Brief introduction of Technical ceramic, precision machining method, and what ultrasonic machining can achieve

2020-10-10 15:27:04



The Definition of Technical Ceramic:

Technical ceramic is also referred as precision ceramic and advanced ceramic. Technical ceramic can be classified with applications or the compositions of materials, such as technical ceramic and engineered ceramic, or silicate ceramic and oxide ceramic. Popular types of technical ceramic are alumina, zirconia, SiC and AIN.

The differences between technical ceramic and traditional ceramic are derived from raw materials and manufacture process. Traditional ceramic is naturally-occurring and commonly combined with clay and quartz sands. With three main procedures, mixing, shaping and firing, traditional ceramic is often applied to artwork and furniture, such as bricks, tiles and pottery.  Technical ceramics were made by a totally different way. First, it requires to be highly purified inorganic compounds which are formed from finely divided powders. The forming procedure is also including mixture with organic binder to help consolidate the powder, so that it can shape more precisely. If dimensional spec is not needed to be precise, material can machine before sintering to prevent extreme hardness and brittleness.  

The second step is sintering, which means heating the blank in high temperature condition to strengthen its structures. Apparent shrinkage about 10-40% after sintering is a big problem when it comes to precision demands, the extreme hardness after sintering is also a challenge. Consequent procedures such as secondary machining and polishing are depends on the requirements of final workpiece.

To sum up, technical ceramic is highly purified powder and manufactures by multiple procedures to make sure it is strong enough to apply in harsh environment. We can think technical ceramic is a kind of upgrading product compared to traditional ceramic.



Pros and Cons of Different Methods in Technical Ceramic Processing

1. CNC Milling/Grinding/Drilling

Most common way to process technical ceramic, and it is also suitable for various shapes and features without restrictions of thickness. Take equipment cost and versatility into consideration, conventional CNC is the most economist way.

However, because the hardness and brittleness of technical ceramic, so it is susceptible to micro-cracks, and improper cutting force and accumulated cutting heat also cause short tool life and low efficiency.

2. Water-jet cutting

Water-jet cutting method can apply to various materials with no limitations of thickness and hardness, and it is relatively user-friendly to manufacturers.

The tolerance of water-jet cutting is about 0.03mm-0.05mm, which can be acceptable in many applications. Moreover, the principle of water-jet cutting is using high-pressured water column jetting straightly to objects, so that theres no need to worry about thermal impact and chemical effect. Although it seems to be perfect in all aspects, water-jet cutting is hard to cut small piece materials and the expensive selling price might to too hard to invest. Water-jet cutting is popular in aerospace industries to cut composites currently due to precision demands, huge workpiece and the consideration of thermal impact.

3. Laser cutting

Laser cutting is a kind of non-contact machining without frictions in cutting. By high energy of laser spotlight heating the material to ultra-high temperature instantaneously, it can easily melt or even gasify the surface of materials. The principle of laser cutting is using instant-heating to penetrate materials, the problems of materials thickness can be a challenge. Generally speaking, the drilling availability of laser cutting in alumina and zirconia ceramic is about 0.5mm, it is the least depth than all kinds of machining methods. Despite tolerance of laser cutting (about 0.02mm) is more precise than water-jet and conventional CNC machining, we cannot ignore the carbonize surface of the material and extremely expensive price of laser cutting machine.

4. LS- Wire EDM

Low-Speed Wire cut EDM is commonly applied to extremely hard materials, thin-walled materials and hard to cut materials since it has low cutting force with high precision. The electrode wire moves in one direction at a low speed, the wire speed is generally lower than 0.2mm/s, the accuracy is 0.001mm, and the surface quality is close to the grinding level. According to the sophisticated machined performance, the shortage is apparent, either. Slow speed and special purpose machine will be a dilemma for manufacturers.



Ultrasonic Technology

Ultrasound technology is widely applied in diverse areas, from ultrasonic cleaner to food cutter. The whole process of ultrasonic machining has no thermal and chemical impact. With 20000-40000Hz high frequency ultrasonic vibration in Z-axis dimension, it can slightly remove materials from surface and prevent micro-cracks hard and brittle materials machining. Also, the amplitude of ultrasonic vibrations can effectively reduce cutting force and enable coolant directly drip to the tool edge, so that the tool life can be prolonged greatly.



Ultrasonic Machining Applied in Semiconductor Ceramic Parts

High standard of surface quality is the basic in semiconductor industries because of the processing environment cannot withstand any pollution. The high cost per workpiece requires stable processing, and tool life is an important factor. Ultrasonic machining prolongs tool life, and it can both reduces tool costs and lower the surface roughness.

Ultrasonic micro-machining is commonly applied in semiconductor parts fabrication. The oscillation removes materials in each micro-oscillation and avoid improper cutting force from damaging workpiece. The vibrations also prevent cutting accumulation in micro-holes drilling and the coolant can flow to the processing area more easily.

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