How to make the aperture stable during optical lens processing?

Middle and high-end optical systems have increasingly high requirements for optical lenses, and how to make the aperture stable in the processing process, without affecting the efficiency of the operation, without increasing the cost and ensuring the quality. Now it has become a "hot topic" for discussion. Therefore, for representative parts (representative finger shape accuracy is difficult to process, local error requirements are strict), to find the basic conditions for aperture stability.

Aperture instability reference

1, processing conditions:

1) The size of the particle diameter of the grinding powder, and the size of the concentration ratio, the impact on the aperture; If the particle diameter and concentration of grinding powder are too large, the curvature radius of grinding dish will change more. Smaller curvature radius of the concave dish) if compared with water, the aperture will change to a higher direction; Easy to cause edge sag.

2) The speed of the rotation speed affects the local irregularity of the aperture, and the line speed of the edge of the grinding dish is different from the line speed of the center. The more the lens edges out the pan, the more the lens aperture changes to negative. Can cause the center and edge of the lens is not balanced wear, low and high, the lens adjustment and adjustment is the truth.

3) The size of the pressure has a direct impact on the center thin and D/T > 10 lenses, (especially obvious when using string processing) the size of the pressure has a direct impact on the shape of the lens is mainly caused by the uneven force on the entire surface of the lens.

4) The processing time also affects the change of surface shape accuracy, because the grinding follows cosine grinding, and the radius of curvature of the grinding dish * the time when the sand is finished is corrected. (Because the radius of curvature of the grinding dish must always be maintained, the center of the grinding dish is inevitable to wear fast).

5) Adjustment of the swing size: the swing is too large, the lens aperture changes to the low aperture, and is accompanied by the appearance of medium and low; The swing is too small, the lens aperture changes to the highlight, and is accompanied by the appearance of medium height.

6) Adjustment of the ball core: the adjustment of the ball core is good and bad, which affects whether the pressure is uniform.

7) coaxiality adjustment: coaxiality refers to the spindle, relay fixture, grinding dish center point requirements are consistent. If the center point is not consistent, the lens will beat in the operation, and the operation will affect the surface shape accuracy. zI&).

8) Adjusting the height of the string rod: the string rod presses the fixture; The fixture drives the lens to rotate, and the transmission pressure cannot be guaranteed when the string rod is high, and it is easy to scratch the plate skin when the string rod is low.

9) Confirm the stability and locking parts of each part.

10) The offset of the lens on the grinding dish.

11) The lens is put out more, the lens is easy to produce impression, the surface number is easy to change low, and it is easy to swing when it is swung to the edge. Set out less wear, easy edge drop.

12) The parallel of the swing arm rod: the swing arm rod does not affect the center line of the lens, and the center line of the grinding dish cannot overlap.

2. Equipment

1) The spindle runout of the machine is the deviation of the center point of the shaft, which causes the lens to run unsmoothly during processing.

2) The gap between the movable joint parts of the machine is too large, the force of the lens is large and small when the lens is placed in and out, and the force of the lens is uneven.

3) Inactive activity of cylinder expansion, abnormal sound and vibration of the machine.

4) The stable point of the string rod is not strong, the distance between the string rod and the grinding dish is too large, and the shake of the string rod tip affects the change of surface shape accuracy during processing.

3. Treating tools

1) Whether the matching of the outside diameter size of the tool is accurate, that is, the size ratio of the closing dish to the drilling dish, the size ratio of the drilling dish to the grinding dish, and the size ratio of the grinding dish to the lens.

2) The local error of the drilling dish is equal to the local error of the lens.

3) The precision of the grinding plate and the curvature surface of the fixture is an important link to determine the complete match between the lens processing surface, the stress surface and the fixture.

4) Fixture end hole, height design.

5) End face flatness and height of trunk fixture.

6) The grinding shape of the string rod: the grinding of the string rod is the key to the smooth operation of the fixture table, and the string rod is too dull, which affects the smooth operation; The string rod is too sharp, and the terminal hole is easy to wear and become deep.

7) Finishing of the grinding dish: it is difficult to average the surface finishing of the grinding dish by hand, because the swing momentum of the grinding dish is controlled by hand, and the rotation speed of the grinding dish is unbalanced, so it is not recommended to use the hand repairing.

8) The attachment and tightness check of the fixture shell: this can most cause the deformation of the lens surface (scattered, saddle-shaped).

9) Flat treatment of pad paper and pad: elastic selection of pad paper and pad paper, outer diameter and thickness of pad, smooth and clean.

10) The influence of terminal depth: terminal depth; The string rod and the terminal interfere when they swing. Shallow terminal; The string rod and terminal are easy to fall out when they swing.

11) Adjust the time when the surface shape accuracy changes: adjust the surface shape accuracy when it changes, do not wait until the surface shape exceeds the specification. By then, the accuracy of the surface shape will not be easy to control.

12) Surface inspection frequency: high surface inspection frequency, understand the change law of surface shape accuracy, change trend, easy to control.

Second, the necessary conditions for aperture stability

1) When the aperture changes to the high aperture, the medium and high debugging is difficult, the side vertical is large, and the surface shape accuracy is difficult to process, the concentration ratio should not be too thick, and the concentration of the grinding liquid can be controlled not higher than 1.020; Choose a smaller particle size for grinding powder. For example, when the aperture changes to the low aperture, the opposite is difficult to debug.

2) The speed is too fast will increase the side sag, such as adding the coaxial pulsation is too large, the lens is suspended, the center is difficult to contact for grinding. The surface of the lens is not in equilibrium wear. Large outer diameter with low speed (< 1500 RPM), small outer diameter with high speed (> 2500 RPM) processing. Large pressure, large local force; The pressure is small, and the force on the surface of the lens is more uniform. Lens with thin center and D/T > 1.0, pressure should be light rather than heavy. Therefore, if the surface shape accuracy is stable on the parts that are difficult to process, the setting of processing conditions should consider the concentration, light pressure, slow speed, short time and so on.

3) Examples: gg parts according to the above Settings considered, not only did not increase the working time; On the contrary, the working time can be reduced, the investment of equipment and personnel is reduced, and the disadvantages of lens taking action are overcome.

4) The ideal size of the fixture must be calculated according to the formula, and the error of the production must be controlled. The local error correction of the drilling dish is within 0.0005mm.

5) The outflow of "face not" does not mean that the face is unstable, but only the evaluation of the quality of the opposite control. Generally, 1/4 to 1/5 of the outer diameter of the lens is set as the swing size. (Different machine types set different values).

6) The adjustment of the ball core is to increase the swing and then determine. Small swing is difficult to distinguish the accuracy of the ball core.

7) The specific method of adjustment of coaxiality is that the grinding dish is installed on the relay fixture, and the ball core correction instrument is used for correction. The runout deviation should be within 0.03mm, the height of the string rod and the grinding dish should be adjusted at 0.1mm, the swing amount of the lens on the grinding dish is about 1/5 of the diameter of the lens, and the swing arm rod should be adjusted and operated in parallel, and the grinding shape of the string rod should be conical and consistent with the shape of the terminal hole. Grinding dish machine repair, do not put out more to overcome the low surface, such as the surface of the low direct drilling repair dish, I believe that each time not so hard, the surface will be stable.

8) When attaching the fixture shell, the glue should not overflow into the curvature surface of the fixture table