Edge grinding processing method of prism glass optical lenses

It is capable of edging lenses of various prismatic degrees according to prescription requirements, as well as lenses that have both prism degrees and require center shifting during processing. Be proficient in operating prototype machines and making prototypes by hand.

After measuring the processing center and processing reference line of the prism lens, make a template according to the frame, then place the template on the axis-fixing machine, and place the lens above it. The reference line of the presbyopia lens coincides with the reference line of the template. The machining center is aligned with the center of the sample. The reference line of the myopia lens is 1.5~2mm above the reference line of the sample. If the prescription has special requirements, adjust the position of the processing center and the reference line as required, and then place the suction cup. Due to the thickness difference between the bottom and the tip of prism lenses, especially lenses with large prisms, the suction cup is prone to shift when processed by an automatic edge grinding machine, affecting the accuracy of processing. Therefore, fixing the suction cup is an important part of processing prism lenses.

First, grinding the lens into the geometric shape of the frame is called edging, and then grinding the edge of the lens to a certain angle, commonly known as "sharp edge". Generally, the groove depth of the frame is 0.5~1.0mm. Therefore, the height of the sharp edge should also be equal to the groove depth of the frame. The angle of the frame groove is 110°~120°. Therefore, the angle between the sharp edges of the lens must also be ground to a corresponding angle. In addition, for lenses with larger diopters and larger prisms, the ratio of the edge positions of the sharp edges should be adjusted according to the style of the frame. The usual ratio is 6 inside, 4 outside, 7 inside, 3 outside, etc. After grinding, the lens needs to be chamfered. Finally, the position of the optical center point, the direction of the cylinder axis, the direction of the prism bottom, whether there are any scratches on the lens, the condition of the peripheral corners of the lens, etc., are all checked after confirming that they meet the requirements. to fit into the frame.

For frameless glasses, due to prisms, the thickness of the lens edges varies greatly, so pay attention to the angle when drilling. When notching half-frame glasses, use the thin direction as the reference direction, and also pay attention to the depth of the notch.

Precautions

The center shift of lenses containing prism power is based on the prism lens processing center, which is shifted according to the frame size and interpupillary distance. For example, the interpupillary distance is 60mm, the frame size is 52-16, and the prismatic power lens is determined during edge grinding. The processing center basically moves the lens processing center inward by 4mm, instead of moving the optical center of the lens inward by 4mm. If the reference line needs to be moved up and down, the processing center must also be moved up and down.

related information

1. Master the calculation of the minimum unsliced diameter

During the lens edging process, we often encounter the need to shift the reference center or optical center of the lens to solve the problem of optical center positioning after adding prisms and the reference center distance of the frame being inconsistent with the interpupillary distance. In addition to mastering the lens In addition to the relationship with the prism, you also need to understand the diameter calculation of the minimum uncut lens (referring to the standard raw edge lens).  Minimum uncut lens diameter = the longest point on both sides of the geometric center of the frame (left or right) + twice the center shift amount + 2mm reserve. For example, the longest length of a frame is 52mm, and the optical center is displaced inward by 3mm. 52+3×2+2=60mm. The minimum uncut lens diameter is 60mm. Example. The prescription is -4.00DS2△ with the bottom facing outward. The centering is used to achieve the prism effect. The longest part of the lens is 50mm. Find the minimum uncut lens diameter. (1) Find the center shift formula: C=P/F P=△ F=Diopter 2/4×10=5(mm) inward shift

(2)Minimum uncut lens diameter=50+2×5+2=62mm