Machining method of columnar part

Abstract

The invention relates to the field of machining, in particular to a columnar part machining method which comprises the following steps: S1, roughly grinding a bar to obtain a columnar base body; s2, a through hole is formed in the columnar base body in the axial direction through electric spark machining, and the through hole penetrates through the two axial end faces of the columnar base body; s3, a taper hole is formed in an opening in one end of the through hole through electric spark machining; s4, the outer side face of the columnar base body is ground to meet the preset precision requirement; s5, the surface of the taper hole is ground to meet the preset precision requirement; and S6, the end face of the side, deviating from the conical hole, of the columnar base body is sequentially ground and polished. By means of the scheme, the product machining quality can be stably guaranteed, and the qualified columnar part made of the hard alloy material can be rapidly machined.

Description

Technical Field

[0001] This invention relates to the field of machining, and more specifically to a method for machining columnar parts. Background Technology

[0002] With the continuous evolution of diesel engine technology and the gradual maturation of high-pressure common rail technology, new alternative fuels such as methanol and ammonia are increasingly being used in the diesel engine field. However, the combination of the characteristics of new fuels and the special operating conditions of diesel engines not only drives the evolution of component structures towards greater complexity, but also places higher demands on the machining precision of components. To meet the dual requirements of rapid corrosion resistance and high impact strength for parts during use, superhard carbide materials have become the preferred choice. These materials boast high strength and excellent hardness (typically exceeding HRA90), making them widely used in machining. However, their inherent characteristics also result in poor machinability, significantly increasing the difficulty of part processing. To ensure that the machining accuracy of carbide parts meets design standards, technological innovation based on traditional machining processes is essential to overcome processing bottlenecks and key technologies. Only then can the parts be machined successfully, ultimately meeting market applications and user needs. In particular, targeting Figure 1 and Figure 2 The cemented carbide precision part shown includes a cylindrical base 1 with a through hole 2 extending through both ends in the middle of the base 1. The diameter of the through hole 2 ranges from 0.4 to 0.6 mm. Specifically, the through hole 2 includes a first channel 21 and a second channel 22 connected axially, with the inner diameter of the second channel 22 being smaller than that of the first channel 21. The end face of the cylindrical base 1 also has a tiny tapered hole 3 that precisely connects to the second channel 22. The machining difficulty of this part lies in the extremely high tolerance requirements for the diameter of the through hole 2, and the need for both the outer contour of the cylindrical base 1 and the tiny tapered hole 3 to meet stringent dimensional and positional tolerance standards, further increasing the machining difficulty and posing a serious challenge to existing machining technologies. Summary of the Invention

[0003] The purpose of this invention is to provide a method for processing columnar parts, which can reliably guarantee product processing quality and quickly produce qualified columnar parts made of cemented carbide material.

[0004] To achieve the above objectives, the technical solution selected by the present invention is as follows: This invention discloses a method for processing columnar parts, which includes the following steps: S1, coarsely grind the bar stock to obtain a columnar matrix; S2, the columnar substrate is axially formed with through holes by electrical discharge machining, and the through holes penetrate both axial end faces of the columnar substrate; S3, the through hole is formed into a tapered hole by electrical discharge machining at one end; S4, Grind the outer surface of the columnar substrate to the preset accuracy requirement; S5, Grind the surface of the tapered hole to the preset accuracy requirement; S6, grind and polish the end face of the columnar substrate away from the conical hole in sequence.

[0005] Furthermore, step S1 specifically includes: selecting a diamond grinding wheel with a particle size of 20# for rough grinding of the bar stock, setting the feed rate to 0.1~0.2mm, setting the feed speed to 0.5~0.8mm / min, and the surface roughness of the columnar matrix obtained by rough grinding is less than 3.2μm.

[0006] Furthermore, the through hole in S2 includes a first channel and a second channel connected along the axial direction, the inner diameter of the second channel being smaller than the inner diameter of the first channel; the columnar substrate is first subjected to a first electrical discharge machining to form the first channel, and then the columnar substrate is subjected to a second electrical discharge machining to form the second channel.

[0007] Furthermore, the electrode used for the first electrical discharge machining is a copper-tungsten alloy electrode. The discharge gap is set to 0.1~0.2mm, the pulse gap is set to 60~80μs, the servo reference is set to 70~80%, the voltage is set to 140~160V, the peak current is set to 3~5A, the pulse width is set to 4~6μs, the tool lift height is set to 3~5mm, the discharge time is set to 0.4~0.8s, and the upward tool lift speed is set to 2000~3000mm / min. After machining, the diameter tolerance of the first channel is within 0.02, and the surface roughness is less than 1.6μm.

[0008] Furthermore, the electrode used for the first electrical discharge machining is a copper-tungsten alloy electrode. The discharge gap is set to 0.1~0.2mm, the pulse gap is set to 60~80μs, the servo reference is set to 70~80%, the voltage is set to 100~120V, the peak current is set to 2~4A, the pulse width is set to 4~6μs, the tool lift height is set to 3~5mm, the discharge time is set to 0.3~0.6s, and the upward tool lift speed is set to 2000~3000mm / min. After machining, the diameter tolerance of the second channel is within 0.02, and the surface roughness is less than 1.6μm.

[0009] Furthermore, in step S3, the electrode used for electrical discharge machining is a copper-tungsten alloy electrode. The discharge gap is set to 0.1~0.2mm, the pulse gap is set to 60~80μs, the servo reference is set to 70~80%, the voltage is set to 100~120V, the peak current is set to 2.5~5A, the pulse width is set to 4~6μs, the tool lift height is set to 3~5mm, the discharge time is set to 0.25~0.5s, and the upward tool lift speed is set to 2000~3000mm / min. After machining, the angular tolerance of the tapered hole is within 1°, and the surface roughness is less than 1.6μm.

[0010] Furthermore, step S4 specifically includes: firstly, using a diamond grinding wheel with a grit size of 60# to perform rough grinding on the outer surface of the columnar substrate, with the feed rate set to 0.01~0.03mm and the feed speed set to 0.4~0.6mm / min, and grinding for 10s; then, using a diamond grinding wheel with a grit size of 180~220# to perform fine grinding, with the feed rate set to 0.002~0.004mm and the feed speed set to 0.3~0.5mm / min, and grinding back and forth a preset number of times, so that the outer surface of the columnar substrate reaches the preset accuracy requirements.

[0011] Further, step S5 specifically includes: using an internal grinding machine to clamp the outer surface of the columnar substrate after grinding, and performing rough grinding with a diamond grinding wheel of grit size 180~220#. During the rough grinding process, the rotational speed of the columnar substrate is set to 600-1100 r / min, the spindle speed of the grinding machine is set to 50000~80000 RPM, the feed rate is set to 0.003~0.005 mm, and the feed speed is set to 0.05~0.08 mm / min. The grinding process involves a preset number of passes, with a 0.02mm allowance for fine grinding. CBN grinding wheels with a grit size of 320-400# are selected. During fine grinding, the rotational speed of the columnar substrate is set to 800-1500 r / min, the grinding machine spindle speed is set to 50000-80000 RPM, the feed rate is set to 0.001-0.003mm, and the feed speed is set to 0.03-0.05m / min. The preset number of passes ensures that the surface of the tapered hole meets the preset accuracy requirements.

[0012] Furthermore, the grinding in step S6 specifically includes: clamping the outer surface of the columnar substrate, selecting a cast iron grinding plate, rotating the grinding plate, and simultaneously rotating the columnar substrate around the grinding plate; the rotation speed of the grinding plate is set to 50~80 r / min, the rotation speed of the columnar substrate is set to 60~100 r / min, and the revolution speed is set to 30~50 r / min; M10 abrasive is added during the processing; the grinding time is set to 30~60 min, until the flatness of the end face of the columnar substrate is less than 0.0009 mm and the roughness is less than 0.1 μm.

[0013] Furthermore, the polishing in step S6 specifically includes: clamping the outer surface of the columnar substrate, selecting a polyurethane polishing plate, rotating the polishing plate, and simultaneously rotating the columnar substrate around the polishing plate; the rotation speed of the polishing plate is set to 100~150 r / min, the rotation speed of the columnar substrate is set to 60~80 r / min, the revolution speed is set to 20~40 r / min, 600# diamond polishing fluid is added during the processing, and the polishing time is set to 10~15 min.

[0014] The present invention has the following unexpected beneficial effects: The processing method described in this invention is adapted to the high hardness characteristics of cemented carbide. Addressing the problems of high hardness and rapid tool wear and processing difficulties associated with traditional cutting methods, this solution utilizes electrical discharge machining (EDM) to form through holes and tapered holes, eliminating the need for direct cutting with hardened tools. This effectively tackles the processing challenges of hard materials, achieving stable forming of hole systems and tapered holes. Subsequent precision grinding and polishing processes are also specifically adapted to the material characteristics, avoiding surface damage or dimensional deviations caused by material hardness during processing, ensuring controllable processing. Furthermore, EDM can initially control the forming accuracy of the hole system and tapered holes, laying the foundation for subsequent grinding; the precision grinding in steps S4 and S5 specifically optimizes the shape and position accuracy of the outer surface of the cylindrical part and the surface flatness of the tapered hole; the grinding and polishing in step S6 further improves the end face surface quality, ensuring that all key parts of the part meet the preset accuracy requirements, thus solving the core need for high-precision machining of cemented carbide parts. Attached Figure Description

[0015] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention.

[0016] Figure 1 A schematic diagram of the columnar part is shown.

[0017] Figure 2 It shows Figure 1 A magnified view of a portion of region A.

[0018] Figure 3 A schematic flowchart of the processing method for the columnar part according to an embodiment of the present invention is shown. Detailed Implementation

[0019] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0020] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0021] In one embodiment, see Figure 1 As shown, this invention discloses a method for processing a columnar part, which includes the following steps: S1, coarsely grind the bar stock to obtain a columnar matrix; S2, the columnar substrate is axially formed with through holes by electrical discharge machining, and the through holes penetrate both axial end faces of the columnar substrate; S3, the through hole is formed into a tapered hole by electrical discharge machining at one end; S4, Grind the outer surface of the columnar substrate to the preset accuracy requirement; S5, Grind the surface of the tapered hole to the preset accuracy requirement; S6, grind and polish the end face of the columnar substrate away from the conical hole in sequence.

[0022] The processing method described in this invention is adapted to the high hardness characteristics of cemented carbide. Addressing the problems of high hardness and rapid tool wear and processing difficulties associated with traditional cutting methods, this solution utilizes electrical discharge machining (EDM) to form through holes and tapered holes, eliminating the need for direct cutting with hardened tools. This effectively tackles the processing challenges of hard materials, achieving stable forming of hole systems and tapered holes. Subsequent precision grinding and polishing processes are also specifically adapted to the material characteristics, avoiding surface damage or dimensional deviations caused by material hardness during processing, ensuring controllable processing. Furthermore, EDM can initially control the forming accuracy of the hole system and tapered holes, laying the foundation for subsequent grinding; the precision grinding in steps S4 and S5 specifically optimizes the shape and position accuracy of the outer surface of the cylindrical part and the surface flatness of the tapered hole; the grinding and polishing in step S6 further improves the end face surface quality, ensuring that all key parts of the part meet the preset accuracy requirements, thus solving the core need for high-precision machining of cemented carbide parts.

[0023] In a preferred embodiment of the present invention, step S1 specifically includes: selecting a diamond grinding wheel with a particle size of 20# for rough grinding of the bar stock, setting the feed rate to 0.1~0.2mm, setting the feed speed to 0.5~0.8mm / min, and the surface roughness of the columnar matrix obtained by rough grinding is less than 3.2μm.

[0024] This preferred embodiment uses a diamond grinding wheel, whose hardness and wear resistance are suitable for machining high-hardness alloy materials. Compared to ordinary grinding wheels, diamond grinding wheels can effectively cope with the high wear resistance during the cutting of hard materials, avoiding the problems of decreased machining efficiency or insufficient cutting force caused by rapid wear of the grinding wheel, ensuring a stable and controllable rough grinding process, while reducing the frequency of grinding wheel replacement and lowering machining costs.

[0025] In this preferred embodiment, a 20# coarse-grained grinding wheel is selected, along with a feed rate of 0.1~0.2mm and a feed speed of 0.5~0.8mm / min. This allows for rapid removal of excess material through the large cutting capability of the coarse-grained grinding wheel, while the reasonable feed parameters prevent machining vibration or bar deformation caused by excessive cutting. This ensures machining efficiency while reserving a stable machining allowance for subsequent processes, reducing ineffective machining steps. For example, after rough grinding, a grinding allowance of 0.3~0.5mm is reserved on the outer diameter of the cylindrical substrate, and a machining allowance of 0.05~0.1mm is reserved on the end face.

[0026] In a preferred embodiment of the present invention, the through hole in S2 includes a first channel and a second channel connected along the axial direction, wherein the inner diameter of the second channel is smaller than the inner diameter of the first channel; the columnar substrate is first subjected to a first electrical discharge machining to form the first channel, and then the columnar substrate is subjected to a second electrical discharge machining to form the second channel.

[0027] For through-hole structures consisting of a first channel with a larger inner diameter and a second channel with a smaller inner diameter, a step-by-step EDM (Electrical Discharge Machining) method is adopted, machining the first channel first and then the second channel. This allows the first channel, formed earlier, to serve as the positioning reference for the subsequent machining of the second channel. This effectively avoids positioning deviations or out-of-tolerance coaxiality issues that can occur when machining the first and second channels in a single pass due to their different inner diameters. Furthermore, step-by-step machining allows for the matching of custom electrodes with appropriate inner diameters for both the first and second channels, precisely controlling the dimensional tolerances of channels with different inner diameters and meeting the fundamental requirements for dimensional accuracy in subsequent precision machining.

[0028] Furthermore, due to the different inner diameters of the first and second channels, the discharge parameters required for EDM differ. Specifically, the first channel, with its larger inner diameter, can achieve efficient material removal through relatively suitable parameters, while the second channel, with its smaller inner diameter, requires more precise parameters to avoid machining overload. Step-by-step machining allows for separate parameter optimization for each channel, avoiding defects such as rough hole walls and microcracks caused by uniform parameter settings. This ensures that the surface roughness of both the first and second channels meets the requirements for subsequent processes, reducing the burden of subsequent grinding and correction.

[0029] In a preferred embodiment of the present invention, the electrode used for the first electrical discharge machining is a copper-tungsten alloy electrode. The discharge gap is set to 0.1~0.2mm, the pulse gap is set to 60~80μs, the servo reference is set to 70~80%, the voltage is set to 140~160V, the peak current is set to 3~5A, the pulse width is set to 4~6μs, the tool lift height is set to 3~5mm, the discharge time is set to 0.4~0.8s, and the upward tool lift speed is set to 2000~3000mm / min. After machining, the diameter tolerance of the first channel is within 0.02, and the surface roughness is less than 1.6μm.

[0030] This preferred embodiment uses a copper-tungsten alloy electrode, which combines high conductivity, high temperature resistance, and low loss characteristics, precisely matching the EDM requirements of cemented carbide materials. On one hand, the high hardness of the copper-tungsten alloy resists frictional wear between the electrode and the workpiece during machining, avoiding dimensional deviations in the hole due to rapid electrode wear and ensuring controllable dimensional accuracy throughout the first hole machining process. On the other hand, its excellent conductivity and heat dissipation can stably transfer discharge energy, avoiding electrode deformation or micro-damage to the workpiece surface caused by localized overheating, ensuring discharge stability during the machining of high-hardness materials, and reducing machining interruptions or rework due to electrode failure.

[0031] For the machining requirements of the first channel (with a relatively large inner diameter), this preferred embodiment limits the process parameters of electrical discharge machining, namely: the discharge gap is set to 0.1~0.2mm, the pulse gap is set to 60~80μs, the voltage is set to 140~160V, the peak current is set to 3~5A, and the pulse width is set to 4~6μs. This forms a suitable discharge energy and machining rhythm. The higher voltage and peak current can provide sufficient energy to efficiently remove the excess cemented carbide material and meet the efficiency requirements of the roughing stage. The reasonable discharge gap and pulse gap can avoid excessive concentration of discharge energy—preventing the risk of short circuit due to too small a gap, and achieving the initial discharge of electro-erosion products (such as metal chips) through the pulse gap, reducing chip accumulation or arc burns on the hole wall, and ultimately making the surface roughness of the hole wall less than 1.6μm. This provides a high-quality surface foundation for the subsequent machining of the second channel and precision grinding, reducing the correction burden of subsequent processes.

[0032] Setting the servo reference to 70-80% sets the "gap control reference threshold" for the servo system. Specifically, when the discharge gap changes during machining due to factors such as material erosion or the accumulation of electro-erosion products, the servo system will use this reference value as a reference to automatically adjust the electrode feed rate or tool lifting action, correcting the discharge gap back to the set range of 0.1-0.2mm in real time. The selection of 70-80% is to balance gap stability and machining efficiency, avoiding sluggish servo response due to an excessively low reference, and avoiding excessive servo sensitivity due to an excessively high reference, i.e., frequent tool lifting / feeding, which reduces machining efficiency. It also adapts to the high hardness characteristics of cemented carbide materials, ensuring stable and compliant machining quality for precision features such as through holes and tapered holes.

[0033] Meanwhile, in this preferred embodiment, the lifting height is set to 3-5mm, and the lifting speed is set to 2000-3000mm / min. The appropriate lifting height can fully open the space of the discharge area, making it easier for the electro-erosion products to be discharged with the working fluid, and avoiding uneven discharge caused by the accumulation of debris. The faster lifting speed can reduce non-machining time, ensuring chip removal effect while avoiding the reduction of overall machining efficiency due to excessive lifting time. It is especially suitable for the characteristics of slow cutting and frequent chip removal when machining high-hardness materials, ensuring continuous and stable machining of the first channel and reducing dimensional fluctuations.

[0034] In a preferred embodiment of the present invention, the electrode used for the first electrical discharge machining is a copper-tungsten alloy electrode. The discharge gap is set to 0.1~0.2mm, the pulse gap is set to 60~80μs, the servo reference is set to 70~80%, the voltage is set to 100~120V, the peak current is set to 2~4A, the pulse width is set to 4~6μs, the tool lift height is set to 3~5mm, the discharge time is set to 0.3~0.6s, and the upward tool lift speed is set to 2000~3000mm / min. After machining, the diameter tolerance of the second channel is within 0.02, and the surface roughness is less than 1.6μm.

[0035] Compared to the first channel machining, this embodiment optimizes the discharge parameters—voltage 100-120V, peak current 2-4A, and pulse width 4-6μs—to address the smaller inner diameter of the second channel. The lower voltage and peak current prevent over-cutting or microscopic damage to the small-diameter channel due to excessive energy concentration, thus meeting the higher precision requirements of small-sized channels. The stable pulse width ensures uniform electro-erosion, reduces surface roughness, and ultimately achieves a surface roughness of less than 1.6μm. This provides a low-defect foundation for subsequent processes, reducing the burden of later corrections.

[0036] In a preferred embodiment of the present invention, the electrode used for electrical discharge machining in step S3 is a copper-tungsten alloy electrode. The discharge gap is set to 0.1~0.2mm, the pulse gap is set to 60~80μs, the servo reference is set to 70~80%, the voltage is set to 100~120V, the peak current is set to 2.5~5A, the pulse width is set to 4~6μs, the tool lift height is set to 3~5mm, the discharge time is set to 0.25~0.5s, and the upward tool lift speed is set to 2000~3000mm / min. After machining, the angular tolerance of the tapered hole is within 1°, a grinding allowance of 0.1~0.2mm is reserved, and the surface roughness is less than 1.6μm.

[0037] For the characteristics of machining curved surfaces requiring uniform etching to transition into tapered holes, this embodiment sets discharge parameters of 100~120V voltage and 2.5~5A peak current, coupled with a pulse width of 4~6μs. Compared to the second channel, the slightly higher peak current provides sufficient and uniform discharge energy, ensuring that the cemented carbide material is effectively etched at all points on the tapered surface, avoiding tapered surface defects or incomplete machining due to insufficient energy. The stable pulse width and voltage control the uniformity of the electro-etching process, reducing unevenness on the tapered surface and ultimately achieving a surface roughness of less than 1.6μm. This provides a low-defect surface foundation for subsequent precision grinding of the tapered hole, reduces the burden of subsequent grinding correction, and avoids uneven grinding allowance due to poor initial surface quality.

[0038] In a preferred embodiment of the present invention, step S4 specifically includes: firstly, using a diamond grinding wheel with a grit size of 60# to perform rough grinding on the outer surface of the columnar substrate, with the feed rate set to 0.01~0.03mm and the feed speed set to 0.4~0.6mm / min, and polishing for 10s; then, using a diamond grinding wheel with a grit size of 180~220# to perform fine grinding, with the feed rate set to 0.002~0.004mm and the feed speed set to 0.3~0.5mm / min, and polishing back and forth a preset number of times, so that the outer surface of the columnar substrate reaches the preset precision requirements.

[0039] To address the characteristics of cemented carbide—high hardness, high brittleness, and susceptibility to surface cracks or deformation due to improper machining parameters—this implementation method controls the unit cutting force during the cutting process by combining medium feed rates in rough grinding with small feed rates in finish grinding. In the rough grinding stage, localized stress concentration caused by excessive feed rates is avoided, while in the finish grinding stage, small feed rates reduce cutting impact. Both methods effectively prevent microscopic damage to the outer surface of the cemented carbide. Simultaneously, the stable cutting characteristics of the diamond grinding wheel reduce vibration interference during machining, further ensuring the integrity of the columnar matrix structure. This provides a defect-free workpiece foundation for subsequent precision machining processes, reducing the risk of subsequent process defects caused by early damage.

[0040] In a preferred embodiment of the present invention, step S5 specifically includes: using an internal grinding machine to clamp the outer surface of the columnar substrate after grinding, and performing rough grinding with a diamond grinding wheel of grit size 180~220#. During the rough grinding process, the rotational speed of the columnar substrate is set to 600-1100 r / min, the spindle speed of the grinding machine is set to 50000~80000 RPM, the feed rate is set to 0.003~0.005 mm, and the feed speed is set to 0.05~0.08 mm. The grinding speed is set to 800~1500r / min, the grinding machine spindle speed is set to 50000~80000RPM, the feed rate is set to 0.001~0.003mm, the feed speed is set to 0.03~0.05m / min, and the grinding speed is set to 0.03~0.05m / min. The grinding speed is set to 0.02mm, and the grinding speed is set to 0.02mm ...

[0041] In this preferred embodiment, the positioning method of using an internal cylindrical grinding machine to clamp the outer surface directly transfers the high stability of the outer surface to the machining of the tapered hole. This effectively avoids the coaxiality deviation between the tapered hole and the through hole, or the offset of the center of the tapered hole itself, caused by insufficient positioning datum accuracy. This setup controls the positional error of the tapered hole machining from the source, laying a core foundation for meeting subsequent geometric tolerance requirements such as taper surface runout <0.02mm, and ensuring the precision forming of the part.

[0042] The rough grinding stage efficiently removes excess material, leaving precise space for fine grinding. Specifically, 180~220# diamond grinding wheels are used for rough grinding. Their high hardness is compatible with the high wear resistance of cemented carbide, avoiding a decrease in grinding efficiency caused by rapid wheel wear. Furthermore, a high-speed combination of 600~1100 r / min for the cylindrical substrate, 50000~80000 RPM for the spindle, and a feed rate of 0.003~0.005 mm and a feed speed of 0.05~0.08 mm / min allows for the stable removal of excess material from the tapered hole after EDM, while correcting dimensional fluctuations after rough grinding through a preset number of finishing passes. Finally, a 0.02 mm fine grinding allowance is reserved, avoiding both excessive allowance that increases the burden on fine grinding and insufficient allowance that prevents fine grinding from correcting earlier errors, achieving a balance between efficient material removal and precise allowance.

[0043] In the finish grinding stage, fine-grained CBN grinding wheels are used to improve the accuracy and surface quality of the tapered hole. Specifically, during finish grinding, 320~400# fine-grained CBN grinding wheels (cubic boron nitride grinding wheels) are switched to. Their wear resistance and cutting accuracy are superior to ordinary grinding wheels, making them particularly suitable for the fine grinding requirements of cemented carbide. The fine abrasive grains reduce grinding marks. Combined with parameters such as a columnar matrix rotation speed of 800~1500 r / min (improved compared to coarse grinding, enhancing grinding uniformity), feed rate of 0.001~0.003 mm (reducing unit cutting force), and feed speed of 0.03~0.05 mm / min (reducing grinding impact), the surface roughness and shape accuracy of the tapered hole can be gradually optimized. The preset number of finishing passes further corrects minor dimensional deviations, ultimately helping the tapered hole achieve the required precision indicators such as roundness <0.0005 mm and roughness <Ra0.05, solving the pain point of difficult finish machining of cemented carbide.

[0044] Fine grinding, also known as finishing grinding, is an auxiliary machining step performed after the main cutting stage of rough or fine grinding. It involves maintaining contact between the grinding wheel and the workpiece, but significantly reducing or stopping the feed rate, allowing the grinding wheel to lightly polish the workpiece surface with extremely low cutting intensity. The core purpose of fine grinding is to correct minor dimensional deviations after the main grinding, improve surface flatness and smoothness, reduce machining stress, and adapt to the high hardness and slight deformation characteristics of cemented carbide materials.

[0045] In a preferred embodiment of the present invention, the grinding in step S6 specifically includes: clamping the outer surface of the columnar substrate, selecting a cast iron grinding plate, rotating the grinding plate, and simultaneously rotating the columnar substrate around the grinding plate; the rotation speed of the grinding plate is set to 50~80 r / min, the rotation speed of the columnar substrate is set to 60~100 r / min, and the revolution speed is set to 30~50 r / min; M10 abrasive is added during the processing; the grinding time is set to 30~60 min, until the flatness of the end face of the columnar substrate is less than 0.0009 mm and the roughness is less than 0.1 μm.

[0046] In this preferred embodiment, a cast iron grinding plate is selected as the grinding carrier. It has the characteristics of uniform hardness, strong wear resistance and easy flatness maintenance, and can maintain a high-precision grinding reference for a long time, providing a stable reference surface support for end face flatness control.

[0047] This preferred embodiment employs a composite motion mode of grinding plate rotation, columnar substrate rotation, and revolution. The grinding plate rotation provides continuous grinding power, while the columnar substrate rotation and revolution ensure uniform contact between the grinding plate and the grinding compound at all points on the end face. This avoids localized over-grinding or under-grinding of the end face caused by a single motion, effectively eliminating minor unevenness left by previous processing (such as grinding), helping to achieve the stringent requirement of flatness <0.0009mm, and solving the pain point of uneven machining of cemented carbide end faces.

[0048] By setting the grinding plate speed to 50-80 r / min, the columnar substrate's rotation speed to 60-100 r / min, and its revolution speed to 30-50 r / min, the grinding compound splashing and localized overheating on the end face caused by excessively high plate speed are avoided, while the low grinding efficiency caused by excessively slow speed is also prevented. Simultaneously, the columnar substrate's rotation speed is slightly higher than the grinding plate speed, which enhances the relative friction between the end face and the grinding compound, improving the grinding effect. The lower revolution speed ensures stable movement of the substrate on the plate, preventing positioning misalignment caused by centrifugal force.

[0049] This preferred embodiment uses M10 abrasive, whose grit size is suitable for the semi-finishing requirements of carbide end faces. It can effectively remove surface marks left by previous grinding and will not cause end face scratches due to excessively coarse grit. The grinding time setting of 30~60 minutes ensures that the flatness of the end face is fully corrected while avoiding over-grinding.

[0050] In a preferred embodiment of the present invention, the polishing step S6 specifically includes: clamping the outer surface of the columnar substrate, selecting a polyurethane polishing plate, rotating the polishing plate, and simultaneously rotating the columnar substrate around the polishing plate; the rotation speed of the polishing plate is set to 100~150 r / min, the rotation speed of the columnar substrate is set to 60~80 r / min, the revolution speed is set to 20~40 r / min, 600# diamond polishing fluid is added during the processing, and the polishing time is set to 10~15 min.

[0051] This preferred embodiment uses a polyurethane polishing plate as the polishing carrier, which possesses the characteristics of good flexibility, high fit, and strong wear resistance. On the one hand, the flexible material can avoid scratches or indentations caused to the end face of the cemented carbide during the polishing of the hard plate. Although cemented carbide has high hardness, the polishing stage needs to eliminate minor surface defects rather than create new damage. On the other hand, the good fit allows the plate to fully contact the end face, ensuring uniform polishing of all areas of the end face and avoiding local unpolished or over-polished situations. This meets the need for improving the fine surface quality of the cemented carbide end face from Ra0.1 after grinding to Ra0.05 after polishing, solving the pain point of uneven surface that easily occurs during the fine polishing of hard materials.

[0052] The high-speed setting of the polishing plate is 100~150r / min, which is a significant increase compared to the 50~80r / min speed of the grinding plate in the grinding stage. The higher relative speed enhances the friction between the polishing fluid and the end face, thereby improving the polishing efficiency and quickly removing the fine surface marks left after grinding.

[0053] The columnar substrate has a rotational speed of 60~80 r / min and a revolution speed of 20~40 r / min, which are lower than the rotational speed and revolution speed of the grinding plate, respectively. This can avoid centrifugal force deviation caused by excessive movement of the substrate and ensure that the end face always fits the plate stably.

[0054] 600# fine-grit diamond polishing slurry is selected, its grit size being suitable for the fine polishing requirements of carbide end faces. The fine abrasive effectively removes the minute surface textures left from the grinding stage without causing new surface damage due to excessively coarse grit. The 10-15 minute polishing time setting ensures sufficient time to remove grinding residue and improve surface smoothness, avoiding assembly and fitting problems caused by excessively long polishing time leading to out-of-tolerance end face dimensions or excessively smooth surfaces, thus achieving a balance between fine polishing effect and processing efficiency and dimensional control.

[0055] In summary, after processing using the above methods, the cylindrical parts have an outer circle cylindricity of less than 0.001 mm and a surface roughness of less than 0.1 μm. The conical holes have a conical surface roundness of less than 0.0005 mm, a runout of less than 0.02 mm, and a surface roughness of less than 0.05 μm. The lower end face of the cylindrical parts has a flatness of less than 0.0009 mm and a surface roughness of less than 0.05 μm. All technical indicators meet the product requirements.

[0056] This invention, through the rational design of processing steps, utilizes electrical discharge machining (EDM), precision grinding, and precision polishing technologies. By designing specialized tooling fixtures and selecting appropriate grinding methods and parameters, it consistently ensures the machining accuracy of parts. Practical verification has shown that the machining method for high-hardness alloy cylindrical parts described in this invention can consistently guarantee product quality and quickly produce qualified cylindrical parts.

[0057] Meanwhile, the cemented carbide columnar parts produced by the processing method of this invention achieve micron-level dimensional tolerances and ultra-low surface roughness through precision electrical discharge machining, grinding, and polishing processes. Furthermore, the cemented carbide substrate itself possesses excellent resistance to methanol corrosion, allowing it to be directly adapted to core functional components of methanol diesel engine systems. For example, when used as a tapered orifice guide post for a methanol high-pressure common rail injector, the precise fit between its tapered orifice and the injector needle valve effectively blocks high-pressure methanol leakage. When used as a through-hole valve core for a methanol fuel metering pump, the high precision of its through-hole ensures a methanol flow control error of ≤0.5%, solving industry pain points such as fuel waste, excessive emissions, and component jamming caused by corrosion and insufficient precision in methanol systems. This provides key component support for the efficient and stable operation of methanol fuel diesel engines.

[0058] The above embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A method for machining a columnar part, characterized in that, Includes the following steps: S1, coarsely grind the bar stock to obtain a columnar matrix; S2, the columnar substrate is axially formed with through holes by electrical discharge machining, and the through holes penetrate both axial end faces of the columnar substrate; S3, the through hole is formed into a tapered hole by electrical discharge machining at one end; S4, Grind the outer surface of the columnar substrate to the preset accuracy requirement; S5, Grind the surface of the tapered hole to the preset accuracy requirement; S6, grind and polish the end face of the columnar substrate away from the conical hole in sequence.

2. The method for processing columnar parts according to claim 1, characterized in that, Step S1 specifically includes: selecting a diamond grinding wheel with a particle size of 20# for rough grinding of the bar stock, setting the feed rate to 0.1~0.2mm, setting the feed speed to 0.5~0.8mm / min, and the surface roughness of the columnar matrix obtained by rough grinding is less than 3.2μm.

3. The method for processing columnar parts according to claim 1, characterized in that, The through hole in S2 includes a first channel and a second channel connected along the axial direction, wherein the inner diameter of the second channel is smaller than the inner diameter of the first channel. First, the columnar substrate is subjected to a first electrical discharge machining (EDM) to form the first channel, and then the columnar substrate is subjected to a second EDM to form the second channel.

4. The method for processing columnar parts according to claim 3, characterized in that: The electrode used for the first electrical discharge machining (EDM) is a copper-tungsten alloy electrode. The discharge gap is set to 0.1~0.2mm, the pulse gap to 60~80μs, the servo reference to 70~80%, the voltage to 140~160V, the peak current to 3~5A, the pulse width to 4~6μs, the tool lift height to 3~5mm, the discharge time to 0.4~0.8s, and the upward tool lift speed to 2000~3000mm / min. After machining, the diameter tolerance of the first channel is within 0.02mm, and the surface roughness is less than 1.6μm.

5. The method for processing columnar parts according to claim 3, characterized in that: The electrode used for the first electrical discharge machining (EDM) is a copper-tungsten alloy electrode. The discharge gap is set to 0.1~0.2mm, the pulse gap to 60~80μs, the servo reference to 70~80%, the voltage to 100~120V, the peak current to 2~4A, the pulse width to 4~6μs, the tool lift height to 3~5mm, the discharge time to 0.3~0.6s, and the upward tool lift speed to 2000~3000mm / min. After machining, the diameter tolerance of the second channel is within 0.02mm, and the surface roughness is less than 1.6μm.

6. The method for processing columnar parts according to claim 1, characterized in that, In step S3, the electrode used for electrical discharge machining is a copper-tungsten alloy electrode. The discharge gap is set to 0.1~0.2mm, the pulse gap is set to 60~80μs, the servo reference is set to 70~80%, the voltage is set to 100~120V, the peak current is set to 2.5~5A, the pulse width is set to 4~6μs, the tool lift height is set to 3~5mm, the discharge time is set to 0.25~0.5s, and the upward tool lift speed is set to 2000~3000mm / min. After machining, the angular tolerance of the tapered hole is within 1°, and the surface roughness is less than 1.6μm.

7. The method for processing columnar parts according to claim 1, characterized in that, Step S4 specifically includes: first, using a diamond grinding wheel with a grit size of 60# to rough grind the outer surface of the columnar substrate, setting the feed rate to 0.01~0.03mm and the feed speed to 0.4~0.6mm / min, and grinding for 10s; then, using a diamond grinding wheel with a grit size of 180~220# to fine grind, setting the feed rate to 0.002~0.004mm and the feed speed to 0.3~0.5mm / min, and grinding back and forth a preset number of times, so that the outer surface of the columnar substrate reaches the preset accuracy requirements.

8. The method for processing columnar parts according to claim 1, characterized in that, Step S5 specifically includes: using an internal cylindrical grinding machine to clamp the outer surface of the columnar substrate after grinding, and using a diamond grinding wheel with a grit size of 180~220# for rough grinding. During the rough grinding process, the rotation speed of the columnar substrate is set to 600-1100 r / min, the spindle speed of the grinding machine is set to 50000~80000 RPM, the feed rate is set to 0.003~0.005 mm, the feed speed is set to 0.05~0.08 mm / min, the preset number of finishing grinding cycles is set, and a fine grinding allowance of 0.02 mm is reserved. CBN grinding wheels with a grit size of 320-400# are selected. During the fine grinding process, the rotation speed of the columnar matrix is ​​set to 800~1500 r / min, the spindle speed of the grinding machine is set to 50000~80000 RPM, the feed rate is set to 0.001~0.003 mm, the feed speed is set to 0.03~0.05 m / min, and the number of grinding cycles is preset to ensure that the surface of the tapered hole meets the preset accuracy requirements.

9. The method for processing columnar parts according to claim 1, characterized in that, The grinding process in step S6 specifically includes: clamping the outer surface of the columnar substrate, selecting a cast iron grinding plate, rotating the grinding plate, and simultaneously rotating the columnar substrate around the grinding plate. The grinding plate is set to rotate at a speed of 50-80 r / min, the columnar substrate is set to rotate at a speed of 60-100 r / min and to revolve at a speed of 30-50 r / min. M10 abrasive is added during the processing, and the grinding time is set to 30-60 min until the flatness of the end face of the columnar substrate is less than 0.0009 mm and the roughness is less than 0.1 μm.

10. The method for processing columnar parts according to claim 1, characterized in that, The polishing in step S6 specifically includes: clamping the outer surface of the columnar substrate, selecting a polyurethane polishing plate, rotating the polishing plate, and the columnar substrate rotating on its own axis while revolving around the polishing plate. The rotation speed of the polishing plate is set to 100~150 r / min, the rotation speed of the columnar substrate is set to 60~80 r / min, and the revolution speed is set to 20~40 r / min. 600# diamond polishing fluid is added during the processing, and the polishing time is set to 10~15 min.

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