How to Make Ceramic Cutting Tools from Scratch?

Many people understand how carbide tools are made, but do you know how ceramic tools are made?

In this article, we will discuss the process of making ceramic tools.

1. Blending process:

This is the process of making the base of the ceramic insert. It consists of two main processes.

① Crushing and mixing process

The raw materials, powder and water, are mixed and pulverised by a ball mill (grinder). The process of creating a homogeneous fine-grain material makes the later firing process easier. This stage is important for making hard and strong ceramic tools.

② Drying and granulation processes

Hot air is blown onto the material mixture from stage ① which causes the fine grains to coalesce into larger round forms. This makes it easier to press the mixture in a later process and create ceramic inserts in various shapes.

2. Pressing process:

This stage produces various insert shapes from the powders created in the previous process.

Powder is packed into a mold to which high pressure is applied to form inserts. A pressing force of 1 – 2 tons/cm2 is applied in order to solidify the ceramic powder. To put it into perspective, this would be equivalent to a hippopotamus stepping on the insert mold. Ceramics have a lighter specific gravity compared to cemented carbides. So, using the carbide pressing process would result in cracks and distortions of the ceramic after sintering. Therefore, the pressing process is exclusive to ceramic tools. The insert pressing process compacts the ceramic material, but there are still gaps between the particles and the inserts are fragile. The process then moves to the firing stage.

3. Sintering process:

This is the baking and solidifying stage for ceramic insert manufacturing.

By heating the pressed shapes, (aggregates of ceramic powders) the ceramic particles adhere to each other reducing the gaps and thereby solidifying and hardening the insert. To make ceramic tools that can withstand high-speed machining, it is essential to manage sintering temperature and time more finely than cemented carbide tools. This process produces hard, strong ceramic tools and also changes the colour of the material due to a chemical reaction between the insert components.

Inserts then proceed to the polishing process to finalise the insert dimensions and corner R.

4. Polishing process:

Polishing the inserts after the sintering stage will minimise dimensional variations of the inserts. Polishing ceramic inserts is performed with the following process.

5. Coating:

When machining cast iron at high speeds, wear may progress more rapidly due to an increase in temperature at the cutting edge. Applying a coating will suppress the progression of wear and effectively improves tool life.

NTK has CVD coated ceramic grades for cast iron machining.

CVD coating is also used for cemented carbide tools, but the coating components and formulations are customised specifically for ceramic tools.

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