Tooling under pressure
A new tooling system for high-pressure coolant applications, solves chip removal and swarf control problems, supports higher speed cutting data and increases productivity. Graham Smith of Sandvik Coromant discusses the need for a new approach and what has been achieved.
Heat-resistant super alloys (HRSA) such as titanium and nickel based materials and other advanced composite materials have characteristics that make them suitable for aerospace, medical and chemical applications. They are widely used by manufacturers of aerospace engines and landing gear and by producers of high quality, medical hip joint replacements and specialist component suppliers for their stability at high temperatures, excellent resistance to corrosion and low weight to strength ratio.
Manufactured from forgings, final components are usually only 50 to 80 per cent of the original work piece sizes, therefore the machine and cutting tools used need to be capable of machining the size down substantially.
Additionally, many HRSA alloys can be particularly difficult to machine with the result that they make extreme demands on the machine systems and the tools used to cut them. Traditional machines and methods are no longer productive enough.
The HRSA - high pressure requirement
Manufacturers that produce components in HRSA are installing advanced machine tools that incorporate coolants at high pressure (70 bar and above) instead of normal pressure. To gain maximum benefit, a tool holder designed to optimise high-pressure coolant delivery is essential because traditional tool holders are unable to deliver the productivity improvements that HP coolant machines are capable of delivering.
There have been few effective solutions until now, but a new tool holder system from Sandvik Coromant effectively delivers high-pressure coolant to the place that most needs it. The system is a combination of Coromant Capto and CoroTurn HP, known jointly as the CoroTurn HP (High Pressure) tooling system; this has already demonstrated its value for high-pressure coolant machining at an international aero engine manufacturer.
The system is designed specifically for use on machines using 70-80 bar coolant. The tool holder guides the coolant through the Coromant Capto coupling and via the CoroTurn HP nozzles to a precise point on the insert. It delivers improved chip control and extends tool life. Demonstrated to an aerospace engine manufacturer in its prototype form, and subsequently implemented in its production process, CoroTurn HP cutting tools achieved increased cutting data and higher productivity for the customer. Additionally, it was both safer than the alternative and extremely easy to use.
In the specific application for which the tool holder system first demonstrated its value, the shaft component materials are CMV and Super CMV which are turned on multi-task CNC lathes equipped for high-pressure (70 bar) coolant. Results included a 25 per cent increase in feed rate and 50 per cent faster cutting speed.
‘The existing cutting tools were cutting well but chipping poorly’ says a senior manufacturing engineer at the aero engine supplier. ‘Swarf was bad too - and this was causing health and safety issues. Operators had to open the machine frequently to remove swarf - in sharp, long strands’. Consequently, there was an increased risk of cuts and potential for injuries to the operator.
‘CoroTurn HP was far easier to use than the competitor product and managed the swarf far better too; on the competitor product it was coming over the work piece and could potentially cause damage to the tool holder. And compared to the competitive product under test, the Sandvik system was ergonomically better; it needed only one Allen key to index inserts instead of three with the other system.’
Sandvik Coromant’s system is now implemented and operational in the machining process. The manufacturer is currently engaged in evaluating the Capto/CoroTurn HP tools against existing products on other machining operations, including finish boring, in the anticipation of achieving the same benefits of increased cutting data and better swarf control.
How does it work?
CoroTurn HP construction incorporates small nozzles; these deliver a high-pressure coolant jet that penetrates into the heat-affected zone, cooling the insert more effectively and faster and thereby optimising chip control. The jet creates a hydraulic wedge between the top surface of the insert and the underside of the chip being removed from the component or material. This has two benefits; it helps reduce insert wear and breaks the chips into smaller pieces for quicker evacuation from the cutting edge. The nozzles, mounted close to the insert cutting edge, also help increase the velocity of the coolant jet at lower pressures while keeping the insert freely accessible for easy, unobstructed indexing. CoroTurn HP can work with any machine that is equipped with high-pressure coolant and Coromant Capto couplings, including multitasking machines, vertical lathes and turning centres.
In roughing, chip control is rarely a problem. Applying the coolant precisely reduces the cutting temperature which thereby allows either increased tool life or increased cutting speed in any material. Chip control is always more difficult in finishing operations owing to the reduced depth of cut and feed rate. Also, automated production processes, whether high volume mass production using multi-task machines or vertical turning lathes with automatic tool changing, suffer costly machine stoppages if chips gather around the tool. The Coromant Capto/CoroTurn HP system provides total chip control and therefore security for unmanned production and finishing.
To summarise, the benefits demonstrated from this high pressure through tool coolant system include 25 per cent increase in feed rate, 50 per cent faster cutting speed plus supercharged chipping and no swarf problems.
Sandvik Coromant
