Precautions for the use of end mills in ceramic material processing

When using end mills in the processing of ceramic materials, attention should be paid to aspects such as tool selection, cutting parameter setting, machine tool requirements, cooling methods and processing strategies. The following is a specific analysis:

Tool selection:

Material matching: Different types of ceramic knives have different application scopes. The type and grade of the tool ceramic should be correctly selected based on the characteristics of the ceramic material to be processed. For example, alumina-based ceramics are suitable for processing various steels and cast irons, but not for processing aluminum alloys and titanium alloys. Si₃N₄ -based ceramics are most suitable for high-speed machining of cast iron and superalloys. Sialon ceramics are most suitable for processing various cast irons and nickel-based superalloys, but are not suitable for processing steel materials.

Tool characteristics: Ceramic tools have good heat resistance and wear resistance, but they are brittle materials after all, with relatively low bending strength and high compressive strength. To fully leverage the high compressive strength of ceramic cutting tool materials, negative rake angles are generally adopted for ceramic cutting tools. However, the tool after chamfering increases the cutting force, so negative chamfering should not be ground when processing workpieces with poor rigidity.

Cutting parameter setting

Back depth of cut and cutting speed: Under the premise that the machine tool power, the rigidity of the process system and the strength of the cutting blade permit, a larger back depth of cut and cutting speed should be selected as much as possible for cutting to give full play to the good high-temperature performance of ceramic tools. For example, when Changzhou Diesel Engine Factory used a indexable face milling cutter with Si₃N₄ inserts (SM grade) (diameter 250mm, 7 teeth) to mill the lower plane of the HT200 cylinder head (160mm × 134mm), the cutting speed was 471m/min, the depth of cut was 3mm, and the feed rate was 300-1180mm/min. The work efficiency is 2.5 to 10 times higher than that of carbide face milling cutters.

Feed rate: As the feed rate is the most sensitive to tool breakage, the feed rate at the beginning of cutting should be set relatively small, and gradually increased through trial cutting until no tool breakage occurs.

Machine tool requirements:

Machine tool performance: Machine tools using ceramic cutting tools must have high rigidity, high power and high rotational speed, so as to fully exert their performance and achieve good economic benefits. In addition, the machine tool should have good precision, and the fixture and clamping device for holding the workpiece must be reliable to avoid vibration during processing and damage to the ceramic cutting tool.

Cooling method:

Wet cutting: When ceramic tools are in operation, they are usually cut dry. However, if wet cutting is used, the tool life will be longer. Before the tool cuts into the workpiece, the cutting fluid should be poured until the cutting is completed. The cutting fluid must be supplied continuously and not intermittently; otherwise, it is easy to cause tool damage or chipping. Similarly, during the cutting process, it is also necessary to avoid stopping the machine halfway or changing the cutting parameters as much as possible.

Processing strategy:

Path planning: When writing processing programs, it is necessary to ensure that the paths are clear and straightforward, avoiding unnecessary movements and generating redundant processing trajectories to enhance processing efficiency.

Avoid impact: Ceramic cutting tools are brittle, with low strength and toughness. Their bending strength is only one half to one fifth of that of hard alloys. Therefore, when in use, they must avoid being subjected to impact loads to prevent chipping and damage.