The importance of the tool holder is still understated, especially when it comes to roughing and heavy dutymachining. Metal removal rates in these types of processes are absolutely crucial for the productivity of the machining operation. By using special shrink fit chucks with drive pins and spiral grooves in the tool shank it is now possible to performhigh-feed full slotting of up to 2 x D (50 mm) or more indifficult to machine materials. Application studies conducted by the machine tool manufacturer Heller have proven the effect of the HAIMER Safe-Lock system.

Especially within the aerospace, energy and mechanical engineering sector, production managers have to bridge the gap between economic efficiency and high process reliability when working with materials that are difficult to machine. Fortunately there is peace of mind in knowing that the machine technology innovations continue to develop to meet the ongoing demands of manufacturing.Heller machine tools is known as a source of inspiration for these kinds of innovations. The company, located in Nuertingen, Germany, is known for its high quality 4 and 5-axis CNC machining centres, CNC mill/turning centres, CNC machines for crankshaft and camshaft machining as well as flexible manufacturing systems. Customers value their availability of products and their competency in managing special processing demands. Both qualities stem from Heller’s in-house manufacturing, which relies on closer collaboration with customers, suppliers and researchinstitutes to remain on the forefront of innovation.

Roughing is a highly promising process

Werner Kirsten, who is working in the Technology Development Department at Heller and is responsible for the area of “difficult to machine materials“, explains: “our service includes optimizing the machining processes together with our customers and suppliers. To support such services with practical trials, our Technology Center is equipped with a variety of machines”. In most cases the aim is to increase the productivity without compromising the process reliability. Technologist Kirsten adds, “We often achieve this aim with an optimized roughing operation which ultimately results in a reduced finishing process. By maintaining the same technological values, but shortening the finishing depth of cut by 50%, the overall machining time is reduced to half. However, this requires process reliable and controllable systems during roughing.”

In this regard,all machining components in the process chain have to be considered in order to improve productivity. The machine tool is the most evident component of the machining process, however the tool, the tool holding system, the coolant supply and other elements are also essential for a successful operation. “In the end the weakest link of the process chain limits the success,” Werner Kirsten emphasizes. In his opinion most machine shops don’t pay attention to the tool holder even though it is especially significant for high performance cutting. “Many of the trials which we carried out during the last few years have proven this point”, Werner Kirsten explains. We realized that the tool holder hasan incredible influence on the machining process. In the case of reinforced shrink fit chucks, for example, the vibration node is closer to the bearing point (due to the larger mass). The result is a smoother machining process with less vibration and a better surface finish quality while using the same tool, machine, process parameters and fixturing technology.”

Tool holding – an important factorfor productivity

By selecting the right tool holder you can even achieve good productivity and surface quality results using basic standard cutting tools. Werner Kirsten refers to comparative tests with basic four-edge cutting tools without an inner coolant supply. As an alternative to a standard shrink fit chuck he selected a HAIMER Power Shrink Chuck with Cool Flash which ensures that the coolant is transported directly to the cutting edges. “Compared to using a normal shrink fit chuck and externalcoolant, we were able to achieve significantly better results.”

When a group of representatives from the aerospace industry, the Technical University of Dortmund and Technical University of Hamburg-Harburg visited Heller,an especially extensivemilling application study was conducted in Titanium Ti-6AI-4V.

Gaining new insights from difficult cases

The available machining center was a four axis Heller H 5000 with a gear unit and HSK-A100 spindle, which yields torques up to 2.290 Nm. In order to demonstrate the machining potential, different 25mm diameter end mills were used to mill full slots into a titanium plate. To simulate holder conditions used in the aerospace industry, the tools were clamped into reinforced shrink fit chucks. At an axial cutting depth of0.5 to 1.0x D the machining process was found to be very reliable. Since the spindle was not running at full capacity, the trial participants agreed to increase full slottingdepth to 2 x D. Werner Kirsten explains: “Under these conditions the tool pulled out of the shrink fit chuck during the machining operation, creating a slot closer to 2.5xD as it progressed through the part. Towards the end of the slot the tool finally broke as a result of increased cutting forces.”

The milling specialists all agreed that the clamping force of the chuck was the limiting factor in this process. As soon as the axial pressure and process related vibrations are too high the tool moves out of the chuck and further into the workpiece. At the same time the cutting pressure increases such thatin the end the tool breaks and the workpiece is irreversibly damaged.

Reasons and possible countermeasures were discussed intensively. In the end, Werner Kirsten developed the idea that the tools are forced to navigate towards the spindle when the holding forces are exceeded. This is how he ultimately noticed the patented HAIMER Safe-Lock system which in addition to frictional clamping forces, has the same helix pattern as the tool. Theoretically, he realized that even if the tool got loose while using Safe Lock, it would be pulled into the holder through the helical drive keys and not into the part. A movement that can be easily prevented through the use of length presetting screws.

Prevent tool pull-out

Werner Kirsten got in contact with HAIMER, the European market leader for tool holding technology, in order to test the Safe-Locksystem: “we wanted to know if our ideas could be put into practice using the HAIMER system in an even less forgiving environment.” The Heller technology developer repeated the described trial,with a few major changes. HAIMER Safe-Lock grooves were subsequently added on similar solid carbide tools, but the application would be run again with a reduced spindle taper interface (HSK 63 instead of HSK 100), with a less rigid 5-axis gear driven spindle and a less stable diagonally fixtured workpiece.

The result: Despite these additional limiting factors, the tool was able to process a full slot of 2 x D = 50mm with complete process reliability. Werner Kirsten says: “this way we were able to indirectly prove that Safe-Lock works and that the shrinking technology has even more potential with HSK-A100, especially on 5-axis machining centers withgear spindles.” Afterwards this samplemachining on Ti-6AI-4V was carried out various times, including during the Airshow in Farnborough, whereby it was proven that the previous limit of 1 x D = 25 mm full slotting in titanium could be doubled with the use of Safe-Lock.

Kirsten summarizes the results as follows: “For roughing operations this is a reliable process. Therefore I consider the HAIMER Safe-Lock system a practical, easy to handle and process reliable addition to the shrinking technology which we already utilize, especially in connection with standardized tools of other manufactures.”

A number of tool manufacturers are offering Safe-Lock products

From the onset of its creation, HAIMER recognized the incredible potential of the Safe-Lock system, which is why the company created a licensing program to give innovative tool manufacturers the ability to integrate the patented pull-out protection system into their tools. The result of their

vision to create a more open system has been a tremendous success, with leading cutting tool manufacturers having now signed licensing agreements, including Walter, Widia, SandvikCoromant, Seco Tools, Sumitomo, Kennametal, Helical, Emuge Franken, Data Flute, Niagara, OSG,SGS Tools and recently Mapal.

Through the steady increase of Safe-Lock tooling in the market via Haimer and its licensed partners, the system has become the new standard for heavy machining and roughing. In fact, the popularity and simplicity of Safe-Lock is such that it is also replacing the old Weldon clamping system, particularly when new milling strate-gies such as trochoidal (dynamic) milling are involved. President of HAIMER Group Andreas Haimer explains: “With our Safe-Lock system we found a solution that combines a high runout accuracy with 100% pullout protection. The system has es-tablished itself successfully as a standard in the aerospace industry and generally speaking for roughing and heavy duty machining. And now more and more compa-nies that make use of the trochoidal (dynamic) milling strategy are also making the switch to Safe-Lock, and for a good reason.”

During trochoidal milling operations, where the cutting speed and axial depth of cut can be increased through software support, productivity is significantly improved. However, the increased cutter engagement and cutting forces that result from the higher cutting performance create a situation where tool-pullout can occur very easily. Prior to Safe-Lock, this problem was prevented with Weldon shanks and chucks.However customer had to sacrifice speed and accuracy due to the nature of this clamping system. A shrink fit chuck with Safe-Lock offers the same safety as the Weldon system, but provides the additional advantage of accuracy and balance. The ideal balancing and runout characteristics of the shrinking technology in combi-nation with the clamping safety of the Safe-Lock system permit greater productivity achieve through fasterpermissiblespeedsand increased tool lif e all with complete tool security assurance

The fully automated SCHUNK PRISMO3 grinding toolholder is a high-precision all-round solution for automated production grinding and sharpening of tools. By means of direct clamping, i.e. without the use of collet chucks or intermediate sleeves, SCHUNK PRISMO3 steplessly clamps all shank diameters between 3 mm and 20 mm on the fly. The clamping repeat accuracy is permanently ≤ 0.005 mm and the run-out accuracy is ≤ 0.01 mm at an unclamped length of 45 mm. During the clamping process the tool shank is automatically centered in the toolholder. An optimized contour assures that the grinding wheel can run out unimpeded, even in demanding operations. In comparison with conventional multi-area grinding toolholders, the set-up time is reduced by up to 75%. In addition, users save by not having to invest in intermediate sleeves and collet chucks. Since the X-axis always remains unchanged, regardless of the tool diameter, which means all clamping jaws remain in the identical axial position, it is possible to machine a broad range of drilling, reaming and milling tools around the clock in unmanned operation without reprogramming the L1 measurement, even when working with small quantities. The expense of additional pro-gramming and the danger of a crash due to unnoticed axis misalignment are therefore eliminated.

Compact dimensions and durable design

The layout, the base sleeve and the robust construction give the toolholder its exception-ally high rigidity. Its sturdy jaw guides prevent the grinding discs from swinging up and al-most completely eliminate axial eccentricity. The chuck jaws are hard-coated and therefore very robust and durable. Nevertheless, if the jaw set is ever damaged, it can be replaced as a unit. In order to prevent dirt accumulation and to permanently maintain the high precision, the chuck is flushed with clean oil during the grinding operation. Whether for axial clamping cylinders, radial rear-end toolholders or custom machine interfaces: SCHUNK PRISMO3 is compatible with the grinding machines of all renowned manufacturers. Compact dimensions of 125 mm x 125 mm leave ample space for the tools, grinding process and loading. The precision grinding toolholder is available starting immediately.

With the SCHUNK SRM high-performance rotary unit the competence leader for clamping technology and gripping systems presents a new benchmark in the area of pneumatic rotation. Even the outer features of the unit different from other rotary modules on the market. The most striking features are the low interfering contour, the specially developed internal high-capacity dampers for maximum performance in a compact space and the large center bore for the feed-through of cables, hoses, workpieces or for the use of a camera. The inner workings of the unit are just as impressive: the torque, mass moment of inertia and rotating time of the SRM significantly exceed predecessor, the SCHUNK SRU-plus. In the size 40 version, for example, the torque was increased by 25%. The increased mass moment of inertia is just as impressive: the compact SRM 16, for example, can rotate loads three times higher than the SRU-plus 20. The screw connection pattern of the new high-performance module is accordingly large and robust.

Correspondingly compact, it ensures a customized design at an affordable ratio that is unique for the market. SCHUNK optionally offers an air feed-through for compressed air or gases as well as an electric rotary feed-through for the reliable feed-through of sensor and actuator signals. It also offers the possibility of inductive monitoring. Future versions will feature multiple damping options for high loads, short cycle times in minimal installation space and highly efficient high-speed applications with a maximum number of cycles. An optional pneumatic or locked center position will also be developed. To speed up commissioning, the SRM features a pre-defined shock absorber stroke and fast clamping of the end position. In addition, a marking facilitates setting of the angle of rotation. The SCHUNK SRM is initially available in sizes 16, 32 and 40. Other sizes and options are in development.

SCHUNK presents more robot applications than ever at the AUTOMATICA 2014. Is it chance or strategy? 
As a leading full service components provider for robots, we want to show users, plant builders, and system integrators the possibilities of how the productivity potentials of modern robotics can be comprehensively developed. I don’t know any branch of industry, which currently offers so many complex opportunities as robotics. While the innovative automotive industry focuses on mobile and collaborative robots, the medium-sized companies are still at the beginning of using robot-based production automation. There is still plenty of space at the top. Particularly in the machine tool building, consumer goods, plastics, and electronics industry, as well as in the medical technology and optical industry, robotics has tremendous uncovered productivity potentials, which are still waiting to be discovered. We will show the possible potentials at the AUTOMATICA.

What are the focal points? 
SCHUNK has three main focuses, the first being, “intelligent mechatronics.” This is the answer to the demands of greater flexibility in the smart factory, and is the basis for safe gripping. The second is “high speed,” for meeting the productivity demands in assembly automation, and last but not least the “networked systems,” which allow new production processes. In a few years, intuitive control units, and communication via web technology will be standard in modern automation, such as an interruption-free cooperation between human and robot. In this connection, the world’s first certified safety gripping system, which will be presented by SCHUNK at the AUTOMATICA, is surely a milestone.

Does this transfer aspects of service robotics to industrial robotics? 
The certified SCHUNK safety gripping system is the key for ensuring safe, industrial handling processes within the human environment – no matter if a conventional industrial robot is used, or a lightweight robot for the service robotics is concerned. This creates completely new options in process design, and offers the potential in increasing the possibilities of the development dynamics in both areas.

When will service robotics be a real economic factor? 
Soon! Amazon, Google, Bosch, all of the great automotive and robot manufacturers have service robotics on their agenda, and are making huge investments to establish new solutions and to develop the market. Here at the AUTOMATICA, you will notice the dynamics: More and more companies recognize the potential, and the number of market-oriented solutions and potential applications are rapidly increasing.

Which industry has the strongest growth in service robotics? 
In the agriculture, defense technology, medical technology, road transport, and also in industry there are considerable potential. Particularly industrial applications will gain in importance in the coming years, where humans and robots mutually support each other. There is the stationary application of service robots in assembly and inspection applications, but also new mobile robotics applications will arise, e.g. during the flexible connection of assembly and manufacturing stations, or in lab automation. We will showcase at the AUTOMATICA how service robotics have already taken over the wafer transport in semi-conductor factories, or component transport between machine tools or assembly stations.

What are the next challenges which have to be solved? 
The greatest challenge and at the same time the biggest opportunity is the system integration. Numerous standardized components are available – grippers, lightweight arms, drives, sensors, mobile platforms, mapping systems, system software – which are waiting for being combined to market-oriented systems. Here, more entrepreneurial thinking people are needed, who will recognize that the stage has been set, and who are prepared to establish such new solutions. This also includes the development of new business models, such as leasing of service robots. From the user’s view it is important that the operation of service robots will be as easy and intuitive as a smart phone in the future.

Courtesy: SCHUNK GmbH & Co. KG