A small box type part batch production of fine boring tooling

Abstract

The utility model relates to the technical field of machining frock, disclose a kind of precision boring frock for batch production of small box body class parts, including box, backing plate and split type positioning pin, the backing plate is set at the right side of box, the backing plate left side is part positioning surface, the part positioning surface of the backing plate is equipped with the four first group coarse positioning counterbore of rectangular vertex type distribution, the inner wall of the first group coarse positioning counterbore is equipped with backing plate precision positioning pin hole, the inner wall of the backing plate precision positioning pin hole is equipped with split type positioning pin fixed screw hole, the part positioning surface of the backing plate is equipped with the four second group coarse positioning counterbore of rectangular vertex type distribution. In the utility model, positioning pin precision cooperation is adopted, and cutting deformation and tool wear have no influence on positioning accuracy, so that multiple parts can be used universally, and the same type of parts do not need to be individually fitted with frock. The utility model is suitable for multiple machine tools, and the semi-finish or finish machining process is shared. The frock interchange rate reaches 100%.

Description

Technical Field

[0001] This utility model relates to the field of machining tooling technology, and in particular to a precision boring tooling for mass production of small box-shaped parts. Background Technology

[0002] Small box-shaped parts are core load-bearing components of precision instruments and equipment. Their machining accuracy, such as hole diameter tolerance, coaxiality, and end face perpendicularity, directly determines the assembly performance of the equipment. Traditional processes for manufacturing these parts have the following problems: 1. High equipment costs: Precision machining typically uses high-priced equipment such as five-axis machining centers and horizontal coordinate boring machines, which significantly increases labor costs during medium and large-volume production. 2. Poor tooling interchangeability: In the prior art, such as "a precision milling device for batch production of small frames" (application publication number CN115229250A), although the clamping problem of small-batch precision milling of small frames is solved, the precision milling device relies on the fit between the pallet step and the inner cavity of the part (fitting clearance 0.02~0.04mm). Due to the influence of cutting deformation and tool wear, multiple trial fittings are required according to the actual inner cavity size of the part, which increases the manufacturing time of a single tooling. Moreover, in medium and large batch production, as the number of parts in each batch increases, the consistency of the fitting clearance deteriorates, making it impossible to achieve universality of all parts in each batch or shared use of semi-finishing / finishing processes. 3. Low positioning accuracy: In existing technologies, such as "a precision boring device for aluminum alloy thin-walled frames" (application publication number CN112658334A), although the clamping problem of high-precision machining of small frames is solved, the tooling needs to be disassembled and re-clamped and corrected when changing parts in batch production, resulting in poor dimensional consistency of batch production parts; although the pressure plate clamping method takes certain measures to balance the force and reduce the amount of clamping deformation, it still cannot better eliminate the deformation of parts caused by clamping force; 4. Long auxiliary time: It is well known that changing parts in precision boring requires disassembling and assembling the tooling and repeated alignment. Auxiliary time accounts for more than 30% of the total processing time, resulting in low production efficiency.

[0003] While existing technologies have solved the clamping problem for small-batch precision milling and boring of small box-shaped parts, they cannot meet the higher requirements for interchangeability and positioning accuracy in medium- and large-batch precision boring (milling) machining. Therefore, there is an urgent need for an integrated tooling for precision boring (milling) that is suitable for medium- and large-batch production and combines high interchangeability, high precision, and low cost. Utility Model Content

[0004] To overcome the above shortcomings, this utility model provides a precision boring tooling for the mass production of small box-shaped parts, aiming to solve the problems of high equipment cost, poor tooling interchangeability, low positioning accuracy, and long auxiliary time in the prior art.

[0005] To achieve the above objectives, this utility model adopts the following technical solution: a precision boring fixture for mass production of small box-shaped parts, comprising a box body, a pallet, and split-type locating pins. The pallet is located on the right side of the box body, and the left side of the pallet is the part positioning surface. The part positioning surface of the pallet has four first-group coarse positioning countersunk holes arranged in a rectangular vertex pattern. The inner wall of each of the first-group coarse positioning countersunk holes is provided with a pallet precision locating pin hole. The inner wall of each of the pallet precision locating pin holes is provided with a split-type locating pin fixing screw hole. The part positioning surface of the pallet has four second-group coarse positioning countersunk holes arranged in a rectangular vertex pattern. The inner wall of each of the second-group coarse positioning countersunk holes is provided with a part fixing hole. The part positioning surface of the pallet also has four pallet fixing holes one, four pallet fixing holes two, and a reference. Holes; the split-type positioning pin is set on the inner wall of the split-type positioning pin fixing screw hole, and the split-type positioning pin has a through positioning pin fastening hole in the central axis. The split-type positioning pin and the fine positioning pin hole of the support plate are fixedly connected by positioning pin fastening screws; the right side of the box is the part machining positioning surface. The part machining positioning surface of the box is provided with four process bosses one corresponding to the first set of coarse positioning countersunk holes on the support plate. The end face of the process boss one is provided with part fine positioning pin holes corresponding to the fine positioning pin holes of the support plate. The inner wall of the part fine positioning pin holes is provided with screw head clearance holes. The part machining positioning surface of the box is provided with four process bosses two corresponding to the second set of coarse positioning countersunk holes on the support plate. The end face of each process boss two is provided with part fastening screw holes corresponding to the part fixing holes on the support plate.

[0006] As a further description of the above technical solution: The pallet is a rectangular plate structure made of No. 45 steel with a surface heat treatment of HRC28~32. The flatness of the pallet parts positioning surface is no more than 0.005mm.

[0007] As a further description of the above technical solution: The split positioning pin has a cylindrical structure, is made of 4Cr5MoSiV1, and has a surface hardness of HRC58~62. The end of the positioning pin is provided with a 15° guide cone surface for guiding and positioning during part assembly.

[0008] As a further description of the above technical solution: The outer diameter of the head of the positioning pin fastening screw is machined to be 1mm smaller than the outer diameter of the split positioning pin, and the height of the head of the positioning pin fastening screw is 0.5mm less than the depth of the screw head clearance hole on the process boss of the part.

[0009] As a further description of the above technical solution: The outer circle of process boss one and process boss two has a clearance of 0.2-0.3mm when it fits with the rough positioning countersunk hole of the support plate, the clearance between the split positioning pin and the fine positioning pin hole of the part is 0.005-0.01mm, and the length of the split positioning pin and the fine positioning pin hole of the part is 5mm.

[0010] As a further description of the above technical solution: The heights of process boss one and process boss two on the machining positioning surface of the part are both less than the depth of the coarse positioning countersunk hole of the pallet, the flatness of the machining positioning surface of the part is not greater than 0.008mm, and the contact area with the positioning surface of the pallet part is ≥90%.

[0011] This utility model has the following beneficial effects: 1. In this utility model, the positioning pin is used for precision fit. Cutting deformation and tool wear have no effect on positioning accuracy. It can realize the common use of multiple parts. Parts of the same model do not need to be individually tested with tooling. It is universal for multiple machine tools and can be used for semi-finishing or finishing processes. There is no need to change tooling, and the tooling interchangeability rate reaches 100%.

[0012] 2. In this utility model, the clearance of the positioning pin is only 0.005 to 0.01 mm, which is an order of magnitude higher than that of the known four-axis precision milling fixture; the screw fixing is used instead of the pressure plate clamping, and the clamping deformation is ≤0.003 mm.

[0013] 3. In this utility model, under medium and large batch production, after the first piece is corrected, replacing parts only requires clamping and tightening, which greatly reduces the auxiliary time for each batch and significantly reduces the processing cost. Attached Figure Description

[0014] Figure 1 This is a three-dimensional structural diagram of the overall structure of this utility model; Figure 2 This is a three-dimensional structural diagram of the tray in this utility model; Figure 3 This is a three-dimensional structural diagram of the box body in this utility model; Figure 4 This is a three-dimensional cross-sectional view of the split positioning pin in this utility model; Figure 5 This is a three-dimensional cross-sectional view of the process boss one in this utility model.

[0015] Legend: 1. Housing; 2. Pallet; 3. Four-axis indexing plate; 4. Split-type locating pin; 5. Locating pin fastening screw; 6. First set of coarse locating countersunk holes; 7. Pallet fine locating pin hole; 8. Split-type locating pin fixing screw hole; 9. Second set of coarse locating countersunk holes; 10. Part fixing hole; 11. Pallet fixing hole one; 12. Pallet fixing hole two; 13. Reference hole; 14. Process boss one; 15. Part fine locating pin hole; 16. Screw head clearance hole; 17. Process boss two; 18. Part fastening screw hole; 19. Guide cone surface; 20. Locating pin fastening hole. Detailed Implementation

[0016] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0017] Reference Figure 1 - Figure 3 This utility model provides an embodiment of a precision boring tooling for mass production of small box-shaped parts, including a box body 1, a support plate 2, and a split positioning pin 4. The support plate 2 is located on the right side of the box body 1. The support plate 2 is machined as follows: CNC milling rough milling of the outline → heat treatment HRC28~32 → CNC milling fine milling of the outline and parallelism of both ends ≤0.03mm → aging treatment → surface grinding of both ends with flatness ≤0.005mm and parallelism ≤0.008mm → drilling φ12+0.3+0.2 and φ15+0.3+0.2 rough positioning countersunk holes corresponding to the first group of rough positioning countersunk holes 6, the second group of rough positioning countersunk holes 9, φ9 part fixing hole 10, support plate fixing hole one 11 adapted to M10 T-shaped nuts 4×φ11 and countersunk hole φ18, support plate fixing hole two 12 adapted to M12 T-shaped nuts. The nut has 4×φ13.5 and a countersunk hole φ22. Drill and ream the precision positioning pin hole 7φ8H7 of the support plate. Drill and tap the M5 split positioning pin fixing screw hole 8. The center of the support plate 2 is precision milled with a reference hole 13 with a diameter of φ30mm and a depth of 8mm. The left side of the support plate 2 is the part positioning surface. The part positioning surface of the support plate 2 has four first group coarse positioning countersunk holes 6 distributed in a rectangular vertex pattern. The inner wall of the first group coarse positioning countersunk holes 6 is provided with the support plate precision positioning pin hole 7. The inner wall of the support plate precision positioning pin hole 7 is provided with the split positioning pin fixing screw hole 8. The part positioning surface of the support plate 2 has four second group coarse positioning countersunk holes 9 distributed in a rectangular vertex pattern. The inner wall of the second group coarse positioning countersunk holes 9 is provided with the part fixing hole 10. The part positioning surface of the support plate 2 also has four support plate fixing holes one 11, four support plate fixing holes two 12 and a reference hole 13.

[0018] Reference Figure 2 - Figure 4The split-type locating pin 4 is set on the inner wall of the split-type locating pin fixing screw hole 8. The processing steps of the split-type locating pin 4 are as follows: forging material → annealing → rough turning the outer diameter φ8mm and the 15° guide cone surface 19 with grinding allowance, drilling the locating pin fastening hole 20φ5.2mm to the size, turning the total length to leave 4 pieces of chucks → quenching treatment HRC58~62, using a high-temperature resistant protective plug to protect the inner hole → fine grinding the outer diameter φ8 to match the gap of 0.005~0.01mm with the precision locating pin hole 7 of the support plate, and grinding the 15° guide cone surface 19 → wire cutting the total length of the chuck to 10mm to the size; pre-installing the split-type locating pin 4: insert the four split-type locating pins 4 into the precision locating pin holes 7 of the support plate respectively, and use the locating pin fastening screws 5 to secure the split-type locating pins. Pin 4 is fixed in the precision positioning pin hole 7 of the support plate; the support plate 2 is installed on the four-axis indexing plate 3, and the screw corresponding to the T-nut specification is connected to the T-nut in the T-slot of the table but not tightened; the inner circle of the reference hole 13 of the support plate 2 is checked with a dial indicator, and the position of the support plate 2 is adjusted so that the coaxiality of the reference hole 13 and the axis of the four-axis indexing plate 3 is ≤0.005mm. The screws are tightened symmetrically in a cross pattern using a torque wrench to achieve fixation (tightening torque: 8.8 grade hexagon socket screw M1040N.m, M1275N.m). The split positioning pin 4 has a through positioning pin fastening hole 20 in the center axis, and the split positioning pin 4 and the precision positioning pin hole 7 of the support plate are fixedly connected by positioning pin fastening screws 5.

[0019] Reference Figure 1 , Figure 3 and Figure 5 The right side of the housing 1 is the part machining positioning surface. During rough milling of the housing 1, the φ12 process boss 14 and φ15 process boss 27 are milled on the machining positioning surface of the housing 1. The process bosses are retained after rough milling. During finish milling, the 8 process bosses (the end faces of process boss 14 and process boss 27) are first milled using a CNC milling machine in vertical milling mode. The φ8H7 part precision positioning pin hole 15 is drilled and reamed, the φ7.2 screw head clearance hole 16 is drilled with a depth greater than the head height of the positioning pin fastening screw 5 by 0.5mm, and the M8 part fastening screw hole 18 is drilled and tapped. The part machining positioning surface of the housing 1 is then finish milled, with a flatness of no more than 0.008mm. The part machining positioning surface of the housing 1 is provided with four process bosses 11 corresponding to the first set of rough positioning countersunk holes 6 on the support plate 2. 4. The end face of the process boss 14 is provided with a fine positioning pin hole 15 corresponding to the fine positioning pin hole 7 of the support plate. The inner wall of the fine positioning pin hole 15 is provided with a screw head clearance hole 16. The part processing positioning surface of the box body 1 is provided with four process bosses 2 17 corresponding to the second set of coarse positioning countersunk holes 9 on the support plate 2. The end face of each process boss 2 17 is provided with a part fastening screw hole 18 corresponding to the part fixing hole 10 on the support plate 2. Small box-type parts are coarsely positioned by the outer circle of the process boss 14 and process boss 2 17 cooperating with the coarse positioning countersunk hole of the support plate, and radial and axial fine positioning by the cooperation of the split positioning pin 4 with the fine positioning pin hole 15. The parts are fixed by the part fixing screw passing through the part fixing hole 10 of the support plate and connecting with the part screw hole.

[0020] Reference Figure 1 , Figure 2 and Figure 4 The support plate 2 is a rectangular plate structure made of 45# steel with a surface heat-treated surface of HRC28-32. The flatness of the positioning surface of the support plate 2 is no greater than 0.005mm. The split positioning pin 4 is a cylindrical structure made of 4Cr5MoSiV1 with a surface hardness of HRC58-62. The end of the positioning pin has a 15° guide cone surface 19 for guiding and positioning during part assembly. The outer diameter of the head of the positioning pin fastening screw 5 is machined to be 1mm smaller than the outer diameter of the split positioning pin 4, and the head height of the positioning pin fastening screw 5 is 0.5mm less than the depth of the screw head clearance hole 16 on the process boss 14 of the part. The outer diameters of process bosses 14 and 17 and the first set of coarse positioning countersunk holes 6 and 9 of the support plate 2 have a clearance of 0.2-0.3 mm. The clearance between the split positioning pin 4 and the fine positioning pin hole 15 of the part is 0.005-0.01 mm. The length of the fit between the split positioning pin 4 and the fine positioning pin hole 15 of the part is 5 mm. This tooling has good interchangeability. The support plate 2 is provided with at least two sets of support plate fixing holes with different spacings (support plate fixing hole 11 and support plate fixing hole 22), which can be adapted to different manufacturers. The four-axis indexing plate has a 3T-slot spacing and is suitable for semi-finishing milling and finishing boring processes of small box-type parts. It can realize multi-machine collaboration and rolling operation of production scheduling for medium and large batch production. The height of the process boss 14 and process boss 27 on the machining positioning surface of the box 1 part is less than the depth of the first group of coarse positioning countersunk holes 6 and the second group of coarse positioning countersunk holes 9 of the support plate 2. The flatness of the machining positioning surface of the box 1 part is not greater than 0.008mm, and the contact area with the positioning surface of the support plate 2 part is ≥90%.

[0021] Working principle: During use, the guide cone surface 19 of the split-type locating pin 4 assists in insertion, mounting the housing 1 onto the support plate 2. The contact area between the housing 1 and the part locating surface of the support plate 2 is ≥90%. Coarse positioning is achieved by the outer circle of the process boss 14 and process boss 17 of the housing 1 engaging with the first set of coarse positioning countersunk holes 6 and the second set of coarse positioning countersunk holes 9 of the support plate 2. Radial and axial fine positioning is achieved by the split-type locating pin 4 engaging with the fine positioning pin hole 15 of the part. The zero point of the process boss 14 of the housing 1 is then positioned. Align the precision positioning pin hole 15 of the component with the split positioning pin 4 of the support plate 2. Connect the M8 component fixing screws through the component fixing holes 10 of the support plate 2 and the component fastening screw holes 18 of the housing 1. If not tightened, press the dial indicator head against the surface to be machined on the housing 1. Use a torque wrench to tighten the screws symmetrically in a crisscross pattern to achieve fixation. The tightening torque for the M8 8.8 grade hex socket screws is 40 N·m. Simultaneously measure the change in the dial indicator reading before and after tightening the screws. The change should be controlled within 0.003 mm. The clamping deformation of housing 1 in this state meets the machining requirements; the solidified precision milling CNC program is invoked, and the four-axis indexing plate 3 rotates 0°, 90°, 180°, and 270° to perform a one-time precision milling of the circumferential grooves, bosses, end faces, holes, and other structures of housing 1. Allowances are left for the mounting end faces and mounting holes with dimensional and geometric tolerance requirements, and other dimensions are precision milled to the required specifications; without disassembling the tooling, the solidified precision boring CNC program is invoked, and the four-axis indexing plate 3 rotates 0°, 90°, 180°, and 270° to perform a one-time precision boring of the housing. The structure, including the mounting end face and mounting holes, is completed to the required specifications. After machining, the tooling interchangeability of the multi-machine-tooled box 1 parts, which are machined using a shared precision boring and milling fixture for semi-finishing / finishing processes, is 100%. The hole diameter tolerance φ50H7, the coaxiality of the two holes φ0.01mm, the perpendicularity to the mounting end face 0.01mm, and the perpendicularity of the two sets of cross-shaped hole axes 0.01mm are all qualified. When changing to the next box 1 part for machining, it is only necessary to remove the part fixing screws and repeat the above steps.

[0022] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A precision boring fixture for mass production of small box-shaped parts, characterized in that: The device includes a housing (1), a tray (2), and a split positioning pin (4). The tray (2) is located on the right side of the housing (1). The left side of the tray (2) is a part positioning surface. The part positioning surface of the tray (2) is provided with four first group of coarse positioning countersunk holes (6) distributed in a rectangular vertex pattern. The inner wall of each of the first group of coarse positioning countersunk holes (6) is provided with a tray fine positioning pin hole (7). The inner wall of each of the tray fine positioning pin holes (7) is provided with a split positioning pin fixing screw hole (8). The part positioning surface of the tray (2) is provided with four second group of coarse positioning countersunk holes (9) distributed in a rectangular vertex pattern. The inner wall of each of the second group of coarse positioning countersunk holes (9) is provided with a part fixing hole (10). The part positioning surface of the tray (2) is also provided with four tray fixing holes one (11), four tray fixing holes two (12), and a reference hole (13). The split positioning pin (4) is set on the inner wall of the split positioning pin fixing screw hole (8). The split positioning pin (4) has a through positioning pin fastening hole (20) in the central axis. The split positioning pin (4) is fixedly connected to the fine positioning pin hole (7) of the support plate by positioning pin fastening screw (5). The right side of the box body (1) is the part processing positioning surface. The part processing positioning surface of the box body (1) is provided with four process bosses (14) corresponding to the first set of coarse positioning countersunk holes (6) on the support plate (2). The end face of the first process boss (14) is provided with a fine positioning pin hole (15) corresponding to the fine positioning pin hole (7) of the pallet. The inner wall of the fine positioning pin hole (15) is provided with a screw head clearance hole (16). The part processing positioning surface of the box body (1) is provided with four second process bosses (17) corresponding to the second set of coarse positioning countersunk holes (9) on the pallet (2). The end face of the second process boss (17) is provided with a fastening screw hole (18) corresponding to the part fixing hole (10) on the pallet (2).

2. The precision boring fixture for mass production of small box-type parts according to claim 1, characterized in that: The pallet (2) is a rectangular plate structure made of No. 45 steel. The surface is heat-treated to HRC28-32. The flatness of the positioning surface of the pallet (2) is no more than 0.005mm.

3. The precision boring fixture for mass production of small box-type parts according to claim 1, characterized in that: The split positioning pin (4) is a cylindrical structure made of 4Cr5MoSiV1 with a surface hardness of HRC58~62. The end of the positioning pin is provided with a 15° guide cone surface (19) for guiding and positioning during part assembly.

4. The precision boring fixture for mass production of small box-type parts according to claim 1, characterized in that: The outer diameter of the head of the positioning pin fastening screw (5) is machined to be 1 mm smaller than the outer diameter of the split positioning pin (4), and the height of the head of the positioning pin fastening screw (5) is 0.5 mm less than the depth of the screw head clearance hole (16) on the process boss (14) of the part.

5. The precision boring fixture for mass production of small box-type parts according to claim 1, characterized in that: The outer circle of the process boss one (14) and process boss two (17) has a clearance of 0.2 to 0.3 mm with the rough positioning countersunk hole of the support plate, the clearance between the split positioning pin (4) and the fine positioning pin hole (15) of the part is 0.005 to 0.01 mm, and the length of the split positioning pin (4) and the fine positioning pin hole (15) of the part is 5 mm.

6. The precision boring fixture for mass production of small box-type parts according to claim 1, characterized in that: The heights of the process boss one (14) and process boss two (17) on the part machining positioning surface are both less than the depth of the coarse positioning countersunk hole of the pallet, the flatness of the part machining positioning surface is not greater than 0.008mm, and the contact area with the part positioning surface of the pallet is ≥90%.

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