마이크로 구형 부품 가공

2021/08/19


이 논문은 새로운처리method using optical surface grinder with self-made special tooling, which has the advantages of high qualification rate, simple operation and controllable 처리accuracy, and solves the problem of 처리tiny ball head parts.



1 서문
The ball can be seen as a circular arc rotating around its axis to become a surface. Ball head class parts due to the existence of complex surfaces, so usually use CNC machining to ensure the size, position accuracy and surface quality requirements. With the continuous improvement of machine tool performance and tool material and performance, the ball head class parts with ball head diameter ≥8mm and material hardness ≤64HRC can be processed by traditional methods, including: ① using omnidirectional turning tool or cycloid tool for CNC lathe processing. ② using the rotary milling 처리with high requirements for tool position adjustment. ③Processing by profile grinding with special grinding wheel dressing device. ④Spreading method grinding 처리with customized cup-shaped grinding wheels. ⑤ Mass production filing 처리using a special grinding block (only hemispherical shaft ends with regular shapes can be processed).
However, the analysis of the structural characteristics of the tiny spherical parts suggests that it is difficult to realize the precision forming 처리of the tiny spherical parts by using the traditional 처리method.

2 마이크로 볼 헤드 부품 특성
The characteristics of micro ball head parts: ① in the shaft end has a curved ball head structure, divided into small semi-spherical, hemispherical and large semi-spherical structure, as shown in Figure 1, the hardness of about 60HRC. ② ball diameter is small, the general ball diameter ≤ 3.5mm. ③ 처리ball transition section by radial force section easy to break. ④The size of the part is small, and the tool structure has a greater impact on the workpiece processing. ⑤ forming grinding wheel dressing is more difficult.



From the characteristics of the tiny ball head class parts, it can be seen that the traditional 처리method for forming the tiny ball head at the end of the shaft appears to be incompetent.

For a small number of general precision requirements of the tiny ball head class parts, can be used under the soft state carving and milling rough machining, heat treatment after polishing to achieve. But for the high precision requirements of the tiny ball head class parts, still need to find a more suitable 처리method.

Because of the difficulty of precision hard machining of tiny ball-like parts, it is not easy to achieve batch processing, so according to the formation mechanism of the ball end of the shaft (let the bar material high-speed rotation, in the form of circular arc envelope to form a ball head) and the 처리principle of the equipment, proposed a tiny shaft end of the large half ball-like ball parts 처리method: the production of special tooling, let the rod high-speed rotation, with the optical curve grinder set point into line 처리The principle is to process the ball head in the form of an envelope for precision forming.

3 Optical curve grinding machine 처리method
광학 곡선 연삭기는 주로 베드, 좌표 테이블, 연삭 휠 테이블 및 투영 시스템으로 구성됩니다. 테이블은 세로, 가로 및 세로 방향으로 이동할 수 있습니다. 연삭 휠은 연삭 휠 테이블의 가이드 레일에서 주요 회전 및 선형 운동을 할 수 있습니다. 연삭 휠 테이블은 X/Y/Z 축을 중심으로 세로 및 가로 이송 동작 및 회전을 수행할 수 있습니다. 다중 원형 표면, 대수 표면 또는 아르키메데스 나선형 표면의 연삭을 실현할 수 있습니다.
Optical curve grinder 처리uses an optical projection magnification system to project the workpiece magnification onto the screen against the magnified image of the workpiece on the screen, and operates the grinding wheel to grind the workpiece to grind off the excess material beyond the contour line of the magnified image until the contour of the object image fully coincides with the magnified image. It is possible to compare 25 times or 50 times magnification. The types of diamond grinding wheel structures used in optical curve grinders are flat grinding wheels, sharp grinding wheels, etc., as shown in Figure 2.


연삭 휠의 구조에 따라 그림 2b에 표시된 날카로운 연삭 휠을 디지털 제어 시스템과 함께 사용하여 직경 0.2mm의 표면을 연삭할 수 있습니다. 공작물의 회전과 결합하면 해당 곡면 회전 표면을 성형하고 가공할 수 있습니다.

4 가공 사례 분석
The structure of a ball head rod for a certain type of product is shown in Figure 3. The surface roughness of the spherical surface is Ra=0.4μm, and the spherical surface should not have obvious cutter patterns such as joint marks; the size, position accuracy and hardness of the spherical part are high, the diameter of the transition section between the spherical head and the shaft is only 1.2mm, and the machining quantity is 500. The following difficulties exist in the 처리of this part: ①Higher dimensional accuracy requirements for the ball head and smaller shaft diameter of the part. ②The diameter of the transition section of the ball head is only 1.2mm, the 처리stiffness is low, and the force is easy to break. ③ 처리allowance, the 처리technology, clamping convenience, stability and bar rotation radial runout and other aspects of the higher requirements. ④Higher requirements for the surface roughness quality of the ball head.

If the optical curve grinder is used to realize the precision forming 처리of the ball head bar, special tooling also needs to be made to ensure that when the grinding wheel moves along the contour of the workpiece, the ball head bar rotates around the axis to form the ball head structure. Due to the small size of the ball-head rod, if the grinding wheel moves up and down along the grinding wheel holder, it will reduce the effective contact time between the grinding wheel and the rotating workpiece. Therefore, in order to improve the 처리efficiency, the height position of the grinding wheel is adjusted and fixed during the workpiece processing, and the reciprocating motion of the grinding wheel along the grinding wheel holder is canceled, so that the grinding wheel is always in effective contact with the surface of the workpiece when rotating, and the grinding wheel only moves along the forming contour line when rotating at high speed.
5 툴링 설계
소형 동력 모터(속도 1400r/min)와 소형 선반 척을 채택하고 작업 테이블에 척을 고정하고 스프링 척(직경 10mm 이내의 다양한 공작물을 고정할 수 있음)을 사용하여 공작물을 고정합니다. 공작물의 투사 초점 거리가 연삭 휠의 정상 이동 범위 내에 있도록 테이블 높이를 조정합니다. 벨트 풀리 구동을 통해 척킹 속도는 2000 r/min에 도달하고 회전 방향은 연삭 휠의 회전 방향과 반대입니다. 디버깅 후 공작물의 방사형 원형 런아웃은 ‰¤0.005mm이고 공작물의 구조는 그림 4에 나와 있습니다.

6 공정 설계
Considering the number of workpieces, ball head rod and grinding wheel structure, due to the small round angle of the sharp grinding wheel, 처리loss is large, in order to reduce the loss of the sharp grinding wheel and improve the 처리efficiency, choose to use flat grinding wheel 처리when removing the large residual, step-by-step 처리process is shown in Figure 5. Develop the ball head rod 처리process as follows.

(1) 평면 연삭 휠이 있는 볼 헤드 로드의 황삭 가공, 연삭 휠 병진 속도 3mm/min 및 연삭 휠 속도 12000r/로 A 및 B 섹션에 대해 0.02mm 및 C 섹션에 대해 0.1mm의 여백 남기기 분

2)Processing the contour of the ball-head rod with the sharp grinding wheel, 처리the A and B sections to control the dimensional accuracy, leaving a margin of 0.01mm in the C section, the grinding wheel translation speed of 1.5mm/min, and the grinding wheel rotation speed of 12000r/min.

(3) 0.5mm/min의 숫돌 병진 속도와 12000r/min의 숫돌 회전 속도로 날카로운 연삭 숫돌로 C 섹션의 볼 헤드를 마무리합니다.

7 가공효과 검사
볼 헤드로드는 단계적으로 처리되며 평면 연삭 휠에 자동 재연삭 기능이 있기 때문에 가공 실린더의 표면 품질이 좋습니다. 날카로운 연삭 휠은 가공 여유가 적고 연삭 휠 손실이 작은 마무리 작업을 주로 담당합니다. 볼 엔드 로드 500개를 가공하는 과정에서 날카로운 연삭 휠이 4번 다시 연마되었습니다. 가공된 부품은 Fig. 6과 같으며, 부품의 시험 데이터는 Table 1과 같다. 시험 결과에서 볼 헤드 로드 가공 방법이 설계 요구 사항을 만족함을 알 수 있다.



8 결론
마이크로 볼 팁 부품은 자체 구조적 특성으로 인해 기존 샤프트 엔드 볼 팁 부품으로 가공할 수 없습니다. 수제 특수공구로 광곡선그라인더를 사용하여 단계별로 설계하여 처리process, the radial force on the ball head rod is small and the transition section is not easy to break. The grinding method has solved the problem of 처리small-sized ball-end parts with the advantages of high qualification rate, simple operation, controllable 처리accuracy and good product consistency.