PCBN solid inserts for finish hard turning
23:17

Base on requirements from customers, the evolution of PCBN has led to the development of different PCBN insert types. What is commonly referred to as the PCBN “format” is how the PCBN appears. As shown below, there are four main groups.

Tipped inserts

A small PCBN-tip is brazed onto a carbide insert. The tips can be on one side or on both sides of the insert.

Multi-bar inserts

PCBN bars are brazed onto a carbide insert. These inserts are double sided, and therefore only available as negative inserts.


Full faced inserts

These inserts have full PCBN-layer on one side of the inserts.

  

Solid inserts

The whole insert is made of PCBN. All corners on the insert can be used.


 

The most common application area for PCBN is hard turning of case hardened steel components, and traditionally tipped inserts are used. By converting to solid inserts, a much more cost efficient production can be achieved. On a solid insert the cost per edge is considerably lower than on a tipped insert.

Depending on if you are doing a copying operation, a straight internal, external or facing operaton, you might need a different shape of the insert. Rigidity and stability of the setup will also influence the choice of insert shape.

For these reasons, solid inserts are available in six different shapes from Seco Tools:
  • TNGN11.. fixed pocket position, 6 edges/insert
  • CNGN09.. fixed pocket position, 4/8 edges/insert
  • DNGN11.. fixed pocket position, 4 edges/insert
  • SNGN06/09.. fixed pocket position, 8 edges/insert
  • RNGN09.. can be rotated freely in the pocket, depth of cut will determine number of edges/insert
  • WNGA06.. fixed pocket position, 6 edges/insert

To improve productivity and efficiency in the operation even more, wiper geometries are available on several of these shapes.

A round insert has the largest “nose radius” of all inserts, and this will act as wiper, improving surface finish significantly. A round insert will also give maximum number of edges per insert. The table below shows the number of edges per side at different depth of cuts.


 


In an existing operation, it is not always easy to change tool holders, and presenting a solution with solid inserts is often met with skepticism, but after explaining the advantages with:
  • number of edges per insert
  • parts per insert
the initial reaction is often replaced by a keen interest. This has been the case at many customers over the years that these inserts have been available, and after implementation, it has helped them to improve efficiency, productivity and cost effectiveness. A few examples are shown below where tool life per insert has been increased significantly.

Hard turning of a gear bore was previously done with a CNGA120408 insert with 4 edges, with a total tool life of 800 components per insert. By changing to a solid round insert in CBN060K, tool life was increased to 3,200 components per insert (16 edges per insert). A rigid setup and a stable tool holder design eliminated the risk for vibrations.

Old solution:                                          New “Solid” solution:
CNGA120408                                         RNGN090300S-01525
Competitor PCBN                                   CBN060K
4 edges/insert                                          16 edges/insert
Tool life: 800 parts/insert                        Tool life: 3,200 parts/insert

 




















Hard turning of another gear bore was previously done with a CCGW090308 insert with 2 edges, with a total tool life of 166 components per insert. By changing to a solid triangular insert in CBN060K, tool life was increased to 858 components per insert (6 edges per insert). A rigid setup and a stable tool holder design eliminated the risk for vibrations.

Old solution:                                           New “Solid” solution:
CCGW09T308                                         TNGN110308S-01525
Competitor PCBN                                    CBN060K
2 edges/insert                                            6 edges/insert
Tool life: 166 parts/insert                         Tool life: 858 parts/insert

 
















Another advantage of solid inserts, the possibility to “plunge” a feature instead of using conventional axial turning will be discussed in a coming newsletter.

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

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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

 
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Finish turning of Ductile iron with PCBN
05:33

Grey cast iron and ductile (nodular) cast iron are the two main types of cast iron used in today’s industry. The main difference is how the graphite appears. In grey cast iron, the graphite is in the form of flakes, while in ductile iron, the graphite is in the form of nodules. The composition is basically the same, but the demand for purity requires the Sulphur content to be very low in nodular iron.

Grey cast iron
Nodular cast iron
Both grey cast iron and ductile cast iron are very abrasive materials, but ductile iron is regarded as the more difficult one to machine. Ductile iron components can be various housings, shafts and other components mainly for the automotive segment.

Differential case, Gearbox house and Cam-shaft


Generally ductile iron is machined with carbide inserts, both roughing and finishing but when there are high requirements on dimensional tolerances and surface finish, PCBN can be an alternative for the finishing tool. The higher wear resistance of PCBN allows for longer tool life with maintained edge quality, resulting in superior tolerances and surface finish.

Roughing is best done with a hard and wear resistant carbide. Seco’s range of turning grades include TK1001, mainly recommended for grey cast iron, and TK2001, mainly recommended for ductile iron.


For finishing, Seco’s CBN150C is the preferred grade. Grade CBN150C combines the optimum balance between substrate, coating and edge preparation for successful finish machining of high quality ductile iron components.

Depth of cut should be kept as low as possible, 0.1-0.3 mm. Cutting data is similar for carbide and PCBN, about 300 m/min, and feed rates will in finishing depend on surface finish requirement, but is in the range of 0.1 – 0.3 mm/rev. Wiper technology will allows for higher feed rates while maintaining surface finish.


Roughing with Seco's carbide grade TK2001


Finishing with Seco's PCBN grade CBN150C



For more information, please contact your local Seco representative, or our PCBN team:
 
 
Author:
Henrik Sandqvist
Product Specialist SECOMAX PCBN/PCD
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
SECO TOOLS AB
737 82 Fagersta, Sweden
Office +4622340254
Mobile +46703431200
e-mail:anders.wickman@secotools.com


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