PCBN Chip Breaker Inserts – A New Generation of PCBN Inserts 06:56

The most common application area for PCBN is hard turning of case hardened steel components. Case hardened steel is a unique material combining a hard and wear resistant outer layer (the case) with a very tough core. Below the surface, the hardness decreases with the depth below the surface. A case hardening layer is usually defined by the case hardening depth, equal to where the hardness is below a certain limit, usually 550 HV1 (=52 HRC). The result is a material with desirable properties for harsh environments such as automotive gearbox and drive train components.

Normally in finish hard turning chip control is not a problem, depth of cut is less than 0.5 mm, the hardness is over 550 HV1, and chips generated are brittle and will break without a chipbreaker.

If conventional PCBN inserts are used for machining into softer (< 50 HRC) material, long uncut chips can be a problem. In some processes, it is necessary to remove that case hardened layer, e.g. when preparing for welding. Chips can then become very long and stringy, and get entangled in the chuck, the component, the conveyor equipment etc, leading to problems and even causing the machine to be stopped for removing of the chips.

The main two application areas for PCBN chip breaker inserts are:

• Removing of case hardened layer on e.g. case hardened steel components
• Machining from hard to soft(er) material on e.g. induction hardened components

Another area where PCBN chip breaker inserts can be beneficial is:

• Inner diameter machining with poor chip evacuation

The SecomaxTM chip breaker geometry is laser machined, and this provides several benefits over conventional production technologies such as grinding. Laser technology meets the highest requirements regarding dimensional accuracy, geometrical precision and surface quality for the machining of intricate, three-dimensional geometries. These advantages and possibilities have led to a complex formed chip breaker with “bumps” that would have been impossible to produce with any other production technology.

The laser machined chip breaker comes in two different styles, one for low (non-wiper) and one for high (wiper) feed applications. The non-wiper chip breaker insert makes it possible to have good chip control when low feed rates are used. The wiper chip breaker insert provides improved chip control when using high feed rates.

Below is an enlargement of the “chip breaker geometry” (left), and close-ups of the chip formation without chip breaker (middle) and with chip breaker (right).                    

The addition of a chip breaker can substantially improve process reliability and productivity. The left example below is an example of removing the case hardened layer (preparing for welding). In the right example below, the customer had problems with chip evacuation, and had to stop the machine and manually remove chips from the component and tool holder. After introducing chip breaker inserts, they could run without stops. As an additional benefit, tool life was also increased.

For more information, please contact your local Seco representative, or our Advanced material (PCBN/PCD/CERAMIC) team.

Author: Henrik Sandqvist Product Specialist SECOMAX PCBN/PCD/CERAMIC SECO TOOLS Shanghai CO., Ltd. Level 2, Building 8, 456 HongCao Rd., Shanghai 200233, China Office: +86 21 5426 5849 Mobile: +86 186 167 90063 e-mail: henrik.sandqvist@secotools.com

Product Manager: Anders Wickman Product Manager SECOMAX PCBN/PCD/CERAMIC SECO TOOLS AB 737 82 Fagersta, Sweden Office +4622340254 Mobile +46703431200 e-mail:anders.wickman@secotools.com