K&M Präzisionstechnik in Kunststoff und Metall GmbH (K&M), a company in the Müller Group, is located near Ravensburg in Germany. K&M manufactures complex turned parts for the electrical (sensors), mechanical and medical engineering industries and for the aerospace industry. Markus Müller, Executive Assistant at K&M, emphasises: “We see ourselves as systems supplier for finished assemblies, not only as a manufacturer of turned parts.” This ranges through to complex parts such as servos consisting of 150 to 200 individual parts for ICE high-speed trains.

Flexibility requires a wide range of tools

We design, manufacture and assemble parts which we machine by turning or milling, grinding, 3D printing, eroding and produce moulded parts in-house in 3-shift operation. Some of these parts are made of materials that are difficult to machine. Our everyday work often involves keeping to high accuracies and complex geometries with diameters ranging from 3 to 200 mm for turned parts. With batch sizes from one to 100,000 units, anything is possible. This flexibility demands a wide selection of tools. Luckily, the basis for many applications is already laid thanks to the comprehensive systems from ARNO Werkzeuge, a manufacturer of precision tools for grooving, turning, drilling and milling based near Stuttgart. “From the start, we’ve had our fingers on the pulse of time and we have kept up with a variety of technologies. This also applies to tools.” says Martin Hager, Mechanical Engineer Design/Programming at K&M. “What’s the degree of automation in our production? Actual automation takes place with bar material on Swiss type machines. Once the machine is set up, all the operator has to do is check and make minor adjustments as necessary.” Process reliability is top priority. The machines run at a capacity utilisation of 90% and the tool has to keep up with this rate. So when we receive new tools, we test them to see whether they meet our expectations when it comes to tool life and simplicity.

The challenge: process reliability and simple handling

After we successfully introduced the ARNO SA system for parting off and grooving with ACS internal cooling in K&M at the end of 2017, the focus was on the complicated tool changes for Swiss type machines. Here, the tool holders in the sliding head are connected to the coolant feed system via several adapters, copper pipes and hoses. It means long set-up times and high costs for connecting the internal cooling system. Tool changes are complicated. Even loosening and tightening the screws is not easy in the limited space. Very often the tool holder has to be removed from the sliding head to change the tool and after the change, the tool length has to be recalibrated. This work step takes a long time and leads to relatively frequent errors. “As opposed to fixed head machines which can move the revolver into a convenient position to change the tool, machine operators have to change the tool on a Swiss type machine almost blind,” explains Christoph Hipp, sales engineer at ARNO Werkzeuge. Alexander Stein, Turning foreman at K&M, adds: “It’s just not good for process reliability and takes so much time. This urgently needs a solution!”

The solution: the ARNO Fast Change system

The ARNO team accepted the challenge, analysed the problem and found a solution that is simple and just as reliable in the application: the AFC system (short for ARNO Fast Change). This is a two-part tool holder for grooving and turning available with or without internal cooling. Thomas Ament, Application Engineer at ARNO Werkzeuge, explains: “The AFC system has a chamfer at the front of the tool holder and at the corresponding back part, the fixed stop. This is how we achieve the exact clamping effect. Coolant transfer is fitted with a flexible tube which is economical even when compared to the competition.” But the special feature of the two-part tool holders is their easy handling. Due to the integrated O-ring, the front part does not drop into the chip tray after the screw is loosened. It stays safely in the head until it is removed. In addition, the O-ring in the tools provides an optimised seal and prevents any coolant loss or dirt from entering. After the front part is removed, either the insert is changed or replaced by a different insert. The front part can be easily changed by fixing the new part on the fixed stop which remains in the machine. It is safely merged and immediately connected to the internal coolant supply. The floating mount compensates for any misalignment when the tool holder is clamped and this achieves a high rate of repeatability. Accuracy during a change lies within a range of hundredths and saves the operator from carrying out correction work thanks to the identical length inside the tool system.

Impressive results: 3 minutes saved, tool life increased by 45%

We first tested the SA system for parting off and grooving with internal cooling in AFC variant for four weeks. Tool life was not only maintained but increased from 550 units to 800 units straight away. On top of this came the change times. “In the past, a trained machine operator needed 5 minutes to change a tool. Then the tool had to be recalibrated to 0. With the new AFC system, he only needs 1 to 2 minutes for everything,” says Alexander Stein delighted. With a batch size of 40,000 parts, this is a very profitable time saving.

After about six months in use on the machine, the outstanding results more than impressed K&M GmbH. Besides improvements in change times and tool life, the easier handling is a blessing, simply because the machine operators are often untrained – the keyword here is the lack of skilled workers. Reliable internal cooling is also an enormous relief, as Christoph Hipp discovered: “To offer flexible production processes, internal cooling should be ensured right from the start. Flexible workpieces, flexible applications and materials make internal cooling an absolute necessity. With internal cooling, chip evacuation is assured right from the start and this minimises thermal stress on the cutting edge.” This is all about risk minimisation and also about meeting all the customer’s requirements – both at K&M and ARNO Werkzeuge.