Cover Story

Milling Technology: 5 New Trends

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Highlighting the most significant developments in milling technology.

The development of machining technologies and practices over recent years has reached to a level which were difficult to manufacture with required tolerance and quality, can now be attained by much more ubiquitous equipment with added value. A broader picture of change exists outside of the field of machining as manufacturing companies demonstrate a trend to concentrate on core competencies and retain their internal capabilities in design, product assembly and niche skills. However, Vikas Taneja, Vice President – Marketing at Jyoti CNC Automation Ltd observes, “The sector is underpinned by mature, robust technologies that through a more general appreciation of their capabilities can bring benefits to users, delivering bottom-line benefits in productivity, quality and market response.”

He continues: “There are mainly three areas which have made revolutionary movement in milling technologies – Digital evolution, Bridging CAD/CAM gap and Additive Manufacturing. Due to development in these areas standalone machining has been moved to automation and robotic aligned manufacturing.”

1
Make It Easy
Machining of much complex component with desired quality outcome can be possible with software incorporations. “Additive Manufacturing has moved to part prototyping and low-volume production to making mass manufacturing and it is going to shape up future of the existing technology with a different concept of designing and manufacturing,” said Taneja. He adds, “Capabilities of extending 3-axis to 5-axis machining in milling technology has made it most versatile way of metal cutting process with mass and precision.”

2
High productivity milling options
“Milling developments are primarily moving in two directions. One direction is towards very high speeds and low chip cross-section. More the case for high-speed machining centres with 30 to 40,000 rpm. The second direction is towards high feeds and depths of cut at moderate cutting speeds to increase metal removal rates,” opines Naveen Vastrad, Senior Manager – Marketing (Products), TaeguTec India. He informs, “TaeguTec is concurrently working in both directions to offer optimum solutions to customers, based on application and machine capabilities. In this connection, we have an entire range of high productivity milling options.”

For instance, TaeguTec’s chip splitter inserts, which reduce cutting forces during heavy milling, while achieving high table feed without the vibrations and the noise. The insert’s helical cutting edge geometry enables double feed rates and improved chip evacuation with minimal heat generation. These chip splitter inserts are an economical option and development over the conventional and expensive vibration dampening cutters, claims Vastrad. Traditionally, when vibrations and unfavourable conditions were encountered (long reach, unstable fixture, chip removal issues, machine power limitations), anti-vibration milling cutters were considered, but chip splitters are easily an optimum and convenient alternative.

3
Increasing demand for fast metal removal solutions
In the last few years, there have been many exciting developments in high-speed machining relative to machining centres and controls, tooling and CAD/CAM systems. Today, according to Vastrad, the machining centre market constitutes at least 60 per cent of the total market, primarily used for milling and drilling operations in small, medium and large batch production. He believes, “Tools and designs which significantly increase the metal removal rates (MRR), particularly in roughing operations, with shorter cycle times, fewer tool changes and inventories can go a long way in ensuring bottom line growth for customers.”

Among TaeguTec’s fast metal removal solutions are the very successful and popular Chase Feed and Chase2Feed Families which make possible high-productivity high-feed milling: maximum feed or tooth up to 5 mm at 1 mmDOC.

4
One cutter, many choices
According to Gautam K. Ahuja, Managing Director, Dormer Tools India Pvt Ltd, the most significant milling technology developed this year, in Dormer Pramet is one of the most versatile cutters in the world – “One Cutter, Many Choices”. A wide range of insert shapes can be used in operations from roughing to finishing – octagonal, round and square inserts can be mounted on the same cutter, depending on application.

The new SOD05 cutter, developed under the Pramet brand, reduces tool change-over time and inventory costs with its universal pocket capable of carrying octagonal (OD), round (RD), and square (SD) inserts.

The OD insert has eight cutting edges and low cutting forces, promoting an economical option for face milling, while the RD inserts are suitable for high feed roughing, shallow profiling and ramping. Its SD inserts have four cutting edges and offers a 90-degree option for square shoulder milling, providing high depths of cut up to 10mm. All types of inserts have the same radial and axial positions of edges – allowing for easier CNC programming and manual operations.

“The user-friendly cutter, available in a wide range of diameters from 32 – 125 mm, can perform face milling, shoulder milling, slotting, plunging and ramping in steel, stainless steel, cast iron and non-ferrous materials,” Ahuja informs.

5
Highly rigid clamping tools
“The recent development of HELLER by introducing the 160 mm diameter face clamping with XPC spindle unit makes the clamping of tool very rigid by which we can go with very high feeds,” said Mahesh Tyagi, Managing Director at HELLER India Pvt Ltd.

Latest development is to use new cutter bodies that offer better heat resistance with differential pitch for vibration-prone applications. The light-cutting insert geometries and high-performance grades of this cutter provide secure milling in all material groups. “At the end the development of the new milling technology directly relates with the spindle and the XPC unit is the best example,” he adds.

A success story
Automated precision milling in the medical technology sector
Fetzer Medical GmbH & C. KG is a medium-sized company based in Tuttlingen/Germany, which was established in 2008 by Peter Fetzer. In order to build further on the family business’ long-standing tradition in the development and manufacture of surgical instruments and medical devices, Peter Fetzer took the decision. With the aim of operating exclusively as an independent OEM, establishing all the necessary human and technical resources to that end, Fetzer Medical launched an extensive capital investment, qualification and certification programme, beginning its five-axis machining in 2008. This was rolled out with the aim of offering a flexible and swift approach to delivery for varying product and batch sizes. All relevant materials, including titanium, are machined and Fetzer Medical supplies its customers with ready-to-use products – from prototypes/individual parts to large production runs and complete systems. The business currently employs 45 highly-qualified employees and state-of-the-art equipment. Roughly 75 per cent of the work involves complex milling/drilling operations which have been performed at Fetzer Medical from day one using high-performance five-axis machining centres from Maschinenfabrik Berthold Hermle AG in Gosheim.

From manual single part fabrication to industrial production
Fetzer Medical production manager Bernd Zepf comments on the choice of Hermle machines: “The Hermle machines featuring a robust gantry design, the machine concept of three-axis in the tool and two-axis in the workpiece, which results in optimum tool accuracy, and last but not least excellent accessibility are ideal for five-axis complete machining in one or two setups. Further, our employees, including myself, had already had very good experience in the past with Hermle machines: their control and programming, their comparatively simple operator control, including responsive and highly competent service backup. That experience helped us to immediately get started with five-axis technology, which we launched in 2008 by acquiring a Hermle C 40 U high-performance five-axis CNC machining centre.”

As the business flourished, capacity had to be increased, and a number of Hermle machining centres – some of them highly automated – were added. Fetzer Medical today runs five machining centres assuring the prompt execution of its OEM production orders. While the first purchased five-axis C 40 U machining centre was initially used to cement the business’ manufacturing expertise and add valuable additional know-how, the machine is now primarily used for pre-fabrication and for machining prototypes, samples and short runs. Additionally, two further C 22 U high-performance five-axis machining centres are equipped with 11-pallet changers/magazines of type PW 150, and are used for the automated flexible production of a wide range of components in runs of up to 300 pieces.

Validated and certified: Production processes on Hermle machining centres
A further automation level includes a C 12 U high-performance five-axis machining centre combined with an RS 05 robot cell for the production of modular designed scissors. A C 800 V CNC machining centre was added to the range of Hermle machines to provide flexible and universal operation in pre-production, including making reference surfaces and jigs and fixtures. Since all the installed Hermle machining centres are essentially based on the same concept and on the same control and operating philosophy, operators are quickly familiarised with running the various machines, and staff confidence and acceptance of the machinery is enhanced as a result. This is definitely advantageous in terms of the productivity of the machines which are run basically in single-shift mode under operator control.

Since – according to specifications of EU and US institutions – production and quality assurance equipment needs to be fully validated and certified in the surgical and medical technology sector, it is a major advantage in terms of US certification that many US medical technology firms use already validated Hermle machining centres for their production lines. This also ensures simpler and faster validation cycles for Fetzer Medical, thus resulting in a faster time-to-market for the company’s customers.

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