A semi-additive forming method for a hard alloy inclined counterbore

Abstract

The present invention discloses a semi-additive forming method for a hard alloy inclined counterbore. The method comprises the following steps: (1) Machining preparation: Determine the center alignment point A, the vertical milling cutter machining straight hole alignment point B, and the forming milling cutter machining tapered hole alignment point C according to the actual shape of the hard alloy compact; (2) Aligning the machining center: Make the vertex of the aligner approach the alignment point A to preliminarily align the machining center of the compact; (3) Bottom hole machining: Machine the bottom hole through a vertical milling cutter; (4) Counterbore I / II machining: Machine the two-end counterbores through a forming milling cutter. This semi-additive forming method uses an ordinary press to press the compact without pressing out the inclined counterbore. The inclined counterbore of the compact is machined mechanically, thereby ensuring the uniformity of the compact density, resulting in extremely small deformation of the sintered product, low machining cost, high machining efficiency, and better ensuring the quality of the blank, which is conducive to mass production and reducing production costs.

Description

Technical Field

[0001] The present invention belongs to the technical field of cemented carbide processing, and particularly relates to a semi-additive forming method for inclined counterbores in cemented carbide. Background Art

[0002] Cemented carbide is an alloy material made by powder metallurgy process from refractory metal hard compounds and binding metals. Cemented carbide has a series of excellent properties such as high hardness, wear resistance, good strength and toughness, heat resistance, corrosion resistance, etc. Especially its high hardness and wear resistance remain basically unchanged even at a temperature of 500°C and still have a very high hardness at 1000°C. Cemented carbide is widely used as a tool material, such as turning tools, milling cutters, planing tools, drills, boring tools, etc., for cutting cast iron, non-ferrous metals, plastics, chemical fibers, graphite, glass, stone materials and ordinary steel, and can also be used to cut difficult-to-machine materials such as heat-resistant steel, stainless steel, high-manganese steel, tool steel, etc.

[0003] In some cemented carbide products, inclined counterbores are designed, and the structure of the inclined counterbore is as Figure 1 shown, including a bottom hole with a certain inclination angle and counterbores connected at both ends of the bottom hole. The forming of inclined counterbores is more difficult, and generally, die pressing is used. Die pressing of powder materials is a process of loading a mixture of a certain mass (volume) of alloy powder, inorganic non-metallic powder and a certain molding agent into a rigid die cavity, and then applying a certain amount of pressure to the powder along a single axial direction by the upper and lower die punches, so that the loose powder material is compressed into a green compact with a certain size, shape, density and strength in the closed die cavity, and then the green compact is removed from the die. The whole process includes three steps: powder loading, pressing and demolding. The basic purpose of die pressing is to compact the loose powder body into a semi-finished green compact with a certain size, shape, density and strength, laying a foundation for the next sintering. Generally speaking, in the pressing process, it is relatively easy to achieve a certain size, shape and average density, but it is relatively difficult to make the density distribution of the green compact uniform. The more complex the shape, the more difficult it is to make the density distribution of the green compact uniform. The non-uniformity of the density distribution of the green compact not only ultimately affects the mechanical properties of the product, but also is an important reason for pressing rejects such as cracking, delamination, edge and corner chipping, uneven sintering shrinkage, product deformation, and out-of-tolerance precision of the green compact.

[0004] At present, the presses used for molding are divided into ordinary presses without side pressure and presses with side pressure. If an ordinary press without side pressure is used, it is difficult to ensure the uniformity of the green compact density, resulting in serious deformation and low precision of the sintered product, extremely low pressing efficiency, and extremely low precision grinding efficiency due to the serious deformation and low precision of the sintered product. If a press with side pressure is used, the uniformity of the green compact density can be ensured, achieving the purpose of small deformation of the sintered product, but the investment cost of the press with side pressure is 1 to 2 times higher than that of the ordinary press. When the product output is small, investing in a press with side pressure will make the product production cost too high. Summary of the Invention

[0005] Aiming at the problems of serious deformation, low precision, and extremely low pressing efficiency of the sintered product in the production of hard alloy products with inclined counterbores by using an ordinary press in the prior art, and the high production cost of using a press with side pressure for molding, the purpose of the present invention is to provide a semi-additive manufacturing method for hard alloy inclined counterbores. An ordinary press is used to press the green compact (blank), and the inclined counterbore is not pressed out. The inclined counterbore of the green compact is machined mechanically, that is, the inclined counterbore is machined by using the mechanical machining method of hard alloy green compact (commonly known as semi-additive manufacturing), so as to ensure the uniformity of the green compact density, minimize the deformation of the sintered product, reduce the processing cost, improve the processing efficiency, and better ensure the quality of the blank, which is beneficial to mass production and reduce the production cost.

[0006] To achieve the above purpose, the present invention provides a semi-additive manufacturing method for hard alloy inclined counterbores. The inclined counterbore is designed on the hard alloy product, including a counterbore I, a bottom hole, and a counterbore II with an inclination angle of β and connected in sequence. The counterbore I and the counterbore II are conical hole structures that are centrosymmetric with the bottom hole as the center, the bottom hole is a straight hole structure, and the aperture of the bottom hole is smaller than that of the counterbore I and the counterbore II. When machining the inclined counterbore by the semi-additive manufacturing method, a vertical milling cutter is used to machine the bottom hole, and a forming milling cutter is used to machine the counterbore I and the counterbore II, including the following steps:

[0007] (1) Machining preparation

[0008] Determine the center alignment point A, the vertical milling cutter machining straight hole alignment point B, and the forming milling cutter machining conical hole alignment point C according to the actual shape of the hard alloy green compact and the hole shape size of the inclined counterbore to be machined.

[0009] (2) Aligning the machining center

[0010] Fix the hard alloy green compact on a numerically controlled drilling and milling machine, and adjust the inclination angle of the green compact to β through the numerically controlled drilling and milling machine, so that the central axis of the inclined counterbore to be machined on the green compact is parallel to the main shaft of the numerically controlled drilling and milling machine. Install a centering device on the spindle chuck of the numerically controlled drilling and milling machine, and make the vertex of the centering device close to the alignment point A to preliminarily align the machining center of the green compact.

[0011] (3) Bottom hole machining

[0012] The spindle chuck of the CNC drill - milling machine installs a vertical milling cutter. The vertical milling cutter approaches the alignment point B to determine the starting point of machining. A straight hole with the same diameter as the bottom hole is machined, and the machining depth exceeds the K section of the green compact by 1.5 - 2.0 mm and does not directly drill through the green compact. The K section is the position where the bottom hole is located. The green compact is turned over and fixedly installed on the CNC drill - milling machine, and the vertical milling cutter is used to machine and connect the straight hole, ensuring that the K section of the green compact is not machined.

[0013] (4) Counterbore Ⅰ / Ⅱ machining

[0014] The spindle chuck of the CNC drill - milling machine installs a form - milling cutter. The form - milling cutter approaches the alignment point C to determine the starting point of machining, and a tapered hole Ⅰ with the same hole shape as counterbore Ⅰ is machined. The green compact is turned over and fixedly installed on the CNC drill - milling machine, and a tapered hole Ⅱ with the same hole shape as counterbore Ⅱ is machined.

[0015] For the above semi - finishing forming method of the hard alloy inclined counterbore, the commonly used equipment for the mechanical processing and forming method of hard alloy green compacts (commonly known as semi - finishing forming) is a CNC drill - milling machine and its auxiliary fixture. The present invention has no special restrictions on the processing equipment. In the present invention, the CNC drill - milling machine includes a CNC drill - milling machine body and an accessory tilting rotary worktable. The tilting rotary worktable is installed at the central position of the CNC drill - milling machine body. A vise is also installed at the central position of the tilting rotary worktable, and the hard alloy green compact is fixed on the vise.

[0016] The hard alloy green compact can be fixed on the vise by a conventional fixing method in the art. Preferably, the hard alloy green compact is fixed on the vise through a clamping and positioning device and a clamping device. The clamping and positioning device includes a positioning block installed on the vise, and the clamping device includes two rectangular strip blocks respectively adhered to the two jaws of the vise. The positioning block should be adapted to the outer shape of the product and is provided with a green compact limiting structure. The hard alloy green compact is limited by the positioning block and clamped and fixed by the rectangular strip blocks. Further, on the positioning block.

[0017] For the above semi - finishing forming method of the hard alloy inclined counterbore, in step (3), when machining the bottom hole, trial drilling can be carried out first: measure the center dimension of the hole and finely adjust the coordinate position of the vertical milling cutter to ensure that the center position of the hole meets the processing requirements. In step (4), when machining counterbore Ⅰ, trial drilling can be carried out first: measure the center dimension of the hole and finely adjust the coordinate position of the vertical milling cutter to ensure that the center position of the hole meets the processing requirements. Preferably, when machining the bottom hole, to ensure that the green compact does not lose corners, the machining depth ≤ - 1.0 - 2.0 mm.

[0018] For the above semi - finishing forming method of the hard alloy inclined counterbore, in steps (3) and (4), during the machining process of the bottom hole and counterbore Ⅰ / Ⅱ, the cutter is lifted according to the program 2 - 4 times to ensure chip removal.

[0019] The above semi-additive forming method for the inclined counterbore of cemented carbide, the end mill is preferably a double-edge composite diamond end mill. The forming mill is preferably a double-edge composite diamond forming mill. The tool material uses composite diamond to achieve the purpose of tool durability and dimensional stability. The double edges achieve the purpose of dimensional stability and good chip evacuation. The forming mill achieves the purpose of improving processing efficiency.

[0020] The above semi-additive forming method for the inclined counterbore of cemented carbide, the cemented carbide compact is preferably pressed by a common press without side pressure.

[0021] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0022] (1) The semi-additive forming method for the inclined counterbore of cemented carbide provided by the present invention can use a common press to press the compact, and use the cemented carbide compact to mechanically process the inclined counterbore (commonly known as semi-additive forming), so as to ensure the uniformity of the compact density. After sintering, the product deformation is extremely small, the blank allowance is uniform, and the symmetry is good. Therefore, the blank and precision grinding processing efficiency are high, thus effectively ensuring the product quality.

[0023] (2) The semi-additive forming method for the inclined counterbore of cemented carbide provided by the present invention does not need to invest in a press with side pressure, reduces the processing cost, the processing equipment is conventional, the operation is simple, the manufacturing cost of the clamping and positioning device and the clamping device for fixing is low, and it is easy to manufacture, which is conducive to mass production and is worthy of popularization and application in this field. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of a cemented carbide product designed with an inclined counterbore;

[0025] Figure 2 It is a schematic diagram of the double-edge composite diamond end mill in the embodiment;

[0026] Figure 3 It is a schematic diagram of the double-edge composite diamond end mill in the embodiment;

[0027] Figure 4 It is a schematic diagram of the alignment for machining the inclined counterbore in the embodiment, where (a) represents the alignment of the center of the centering device, (b) represents the alignment of the end mill for machining the straight hole, and (c) represents the alignment of the forming mill for machining the tapered hole.

[0028] Description of the reference numerals: 1, centering device; 2, end mill; 3, forming mill. DETAILED DESCRIPTION OF THE INVENTION

[0029] In order to clearly and completely describe the technical solutions of the embodiments of the present invention with reference to the accompanying drawings, it is obvious that the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the present invention.

[0030] The semi-additive forming method of the hard alloy inclined counterbore provided in this embodiment has the inclined counterbore designed on the hard alloy compact, and its structure is as Figure 1 shown. The length of the hard alloy compact is L, the height is H, and the width is A; the inclined counterbore includes a counterbore I, a bottom hole, and a counterbore II with an inclination angle of β and connected in sequence. The bottom hole is a straight hole structure, that is, a straight hole Φ1; the counterbore I and the counterbore II are conical hole structures that are centrosymmetric with the bottom hole as the center, that is, a conical hole Φ2, and the conical hole Φ2 includes an α1 angle and an α2 angle; the aperture of the bottom hole is smaller than that of the counterbore I and the counterbore II. In this embodiment, a small CNC drill milling machine is used as the processing host, and the auxiliary fixtures are a tilting rotary table and a vise. The tilting rotary table is installed at the middle position on the workbench of the small CNC drill milling machine, and the vise is installed at the middle position on the tilting rotary table. The hard alloy compact is fixed on the vise through a clamping and positioning device and a clamping device; the clamping and positioning device is a positioning block installed on the vise, and the clamping device is two rectangular blocks respectively adhered to the two jaws of the vise. The positioning block should be adapted to the outer shape of the product, and it is provided with a compact limiting structure. The hard alloy compact is limited by the positioning block, and the hard alloy compact is clamped and fixed by the rectangular blocks.

[0031] The cutting tool material for processing is composite diamond. A customized double-edge composite diamond end mill is used for the bottom hole, and the structure of the double-edge composite diamond end mill is as Figure 2 shown. The maximum diameter of the cutter head of the end mill is the same as the diameter of the bottom hole; customized double-edge composite diamond forming mills are used for the two end counterbores, and the structure of the double-edge composite diamond forming mill is as Figure 3 shown. The size of the cutter head of the forming mill is adapted to the shape size of the counterbore, and the cutter head of the forming mill has an α1 angle and an α2 angle. The purpose of using composite diamond is to achieve the durability and dimensional stability of the cutting tool, the purpose of using double edges is to achieve dimensional stability and good chip evacuation, and the purpose of using the forming mill is to improve the processing efficiency.

[0032] The aforementioned inclined counterbore is processed by the semi-additive forming method, which specifically includes the following steps:

[0033] (1) Processing preparation

[0034] Draw a semi-additive product drawing according to the product drawing and the shrinkage coefficient, customize an end mill for processing the bottom hole and a forming mill for processing the counterbore I and the counterbore II according to the hole shape size of the semi-additive product drawing, and make a centering device, as Figure 4As shown, according to the actual shape of the cemented carbide compact and the hole shape dimensions of the inclined counterbore to be machined, use a height gauge to draw the center alignment point A, the straight hole machining alignment point B for the end mill, and the tapered hole machining alignment point C for the form milling cutter;

[0035] (2) Align the machining center

[0036] Fix the cemented carbide compact on the numerically controlled drill and milling machine. The length direction (L direction) of the compact is parallel to the X-axis, and adjust the inclination angle of the compact to β through the numerically controlled drill and milling machine so that the central axis of the inclined counterbore to be machined on the compact is parallel to the spindle of the numerically controlled drill and milling machine; Install a centering device 1 on the spindle chuck of the numerically controlled drill and milling machine. As Figure 4 (a) shown, make the vertex of the centering device 1 close to the alignment point A to preliminarily align the machining center of the compact;

[0037] (3) Machining of the bottom hole

[0038] Install an end mill 2 on the spindle chuck of the numerically controlled drill and milling machine. As Figure 4 (b) shown, make the end mill 2 close to the alignment point B to determine the machining starting point, and machine a straight hole Φ1 with the same diameter as the bottom hole:

[0039] Drill Φ1 for trial, measure the center dimension of the hole, and finely adjust the coordinate position of the end mill to ensure that the center position of the hole meets the requirements of the drawing; Machine Φ1. To ensure that the product does not have corners broken off, the machining depth H1 ≤ -1.0 to 2.0 mm, the machining depth exceeds the K section of the compact by 1.5 to 2.0 mm and does not directly drill through the compact. During the machining process, lift the tool according to the program 4 to 6 times to ensure chip evacuation. The K section is the position where the bottom hole is located; Turn the compact over and fix it on the numerically controlled drill and milling machine, and use the end mill 1 to machine and connect the straight hole, and ensure that the K section of the compact is not machined. During the machining process, lift the tool according to the program 2 to 4 times to ensure chip evacuation;

[0040] (4) Machining of counterbore Ⅰ / Ⅱ

[0041] Install a form milling cutter 3 on the spindle chuck of the numerically controlled drill and milling machine. As Figure 4 (c) shown, make the form milling cutter 3 close to the alignment point C to determine the machining starting point, and machine a tapered hole Ⅰ Φ2 with the same hole shape as counterbore Ⅰ:

[0042] Drill Φ2 for trial, measure the size of the hole center, and finely adjust the coordinate position of the form milling cutter 3 to ensure that the center position of the hole meets the requirements of the drawing; Machine Φ2, α1, α2, with a depth of H2. During the machining process, lift the tool according to the program 2 to 4 times to ensure chip evacuation; Turn the compact over and fix it on the numerically controlled drill and milling machine, and machine a tapered hole Ⅱ on the other side of the compact, that is, Φ2, α1, α2 on the other side of the compact, with a depth of H2. During the machining process, lift the tool according to the program 2 to 4 times to ensure chip evacuation.

[0043] It should be noted that during the entire machining process, the machining surface of the product must be gently blown with compressed air to ensure chip evacuation.

[0044] Those of ordinary skill in the art will realize that the embodiments described herein are for helping readers understand the principles of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific deformations and combinations that do not depart from the essence of the present invention based on these technical revelations disclosed in the present invention, and these deformations and combinations are still within the protection scope of the present invention.

Claims

1. A semi-additive forming method for a hard alloy inclined counterbore, characterized in that: The inclined counterbore is designed on the cemented carbide product, including a counterbore I, a bottom hole, and a counterbore II with an inclination angle of β and connected in sequence. The counterbore I and the counterbore II are conical hole structures that are centrosymmetric with the bottom hole as the center, the bottom hole is a straight hole structure, and the aperture of the bottom hole is smaller than that of the counterbore I and the counterbore II. The semi-additive manufacturing method is used to machine the inclined counterbore. When machining, a end mill is used to machine the bottom hole, and a form milling cutter is used to machine the counterbore I and the counterbore II, including the following steps: (1) Machining preparation Determine the center alignment point A, the end mill machining straight hole alignment point B, and the form milling cutter machining conical hole alignment point C according to the actual shape of the cemented carbide compact and the hole shape dimensions of the inclined counterbore to be machined. (2) Align the machining center Fix the cemented carbide compact on the CNC drill and milling machine, and adjust the inclination angle of the compact to β through the CNC drill and milling machine, so that the central axis of the inclined counterbore to be machined on the compact is parallel to the spindle of the CNC drill and milling machine. Install a centering device on the spindle chuck of the CNC drill and milling machine, and make the vertex of the centering device close to the alignment point A to preliminarily align the machining center of the compact. (3) Bottom hole machining Install an end mill on the spindle chuck of the CNC drill and milling machine. The end mill approaches the alignment point B to determine the machining starting point, and machine a straight hole with the same aperture as the bottom hole. The machining depth exceeds the K section of the compact by 1.5 - 2.0 mm and does not directly drill through the compact. The K section is the position where the bottom hole is located. Turn the compact over and fix it on the CNC drill and milling machine, and use the end mill to machine and connect the straight hole, and ensure that the K section of the compact is not machined. (4) Counterbore I / II machining Install a form milling cutter on the spindle chuck of the CNC drill and milling machine. The form milling cutter approaches the alignment point C to determine the machining starting point, and machine a conical hole I with the same hole shape as the counterbore I. Turn the compact over and fix it on the CNC drill and milling machine, and machine a conical hole II with the same hole shape as the counterbore II.

2. The semi-additive forming method of the hard alloy inclined counterbore according to claim 1, wherein: The CNC drill and milling machine includes a CNC drill and milling machine body and an accessory tilting rotary table. The tilting rotary table is installed at the center position of the CNC drill and milling machine body, and a vise is also installed at the center position of the tilting rotary table. The cemented carbide compact is fixed on the vise.

3. The semi-additive forming method of the hard alloy inclined counterbore according to claim 2, wherein: The cemented carbide compact is fixed on the vise through a clamping and positioning device and a clamping device; the clamping and positioning device includes a positioning block installed on the vise and having a compact limiting structure, and the clamping device includes two rectangular strip blocks respectively adhered to the two jaws of the vise.

4. The semi-additive forming method of the hard alloy inclined counterbore according to claim 1, characterized in that: In the steps (3) and (4), during the machining process, the tool is lifted according to the program 2 - 4 times to ensure chip removal.

5. The semi-additive forming method of the hard alloy inclined counterbore according to claim 1, characterized in that: The end mill is a double-edge composite diamond end mill.

6. The semi-additive forming method of the hard alloy inclined counterbore according to claim 1, characterized in that: The form milling cutter is a double-edge composite diamond form milling cutter.

7. The semi-additive forming method of the hard alloy inclined counterbore according to claim 1, characterized in that: The cemented carbide compact is pressed by a press without side pressure.

Images