The production of fixtures is a comprehensive science. It requires us to clarify the design tasks, analyze the part drawings, master the machining process specifications of the workpiece, understand the role, shape, structural characteristics, materials and technical requirements of the workpiece; the surface, requirements, allowance, positioning reference, clamping Surface and other aspects of information. Practice has proved that only by constantly summing up experience, carefully collecting design materials, mastering the design, rationally drafting the structural scheme of the fixture, and correctly arranging the manufacturing process and assembly process. Even on the basis of limited conditions, it is possible to produce a clip structure with reasonable structure, reliable positioning, and economical and practical. The design and application of the fixture greatly facilitates the processing of round or shaft parts, has a simple structure and convenient operation, can reduce cost, improve work efficiency, ensure quality, and has good promotion and application value.

When the groove width of the machined part is less than or equal to 1MM, it is difficult to machine with ordinary mechanical equipment. The smaller the cutting tool, the more difficult the machining is, and even the machining cannot be processed. In this case, the electric discharge wire in special processing must be used. Cutting or other electrical processing equipment can solve the processing of parts in narrow grooves. The circumferentially uniform narrow groove machining on the online cutting machine has always been regarded as one of the more difficult processes. Therefore, the idea of ​​developing auxiliary fixtures has been germinated, and the technical problems of processing batch products on the online cutting machine have been solved through good use. .

Not long ago, a company commissioned us to process a batch of ring products. In the production and processing of the part, a favorable experiment was made on the groove groove width of only 0.2 MM and the circumferentially uniform narrow groove, and good results were obtained. The basic dimensions of the part: φ48MM × 75MM, the material is 45 steel.

First, the technical analysis of the ring

(1) The accuracy of position and position is high;

(2) The perpendicularity of the hole of φ48 with respect to the end face is 0.02;

(3) The coaxiality of the two holes of φ16 and φ27 is 0.025;

(4) The center of the 12 slots relative to the central axis requires 0.02;

(5) The positioning size is higher;

Six of the 12 slots have a circular hole length of 50 mm and the other six lengths are 35 mm. The lengths are separated by one length and one short and the center circle is required to be evenly distributed. The upper deviation of the groove width is 0.02, and the lower deviation is 0.

The processing requirements for the notch are: tolerance of 0.2MM width, length of 50MM and 35MM, surface roughness of RA3.2μM, and 12 slots are required to be evenly distributed on the center circle. To ensure the accuracy requirements, this process is required. In terms of the processing of the workpiece, it is quite difficult to find the correct clamping, so it is necessary to carry out careful analysis and develop the corresponding processing process.

The conventional machining process of the workpiece is: (1) First, six uniform lines are drawn on the workpiece, and then the workpiece is scribed by direct visual inspection. There is an error in finding the positive line with the naked eye, the processing quality cannot be guaranteed, and waste products are often generated, causing great losses to the enterprise. Its characteristic is that it is difficult to ensure the dimensional tolerance and the consistency of the shape and position tolerance during processing, and the accuracy of the clamping position, and the processing efficiency is too low. With this process, only one machine can cut only 2-3 pieces per shift. (2) If the indexing head is used for clamping, considering that the maximum length of the X-axis and Y-axis of the DK7725E wire-cutting machine table is only 250MM, it is too large to be clamped on the machine tool, and at the same time, the whole process requires The operator has a high level of skill, a high degree of concentration, and no errors or omissions in the processing. The adjustment of the machine tool, the selection of electrical parameters, the selection of the amount of cutting fluid, and the labor intensity and production efficiency are not high. By analyzing the parts drawing, considering the high technical requirements and large processing batches, in order to maintain a good cooperative relationship with the enterprise and solve the difficulties for the enterprise, we try to design a set of efficient, simple and practical similarly-shaped head clamps to complete the Product processing tasks.

Second, the fixture design principle

The design is mainly based on the basic requirements of wire cutting and the dimensional accuracy requirements of the part: it can guarantee the processing requirements of the workpiece; it can improve the labor productivity; the production is simple, the maintenance is convenient; the manufacturing cost of the fixture is low.

The principle of the set of clamps is relatively simple. It uses six small blind holes equally divided on the same circumference of the flange and its vertical plate seat. There is a spring in a small round hole of the same diameter, and a steel ball is dragged on the spring, and the spring is used. The elastic force (the elastic force can be adjusted according to the elastic), each time the flange is rotated, the steel ball just falls in the small hole, realizes the rapid positioning of the rotation, and rotates the indexing like the indexing head. The vertical plate seat of the clamp is fastened with the flange to ensure the rotation precision.

Third, the structure of the fixture

The fixture is mainly composed of three parts: a vertical plate seat, a flange and a three-jaw chuck. The utility model is characterized in that the workpiece can be conveniently fixed, loaded and unloaded, and the positioning is ensured quickly; the rotation can be performed freely, and the indexing is accurately performed to ensure uniformity of 12 lines; and the size of the fixture is just suitable for the size of the DK7725E wire-cutting machine table, which is very convenient to use. .

1. Chuck 2. Vertical plate holder 3. Flange 4. Steel ball 5. Spring 6. Adjustment screw 7. Sturdy nut 8. One-way thrust ball bearing 9. Copper sliding sleeve 10. Chuck bolt

Fourth, fixture production and assembly

The main feature of the fixture is to use the protruding part of the steel ball to position the flange to control the rapid indexing and positioning of the flange.

1. Main component requirements

1 Chuck: It adopts K1180 three-jaw self-centering chuck (both positive and reverse), which can be used to clamp different rings or other shafts.

2 vertical plate seat: made of A3 steel material, the piece plays the supporting role, the two plates of the bottom plate and the vertical side plate are connected to each other by 90°, and the bottom and the other side are finished by milling and grinding, and the verticality is completed. To achieve 0.015~0.02, the surface roughness reaches RA1.6M; the height of the fixture center 90MM has a hole of φ35, which is used to fix the copper sliding sleeve. The interference fit clearance should reach H7/P6, and the hole of φ35 is perpendicular to the side plate. The degree is required to be 0.025 and the surface roughness is RA1.6M, which can be completed by milling.

3Flange: The material is made of 45 steel. The φ55 circle and φ30 positioning mandrel of the piece are formed by one turning. The coaxiality error must be strictly controlled within 0.025MM and the roundness error is controlled. Flange front end φ55 length 3MM step and chuck fit tolerance is 0.01 ~ 0.02MM; rear end φ30 is a sliding part, must be locally heated and quenched and tempered, surface hardness reaches HRC40-45, size meets H7 requirements, surface roughness RA1.6M; at the rear end of the flange, based on the central axis, six locating holes with a uniform R3 depth of 1.5 are drilled on the circumference of φ47, and are fixed to the vertical plate seat by the threads of the nut and the mandrel, and Requires a vertical reach of 0.015.

4 steel ball: φ6MM steel ball is selected for positioning.

5 spring: cylindrical spiral compression spring, spring wire diameter 0.8MM, outer ring diameter 6MM, end structure has a tightly grounded YI type, to ensure that the bearing end face is perpendicular to the axis of the spring, so that the spring is not skewed when pressed .

6 adjusting screw: M8×1 flat head screw is used to adjust the spring force of the spring.

7 Fastening nut: M16×1 hex nut is used for clamping.

8 one-way thrust ball bearing: 8203 type rolling bearing (8224GB301-64) is selected for sliding action.

9 sliding sleeve: the material is made of brass and plays a sliding role. The hole of φ35 and φ30 requires coaxiality of 0.02, which can be completed by turning; the clearance of φ30 hole and flange mandrel should reach 0.01~0.02; The blue disk is flexible.

10 Chuck Bolts: Use M6 hexagon socket bolts for fastening connection.

2. Assembly process

Complete the processing of the clip on the milling machine → three-jaw self-centering chuck and flange assembly → vertical plate seat and copper sliding sleeve interference assembly → vertical plate seat and steel ball positioning elastic debugging assembly → flange mandrel It is equipped with the sliding sleeve of the vertical plate seat to adjust the clamping clearance of the mandrel of the flange and the one-way thrust ball bearing.

For the accuracy of the rotation of the mandrel, the assembly of the inner ring of the sleeve and the flange of the flange and the assembly of the outer sleeve of the sleeve and the base of the vertical plate are often carried out by means of directional assembly. Oriented assembly is a method of artificially controlling the direction of the radial runout error of each assembly, so that the errors cancel each other instead of accumulating to improve assembly accuracy.

1, the working process of the fixture:

(1) Fixing and adjusting the fixture Position the fixture on the upper position of the machine table on the cutting machine. Use the dial indicator to correct the reference plane of the vertical plate seat parallel and perpendicular to the X and Y axes of the machine tool, and fasten the clamp with screws. On the workbench. (2) Place the workpiece into the three-jaw chuck (using the anti-claw) to clamp the workpiece so that the end face of the workpiece is in close contact with the side of the chuck. (3) Before processing, the first piece needs to be positioned by the automatic centering function on the machine tool, so that the molybdenum wire is located at the center of the workpiece, and the cutting process can be performed according to the program. After the first part is machined, the coordinate values ​​of the X-axis and Y-axis of the machine tool are locked, and the machining can be continued without further correction. (4) According to the processing technology of the ring, considering the length and shape of the groove processed by the workpiece, there are two methods for working the flange: one is that the processing one by one means that each line is cut, the flange is It is necessary to rotate in the order of the positioning holes in order to process gradually. This method needs to be changed after each line to complete the processing. Second, the stepping method means that after cutting the first line, the flange should be rotated one more in the direction of the positioning hole (ie, rotated twice) before it can be processed according to the same procedure until the program is finished. When the second program is to be processed after the first program is completed, the second program can be continued with the same jump method.

2, the fixture should pay attention to the process problems:

(1) The sliding fit between the mandrel of the flange and the sliding sleeve must be controlled between H7/H6 and ensure that the flange rotates flexibly. If the gap between the mandrel and the sliding sleeve is too small, the flange rotation will be difficult; if the clearance is too large, the radial runout error of the mandrel is large, which affects the accuracy requirements of the workpiece machining. (2) The gap between the steel ball positioning hole and the steel ball of the vertical plate seat must be controlled within 0.05-0.1MM to ensure the flexibility of the steel ball and the spring. (3) The fixture is designed according to the rotary positioning fixture, and is positioned by the elastic component. Therefore, it is necessary to control the center hole pitch and depth dimension of the six uniform holes on the flange to reduce the manufacturing positioning error. Otherwise, the contact gap is too large, which affects the positioning accuracy.

Fifth, the use of results

1. The manufacturing process of the fixture is simple and uncomplicated, the cost is low, and the potential of the machine tool is fully utilized to achieve the purpose of multi-purpose use of one machine.

2. After the workpiece is cut and processed, the dimensional accuracy after the narrow groove processing reaches H8 level, the surface roughness value reaches RA=1.2~3.2M, and the straightness of the groove width is also good. After inspection, it fully meets the dimensions required by the drawings. There are no waste products in the continuous processing of thousands of pieces, which will improve the economic benefits for enterprises.

3. After using this fixture, the processing efficiency is rapidly improved at the same time. Now one machine is processed by about 15 pieces, and the efficiency is improved by nearly four times, which reduces the labor intensity of the operator. This set of fixtures has been used for more than a year and its performance is very stable.

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