How to process threads for alumina ceramics

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Alumina ceramics have been widely used in aerospace, electronic communication, medical equipment and other fields due to their high hardness, high temperature resistance, corrosion resistance and other characteristics. However, its high hardness and brittleness also make thread machining a major technical challenge.

1、 Challenges and Solutions in Aluminum Oxide Ceramic Thread Processing
The Mohs hardness of alumina ceramics is close to level 9, second only to diamond, but its toughness is low and it is prone to problems such as edge breakage and fragmentation during processing. Traditional metal processing methods (such as ordinary tapping) are difficult to directly apply to thread processing of alumina ceramics, and require the following technological innovations:

1. Special equipment: Adopting a ceramic precision carving machine, its high rigidity structure can reduce vibration, and the protective system can effectively isolate the damage of ceramic powder to the machine tool.
2. Superhard cutting tools: Use diamond or cubic boron nitride (CBN) cutting tools to improve wear resistance and cutting efficiency.
3. Parameter optimization: Reduce cutting speed, control feed rate, minimize machining stress, and avoid material damage.

2、 The core process of aluminum oxide ceramic thread machining

1. Tapping processing
   -Applicable scenarios: Internal thread machining with small diameter (<30mm) and moderate precision requirements.
   -Technical points:
   -Using flexible tapping clamps to compensate for axial feed errors of the machine tool and ensure precise pitch.
   -Programming requires strict matching of spindle speed and feed rate (feed rate=speed x lead), and control of right-hand/left-hand threads through G84/G74 commands.
2. Milling thread processing
   -Advantages: Suitable for machining large diameter and high-precision threads, with tool life more than 10 times that of taps.
   -Implementation method: Through a three-axis linkage CNC system, thread milling is completed using G02/G03 spiral interpolation instructions, supporting flexible diameter adjustment, especially suitable for deep threads and large pitch requirements.
3. Ultrasonic assisted machining
   -Principle: Utilizing high-frequency vibration to induce local plastic deformation of ceramics, reducing the risk of brittle fracture, suitable for thin-walled and complex structural threads.
   -Effect: The surface roughness can reach Ra0.4 μ m, and the machining accuracy is improved by more than 30%.
4. Laser processing
   -Features: Non contact machining, no tool wear, capable of handling micrometer level threaded structures, small heat affected zone, suitable for precision electronic components.

3、 Sintering Process for Aluminum Oxide Ceramic Thread Processing
An innovative method for machining aluminum oxide ceramic threads is to achieve thread formation through sintering technology. The specific steps are as follows:

1. Preparation of tire blank: Dry the alumina granulation powder and press it with an isostatic press to obtain the alumina to be processed tire blank.
2. Thread processing: Process threads on the tire blank to obtain a tire blank with threads.
3. Gradient segmented calcination: The threaded tire blank is continuously sintered using gradient segmented calcination process from room temperature to 1600 ° C for 36h-58h, with the temperature continuously increasing stage taking 34h-52h during the continuous sintering process. After sintering, it is cooled to obtain alumina ceramic products with integrated threads.

This process can strictly control the sintering shrinkage rate of alumina ceramics, ensuring that threaded products have uniform specifications and sufficient accuracy after sintering.

4、 Key points of quality control

1. Dimensional accuracy: Real time monitoring through a coordinate measuring instrument, with tolerances controlled within ± 0.01mm.
2. Surface treatment: Diamond polishing solution is used for mirror treatment, with a roughness of ≤ Ra0.2 μ m.
3. Composition testing: Analyze to ensure that the purity of alumina is ≥ 99.5%, and avoid impurities affecting performance.

Through the above methods and processes, the problem of thread processing of alumina ceramics can be effectively solved, promoting its application in more fields.