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Automation is raising grinding technology productivity

November 26th, 2021 1:21 pm | by Admin

GrindingHub to showcase efficient fine machining processes
Fine machining requires a great deal of intuition. That is why many companies still take care of grinding and polishing manually. However, this can quickly become a source of high costs and inconsistencies, especially in series production. Automation solutions deliver reproducible quality at all times. With its combination of grinding technology, automation systems and software, GrindingHub 2022 will be the perfect place for companies to obtain all the information they require on this challenging field.

Unmanned production 24/7
For many manufacturing companies, this is one of the key factors for success in this highly competitive field. This has been the case for turning, milling and drilling technologies for some time, but increasingly now also for fine machining. Exhibitors at GrindingHub will be providing a first glimpse of their solutions for achieving significant increases in productivity and reproducibility levels.

Robot-assisted grinding
Top quality surfaces are essential in metal and woodworking as well as in the automotive and aerospace industries. Fine machining in particular is still performed by hand in many cases, as human sensitivity is difficult to imitate. However, manual polishing, grinding and brushing is time-consuming and exhausting work. Automated processes offer an attractive alternative, allowing flawless surfaces to be created faster and at lower cost. At the same time, they relieve people from monotonous and dusty work.

The new tools for automated machining from Schunk GmbH & Co. KG based in Lauffen am Neckar, have innovative features which compensate for force and positional inaccuracies, allowing near-perfect results to be achieved. For example, a pneumatic random orbit sander with axial compensation is the company’s “specialist” when it comes to grinding and polishing. Its adjustable compliance yields constant contact force and uniform surfaces. Users seeking a highly robust and flexible tool for polishing and brushing workpieces will find a suitable solution in the pneumatic polishing spindle. It shortens machining and start-up times by a significant margin. The compensation force and the axial compliance of the tool are individually adjustable, which yields high-quality and reproducible results regardless of the installation position. Different workpiece geometries can be flexibly machined with just one tool, an economic advantage that almost halves investment costs. Schunk offers its application know-how to support customers in making the change from manual to automatic.

“We don’t just sell the appropriate machining tools for the robots, we keep the entire application in mind. On request, we test and validate every application on the customer’s workpiece in our CoLab robot application centre,” assures Daniel Mayer, director Product Sales Robotic Material Removal. “At the end, you receive a test report and video, giving you certainty that the application works.”

 “The closed loop ensures superior manufacturing quality as well as minute profile tolerances, together with maximum user-friendliness. Even with extremely challenging workpieces, such as grinding wheel bases, turbine blades or grooving inserts, it has proven to be a robust solution on the shopfloor,” says Marie-Sophie Maier-Wember, managing director of Haas Schleifmaschinen in Trossingen. Software is becoming a driver of precision working because mechanical forces are constantly in play during grinding, especially towards the edges of the grinding tools. These forces affect the interaction between the workpiece, grinding tool, clamping device and grinding machine. They result in ever-increasing levels of inaccuracy, which has an adverse effect on workpiece quality, especially if the system does not allow for a continuous exchange of data between the workpiece and the grinding machine. A self-controlling process based on an integrated measuring solution effectively prevents this loss of precision. Any systematic and machine-specific deviations are continuously identified by measurement technology during operation and forwarded to the Haas grinding machine software. This incorporates a large number of compensatory functions which complement each other. Any deviations in shape can thus be compensated down to µ-level precision.

“Without compensation, the tolerance would be several µ. In the closed loop, we create tolerances down to just a few µ without intervention by the machine operator,” explains the managing director. In addition to acting as a driver of precision, Haas grinding machine software solutions have a direct impact on customer shopfloor operations. The Haas grinding machine series can be connected to the ERP system, allowing automatic tool changing and the further processing of production data.

Future-proof: networked and automation
Automation solutions have long been an integral part of the product portfolio of Hamburg-based engineering company Blohm Jung GmbH, part of the United Grinding Group. A typical example of this is the tool changer for the current series of grinding machines. Designed for maximum cost efficiency, the solution offers users numerous benefits from reduced setup times to virtually unmanned processing, even of complex workpieces.

“Automation is only one of the key factors involved in increasing productivity,” explains Stefan Springer, head of Product Management at Blohm Jung. “Machine connectivity is also gaining in importance, as the future of industrial production will be networked.” Machines are communicating with each other, exchanging data, controlling and regulating each other. This makes processes run more efficiently and increases productivity. Blohm Jung’s “digital production monitor”, for example, offers customers the ideal tool for digitally monitoring and optimizing production capacity utilization from anywhere, 24/7. Running and non-running times, piece counts or malfunction times are displayed in real time. This allows any production backlogs to be detected at an early stage. IT security is given top priority here. Online access to the machine is only granted if the customer submits a service request. Data is therefore only exchanged with the customer’s consent and then only the data which is necessary for providing the desired service. Blohm Jung uses a TÜViT-certified connection to ensure that the data is protected from unauthorised access at all times.

The advantages of the latest products and solutions can be clearly explained and discussed in direct meetings with the experts. Do we have the right equipment for the next project? Which is the best fine machining technique for a specific component and how exactly does the software help me with the manufacturing processes? Interested visitors can find out how to future-proof their processes at the individual companies’ stands at GrindingHub 2022 in Stuttgart.

GrindingHub 2022 in Stuttgart
The first ever GrindingHub will be held in Stuttgart from 17 to 20 May 2022 and is the new leading trade fair and centre for grinding technology. It is scheduled to be run every two years by the VDW (German Machine Tool Builders’ Association), Frankfurt am Main, in cooperation with Messe Stuttgart and with Swissmem (Swiss association of mechanical and electrical engineering industries) as its institutional patron. Grinding is one of the top 4 manufacturing processes within the machine tool industry in Germany. In 2020, the sector produced machines to the value of 870 million euros. Almost 80 percent were exported, with about half going to Europe. The largest sales markets are China, the USA and France. Germany, Japan and Switzerland head the list of top global producers. The grinding technology sector produced 4.9 billion euros worth of machines in 2019.

VDW – German Machine Tool Builders’ Association
Tel: 0049 6975 608168
Email: t.beckmann@vdw.de


Latest trends in grinding and tool grinding technology

November 1st, 2021 11:17 am | by Admin

e-mobility, digitalisation and automation: these are just some of the key trends in the grinding technology sector at present.

Research experts and the companies exhibiting at the new GrindingHub trade show will be providing insights into the latest technologies and processes in this rapidly developing industry.

e-mobility is bringing about a change in the entire powertrain in cars. Gear parts must be ever lighter and increasingly precise and robust. Liebherr-Verzahntechnik GmbH has been taking a very close look at the requirements of e-mobility. Flank line modification methods are used to minimise noise and optimise load capacities. Here, generating grinding with dressing-free CBN grinding worms can represent an economical alternative to corundum worms. The process is reliable, ensures long tool life and significantly reduces the amount of time and effort required for measuring and testing.

The grinding process and clamping equipment for the production of finely worked e-bike transmission parts must be fast and precise. Using special clamping solutions, even small and collision-critical components can be machined without any problems. The exclusive Liebherr machine concept with single-table helps achieve optimum concentricity and high reproducibility in the production of parts with quality requirements in the micrometer range. The choice of process ultimately depends on the specific requirements. Liebherr can test all process parameters using its own machines. “Often there is no right or wrong,” explains Dr. Andreas Mehr, an expert in gear grinding. “As a partner and solution provider, we advise customers and show them alternatives, allowing them to make the best decision. That’s precisely what we’ll be doing at GrindingHub 2022.”

Process monitoring during generating grinding of e-gear tooth systems
Although the design of transmissions in electric cars is simpler than that of conventional internal combustion engines, it places far higher demands on the manufacturing accuracy of the gears. Electric motors must deliver constant torque over a wide speed range at rotation speeds of up to 16,000 rpm. There is also another condition, as Friedrich Wölfel, head of Machine Sales at Kapp Niles points out: “Internal combustion engines mask transmission noise. Electric motors, on the other hand, are virtually silent. At speeds of 80 km/h and above, rolling and wind noise are the dominant factors, regardless of the powertrain. But in the range below that, transmission noise can become annoyingly noticeable in electric vehicles.”  The fine machining of these components therefore requires the use of a generating grinding process that is both productive and, above all, optimised in terms of the noise behaviour of the ground gear teeth. It is crucial to avoid so-called “ghost frequencies” which can be caused during component grinding as the result of an unfavorable machine and process design.

It takes much less time to grind gears than to take control measurements: this makes it impossible to inspect 100 percent of all components. The best approach, therefore, is to detect possible defects during the grinding process itself. Process monitoring is crucial here. “Numerous sensors and measuring systems that provide us with a wealth of signals and information are already built into the  machines,” explains Achim Stegner, head of Predevelopment. “We use these to assess the machining process and the expected quality level of each gear in real time in the gear grinding machines themselves. This allows order analysis to be conducted on noise-critical components in a similar way to the checks performed on an end-of-line test bench. In the future, gear grinding will provide significant added value by ensuring that the quality requirements for these components are met. As a GrindingHub exhibitor, we’re very excited by the innovative concept of the show.”

Developments in tool grinding technology
The tool grinding sector is having to meet ever greater challenges. On the one hand, more and more special tools are being produced in small batches, meaning that the process design up to the first in-spec part is gaining in importance from an economic point of view. On the other hand, the robustness and productivity of existing series processes must be continuously optimised so that they can hold their own against international competition even in high-wage countries. The Institute of Production Engineering and Machine Tools (IFW) in Hanover is pursuing several different avenues of research. The first step involves simulative mapping of the tool grinding process to support the process design. The simulation itself predicts the process force-related displacement of the ground blanks before the first cutting tool is produced, allowing this to be compensated for during grinding and thus avoiding any resulting geometric deviations. Furthermore, the load on the grinding tool is analysed, permitting optimum adaptation of the process planning to the grinding tool used. This improves the machining result and minimises the number of rejects.

“Laser-based sensor technology has also been installed in the machine tool to measure the grinding wheel topography. This helps maintain the superior machining quality even at higher volumes,” explains managing director Prof. Berend Denkena, who is also a board member of the WGP (German Academic Association for Production Technology). “This allows continuous evaluation of the grinding tool status. It means it can be used to determine dressing intervals for specific processes. This helps avoid deviations in workpiece geometry due to wear and associated rejects.”

Automation + digitalisation
“There has been a significant increase in the speed of grinding technology development in recent years. Advances in digitalisation are the main reason for this,” says Dr. Stefan Brand, managing director of the Vollmer Group in Biberach, commenting on the latest trends in grinding technology. “At Vollmer we have been using digitalisation in automation and data analysis for years now. We have developed our own IoT gateway that we are feeding more and more data into. The latest trend in grinding technology is the further integration of process data. The resulting knowledge gives users helpful insights into how the grinding process can be optimised. The journey into the digital future is constantly evolving. It is becoming clear how merging classic grinding technology with digital functions is not only influencing the grinding process itself, but also changing the market for grinding technology. Digital and automated processes are being used as optimisation levers by sharpening services, tool manufacturers and globally operating manufacturing companies alike.

“This development is one reason why the new GrindingHub trade show is focusing not only on automation and digitalisation in grinding technology but also on the areas of technology/processes and productivity. That’s why we welcome the opportunity to present our grinding technology to a broad and international audience at GrindingHub.”

VDW (German Machine Tool Builders’ Association)
Tel: 0049 6975 608132
Email: g.kneifel@vdw.de



Are grinding machine safety guards overdesigned?

April 28th, 2020 11:21 am | by Admin

VDW tests the minimum wall thickness of safety guards
Guards on grinding machines are particularly important for ensuring operator safety. Grinding wheels seldom burst, but when they do, there is a great risk of serious injury to the machine operator. Recent studies suggest, however, that the enclosures commonly used in gear grinding machines, for example, could be overdesigned at present. Investigations conducted by the VDW, the German Machine Tool Builders’ Association, and the Institute of Machine Tools and Factory Management (IWF) at TU Berlin reveal that it is possible to use safety guards which are up to 70 percent thinner, depending on the width of the grinding wheel. These findings are now leading to changes in ISO standardisation.

Will overdesigned safety guards soon a thing of the past?
The minimum wall thicknesses for safety guards are specified in ISO Standard 16089 Machine tools – Safety – Stationary grinding machines. There is a directly proportionate link between the requirements concerning primary protective covers for gear grinding machines and those for the full enclosures located further away. The reason for this is that no specific safety precautions were initially specified for the safety guards of gear grinding machines, which do not normally have a primary protective cover. This is because the preceding standard, EN 13218 Safety of machine tools – Stationary grinding machines, did not explicitly include gear grinding machines. However, this proportionate scaling has been repeatedly questioned, for example by the Japanese association JMTBA, because it results in overdesigned polycarbonate safety guards and screens.

Major simplifications are possible
The member companies of VDW Working Group 5, which is responsible for machine tool component safety, therefore concluded that new specification tables were required for the full enclosures of stationary grinding machines. A two-year project was thus launched by the IWF (TU Berlin) in 2012 to develop the necessary test equipment.

“The ensuing burst and impact tests showed that the thickness of the enclosure wall can be reduced by up to 70 percent, depending on the width of the grinding wheel,” explains Simon Thom, group leader for machine tool technology at IWF (TU Berlin). “This is very good news for machine tool manufacturers, who are keen to avoid excess weight in their machines. Reducing the thickness of a sheet steel housing by half a millimetre, for example, will save 4 kg/m2 in weight.” This also yields indirect savings because the motors for opening and closing correspondingly lighter steel gates can be less powerful or are rendered entirely superfluous.

Unity among the partners
It is not only the industrial companies and the scientists who agree that guards are overdesigned in such machines. The DGVU (German Statutory Accident Insurance System) based in St. Augustin and the BGHM trade association in Hanover also carried out similar tests on a burst test stand, with comparable results. The burst tests were conducted over eight years. Then, at the end of 2019, the BGHM presented its report covering a total of over 400 burst grinding wheels and more than 800 usable impact events. Based on this, a safe design convention stipulating 3 mm for sheet steel with different grinding wheel widths was drawn up in conjunction with the VDW.

The consolidation of the results in Germany was motivated not least by comparable studies abroad. The Japanese JMTBA association carried out tests which found that some of the previous standard specifications set out in ISO 16089 could be reduced by up to 30 percent.

Finally, in January 2020, a standardisation meeting was held in Tokyo, where the Japanese and German findings were compared. The experts agreed that the Japanese results for adapting the specification tables for the primary protective cover, and the German results for the design of the full enclosure should be incorporated into the ISO standard. A consolidated working paper will soon be prepared by the ISO Secretariat at DIN in Berlin and submitted to the relevant public as a so-called “Committee Draft” for comments. This is scheduled for completion by October 2020.

Further investigations ongoing
Nevertheless, the existing results of the study on full enclosures in Project 20438 “Safely dimensioned machine enclosures” of the IGF (Industrielle Gemein-schaftsforschung) are being corroborated empirically and theoretically.

“We’re also using simulations to highlight the worst case scenario. As our burst tests have shown, this occurs when the outer edge of the fragment hits the guard. We can reproduce this type of impact in models with different materials, grinding wheel widths and safety guard thicknesses. In this way we have succeeded in simplifying the extremely complex burst tests,” reports Simon Thom. “Our plan for this year is to propose even simpler dimensioning procedures.”  The reduced minimum wall thicknesses which are now to be specified in the ISO standard could therefore be made even thinner on the basis of the further test results.

VDW German Machine Tool Builders’ Association
Tel: 0049 69 756081 13
Email: h.moedden@vdw.de

TU Berlin, Institute of Machine Tools and Factory Management (IWF)
Tel: 0049 30 314 24456
Email: simon.thom@iwf.tu-berlin.de