Closing technical report

METAV 2010 showcased the latest products and design enhancements in terms of manufacturing technology at the exhibition centre in Düsseldorf from 23 to 27 February 2010.

One continuing trend observable among the manufacturers of machine tools is that they are offering all-inclusive production packages, e.g. featuring complete machining of workpieces on a single machine tool, while simultaneously retain-ing the requisite manufacturing flexibility. Besides the combination of turning and milling operations, process integration has been progressed for machine tools used in high-precision surface finishing as well. As exemplified by the manufacture of artificial knee joints, it is obvious that a combination of milling and grinding processes in a single machine tool is a sensible move for the ex-panding market of medical technology. Machine tool control systems, and the generation of NC data, are becoming more and more complex, so that the use of harmonised software support is a boon to the process planning engineer. The manufacturers are offering appropriately configured tools, designed to meet the requirements involved in machining sophisticated bio-compatible materials. Additionally, the steadily growing demand for energy entails the use of ever-larger components in water and energy technology, so that high-precision machining of large parts is gaining in perceived importance.

5-axis complete machining reduced lead times
For machining medium-sized integral components, a 5-axis machining centre was showcased. It is able to accommodate workpieces weighing up to 1,400 kg. Travel distances in the x- and y-axes of 800 mm and in the direction of the z-axis of 1,000 mm, in combination with a swivel head offered specifically for heavy machining to HPC criteria enable workpieces from the aviation sector to be machined or in tool and mould manufacturing processes, exhibiting as they do high time-cutting volumes. A collision monitoring feature incorporated in the control system, factoring in the shape of the unmachined part, supports fric-tionless 5-axis simultaneous machining. If the tool breaks or collides with some-thing during the machining process under 5-axis tool adjustment, the machine’s control system offers tool withdrawal strategies (Messrs. Gebr. Heller Maschinenfabrik GmbH, Nürtingen).

Another manufacturer showcased a 5-axis machining centre that implements the traversing movements of the tool and the headstock using parallel kinemat-ics. By using five struts, swivelling angles of over 90° can be achieved. The ball screw spindles permit a speed of 45 m/min and an acceleration of max. 10 m/s² in rapid traverse mode. There is a modified variant available in gantry construc-tion for machining sizeable workpieces weighing up to 7 t; there is also a mobile variant on offer, which can be used for machining fixed-position workpieces, e.g. for purposes of repair (Messrs Metrom Mechatronische Maschinen GmbH, Chemnitz).

Boring and milling units in travelling-column design enable large structural and connecting parts for energy and water supply installations to be machined. One manufacturer exhibited a production system for medium-sized workpieces, which with a hydrostatic mounting featuring very small gap dimensions reaches fast-traversing speeds of up to 30 m/min. Misalignments of the drill spindle caused by thermal or elasticity-related factors can be compensated for in real-time using position corrections handled by the control system, (Messrs Pama, S.p.A., Rovereto (Tn), Italy).

For machining workpieces with 5-axis simultaneously controlled tool orientation, it is essential to use harmonised CAD-CAM software in order to utilise the machine tools’ performance capabilities to the full. The software packages available offer for NC data generation not only the CAD interface but also an option for surface reconstruction and scan data processing. If feature elements are already being used in the CAD data model at the design stage, these can be detected by the CAM software, appropriate NC sets selected, and incorporated in the NC program. Meanwhile, upgrade software packages are also available for machine tools featuring more than one machining spindle, process combinations, such as rotary milling, laser-cutting or trimming milling of composite components made of fibre-reinforced plastics (Messrs Tebis AG, Martins-ried/Planeggi; Messrs Missler Software, Evry, France).

Manufacturing medical products with modified machine tools
For manufacturing medical products, whose friction and mating surfaces con-sist of complex free-form surfaces with a high quality of surface finish, a 5-axis grinding machine fitted with linear drives was on show. In addition to five to 24 magazine slots for various grinding disks, the machine also features an option for clamping a belt grinding unit and milling tools. Asymmetrical moulds can be cost-efficiently pre-machined by milling with a solid hard-metal ball or grinding tools, and then ground to the final finish. A crawler loader for up to 170 semi-finished products enables the machine’s working area to be supplied and unloaded (Messrs Schütte-Schleiftechnik GmbH, Cologne).

Specifically for manufacturing different threads on rotationally symmetrical components in the surgical and medical categories, such as bone screws, a thread whirling machine was on show: preturned unmachined parts of different length are measured by a photo-cell after aligned feed-in using a oscillating conveyor. The NC program is modified in dependence on the screw length currently being machined, so that bone screws of 10 to 150 mm in length can be produced in any desired sequence. The diameter ranges from 2 to 15 mm. The thread whirling units excel in terms of different cut depths for the individual cuts. Moreover, the position of the tool in relation to the workpiece’s rotation axis is eccentric, adjusted to suit the thread pitch involved. Small process forces and comma-shaped chips are conducive to machining stainless steels and titanium alloys with a high level of process dependability. This enables damage-free components to be produced (Messrs. Leistritz Produktionstechnik GmbH, Nuremberg).

Tool modifications upgrade productivity
Tools based on diamond and boron nitride provide plenty of options for reducing the main process times for machining. To enable chip breakers and chip grooves to be incorporated in these cutting materials, one manufacturer exhibited a laser machining system integrated into a machining centre. Either a fibre, a vanadat or an alternative laser operating in the picosecond range can be used for cutting the tool shape from the diamond or boron nitride blanks, creating chip grooves and generating defined clearance angles. The picosecond laser, thanks to its high rate of pulsation, promises a lower thermal loading in the marginal zones of the component concerned (Messrs. DMG Sauer GmbH, Stipshausen).

Filigree structures and small workpieces require appropriately modified tools. For materials based on chromium-cobalt or titanium, micro-tools were show-cased consisting of ultra-fine and ultra-ultra-fine-grained hard metal and prepared in the areas of the cutting edge to suit the particular application concerned. One manufacturer exhibited a tool for inserting micro-boreholes with a diameter of 50 µm. Further tools were also exhibited for manufacturing small parts, e.g. for forward and backward deburring or for reaming (Messrs SPPW Spanabhebende Präzisionswerkzeuge GmbH, Lich).

When dealing with higher-strength materials that are difficult to machine, such as titanium alloys or nickel-based materials, the use of high-pressure cooling lubricant systems offers advantages in terms of useful tool lifetimes and swarf monitoring. During the turning process, the jet of cooling lubricant is directed over the tool’s face as close as possible to the point desired using high-pressure cooling lubrication sprayed through fixed feed nozzles in the clamping claw of the indexable insert holder, which enables cooling and lubrication of the tool’s free surface to be selectively targeted. In addition, feed on the face side has been optimised by swivelling feed nozzles that can be positionally matched to the process involved (Messrs Iscar Germany GmbH, Ettlingen).

For inserting deep boreholes into steel materials that are difficult to machine, the use of solid hard-metal single-lip deep-drilling tools was exhibited. One manufacturer showcased them for the diameter range of 0.7 to 12 mm. In com-parison to conventional single-lip deep-drilling tools, the use of a tool construc-tion based on hard metal throughout offers increased tool rigidity and a reduced tendency towards torsion. Compared to helically grooved deep-drilling tools, higher feed rates of up to f = 0.18 mm m can be achieved, depending on the material involved. For larger borehole diameters of 15 to 30 mm, a single-lip deep-drilling tool with replaceable indexable inserts and guide strips was on show. To suit the material being machined, the cutting material pairing and the guide strip material can be changed (Messrs botek Präzisionsbohrtechnik GmbH, Riederich).

Metrological technology for in-process monitoring improves workpiece quality
Responsively practical metrological equipment utilises the entire potential of a production system, while at the same time assuring product quality. One manu-facturer presented a structure-borne-noise measuring system, consisting of an acoustic emission sensor (AE sensor), a filter unit and a control and evaluation PC. The AE sensor, enclosed in a steel jacket, facilitates high-frequency proc-ess analysis. In a machining operation, for example, the status of the tool’s cut-ting edge, sharp or already rounded, can be assessed concurrently with the process. When components are being joined by welding or in forming processes, the system can be used for crack detection, for example, when shafts are being bend-straightened. The pressure wave occurring when the crack is created is acquired metrologically. Background noise caused by the production process is, says the manufacturer, usually masked out, since status monitoring is performed at frequencies of between 40 kHz and 100 MHz (Messrs Qass GmbH, Wetter).

Another system exhibited for 100-per-cent monitoring of workpiece quality op-erates using a scattered-light process. The LED light source emits monochro-matic light onto a surface. By acquiring and quantifying the scattered-light dis-tribution, shape deviations like circularity and waviness or surface defects in the form of micro-cracks can be detected. The distance-dependent process oper-ates with a scan rate of 2 Hz. It is suitable for all reflecting surfaces and has been standardised by the VDA (German Association of the Automotive Indus-try). The process is already being used for monitoring workpiece quality during the production of racks, in crankshaft rolling and in polishing processes (Messrs Optosurf GmbH, Ettlingen)

Symposium “The energy-efficient machine tool”
Nowadays, energy costs are already accounting for approximately 6 per cent of a company’s total costs (source: Baden-Württemberg Chamber of Industry and Commerce, Karlsruhe). Whereas in the past it was high costs for raw materials and supplies that constituted a particularly significant cost-driver in production operations, a proportion amounting to of 21 per cent of a machine tool’s operat-ing costs makes it clear that energy-economical production processes are becoming increasingly imperative (Source: Institute for Production Management, Darmstadt).

The symposium on “The energy-efficient machine tool” and the VDW’s Blue Competence Initiative, both of them under the aegis of METAV 2010, showed that the manufacturers of machine tools and production systems are devoting intensive efforts to this issue. The sector’s autonomous initiative is aimed at creating a self-regulation concept to comply with the EuP Guideline. It provides the manufacturers with the requisite scope, and even maps out growth markets by providing new technologies. The manufacturers have already premiered the first components and function modules for energy-saving in production technology. Due to the complex concatenation of production units in users’ facilities, in-telligent interaction of the production system’s individual constituents is essen-tial, thus enabling the energy consumption to be reduced in dependence on the actual situation involved. It is accordingly possible simply to switch off individual systems in order to reduce the base load, within the overall context of the de-sired system availability, e.g. by providing various stand-by modes. The presen-tations given by the various speakers made it clear that the energy-efficiency of existing production systems can be iteratively enhanced: visualise a circuit of energy consumers, identify components with the potential for energy savings, and purposefully modify these constituents of the system.

In the halls of the fair, some manufacturers of machines tools and function modules exhibited products in which modified units do save energy. Regenera-tive-capability spindle and axle motors with an efficiency of up to 96 per cent pass the braking energy into storage, where it is available for subsequent trav-ersing movements or, if not utilised, is fed back into the grid. Hydraulic units can be operated in reservoir charging mode with modified valves and a power consumption of 8 W.

A manufacture of pump systems showcased a screw pump combined with a frequency converter. Depending on the application involved, it can be controlled in terms of the delivery volume. The operating point can thus be matched to variable consumers. A software package supports computation of the pressure drop in dependence on the design and structure of the pump and piping systems, so as to quantify any friction losses (Messrs Brinkmann Pumpen K.H. Brinkmann GmbH & Co. KG, Werdohl).

In the field of clamping devices, one manufacturer exhibited a lightweight chuck made of carbon, which features not only a reduced mass, but also enhanced mechanical strength and rigidity values. The reduced rotational mass moment of inertia produces an improved acceleration and braking capability, so that a spindle’s working speed is reached up to 30 per cent more quickly (Messrs Hainbuch Spanende Technik GmbH, Marbach).

Following the recent premiere of a purely electro-mechanical clamping system for spindles, one manufacturer exhibited a tool revolver for lathes that dispenses with the use of hydraulics. An electric motor in the centre of the revolver is used to adjust and drive tools at a speed of up to 10,000 min-1, with the maximum speed being reached in 0.35 s. Given a duty cycle of 100 per cent, a maximum power of 13 kW is available; the torque is 30 Nm. Dispensing with an articulated gear unit enables the construction to be compactly dimensioned (Messrs Sauter Feinmechanik GmbH, Metzingen).

The additional costs in terms of machinery investment for using energy-saving, energy-efficient systems will be recouped very quickly, thanks to the reduced operating costs of a production system. In the case of the tool spindle seals, for instance, using grease relubrication in comparison to oil-air lubrication enables the operating costs for lubrication to be reduced to 0 euros a year. This is also true for the use of brush seals in comparison to sealing air systems.

Seminar “Production technology on the way to electro-mobility”
The supporting event entitled “Production technology on the way to electro-mobility” of the ProductionNRW Cluster at METAV 2010 provided comprehen-sive insights into the challenges, potentials and opportunities involved in pro-ducing automobiles with an electric drive. Specialist presentations given from different viewpoints mapped out how present-day drive technology and a vehicle concept will alter in the future, and what influences and requirements can be anticipated in regard to the established production technology in automaking and the automotive industry.

From today’s perspective, the market will be dominated over the next few years by micro-, mild- and full-hybrid vehicles. This is confirmed by the ongoing efforts at the automakers’ R& D departments. The multifarious combination and integration options for internal combustion engines and electric motors, with dif-ferent percentage weightings, will constitute the major focus initially. Existing battery technology is still at present restricting universal everyday use of purely electric vehicles. The manufacturers of production equipment can support op-timum concatenation of the drive concepts by making their production expertise available. As long as the internal combustion engine is a constituent of the motor concept, then future design enhancement of all engine components (higher fuel injection pressures and combustion temperatures, use of higher and high-strength materials, tribological aspects, specifically friction minimisation and se-lective marginal zone influencing, lightweight construction, etc.) will demand the technological and commercial expertise of machine-tool, tool and accessory manufacturers.

The global market share of vehicles driven solely by electricity is forecast to reach approximately 10 per cent by 2020. These will be predominantly four-door small cars with a range of 200 km. Electric vehicles are already being used successfully today by local councils, as long as they are specially dimensioned and manufactured for the particular application concerned. In future, China is predicted to be a major producer in this segment of the market. The characteristics and benefits of an electric vehicle depend on various factors. The costs for the battery will account for 50 per cent of a vehicle’s production costs. In order to upgrade the acceptance levels for battery-powered vehicles, there are numerous questions that first have to be answered: such as the mass selection and characterisation of suitable cells, thermal management featuring selective cooling, electrical safety in the event of accidents, plus nationwide provision for charging and recycling stations. Since the economy is changing too, the supply of electricity produced by regenerative systems and power plants will also have to cover the additional demand entailed by electric vehicles.

Dortmund Grinding Seminar “METAV Special” maps out trends for fine surface finishing
The grinding seminar hosted by the Institute for Metal-Cutting Manufacture at Dortmund University of Applied science under the aegis of METAV 2010 dealt with the current design enhancements in grinding technology. A series of specialist presentations from sectoral experts revealed that the vendors of machines for fine surface finishing are integrating a variety of production processes in a single machine, thus offering complete-system solutions.

These were exemplified by a machine tool for combination machining: turning, cylindrical surface grinding and the newly developed interior rotary-cut grinding had been integrated. The last-named has been developed for interior and face machining with high time-cutting volumes coupled with maximised surface quality. For the users of multiple-axis machine tools, programming support is very important for grinding applications as well, enabling the system’s full potential to be utilised. Integration of additional functions in a manufacturing cell, e.g. metrology, cleaning or additional machining such as deburring or brushing processes, is in large-series production essential if workpieces are to be cost-efficiently machined. Achieving low machine purchase costs is in this context not always the determinant consideration. On the contrary, the total costs of ownership have to be given due consideration when it comes to selecting a machine.

The same also applies for the peripherals used in grinding processes, as ex-emplified by a cooling lubricant, a water-based fluid that can be used in an application for deep-grinding hard-metal tools. The cooling lubrication concept scores in terms of doing without constituents featuring a mineral-oil content, and permits its viscosity to be matched to the process concerned. Despite the additional costs for the cooling lubricant, cost advantages are obtained thanks to dispensing with fire protection equipment, simpler component cleaning, and the opportunity to achieve significantly larger time-cutting volumes in comparison to an oil-based cooling lubricant.

Summary
With a broad spectrum of up-to-the-future products and innovations for produc-tion technology, METAV 2010, hosted by the exhibition centre in Düsseldorf, was an impressive event for its visitors. Machine tool manufacturers exhibited machines for complete machining of workpieces using 5 axes or combination machines. Tool manufacturers exhibited a wide range of products for machining sophisticated materials and ultra-small structures. The supporting events in-cluded in-depth presentations of the production processes used for technical medical products, energy-saving machine tools and components, electric drives in the automotive industry, and the latest developments in grinding technology, ensuring experiential enrichment from a visit to the fair.

Author: Dipl.-Wirt.-Ing. Christian Machai, Institute of Machining
Technology Dortmund, Tel. +49 231 755 4641, machai@isf.de

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Tel. +49 69-756081-33
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