of silicon nitride abrasive, deionized water, binder, plasticizer and organic solvent is 95-100:15-30:10-30:5-10:10-40.

6. The method for preparing a parallel coil ceramic spring according to claim 1, characterized in that: In the preparation of the ceramic winding wire, the banburying temperature is 10-20°C; The vacuum degree of mud refining is 0.05-0.1MPa, the mud refining temperature is 16-18℃, the mud refining relative humidity is 55-70%, the single mud refining time is 5-8min, and the mud refining times are 2-4 times; The extrusion diameter is 0.5-3mm.

7. The method for preparing a parallel coil ceramic spring according to claim 1, characterized in that: In the preparation of the coiled ceramic spring, the coating drying temperature is 50-70° C. and the drying time is 5-8 hours; Debinding and sintering are firstly carried out by heating to 330-350°C at a heating rate of 0.4-0.6°C / min, keeping the temperature for a first debinding, then heating to 600-620°C at a heating rate of 0.4-0.6°C / min, keeping the temperature for a second debinding; then, in an inert atmosphere, heating to 1500-1550°C at a heating rate of 20-22°C / min, heating to 1760-1800°C at a heating rate of 4-5°C / min, keeping the temperature for sintering, cooling to 950-1000°C at a cooling rate of 14-15°C / min, and naturally cooling to room temperature to obtain a parallel coil ceramic spring.

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