Quick forming method for wear-resistant part foam mold based on subtractive and additive composite manufacturing

Abstract

The invention relates to the technical field of wear-resistant part foam mold rapid forming, in particular to a wear-resistant part foam mold rapid forming method based on subtractive and additive composite manufacturing, which comprises the following steps: carrying out a steam filling test on a forming mold to obtain the content of organic matters in condensate water in the steam filling test process; the preheating temperature of the forming mold is determined according to the organic matter content; the heated forming mold is filled with foam raw materials of the wear-resistant part foam mold, steam is inflated into the forming mold, and a foam blank is obtained; obtaining a plurality of temperature difference quantities between a cutting edge for performing cutter cutting on the foam blank and the foam blank; determining a feed speed of the cutting tool based on the temperature difference amount; obtaining the temperature drop amount of the corresponding surface of the foam blank and determining the cutting inclination angle of the cutting tool; and the foam blank material reducing process is completed according to the feeding speed and the cutting inclination angle, so that the formed wear-resistant part foam mold is obtained. The forming efficiency of the wear-resistant part foam mold is improved.

Description

Technical Field

[0001] This invention relates to the field of rapid prototyping technology for wear-resistant foam molds, and in particular to a rapid prototyping method for wear-resistant foam molds based on subtractive and additive composite manufacturing. Background Technology

[0002] Wear-resistant parts, such as liners for mining machinery, excavator bucket teeth, and mixer blades, are widely used in harsh working conditions such as ore crushing, engineering excavation, and material conveying. Their quality directly determines the service life and operational economy of complete sets of equipment. Foam mold casting is a common process for producing complex wear-resistant parts. In this process, a foam mold with the same shape as the wear-resistant part is prepared in advance, buried in dry sand, and then hot molten metal is poured in to vaporize and disappear the foam mold, thus obtaining the metal wear-resistant part. Therefore, the dimensional accuracy, surface quality, and internal bead fusion density of the foam mold directly determine the final quality and yield of the wear-resistant part. The expandable polystyrene used to prepare the foam mold comes from the recycling and reuse of plastic waste. With the advancement of plastic pollution prevention and circular economy policies, waste polystyrene foam, such as waste packaging materials, is being recycled through processes such as crushing, washing, granulation, and pre-foaming. The production of expandable polystyrene beads has become an important way to reduce production costs and achieve resource recycling. However, the sources of recycled materials are complex, and their molecular weight distribution, residual impurity content, foaming agent content, and other indicators often differ from those of virgin materials. This results in a narrower process window during the subsequent foaming and molding process, and greater sensitivity to temperature and pressure fluctuations. In existing technologies, due to continuous production, the foaming mold undergoes repeated heating and cooling, leading to thermal expansion and contraction. After long-term use, the parting surface may experience gaps due to thermal fatigue, thermal deformation, or thermal shrinkage, causing the injected steam to leak through short circuits. When using recycled expandable polystyrene bead raw materials, the presence of low molecular weight components or residual impurities may cause a decline in the quality of the blank. Therefore, there is an urgent need for a rapid prototyping method for wear-resistant foam molds based on subtractive and additive composite manufacturing that adapts to the characteristics of recycled materials and achieves closed-loop control throughout the entire process.

[0003] Chinese Patent Publication No. CN119704511A discloses a mold for expandable polystyrene bead foam, relating to the field of expandable polystyrene bead foaming technology. The mold includes a main body structure comprising a support frame. A lower mold is fixedly connected to the inner wall of the support frame, and two hydraulic cylinders are fixedly connected to the inner wall of the support frame. The telescopic ends of the two hydraulic cylinders are jointly fixedly connected to an upper mold. The bottom surface of the upper mold contacts the upper surface of the lower mold. This expandable polystyrene bead foam mold, by incorporating a separation unit, can effectively reduce the foaming process of expandable polystyrene beads. The adhesion surface between the product and the mold cavity wall is reduced, thereby reducing the adhesion force of expandable polystyrene bead foam products inside the mold cavity wall and facilitating demolding. It can be seen that the expandable polystyrene bead foam mold, due to long-term production, is repeatedly heated and cooled by steam filling, resulting in gaps at the parting surface caused by thermal expansion and contraction and thermal deformation or thermal shrinkage. The steam leaks from the gaps due to following the path of least resistance, resulting in insufficient bead fusion density. Furthermore, the steam carries the residue accumulated in the gaps, reducing the vaporization efficiency of the molded wear-resistant foam mold during molten metal pouring. Summary of the Invention

[0004] To address these issues, the present invention provides a rapid prototyping method for wear-resistant foam molds based on subtractive and additive composite manufacturing. This method overcomes the problems in the prior art, such as: long-term production causing repeated heating and cooling of the foam mold during steam filling, resulting in gaps at the parting surface due to thermal expansion and contraction; insufficient bead fusion density due to steam leakage from gaps following the path of least resistance; and reduced vaporization efficiency of the molded wear-resistant foam mold during molten metal pouring due to steam carrying residues accumulated in the gaps.

[0005] To achieve the above objectives, the present invention provides a rapid prototyping method for wear-resistant foam molds based on subtractive and additive composite manufacturing, comprising: The test foam material was filled into the molding mold, and the molding mold was subjected to a steam filling test to obtain the organic matter content in the condensate at the steam outlet pipe during the steam filling test. The preheating temperature of the molding die is determined based on the organic matter content, and the molding die is heated according to the preheating temperature. The foam raw material of the wear-resistant foam mold is filled into the heated molding mold, and steam is introduced into the molding mold to obtain the foam blank. The temperature difference between the cutting edge and the foam blank during the subtractive process of cutting the foam blank by a tool within a unit temperature monitoring cycle is obtained. The feed rate of the cutting tool is determined based on the temperature difference. The temperature drop of the corresponding surface of the foam blank is obtained for a preset duration starting from the moment of cutting at the feed rate; The cutting angle of the cutting tool is determined based on the temperature drop. The cutting tool is controlled according to the feed rate and cutting angle to complete the material reduction process of the foam blank, so as to obtain a foam mold for forming wear-resistant parts.

[0006] Further, determining the preheating temperature of the molding die based on the organic matter content includes: The organic matter content is compared with the preset organic matter content; If the organic content is less than the preset organic content, it is determined that the effect of the reduced air pressure in the mold cavity on the fusion density of the foam blank beads does not meet the requirements, and the preheating temperature of the molding mold is increased.

[0007] Furthermore, the preheating temperature of the molding die is negatively correlated with the organic matter content.

[0008] Further, determining the feed rate of the cutting tool based on the temperature difference includes: Compare the temperature difference with a preset difference. If the temperature difference is greater than the preset difference, it is determined that the residual contaminants in the gap of the molding die do not meet the requirements for the effect on the surface of the foam blank, and the feed speed of the cutting tool is increased.

[0009] Furthermore, the feed rate is positively correlated with the temperature difference, wherein, The temperature difference is the difference between the temperature value of the cutting edge and the temperature value of the foam blank at the monitoring moment within a unit temperature monitoring cycle. The unit temperature monitoring cycle is a number of equal time intervals during the material reduction process of cutting the foam blank with a cutting tool.

[0010] Further, determining the cutting angle of the cutting tool based on the temperature drop includes: The temperature drop of the corresponding surface of the foam blank is compared with the preset temperature drop. If the temperature drop is less than the preset drop, it is determined that the difference in thermal properties between the surface layer formed by residual contamination and the foam blank does not meet the requirements for the effect on the gasification rate of the foam blank, and the cutting angle of the cutting tool is reduced.

[0011] Furthermore, the corresponding surface of the foam blank is the surface of the foam blank directly below the cutting tool that is cutting at the feed rate.

[0012] Furthermore, the cutting angle is positively correlated with the temperature drop.

[0013] Further, the cutting inclination angle is the acute angle formed between the widest line connecting the surfaces of the cutting tool and the normal to the surface of the foam blank, wherein, The widest connecting line is the line perpendicular to the center line of the tool holder.

[0014] Furthermore, the temperature drop is the difference between the temperature value of the corresponding surface of the foam blank at the beginning of the time interval of the preset duration and the temperature value of the corresponding surface of the foam blank at the end of the time interval.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: By conducting a steam filling test on the molding mold and obtaining the organic matter content in the condensate at the steam outlet pipe during the steam filling test, the present invention addresses the issue that the molding mold may have a gap due to the long-term repeated use of the fixing bolts between the upper and lower molds, and the parting surface between the upper and lower molds caused by thermal fatigue, thermal deformation, or thermal shrinkage due to high-temperature steam. Under normal circumstances, the steam needs to penetrate the bead layer of expandable polystyrene beads inside the molding mold cavity and dissolve a small amount of oligomers on the surface of the beads, so that the organic matter content in the condensate is maintained at a certain level. If there is a gap at the parting surface, the steam leaks from the gap through the gap along the path of least resistance and bypasses the bead layer of expandable polystyrene beads, resulting in a reduction in the amount of steam in contact with the beads, which in turn leads to insufficient steam pressure inside the molding mold cavity, and incomplete fusion between the expandable polystyrene beads. This separation creates a high thermal resistance air gap, leading to a decrease in the uniformity of the obtained foam blank. During the steam filling test, the organic content in the condensate at the steam outlet pipe was lower than the preset organic content, indicating that there is steam leakage at the parting surface between the upper and lower molds due to the aforementioned reasons, namely thermal fatigue, thermal deformation, or thermal shrinkage. This causes steam to bypass the bead layer and exit directly, reducing the contact between steam and the organic components in the beads, thus decreasing the dissolved organic content in the condensate. At this point, by increasing the preheating temperature of the molding mold, utilizing the principle of metal thermal expansion of the upper and lower molds (which are made of metal), a slight thermal expansion occurs in the metal bodies of the upper and lower molds, physically closing the gap caused by thermal fatigue, thermal deformation, or thermal shrinkage. This reduces the amount of leaked steam, thereby improving the uniformity of the foam blank.

[0016] Furthermore, this invention heats the molding die according to an adjusted preheating temperature, fills the heated molding die with the foam raw material of the wear-resistant foam mold, and then fills the molding die with steam to obtain a foam blank. By acquiring several temperature differences between the cutting edge of the tool cutting the foam blank and the foam blank during a unit temperature monitoring cycle, it is determined that under long-term production conditions, trace amounts of oligomers or molten expandable polystyrene beads carried by steam leakage remain on the parting surface between the upper and lower molds. When the molding die cools, these expandable polystyrene bead residues carried into the gaps solidify and adhere to the inner wall of the gaps, forming residue plugs. In the next heating cycle... During the molding process, when steam is introduced into the mold, the high-pressure steam impacts the residue plug. The heat energy in the steam disrupts the van der Waals forces between the residue plug molecules, causing the residue plug to transform from a solid state to a viscous or semi-dissolved state. The compatibility between the high-temperature aqueous phase and the residue plug increases, and the oligomers are miscible with trace amounts of oligomers or molten expandable polystyrene beads carried in the steam, such as pentane. The micro-slits on the parting surface form a micro-nozzle. According to Bernoulli's principle, the steam velocity increases sharply as it passes through the narrow slit. The high-speed steam generates longitudinal shear force on the viscous or semi-dissolved residue plug, causing this part of the semi-dissolved residue plug to be detached and suspended in the steam flow as an aerosol or micro-droplet. The steam flow follows the pressure gradient from the slit... When vapor carrying trace amounts of oligomers or molten expandable polystyrene beads enters the mold, its flow rate decreases. Upon contact with the surface of the expandable polystyrene bead layer inside the mold cavity, where the temperature is lower, the aerosol residue condenses and adsorbs onto the bead layer surface. Since this residue is essentially expandable polystyrene bead oligomer, chemically identical to the expandable polystyrene beads inside the mold, according to the self-adhesion principle of polymer physics, these residues undergo molecular chain diffusion and entanglement with the bead layer surface, eventually fusing together. This forms a contaminated skin on the surface of the foam preform, which is a low-density porous structure. The deposited residue... The density of the contaminated skin layer is greater than that of the foam blank. During the subtractive cutting process of the foam blank, the tool friction generates heat. The contaminated skin layer hinders the transfer of heat to the internal porous structure of the foam blank, causing heat to accumulate at the contact area between the contaminated skin layer and the tool. Therefore, when the temperature difference between the cutting edge and the foam blank is greater than the preset difference, it indicates that there is local pyrolysis and carbonization on the surface of the foam blank due to contamination from the gap residue. Therefore, by increasing the feed rate of the cutting tool and shortening the contact time between the cutting tool and the contaminated skin layer, the total amount of heat transferred to the foam blank is reduced, thereby skipping the heat accumulation process of local pyrolysis and carbonization, compensating for the poor heat dissipation of the foam blank caused by the contaminated skin layer resulting from similar dissolution, and improving the uniformity of the foam blank quality.

[0017] Furthermore, this invention obtains the temperature drop of the corresponding surface of the foam blank for a preset duration starting from the moment of cutting at the feed rate. When a contamination layer formed by residual contamination exists on the surface of the foam blank, due to the difference in thermal properties between the contamination layer and the internal porous structure of the foam blank (i.e., the contamination layer has a higher density and different thermal conductivity than the foam blank as the matrix), the heat accumulated during cutting is difficult to be quickly conducted and dissipated to the interior of the foam blank through the contamination layer. Therefore, if the temperature drop of the corresponding surface of the foam blank is less than the preset drop within the preset duration after cutting stops, it indicates that the contamination layer has formed a heat-insulating effect, and the heat is retained on the surface of the foam blank. If such a difference in thermal properties exists, it will cause problems in the subsequent process of pouring molten metal to obtain wear-resistant parts when the high-temperature molten metal is poured... During casting, the contaminated skin layer has a high thermal inertia and a slow vaporization rate, while the internal foam blank has a fast vaporization rate. The asynchronous vaporization of the two leads to turbulent airflow within the mold cavity, ultimately forming pores or inclusions in the molded wear-resistant part. Therefore, by determining that the difference in thermal properties between the surface layer formed by residual contamination and the foam blank poses a risk of different vaporization rates within the foam blank, and by reducing the cutting angle of the cutting tool, the force exerted by the tool on the surface layer is changed from shear force to longitudinal force of extrusion and crushing. The crushing effect of vertical cutting can form micro-cracks on the contaminated skin layer, thereby minimizing the continuous blocking area of ​​the contaminated skin layer, breaking the thermal insulation barrier of the contaminated skin layer, compensating for the asynchronous vaporization rate caused by the difference in thermal properties, and thus ensuring that the foam blank can be uniformly vaporized during the pouring of molten metal, ultimately improving the internal density of the wear-resistant part. Attached Figure Description

[0018] Figure 1 This is an overall flowchart of the rapid prototyping method for wear-resistant foam molds based on subtractive and additive composite manufacturing according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the molding die in the rapid prototyping method for wear-resistant foam molds based on subtractive and additive composite manufacturing according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the cutting angle of the cutting tool and the surface structure of the foam blank in a rapid prototyping method for wear-resistant foam molds based on subtractive and additive composite manufacturing according to an embodiment of the present invention. Figure 4 This is a flowchart illustrating the determination of the cutting angle of the cutting tool in a rapid prototyping method for wear-resistant foam molds based on subtractive and additive composite manufacturing, according to an embodiment of the present invention. Explanation of reference numerals in the attached drawings: 1-Upper mold, 2-Lower mold, 3-Air inlet pipe, 4-Steam outlet pipe, 5-First bolt, 6-Second bolt, 7-Water tank, 8-Water pump, 9-Rapid response online total organic carbon analyzer, 10-Inlet pipe, 11-Hopper, 12-Surface of foam blank, 13-Widest line, 14-Normal line. Detailed Implementation

[0019] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0020] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0021] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0022] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] Please see Figure 1 and Figure 2 The figures shown are an overall flowchart and a schematic diagram of the molding die of a rapid prototyping method for wear-resistant foam molds based on subtractive and additive manufacturing, according to an embodiment of the present invention. The rapid prototyping method for wear-resistant foam molds based on subtractive and additive manufacturing, according to an embodiment of the present invention, includes: The test foam material was filled into the molding mold, and the molding mold was subjected to a steam filling test to obtain the organic matter content in the condensate at the steam outlet pipe during the steam filling test. The preheating temperature of the molding die is determined based on the organic matter content, and the molding die is heated according to the preheating temperature. The foam raw material of the wear-resistant foam mold is filled into the heated molding mold, and steam is introduced into the molding mold to obtain the foam blank. The temperature difference between the cutting edge and the foam blank during the subtractive process of cutting the foam blank by a tool within a unit temperature monitoring cycle is obtained. The feed rate of the cutting tool is determined based on the temperature difference. The temperature drop of the corresponding surface of the foam blank is obtained for a preset duration starting from the moment of cutting at the feed rate; The cutting angle of the cutting tool is determined based on the temperature drop. The cutting tool is controlled according to the feed rate and cutting angle to complete the material reduction process of the foam blank, so as to obtain a foam mold for forming wear-resistant parts.

[0024] Specifically, the foam raw materials for the wear-resistant foam mold and the test foam raw materials are both recycled expandable polystyrene beads.

[0025] Specifically, the additive manufacturing in this invention is a sintering process for expandable polystyrene beads.

[0026] Specifically, the subtractive process of foam blank is the process of removing excess material from the foam blank by cutting tools to obtain a foam mold for molding wear-resistant parts.

[0027] As will be understood by those skilled in the art, the manufacturing process of additive manufacturing and the subtractive process of foam blanks are conventional techniques well known to them, and therefore the manufacturing process of additive manufacturing and the subtractive process of foam blanks will not be described in detail here.

[0028] Specifically, the molding die includes: Upper mold 1 is used to cooperate with lower mold to form a molding space for foam blank; The inlet tube 10 is connected to the upper mold 1 and is used to define the filling position of the foam material in the test foam material / wear-resistant part foam mold; Hopper 11, which is connected to inlet pipe 10, is used to store foam raw materials for testing foam raw materials / abrasion-resistant foam molds; The lower mold 2 is connected to the upper mold 1 and is used to cooperate with the upper mold to form a molding space for the foam blank; Bolt assembly, which is connected to the upper mold and the lower mold respectively, is used to fix the upper mold and the lower mold in place; The air inlet pipe 3 is connected to the upper mold 1 and is used to fill the mold with steam for heating the foam material. Steam outlet pipe 4 is connected to the lower mold 2 and is used to discharge steam; Water storage tank 7 is connected to steam outlet pipe 4 and is used to collect condensate and steam discharged through steam outlet pipe; A water pump, located inside the water storage tank 7, is used to transport water from the water storage tank to the air inlet pipe to cool the molding die.

[0029] Specifically, the bolt group includes the first bolt 5 and the second bolt 6.

[0030] Specifically, the volume of the molding die is 10L.

[0031] Specifically, the steam charging speed for the steam charging test is 0.5 m / s to 5.0 m / s; the steam pressure is 0.2 MPa to 0.4 MPa; the steam temperature is 120℃ to 150℃; and the steam charging time is 10 s to 60 s.

[0032] In one specific embodiment, when conducting a steam filling test, the foam material is filled to 95% of the volume of the molding mold, i.e., 9.5L. The steam pressure is controlled at 0.3MPa and the temperature at 135℃. Steam is injected into the molding mold at a filling speed of 2.0m / s, and the steam filling test lasts for 30 seconds.

[0033] Specifically, after conducting a steam filling test and obtaining the organic matter content, the molding mold is opened, the test foam material remaining inside the molding mold is cleaned and removed, and the clean molding mold is heated according to the preheating temperature.

[0034] Those skilled in the art will understand that the process of cleaning and removing test foam material remaining inside the molding die is a conventional technique known to them, and therefore the process of cleaning and removing test foam material remaining inside the molding die will not be described in detail here.

[0035] Specifically, determining the preheating temperature of the molding die based on the organic matter content includes: The organic matter content is compared with the preset organic matter content; If the organic content is less than the preset organic content, it is determined that the effect of the reduced air pressure in the mold cavity on the fusion density of the foam blank beads does not meet the requirements, and the preheating temperature of the molding mold is increased.

[0036] Specifically, the organic matter content in the condensate at the steam outlet pipe is obtained by using a fast-response online total organic carbon analyzer 9 installed at the connection between the steam outlet pipe and the water storage tank.

[0037] Specifically, after conducting a steam filling test on the molding die, the collected condensate sample is injected into the oxidation chamber. Under the action of ultraviolet light and persulfate, the organic matter in the water is oxidized to produce carbon dioxide. The carbon dioxide content is measured by an infrared detector, and the mass of organic carbon is calculated.

[0038] Those skilled in the art will understand that the process of obtaining the organic matter content in condensate is a conventional technique well-known to them, and therefore the process of obtaining the organic matter content in condensate will not be described in detail here.

[0039] Specifically, the detection cycle of the fast-response online total organic carbon analyzer 9 used in this embodiment is 2 to 5 minutes, the steam charging test lasts for 30 seconds, and after the steam charging test is completed, the molding die is heated according to the preheating temperature after the fast-response online total organic carbon analyzer 9 outputs the organic matter content.

[0040] Specifically, the organic matter content is the ratio of the mass of organic carbon in the condensate to the total volume of the condensate, and the unit of organic matter content is mg / L.

[0041] Specifically, the organic matter refers to the polystyrene segments released by the thermal degradation or dissolution of expandable polystyrene beads under high-temperature steam, as well as the pentane in the expandable polystyrene beads.

[0042] Optionally, the preset organic matter content can be selected within a range of [45 mg / L, 58 mg / L].

[0043] Preferably, the preset organic matter content in the preferred embodiment is 50 mg / L.

[0044] Specifically, the preheating temperature of the molding die is adjusted by adjusting the amount of steam introduced into the molding die.

[0045] Specifically, the preheating temperature of the molding die is negatively correlated with the organic matter content.

[0046] In practice, when the organic matter content is less than the preset organic matter content value within 4 mg / L, the preheating temperature of the molding die is adjusted to 1.1 times the current preheating temperature. When the organic matter content is less than the preset organic matter content value and exceeds 4 mg / L, the preheating temperature is increased by 1℃ for every 1 mg / L exceeding the preset organic matter content value. In a specific embodiment, the current organic matter content is 42 mg / L, the current preheating temperature is 60℃, and the increased preheating temperature is 60℃×1.1+(4mg / L / 1mg / L)×1℃=70℃.

[0047] In practice, this invention involves conducting a steam filling test on the molding die and obtaining the organic matter content in the condensate at the steam outlet pipe during the test. The molding die suffers from gaps caused by the repeated use of the fixing bolts between the upper and lower molds, and by thermal fatigue, deformation, or shrinkage at the parting surface due to high-temperature steam. Under normal circumstances, steam needs to penetrate the expandable polystyrene bead layer inside the molding die cavity and dissolve a small amount of oligomers on the bead surface to maintain the organic matter content in the condensate at a certain level. If gaps exist at the parting surface, steam leaks through the gaps along the path of least resistance, bypassing the expandable polystyrene bead layer, resulting in reduced steam contact with the beads. This leads to insufficient steam pressure inside the molding die cavity, inadequate fusion between the expandable polystyrene beads, and the formation of high-temperature condensate. The air gap caused by thermal resistance leads to a decrease in the uniformity of the obtained foam blank. At this time, the organic content in the condensate at the steam outlet pipe during the steam filling test is less than the preset organic content, indicating that there is steam leakage at the parting surface between the upper and lower molds due to the above reasons, namely thermal fatigue and thermal deformation or thermal shrinkage. This causes steam to bypass the bead layer and be discharged directly, reducing the contact between steam and the organic components in the beads, and reducing the content of dissolved organic matter in the condensate. At this time, by increasing the preheating temperature of the molding mold, and utilizing the principle of metal thermal expansion of the upper and lower molds, the metal bodies of the upper and lower molds undergo a slight thermal expansion, thereby physically closing the fit gap caused by thermal fatigue and thermal deformation or thermal shrinkage, thus reducing the amount of leaked steam and improving the uniformity of the foam blank.

[0048] Specifically, determining the feed rate of the cutting tool based on the temperature difference includes: Compare the temperature difference with a preset difference. If the temperature difference is greater than the preset difference, it is determined that the residual contaminants in the gap of the molding die do not meet the requirements for the effect on the surface of the foam blank, and the feed speed of the cutting tool is increased.

[0049] Specifically, the cutting tool is a wireless temperature-measuring cutting tool. The temperature difference between the cutting edge and the foam blank is obtained by the wireless temperature-measuring cutting tool and the thermocouple set at the corresponding cutting point on the surface of the foam blank.

[0050] Specifically, the wireless temperature-measuring cutting tool includes a K-type thermocouple located 2mm to 3mm from the cutting edge on the tool holder, a processor for converting the temperature value of the cutting edge into a digital signal, and a button battery for powering the processor.

[0051] As will be understood by those skilled in the art, the structure and operation of wireless temperature-measuring cutting tools are conventional technical means well known to them, and therefore the structure and operation of wireless temperature-measuring cutting tools will not be described in detail here.

[0052] Optionally, the preset range for the difference amount is [40℃, 80℃].

[0053] Preferably, the preferred embodiment with a preset difference amount is 50°C.

[0054] Specifically, the feed rate is positively correlated with the temperature difference, wherein, The temperature difference is the difference between the temperature value of the cutting edge and the temperature value of the foam blank at the monitoring moment within a unit temperature monitoring cycle. The unit temperature monitoring cycle is a number of equal time intervals during the material reduction process of cutting the foam blank with a cutting tool.

[0055] Specifically, the duration of a unit temperature monitoring cycle is 1 second.

[0056] In practice, when the temperature difference is greater than the preset difference value but within 2℃, the feed rate of the cutting tool is adjusted to 1.1 times the current feed rate of the cutting tool. When the temperature difference exceeds the preset difference value by more than 2℃, the feed rate of the cutting tool is increased by 0.1 m / min for every 1℃ exceeding the preset difference value. In a specific embodiment, the current temperature difference is 54℃, the current feed rate of the cutting tool is 1.0 m / min, and the increased feed rate of the cutting tool is 1.0 m / min × 1.1 + (2℃ / 1℃) × 0.1 m / min = 1.3 m / min.

[0057] Specifically, the feed rate of the cutting tool is adjusted by changing the speed of the servo motor or spindle motor that drives the cutting tool.

[0058] In practice, this invention heats the molding die according to an adjusted preheating temperature, fills the heated molding die with the foam raw material of the wear-resistant foam mold, and then fills the mold with steam to obtain a foam blank. By measuring the temperature difference between the cutting edge and the foam blank during the subtractive cutting process of the foam blank within a unit temperature monitoring cycle, it is observed that under long-term production conditions, trace amounts of oligomers or molten expandable polystyrene beads carried by steam leakage remain on the parting surface between the upper and lower molds. When the molding die cools, these expandable polystyrene bead residues carried into the gaps solidify and adhere to the inner wall of the gaps, forming residue plugs. In the next heating cycle... During the molding process, when steam is introduced into the mold, the high-pressure steam impacts the residue plug. The heat energy in the steam disrupts the van der Waals forces between the residue plug molecules, causing the residue plug to transform from a solid state to a viscous or semi-dissolved state. The compatibility between the high-temperature aqueous phase and the residue plug increases, and the oligomers are miscible with trace amounts of oligomers or molten expandable polystyrene beads carried in the steam, such as pentane. The micro-slits on the parting surface form a micro-nozzle. According to Bernoulli's principle, the steam velocity increases sharply as it passes through the narrow slit. The high-speed steam generates longitudinal shear force on the viscous or semi-dissolved residue plug, causing this part of the semi-dissolved residue plug to be detached and suspended in the steam flow as an aerosol or micro-droplet. The steam flow follows the pressure gradient from the slit... When vapor carrying trace amounts of oligomers or molten expandable polystyrene beads enters the mold, its flow rate decreases. Upon contact with the surface of the expandable polystyrene bead layer inside the mold cavity, where the temperature is lower, the aerosol residue condenses and adsorbs onto the bead layer surface. Since this residue is essentially expandable polystyrene bead oligomer, chemically identical to the expandable polystyrene beads inside the mold, according to the self-adhesion principle of polymer physics, these residues undergo molecular chain diffusion and entanglement with the bead layer surface, eventually fusing together. This forms a contaminated skin on the surface of the foam preform, which is a low-density porous structure. The deposited residue... The density of the contaminated skin layer is greater than that of the foam blank. During the subtractive cutting process of the foam blank, the tool friction generates heat. The contaminated skin layer hinders the transfer of heat to the internal porous structure of the foam blank, causing heat to accumulate at the contact area between the contaminated skin layer and the tool. Therefore, when the temperature difference between the cutting edge and the foam blank is greater than the preset difference, it indicates that there is local pyrolysis and carbonization on the surface of the foam blank due to contamination from the gap residue. Therefore, by increasing the feed rate of the cutting tool and shortening the contact time between the cutting tool and the contaminated skin layer, the total amount of heat transferred to the foam blank is reduced, thereby skipping the heat accumulation process of local pyrolysis and carbonization, compensating for the poor heat dissipation of the foam blank caused by the contaminated skin layer resulting from similar dissolution, and improving the uniformity of the foam blank quality.

[0059] Please see Figure 4 The flowchart shown is a process for determining the cutting angle of a cutting tool in a rapid prototyping method for wear-resistant foam molds based on subtractive and additive composite manufacturing according to an embodiment of the present invention. The determination of the cutting angle based on the temperature drop includes: The temperature drop of the corresponding surface of the foam blank is compared with the preset temperature drop. If the temperature drop is less than the preset drop, it is determined that the difference in thermal properties between the surface layer formed by residual contamination and the foam blank does not meet the requirements for the effect on the gasification rate of the foam blank, and the cutting angle of the cutting tool is reduced.

[0060] Optional, the preset duration can be selected from [5s, 30s].

[0061] Preferably, the preset duration is 10 seconds.

[0062] Specifically, the cutting angle of the cutting tool is adjusted by adjusting the rotary axis servo drive that controls the tool's oscillation.

[0063] Specifically, the temperature drop of the corresponding surface of the foam blank is obtained by setting a thermocouple at the corresponding cutting point on the surface of the foam blank.

[0064] Optionally, the preset descent amount can be selected within the range of [3℃, 8℃].

[0065] Preferably, the preferred embodiment for the preset descent amount is 5°C.

[0066] Specifically, the corresponding surface of the foam blank is the surface of the foam blank directly below the cutting tool that is cutting at the feed rate.

[0067] Specifically, the cutting angle is positively correlated with the temperature drop.

[0068] In practice, when the temperature drop is less than the preset drop value by less than 0.5℃, the cutting angle of the cutting tool is adjusted to 95% of the current cutting angle. When the temperature drop exceeds the preset drop value by more than 0.5℃, the cutting angle of the cutting tool is reduced by 1° for every 0.1℃ increase. In a specific embodiment, the current temperature drop is 4.3℃, the current cutting angle of the cutting tool is 30°, and the reduced cutting angle of the cutting tool is 30°×95%-(0.2℃ / 0.1℃)×1°=26.5°.

[0069] Please see Figure 3As shown, this is a schematic diagram of the cutting angle of the cutting tool and the surface structure of the foam blank in a rapid prototyping method for wear-resistant foam molds based on subtractive and additive composite manufacturing according to an embodiment of the present invention. The cutting angle is the acute angle formed between the widest line 13 of the tool surface and the normal 14 of the foam blank surface 12. The widest connecting line 13 is a line perpendicular to the center line of the tool holder.

[0070] In practice, this invention obtains the temperature drop of the corresponding surface of the foam blank for a preset duration starting from the moment of cutting at the feed rate. When a contamination layer formed by residual contaminants exists on the surface of the foam blank, the contamination layer has a different thermophysical property from the internal porous structure of the foam blank. That is, the contamination layer has a higher density and different thermal conductivity than the foam blank as the matrix. This makes it difficult for the heat accumulated during cutting to be quickly conducted and dissipated to the interior of the foam blank through the contamination layer. Therefore, if the temperature drop of the corresponding surface of the foam blank is less than the preset drop within the preset duration after cutting stops, it indicates that the contamination layer has formed a heat-insulating effect, and the heat is retained on the surface of the foam blank. If such a thermophysical property difference exists, it will cause problems in the subsequent process of pouring molten metal to obtain wear-resistant parts when the high-temperature molten metal is poured. During casting, the contaminated skin layer has a high thermal inertia and a slow vaporization rate, while the internal foam blank has a fast vaporization rate. The asynchronous vaporization of the two leads to turbulent airflow within the mold cavity, ultimately forming pores or inclusions in the molded wear-resistant part. Therefore, by determining that the difference in thermal properties between the surface layer formed by residual contamination and the foam blank poses a risk of different vaporization rates within the foam blank, and by reducing the cutting angle of the cutting tool, the force exerted by the tool on the surface layer is changed from shear force to longitudinal force of extrusion and crushing. The crushing effect of vertical cutting can form micro-cracks on the contaminated skin layer, thereby minimizing the continuous blocking area of ​​the contaminated skin layer, breaking the thermal insulation barrier of the contaminated skin layer, compensating for the asynchronous vaporization rate caused by the difference in thermal properties, and thus ensuring that the foam blank can be uniformly vaporized during the pouring of molten metal, ultimately improving the internal density of the wear-resistant part.

[0071] Specifically, the temperature drop is the difference between the temperature value of the corresponding surface of the foam blank at the beginning of the time interval of the preset duration and the temperature value of the corresponding surface of the foam blank at the end of the time interval.

[0072] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A rapid prototyping method for wear-resistant foam molds based on subtractive and additive composite manufacturing, characterized in that, include: The test foam material was filled into the molding mold, and the molding mold was subjected to a steam filling test to obtain the organic matter content in the condensate at the steam outlet pipe during the steam filling test. The preheating temperature of the molding die is determined based on the organic matter content, and the molding die is heated according to the preheating temperature. The foam raw material of the wear-resistant foam mold is filled into the heated molding mold, and steam is introduced into the molding mold to obtain the foam blank. The temperature difference between the cutting edge and the foam blank during the subtractive process of cutting the foam blank by a tool within a unit temperature monitoring cycle is obtained. The feed rate of the cutting tool is determined based on the temperature difference. The temperature drop of the corresponding surface of the foam blank is obtained for a preset duration starting from the moment of cutting at the feed rate; The cutting angle of the cutting tool is determined based on the temperature drop. The cutting tool is controlled according to the feed rate and cutting angle to complete the material reduction process of the foam blank, so as to obtain a foam mold for forming wear-resistant parts.

2. The rapid prototyping method for wear-resistant foam molds based on subtractive and additive composite manufacturing according to claim 1, characterized in that, Determining the preheating temperature of the molding die based on the organic matter content includes: The organic matter content is compared with the preset organic matter content; If the organic content is less than the preset organic content, it is determined that the effect of the reduced air pressure in the mold cavity on the fusion density of the foam blank beads does not meet the requirements, and the preheating temperature of the molding mold is increased.

3. The rapid prototyping method for wear-resistant foam molds based on subtractive and additive composite manufacturing according to claim 2, characterized in that, The preheating temperature of the molding die is negatively correlated with the organic matter content.

4. The rapid prototyping method for wear-resistant foam molds based on subtractive and additive composite manufacturing according to claim 3, characterized in that, The process of determining the feed rate of the cutting tool based on the temperature difference includes: Compare the temperature difference with a preset difference. If the temperature difference is greater than the preset difference, it is determined that the residual contaminants in the gap of the molding die do not meet the requirements for the effect on the surface of the foam blank, and the feed speed of the cutting tool is increased.

5. The rapid prototyping method for wear-resistant foam molds based on subtractive and additive composite manufacturing according to claim 4, characterized in that, The feed rate is positively correlated with the temperature difference, wherein, The temperature difference is the difference between the temperature value of the cutting edge and the temperature value of the foam blank at the monitoring moment within a unit temperature monitoring cycle. The unit temperature monitoring cycle is a number of equal time intervals during the material reduction process of cutting the foam blank with a cutting tool.

6. The rapid prototyping method for wear-resistant foam molds based on subtractive and additive composite manufacturing according to claim 5, characterized in that, The determination of the cutting angle of the cutting tool based on the temperature drop includes: The temperature drop of the corresponding surface of the foam blank is compared with the preset temperature drop. If the temperature drop is less than the preset drop, it is determined that the difference in thermal properties between the surface layer formed by residual contamination and the foam blank does not meet the requirements for the effect on the gasification rate of the foam blank, and the cutting angle of the cutting tool is reduced.

7. The rapid prototyping method for wear-resistant foam molds based on subtractive and additive composite manufacturing according to claim 6, characterized in that, The corresponding surface of the foam blank is the surface of the foam blank directly below the cutting tool that is cutting at the feed rate.

8. The rapid prototyping method for wear-resistant foam molds based on subtractive and additive composite manufacturing according to claim 7, characterized in that, The cutting angle is positively correlated with the temperature drop.

9. The rapid prototyping method for wear-resistant foam molds based on subtractive and additive composite manufacturing according to claim 8, characterized in that, The cutting angle is the acute angle formed between the widest line connecting the surfaces of the cutting tool and the normal to the surface of the foam blank, wherein, The widest connecting line is the line perpendicular to the center line of the tool holder.

10. The rapid prototyping method for wear-resistant foam molds based on subtractive and additive composite manufacturing according to claim 9, characterized in that, The temperature drop is the difference between the temperature value of the corresponding surface of the foam blank at the beginning of the time interval of the preset duration and the temperature value of the corresponding surface of the foam blank at the end of the time interval.

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