First, the principle of chip formation

Chip is the material under the action of the tool complex deformation from the surface of the workpiece stripped generated. Tool cutting edge in contact with the workpiece, the material is first compressed to produce elastic and plastic deformation, when the stress reaches the yield strength, in the shear surface slip, extrusion and shear open, and then by the tool front angle to promote the formation of chips. Tool geometry (front angle, rear angle, edge shape), material properties, machining parameters and frictional heat all affect the chip form. For example, large front angle tool is easy to form continuous chips, small front angle or negative front angle tool is easy to form broken chips; processing brittle material is easy to produce broken chips, processing ductile material is easy to form continuous chips.

Second, the type of chip

Continuous chip

Common in the processing of mild steel, aluminum alloy and copper alloy and other ductile materials.

Chips flow smoothly along the front face of the tool, in the form of a long strip or spiral. Advantage is that it can ensure good surface finish under high cutting speed, and the disadvantage is that the chips are too long and easy to wrap around the tool or workpiece, which affects the machining efficiency and safety, and reasonable chip removal is required.

Chip breaking

Usually produced when processing brittle materials such as cast iron and bronze.

Chips in the shear surface quickly rupture, the formation of shorter chips, is conducive to discharge, reduce tool wear, but the surface quality of the workpiece is slightly worse.

Accumulated Chip Tumor Chips

Mostly in the processing of ductile materials and cutting conditions are not ideal (such as low cutting speed, insufficient cooling and lubrication).

When the cutting temperature rises, some of the chips adhere to the front face of the tool to form a chipoma, which will change the geometry of the tool, make cutting unstable, produce scratches on the surface of the workpiece, aggravate the wear of the tool, and affect the machining accuracy, which can be controlled by increasing the cutting speed, using a coolant or coating the tool.

Shear Band Chips

Appears in the processing of titanium alloy or heat-resistant alloys and other high-strength alloy materials.

The material has obvious plastic deformation in the shear zone, forming a wavy shear zone, accompanied by high cutting temperature and large cutting force, easy to lead to rapid tool wear, machining requires high-performance tool materials and adequate coolant system.

C. Difficulty of efficient chip breaking

Difficulty of continuous chip processing

When processing ductile materials, chips are not easy to break, long chips are easy to wrap around the tool or workpiece, resulting in processing interruptions, scratches on the workpiece, machine tool failure, and will block the chip removal channel, increasing frictional heat, accelerating tool wear, reducing machining efficiency, the need for accurate control of cutting parameters and a good chip removal system.

Challenges of chip breaking for non-brittle materials

When machining materials with high ductility, chips are not easy to break naturally, and it is difficult to realize stable chip breaking. If the chip breakage is too frequent, it will increase the cutting vibration and noise, affecting the surface quality of the workpiece and machining accuracy.

Difficulties in chip control for chip tumors

The core problem is the local adhesion and accumulation of chips, which is common in machining ductile metals such as aluminum and copper. Accumulated chips will change the shape of the tool, resulting in changes in cutting force and angle, producing scratches on the surface of the workpiece, irregular roughness and dimensional deviation, increasing tool wear and machining costs, which need to be controlled by cooling and lubrication, selecting the appropriate cutting speed and tool coating.

Shear with chip difficulty

Appears in the high strength alloy or difficult to machine materials cutting, material plastic deformation generated by the shear band will lead to large cutting force and high temperature, so that tool wear increased, high temperature may also make the tool soften or chipping, its wave-like structure will increase processing vibration, affecting the accuracy, need high-performance cutting tool materials, advanced coatings and high-efficiency cooling system.

Fourth, to realize the key points of efficient chipbreaking

Understanding material properties

Processing ductile materials (such as aluminum alloy, mild steel), you can increase the feed (such as 0.2-0.4 mm / tooth), reduce the appropriate cutting speed (such as 300-400 m / min) to increase the shear force to make the chip breakage. Machining brittle materials (such as cast iron), cutting speed control at 100-150 m / min, feed 0.1-0.2 mm / tooth.

Setting cutting parameters

Increasing the feed increases the shear force to promote chip breaking, e.g. when machining mild steel, increase the feed from 0.1 mm/tooth to 0.25 mm/tooth. Increase the depth of cut moderately (1-3 mm, for high strength alloys, cutting speeds of 150-250 m/min are recommended.

Optimization of tool geometry

For ductile materials, set the front angle to 10°-15° and the rear angle to 5°-10°. For machining brittle materials, use negative rake angle (-5°-0°) tools with edge dulling control of 0.05-0.1 mm.

Cooling and lubrication

To cut high-temperature alloys or high-strength materials, use high-pressure coolant (20-50 bar, flow rate 20-30 l/min). Machining ductile materials, oil-based coolants help to reduce chip adhesion and ensure smooth chip removal.