With the rapid development of the information industry,optical components are widely used in various electronic devices,and the requirements for their processing accuracy and quality are becoming increasingly high.Traditional processing techniques and tools are difficult to meet their processing requirements,especially in the field of diamond tools.The requirements for their structure and internal quality are becoming increasingly specialized and targeted.Therefore,the transformation of traditional diamond tool structures and the improvement of internal quality in this field are becoming increasingly important.
The diamond tools in this field mainly include grinding wheels for milling flat and spherical surfaces in rough machining,grinding wheels for edge grinding,precision grinding discs and surface grinding in precision machining,ultra precision discs and polishing discs;In addition,there are also saw blades for cutting.
1.The main types of diamond tools used for optical glass processing
Milling grinding wheel
The milling of optical glass is the main method of rough machining,which involves grinding grinding grinding wheels on flat and spherical surfaces.The diameter of the flat milling grinding wheel is generally greater than 100mm,while the diameter of the spherical milling grinding wheel is generally less than 100mm.The particle size of the grinding wheel is generally 60#~180#,and the concentration is generally 50%~100%.The binder is bronze.
Diamond grinding wheel
Diamond grinding wheels are mainly used for grinding the outer circle of optical components.Their geometric shape and dimensions are shown in Figure 2 and Table 2.There are two types of binders:electroplating nickel based binder and sintering bronze binder.Its particle size is generally between 230/270 to M28/20,with a concentration of 100%-200%for electroplating and 50%-100%for bronze.
Fine grinding disc,ultra fine grinding disc
Precision and ultra precision grinding discs are used to perform precision machining on optical components after rough machining,in order to fully demonstrate their optical performance during use.Fine grinding and ultra fine grinding have both flat and spherical machining.Fine grinding discs generally use bronze,iron based,nickel based or cobalt based binders,while ultra fine grinding generally uses resin organic binders.The particle size of precision grinding discs generally ranges from 325/400 to 10/5,with a concentration of 100%to 35%,while the particle size of ultra precision grinding discs generally ranges from 14/8 to 7/5,with a concentration of 50%to 25%.
Polishing plate
Polishing sheets are mainly used to improve the surface smoothness of optical components,ensure a certain aperture,and reduce the processing of surface deterioration layers.The main shapes are like precision grinding discs and ultra precision grinding discs,with resin as the binder,cerium oxide as the abrasive,and a small amount of diamond powder.
2.Reasonable selection of diamond products in optical glass processing
The reasonable selection of diamond products in optical glass processing mainly refers to the selection of the shape,size,bond type,diamond particle size,diamond concentration,and bond hardness of diamond tools based on the shape,grade,processing quality requirements,and processing technology of the processed optical glass components.The general selection principles are:
(1)Choose the shape,size,and accuracy of diamond tools based on the processing method and the accuracy of the machine tool.
(2)The particle size of diamond tools is selected based on the margin of the processed components and the surface roughness.
(3)The concentration of diamond is selected based on the size of the workpiece and the processing process,as well as the coverage ratio of diamond tools,especially for precision and ultra precision grinding.
(4)Choose the type of binder based on the process of processing the workpiece and the grade of the workpiece,especially for precision grinding and ultra precision grinding.Choose bronze,nickel based,cobalt based,and iron based materials like precision grinding;Ultra precision grinding of resin binder.Bronze and nickel based options are selected for precision grinding of soft glass.For hard glass and glass with high viscosity,iron based and cobalt based materials are preferred.
(5)Select the soft hardness and bond strength of diamond tools based on the grade,hardness,and brittleness of the processed optical components.In general,the hardness of the bonding agent is lower for soft glass and glass with less brittleness;The bond strength is lower.For hard and brittle glass,choose higher hardness;The bond strength is higher.
3.New Manufacturing Technology of Diamond Tools for Optical Glass
At present,the manufacturing technology of diamond tools in this field is becoming increasingly advanced,mainly manifested in the following aspects:in terms of raw materials,the powder of the binder is becoming finer,and the particle diameter is generally less than 40μm.Some can reach up to 10μBelow m,and all are pre synthesized powders.
The particle size composition range of diamond is becoming increasingly narrow,and its crystal shape is getting better,especially at the micro powder level,which tends to be almost isotropic.Various binders have added trace elements and compounds to improve their grinding efficiency.The distribution of diamond in the binder is generally achieved through granulation process or thorough uniform mixing.The forming sintering adopts a hot pressing sintering method with a protective atmosphere.
The mold adopts high-precision high-temperature resistant metal molds,and the fired blanks have almost no pores,and the strength of diamonds has hardly decreased during the sintering process.The manufactured blanks must undergo strict precision machining to ensure their profile and tolerance,while also ensuring their grinding sharpness.
4.The problems and countermeasures that may occur in some diamond tools during optical glass processing
Diamond tools often encounter various problems during use,which affect the yield and efficiency of processing,and have a significant impact on production costs and product performance.This is mainly manifested in the manufacturing technology and inherent performance of diamond tools.
Milling process
The following main problems often occur during the milling process:
(1)Poor roughness
(2)Glass breaking and chipping
(3)Unstable profile
(4)Low efficiency with deep scratches
These problems are mainly related to the particle size,concentricity,concentration,self sharpening of the grinding wheel,as well as the lifespan and durability of the grinding wheel.To solve these problems,it is necessary to analyze the manufacturing technology of the grinding wheel,adjust the strength of the bonding agent,diamond concentration and particle size,and ensure the concentricity of the grinding wheel.Mainly to improve the holding strength of diamonds and reduce the grinding hardness of binders.
Fine and ultra fine grinding and polishing processes
Fine grinding,ultra fine grinding,and polishing processes are the most critical processes in optical glass processing,and are also the most prone to quality problems.The diamond tools in this process are also the most difficult to make,and the main problems that can occur during this process are as follows:
(1)Workpieces are prone to producing pits
(2)Aperture instability and irregular aperture
(3)Poor surface roughness
(4)Workpiece edge breakage or chipping
(5)Regular or irregular scratches
(6)Grinding discs are prone to passivation
(7)Low cutting efficiency
Most of the above issues are related to the quality of diamond tools,and improvements should be made in the following areas:
(1)Choose the appropriate diamond concentration,which is generally high.
(2)Improving the self sharpening of the binder mainly involves reducing its grinding hardness and uniformity,and reducing low melt segregation.
(3)Reduce the coverage ratio of diamond chips,reduce the grinding surface area of diamond pellets,or increase the chip holding space.
(4)Reduce the dispersion of diamond particle size and the irregularity of its shape.Large particles are never allowed,and too many fine particles are also not allowed.
(5)Adding quasi nano level trace elements to the binder to alter its properties.
(6)Add a small amount of fine abrasive particles to the grinding fluid.
(7)Improve the water and temperature resistance of the resin,and enhance its thermal conductivity.
(8)Reduce the pores in the pills and reduce the crystal size of the binder.