How to overcome deformation? Techniques of CNC Turning and Processing Thin-walled Parts

During the cutting process, the thin wall is easily deformed by the cutting force, which leads to the phenomenon of "waist shape" with ellipses or small middle and large ends. In addition, due to the poor heat

dissipation during processing, the thin-walled sleeve is extremely prone to

thermal deformation, and it is not easy to ensure the processing quality of the

parts. The parts in the picture below are not

only inconvenient to clamp, but also difficult to process at the processing

site. It is necessary to design a special thin-walled sleeve and shaft

protection.

1. Process analysis

According to the technical requirements provided in the drawings, the

workpiece is processed with seamless steel tubes. The surface roughness of the

inner hole and the outer wall is Ra1.xn--6m-99b, which can be achieved by turning, but

the cylindricity of the inner hole is 0.03mm. Higher. In mass production, the process route is roughly: blanking-heat treatment-car end face-car outer circle-car inner hole-quality inspection.

2.  Second, the key technology of turning hole

The key technology of turning holes is to solve the problems of rigidity

and chip evacuation of inner hole turning tools. To increase the rigidity of the inner hole turning tool, take the following measures:

a.Increase the cross-sectional area of the shank as much as possible,

usually the tip of the inner hole turning tool is located above the shank, so

that the cross-sectional area of the shank is less than 1/4 of the

cross-sectional area of the hole, as shown in the left figure below. If the tip of the inner hole turning tool is located on the center line of the tool holder, the cross-sectional area of the tool holder in the hole can be greatly increased, as shown in the right figure below.

b. The extension length of the tool shank can be as long as the length of the processed workpiece 5-8mm to increase the rigidity of the turning tool shank and reduce the vibration during the cutting process.

3.    Solve the problem of chip removal

Mainly control the cutting outflow direction. The rough turning tool

requires the chips to flow to the surface to be processed (front row of chips).

During fine turning, the chip flow is required to tilt the front chip evacuation (hole chip evacuation), so pay attention to the grinding direction of the cutting edge when grinding the knife, and the chip evacuation method of the arc to the front edge, as shown in the figure below Knife alloy YA6, the current M type, its bending strength, wear resistance, impact toughness and anti-sticking and temperature with steel are all good.

When sharpening, the rake angle is rounded with an arc-shaped angle of 10-15 °, the back angle is 0.5-0.8mm from the wall according to the processing arc (the tool bottom line is along the arc), c cutting edge angle k direction is §0.5-1 as the edge The cutting edge at point B of the cutting edge is R1-1.5, and the secondary clearance angle is grinded to 7-8 °, and the A point of the inner edge of E is ground to a circle to expel the chips.

4. Processing method

a. A shaft guard must be made before processing. The main purpose of the shaft guard is to cover the inner hole of the thin-walled sleeve of the car with the original size, and fix it with the front and rear centers to make it process the outer circle without deformation, to maintain the quality and accuracy of the outer circle processing. If you

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Therefore, the processing of the shaft protection is a key step in the process

of processing thin-walled sleeves.

45. Carbon structural round steel is used for processing the shaft blank;

the end face of the car is opened with B-type top holes at both ends, the outer

circle of the rough car is left, and the margin is 1mm. After heat treatment, it is tempered and shaped, and then 0.2mm is left for grinding. Re-heat-treat the surface of the crushed fire, hardness HRC50, and then grind it to the external grinder as shown in the figure below, the accuracy meets the requirements, and it will be used after completion。

b. In order to complete the processing of the workpiece at one time, the blanks are kept in the clamping position and the cutting margin.

c. First heat-treated and tempered the embryo, and the hardness is

HRC28-30 (hardness in the processing range).

d. The turning tool adopts C620, first put the front center into the

spindle cone position to fix it, in order to prevent the workpiece deformation

when clamping the thin-walled sleeve, an open-loop thick sleeve is added, as

shown in the following figure.

In order to maintain mass production, the outer end of the thin-walled casing is processed to a uniform size d, the ruler of t is the axial clamping, and the thin-walled casing is compressed to improve the quality of the inner hole of the car and maintain the size. Considering the generation of cutting heat, the expansion dimension of the workpiece is difficult to grasp. It is necessary to pour sufficient cutting fluid to reduce the thermal deformation of the workpiece.

5.Use the self-centering three-jaw chuck to clamp the workpiece firmly, the end face of the car, and the inner circle of the rough car. Remaining

allowance 0.1-0.2mm fine turning, put on the finishing turning tool to process

the cutting allowance to the full protection of shaft protection and roughness

requirements. Remove

the inner hole turning tool, insert the protective shaft to the front center,

use the tailstock center to clamp according to the length requirements, replace

the outer turning tool with a thicker outer circle, and then finish turning to

the drawing requirements. After

passing the inspection, use the cutting knife to cut off according to the

required length. In order

to smooth the cut when the workpiece is disconnected, the blade edge should be

obliquely ground to make the end surface of the workpiece flat; the small

section of the shaft protection is to cut the gap to cut the gap. The reason for falling off bruises.

6. Conclusion

The above method of processing thin-walled sleeves solves the problem of

deformation or size and shape errors that cannot meet the requirements.

Practice has proved that the processing efficiency is high, easy to operate,

and suitable for processing long thin-walled parts, the size is easy to grasp, Once completed, mass production is more practical.

Tina Huang

Shenzhen Rollyu Precision Machining Co., Ltd

email: info(at)rymachining.com