CN102328248B - A grinding method for the outer circle of high-precision slender sleeve workpieces - Google Patents

Abstract

The invention discloses a grinding method of outer circles of high-precision slender casting parts. Workpieces the slenderness ratios of which are more than 10 are generally defined as slender workpieces, the slender workpieces are easy to deform and large in processing difficulty in the grinding process, and the coaxiality of outer circles relative to inner holes is difficult to be ensured. In the invention, a positioning device, a clamping method, grinding parameters and grinding steps of outer circles of high-precision slender casting parts are also provided. Compared with the original grinding method, the grinding method disclosed by the invention has the characteristics that: the original conicity spindle is changed into a cylindrical straight spindle; in the clamping method, the original mode that the conical spindle penetrates into a workpiece hole and the workpiece rotates under the driving of the frictional force is changed into a mode that the workpiece is tensioned by a heart carrier by adopting a double-strand elastic rope to drive the workpiece to rotate in a symmetrical and balanced way; and more reasonable grinding wheel and grinding parameters are selected. The grinding method disclosed by the invention has the advantages that: the index yield of coaxiality of the outer circles relative to the inner holes is improved to 98 percent from 81.6 percent, and the machining efficiency is improved by 25 percent; in addition, the matching grinding difficulty and quantity of the spindles are greatly reduced, and the fixture investment cost is reduced.

Description

A grinding method for the outer circle of high-precision slender sleeve workpieces

technical field

The invention relates to a grinding method for the outer circle of workpieces, in particular to the processing of slender valve sleeve workpieces with a length-to-diameter ratio greater than 10.

Background technique

High-precision slender valve sleeve workpieces are common in aviation hydraulic products, and the aspect ratio is greater than 10. Due to the slender workpieces, high precision requirements, difficult processing, and unstable quality. When finely grinding the outer circle, it is required that the coaxiality of the outer circle relative to the reference inner hole is not greater than Φ0.02mm. Generally, the taper mandrel is used for contact positioning with the reference cylindrical hole of the workpiece for cylindrical grinding. Since the taper mandrel penetrates into the workpiece hole, the workpiece is driven to rotate by the friction torque generated by the slight elastic deformation between the workpiece and the mandrel. The positioning method has high requirements on the geometric accuracy of the positioning reference hole. When the mandrel is inserted, it may be deformed due to the error of the reference hole shape, and the positioning surface is small. The workpiece may be accidentally loosened during grinding. The above reasons may cause coaxial The degree is too bad. Secondly, due to the high precision requirements of the workpiece, the taper of the taper mandrel cannot be too large, the mandrel and the workpiece need to be adapted one by one, and the input of the mandrel is large; in addition, the grinding process of the mandrel and the penetration of the mandrel into the inner hole of the workpiece The degree of tightness requires higher skills for the processor.

Contents of the invention

Purpose of the present invention: the present invention aims at the difficulties that cannot be overcome in the prior art, and explores and designs a grinding method for the outer circle of a high-precision slender sleeve workpiece. Its purpose is to realize the grinding of the outer circle with the inner hole as the reference, to ensure the coaxiality of the outer circle relative to the reference inner hole, and to reduce the accuracy requirements of the reference inner hole, and to greatly reduce the difficulty of mandrel matching and reduce the core The input amount of the shaft is reduced to achieve the effect of quick replacement and cost reduction.

The technical scheme that the present invention takes is:

Step 1: Make a positioning device for grinding the outer circle of high-precision slender sleeve workpieces

The positioning device is a cylindrical mandrel (1) with a positioning piece (2). The two ends of the mandrel (1) are processed with a central hole (10). The positioning piece (2) is located at one end of the mandrel (1). The positioning piece (2) ) The outer diameter is larger than the diameter of the workpiece (3), and the diameter of the mandrel (1) is smaller than the inner diameter of the workpiece (3);

Step 2: Clamping the workpiece (3)

(1) The mandrel (1) penetrates the inner hole of the workpiece (3).

(2) The head of the machine tool and the top of the tailstock (6) push the center holes at both ends of the mandrel respectively, clamp the chicken heart chuck (4) close to the outer circle of the left end of the workpiece (3), and wrap the double-strand elastic rope (5) around the chicken heart on both sides of the chuck (4), and then connected to the balance lever (7);

Step 3: Grinding the outer circle of the workpiece (3)

(1) Coarsely grinding the outer circle

(2) Semi-fine grinding outer circle

(3) fine grinding

The processing parameters are selected as follows

Grinding wheel selection: P400×30×127GC100K8V50m/s

Workpiece speed: 200r/min

Grinding wheel speed: 35m/s

Cutting speed: 0.8m/min

Coarse grinding parameters: feed rate 0.01mm, double-sided feed, processing capacity 0.25mm

Semi-fine grinding parameters: feed rate 0.005mm, double-sided feed, processing capacity 0.03mm

Fine grinding parameters: feed rate 0.005mm, double-sided feed, processing capacity 0.02mm

Step 4: Turn around and clamp the other end of the workpiece

The clamping method is as in step 2 above, and the grinding step is as in step 3.

Further, the positioning piece (2) is 20mm-25mm away from one end of the mandrel (1);

Further, the diameter of the above-mentioned mandrel (1) is 0.05mm-0.15mm smaller than the aperture of the workpiece (3);

In order to better implement the present invention, steps are provided at both ends of the above-mentioned mandrel (1).

Further, the angle a between the double-strand elastic rope (5) and the main shaft is 25°-40°.

The advantages and beneficial effects of the utility model: first, there is a small gap between the mandrel and the inner hole, which avoids the slight deformation of the workpiece caused by the mandrel penetration, and at the same time eliminates the deformation of the mandrel caused by the error of the reference hole shape; The elastic rope tightens the workpiece through the heart chuck, and the symmetrical balance drives the workpiece to rotate, so that the force on the workpiece is balanced to reduce vibration and roundness errors; during the grinding process, the working fluid enters the mandrel and the workpiece from the radial hole of the workpiece. In the gap, a thin layer of liquid film is formed during high-speed rotation, and this layer of liquid film supports the workpiece to form a uniform balance force, thereby ensuring the coaxiality of the outer circle and the inner hole. Secondly, compared with the original tapered mandrel, the difficulty and quantity of the mandrel matching grinding are greatly reduced, which reduces the processing cost and improves the processing efficiency.

Description of drawings

Fig. 1 is the grinding outer circle flow chart of the present invention;

Fig. 2 is a schematic diagram of the positioning device of the present invention, wherein 1-mandrel, 2-positioning piece, 10-center hole, 11-positioning position, 12-two ends;

Fig. 3 is the installation drawing of the grinding outer circle of the present invention, wherein 3-workpiece, 4-heart chuck, 5-double-strand elastic rope, 6-top, 7-balance lever;

Fig. 4 is a diagram of the positioning mechanism of a cylindrical mandrel with a gap in the present invention, in which 8-working fluid, 9-the radial hole of the workpiece.

Detailed ways

Below in conjunction with accompanying drawing and embodiment the present invention is described in further detail:

Taking a high-precision slender valve sleeve as an example, the material of the workpiece 3 is 440C stainless steel, the length is 287mm, and the diameter of the inner hole is Φ11.01mm. Hole coaxiality 0.02mm.

The processing flow is shown in Figure 1 as follows:

Step 1: Make a positioning device for grinding the outer circle of high-precision slender sleeve workpieces

The positioning device is a cylindrical mandrel 1 with a positioning piece 2. The two ends of the mandrel 1 are processed with a central hole 10. The positioning piece 2 is located at a distance of 15 mm to 20 mm from one end of the mandrel 1. The thickness of the positioning piece 2 is between 3 mm and 7 mm; The outer diameter of the sheet 2 is larger than the inner diameter of the workpiece 3, and its function is to limit the axial serial movement of the workpiece 3, and the outer diameter of the mandrel 1 is smaller than the inner diameter of the workpiece 3, as shown in FIG. 2 .

Step 2: Clamping the workpiece 3

(1) Insert the mandrel 1 into the inner hole of the workpiece 3;

(2) The head of the machine tool and the top of the tailstock 6 push the center holes at both ends of the mandrel respectively, clamp the chicken heart chuck 4 close to the outer circle of the left end of the workpiece 3, wrap the double-strand elastic rope 5 around the two sides of the chicken heart chuck 4, and then Connected to the balance lever 7, the angle a between the double-strand elastic rope 5 and the main shaft is 25° to 40°. During the working process, the rotating main shaft first pulls and tightens the elastic rope 5, and then drives the workpiece 3 to rotate, thereby The outer circle of the workpiece 3 is ground.

Step 3: Grinding the outer circle of the workpiece 3

The processing parameters are selected as follows

Grinding wheel selection: P400×30×127GC100K8V50m/s

Workpiece speed: 200r/min

Grinding wheel speed: 35m/s

Cutting speed: 0.8m/min

(1) Coarse grinding of outer circle: feed rate 0.01mm, double-sided feed, processing capacity 0.25mm

(2) Semi-fine grinding outer circle: feed rate 0.005mm, double-sided feed, processing capacity 0.03mm

(3) Fine grinding: feed rate 0.005mm, double-side feed, processing capacity 0.02mm

Fine grinding times: 6 times

During the grinding process, the cutting fluid 8 is continuously injected.

Step 4: Turn around and clamp the other end of the workpiece

The clamping method is as in step 2 above, and the grinding step is as in step 3.

During the grinding process, the cutting fluid 8 enters the gap between the mandrel 1 and the workpiece 3 from the radial hole 9 of the workpiece 3, and forms a thin layer of liquid film during high-speed rotation. This layer of liquid film supports the workpiece 3, forming a Uniform balance force, so as to ensure the coaxiality of the outer circle and the inner hole, as shown in Figure 4.

Further, as a preferred embodiment of the present invention, the diameter of the above-mentioned mandrel 1 is 0.05 mm to 0.15 mm smaller than the diameter of the workpiece 3; the narrow distance between the mandrel 1 and the workpiece 3 is used to drive the workpiece 3 to rotate, thereby completing the workpiece 3. Grinding.

In order to better implement the present invention, steps are provided at both ends of the above-mentioned mandrel 1, which are respectively the positioning part 11 and the step part 12. The outer diameter of the step part 12 is smaller than the outer diameter of the positioning part 11, so that it is more convenient to install during the installation process. , It also makes the mandrel 1 not easy to scratch the workpiece 3.

In order to better implement the present invention, the angle a between the above-mentioned double-strand elastic cord 5 and the main shaft is 25°-40°.

Beneficial effects: there is a small gap between the mandrel and the inner hole in the present invention, which avoids the slight deformation of the workpiece caused by the mandrel penetration, and at the same time eliminates the deformation of the mandrel caused by the error of the reference hole shape; the double-strand elastic rope passes through the chicken heart The chuck tightens the workpiece, drives the workpiece to rotate symmetrically and balances the force on the workpiece to reduce vibration and roundness errors; during the grinding process, the working fluid enters the gap between the mandrel and the workpiece from the radial hole of the workpiece, A thin layer of liquid film is formed during high-speed rotation, and this layer of liquid film supports the workpiece to form a uniform balance force, thereby ensuring the coaxiality of the outer circle and the inner hole. Secondly, compared with the original taper mandrel, the difficulty and quantity of the mandrel matching grinding are greatly reduced, which reduces the processing cost and improves the processing efficiency. Compared with the original process, the present invention improves the pass rate of the coaxiality index of the outer circle relative to the reference inner hole from 81.6% to 98%, and improves the processing efficiency by 25%.

Claims (5)

1. A method for grinding the excircle of a high-precision slender sleeve type workpiece, characterized in that it comprises the following steps: Step 1: Make a positioning device for grinding the outer circle of high-precision slender sleeve workpieces The positioning device is a cylindrical mandrel (1) with a positioning piece (2). The two ends of the mandrel (1) are processed with a central hole (10). The positioning piece (2) is located at one end of the mandrel (1). The positioning piece (2) ) The outer diameter is larger than the diameter of the workpiece (3), and the diameter of the mandrel (1) is smaller than the inner diameter of the workpiece (3); Step 2: Clamping the workpiece (3) (1) The mandrel (1) penetrates the inner hole of the workpiece (3); (2) The head of the machine tool and the top of the tailstock (6) push the center holes at both ends of the mandrel respectively, clamp the chicken heart chuck (4) close to the outer circle of the left end of the workpiece (3), and wrap the double-strand elastic rope (5) around the chicken heart on both sides of the chuck (4), and then connected to the balance lever (7); Step 3: Grinding the outer circle of the workpiece (3) (1) Coarsely grinding the outer circle (2) Semi-fine grinding outer circle (3) fine grinding The processing parameters are selected as follows Grinding wheel selection: P400×30×127GC100K8V50m/s Workpiece speed: 200r/min Grinding wheel speed: 35m/s Cutting speed: 0.8m/min Coarse grinding parameters: feed rate 0.01mm, double-sided feed, processing capacity 0.25mm Semi-fine grinding parameters: feed rate 0.005mm, double-sided feed, processing capacity 0.03mm Fine grinding parameters: feed rate 0.005mm, double-sided feed, processing capacity 0.02mm Step 4: Turn around and clamp the other end of the workpiece The clamping method is as in step 2 above, and the grinding step is as in step 3. 2. The method for grinding the outer circle of high-precision slender sleeve workpieces according to claim 1, characterized in that the positioning piece (2) is 20mm-25mm away from one end of the mandrel (1). 3. The method for grinding the outer circle of high-precision slender sleeve workpieces according to claim 1, characterized in that: the diameter of the mandrel (1) is 0.05mm-0.15mm smaller than the aperture of the workpiece (3). 4. The method for grinding the outer circle of high-precision slender sleeve workpieces according to claim 1, characterized in that steps are provided at both ends of the mandrel (1). 5. The method for grinding the outer circle of high-precision slender sleeve workpieces according to claim 1, characterized in that the angle a between the double-strand elastic rope (5) and the main shaft is 25°-40°.

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