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Machining with driven tool holders

Technology 2017-06-15 Åsa Backman Stefan Estassy

Quick change and driven tool holders reduce total manufacturing time and allow for flexible machining.

​In manufacturing, productivity boils down to how many components you can produce in a certain time. The two main parameters to tune are metal removal rate and machine utilization.

“Metal removal rate is an obvious productivity parameter, but I would say that machine utilization is even more important,” says Mats Backman, project manager for tool holding at Sandvik Coromant. No matter how powerful the machine and how efficient the tools are at removing metal, the machine must be running to produce components.

​Sandvik Coromant has advocated “green light machining” for many years. There are several actions that prevent that green light from shining, such as tool changes, various measurements, coolant pipe settings and moving the component to another machine for a subsequent operation.

Bo Hammarberg, product manager and application specialist for tool holding at Sandvik Coromant, says that more and more customers are using turning centres with driven tool holders (DTH) to reduce their total manufacturing time. This solution allows for flexible machining of several operations in one machine and reduces the number of bottlenecks in production.

“B-axis machines are one option to do turning, milling and drilling in one set-up,” says Hammarberg. “For medium- and high-volume production, however, it’s hard to compete with the quicker tool change on a turning centre with a turret. Turning centres provide much faster tool indexing. The only drawback with driven tool holders is the limited number of tool positions, but that’s easily solved with our Coromant Capto Quick Change system.”

The Coromant Capto Quick Change system is well respected in the industry for the substantial reduction in time spent on measuring, set-up and tool change it allows, as well as for the through coolant that saves valuable time compared with external coolant pipe setting. Instead of changing worn tools in the machine, the solution allows for replacing the whole unit with a sister unit in seconds. The worn tool can then be replaced in the initial unit while the machine is running.

“Every second saved in mounting and measuring means an extra second for metalcutting in that machine,” Backman says. “These parameters have a huge impact on machine utilization.”

To be able to recommend the best milling solution for turning centres, Hammarberg and Backman performed a test in a modern CNC turning centre. They tested milling tools in four different tool-holding set-ups with both standard and short-design tool holders. The short designs are dedicated for DTHs with no gripper-groove required for automatic tool change, allowing the shortest possible length.

Taking it to the test

​Test 1 - Slender and T-version

Testing of two different CoroChuck 930 – a slender version with gripper grooves and a T-version without gripper grooves – along with a CoroMill Plura, diameter 16 millimetres in a full slotting operation.
The T-version exceeded the slender version in terms of both tool run out and metal removal rate, thanks to the shorter tool set-up. The maximum depth of cut, before vibration occurred, was 3 millimetres for the slender version and 12 millimetres for the T-version.

Test 2 - Different Coromant EH adaptors

Testing of two different Coromant EH adaptors – one standard with gripper grooves, and one with short design and no gripper grooves – along with a CoroMill 316, diameter 16 millimetres in a full slotting operation.
Coromant EH adaptors provide a shorter assembly length than using a chuck, which is an advantage in smaller machines. The short length allowed both the normal and the short designs to run with maximum depth of cut.



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