Understanding Graphite Machining

In modern industry, graphite is widely used because of its unique properties, from daily necessities to high-tech industries. Graphite processing is the key link, its technical level is related to product performance and application range. In-depth research is of great significance to industrial development.

Characteristics and classification of graphite

Graphite is composed of carbon atoms, in a layered crystal structure. The atoms in the layer are covalent bond into a hexagonal network, and the layers are acted on by van der Waals forces. This gives it good electrical conductivity, high melting point and excellent lubricity. Graphite is divided into natural and artificial two kinds, natural graphite including flake, soil and block graphite, different uses. Artificial graphite is made of high temperature treatment, controllable performance, used in lithium batteries and other fields.

Graphite machining technology

Cutting technology

Graphite cutting is a common processing method, which uses the relative motion of the tool and graphite to remove the material. High-speed cutting is often used to reduce the contact time between the tool and the material and reduce the impact of the cutting force. Because the graphite is soft and brittle, easy to break the edge and slag. At the same time, it is necessary to choose sharp tools and appropriate cutting parameters. Such as machining high-precision graphite molds, cutting speed of thousands of revolutions per minute, fine-tuning the feed to ensure accuracy.

Grinding process

Grinding is a micro cutting graphite surface to improve surface finish and accuracy. Because grinding tools wear quickly, it is necessary to select appropriate abrasives and grinding fluids. Commonly used abrasives are silicon carbide, diamond, diamond abrasives because of high hardness, wear resistance in graphite grinding widely used. The grinding fluid can cool down, reduce wear, clean and lubricated, and improve the surface quality. Such as the graphite mold used for processing optical lenses, and the surface roughness after grinding can reach Ra0.1μm.

Graphite milling

Graphite milling with rotary milling cutter processing, can achieve complex shape processing, subplane, profile, cavity milling. Surface milling processes the plane, contour milling processes the contour, and cavity milling processes the cavity. Machining with multi-edge milling cutter and optimize the path and parameters, such as processing large graphite molds. With high-speed and five-axis linkage milling, it shortens the processing time, ensuring accuracy and quality.

Drilling process

Drilling is to process holes on graphite, graphite brittle, low hardness, drilling is prone to rough hole wall, aperture deviation and hole edge collapse problems. Need to select the appropriate drill bit and parameters, with carbide drill. And reduce the drilling speed and feed, with cutting liquid cooling lubrication. Such as in the graphite electrode processing cooling hole, optimization parameters can make the aperture accuracy control within ±0.1mm, hole wall roughness up to Ra3.2μm.

Carbon graphite machining

Carbon graphite is a special graphite material, and the processing technology is different from ordinary graphite. Some carbon graphite hardness and strength is high, the need for more wear-resistant tools and greater cutting force. And the coefficient of thermal expansion is low, processing to control temperature to prevent deformation and cracking. You can widely use it in mechanical seals, aircraft engines and other fields, processing quality affects the performance and reliability of equipment.

Detailed explanation of machining equipment and tools

Processing equipment

CNC machining center

Set a variety of machining functions in one, controlled by CNC system tool trajectory. It has high degree of automation, fast efficiency, stable accuracy, and is suitable for batch and high-precision graphite processing.

EDM machine tool

Using discharge to remove graphite, processing graphite electrodes and molds, etc., can process complex shapes and tiny structures. And ensure processing accuracy and surface quality by controlling discharge parameters.

Grinding machine

Used for grinding, surface, cylindrical, internal grinding machine, etc., to ensure the surface finish and precision of graphite products.

Graphite machining tools

Cutter

Including milling cutter, drill, etc., due to the characteristics of graphite, the tool material is selected as carbide or diamond coated tool. Carbide tools are suitable for general processing, diamond coated tools are suitable for high-speed and high-precision processing. And the tool geometry needs to be optimized.

Abrasive tools

Commonly used grinding wheel grinding, abrasive selection of silicon carbide or diamond. Silicon carbide grinding wheel price is low, for ordinary grinding. Diamond grinding wheel grinding efficiency and high precision, for high-precision machining. Grinding wheel parameters should be selected according to the material and processing requirements.

Quality control points

Dimensional accuracy control

To ensure dimensional accuracy, regular calibration and maintenance of equipment, accurate measurement of raw materials and adjustment of parameters before processing. Real-time monitoring with CMM, considering the impact of thermal deformation and tool wear, optimization of process and compensation algorithm.

Surface quality assessment

Evaluate surface quality including roughness, defects and hardness. The roughness measuring instrument is used to measure the roughness, the surface defects are checked with the naked eye and the microscope. And the hardness test ensures that the surface hardness meets the requirements. Select the appropriate parameters in the processing and the process prevents surface damage.

Internal defect detection

Ultrasonic, X-ray, industrial CT and other non-destructive testing technologies are used to detect internal defects. Ultrasonic testing takes advantage of ultrasonic propagation characteristics. X-ray testing is based on the difference of X-ray absorption and scattering of defects. And industrial CT generates three-dimensional images to show internal conditions, ensuring product quality and safety.

Graphite machining industry practice

Graphite electrode machining

The graphite electrode is the key consumable in the field of electric furnace steelmaking. Select high purity, high density artificial graphite, cutting, grinding, drilling and other processes. Processing precision and surface quality requirements are high, size deviation and roughness will affect the conductivity and stability. Such as electric furnace steelmaking, the size is not allowed to affect the efficiency of steelmaking. Roughness inconsistency will cause arc instability and electrode loss fast.

Edm graphite machining

For the manufacture of EDM electrodes, higher requirements for material density, purity and uniformity of organizational structure. In addition to the conventional process, it is also necessary to remove impurities at high temperature, improve crystallinity and electrical conductivity. Impregnation to fill the pores, improve density and strength. Its processing accuracy and quality affect the precision and efficiency of EDM. Such as mold manufacturing, high-precision electrodes ensure mold accuracy and life.

Graphite blocks for machining

Graphite block is a common raw material, made of graphite powder pressed and sintered. And its properties vary according to processing needs and application scenarios. High-precision machining, such as graphite electrodes, requires graphite blocks with uniform density and high purity to ensure stable dimensional accuracy. The aerospace field has high strength requirements, and the graphite block will be reinforced with carbon fiber. Its size and specifications are diverse, the shape is regular. And there are special-shaped customization, providing a variety of options for processing.

Graphite machining channels

There are two ways of graphite processing: independent and commissioned. Independent processing is completed by the enterprise itself, the processing cycle and quality are controllable but the cost is high. It is suitable for enterprises with large demand, high requirements and strong strength. Commissioned processing to find professional manufacturers, can reduce costs and risks, suitable for small or no processing capacity of enterprises.

Conclusion

Industrial development has promoted the performance and quality of graphite products, and promoted the progress of graphite processing technology. By optimizing the process and strictly controlling the quality, the industry can produce high-precision products. In the future, graphite processing will also make breakthroughs in materials, precision and intelligence to help the development of the industry.