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Intelligent production solutions for the future
Clamping technology automation pays off even on the smallest of batch runs / Short clamping times increase machining efficiency for workpieces
QUESTION: Over the past 20 years international usage of machine tools has risen by 70 per cent. Half of all such machines come from Europe alone and are supplied to more than 70 countries. These are figures published by the VDW, the German Machine Tool Manufacturers Association, and they indicate a major opportunity for suppliers of production technology. But in the global competition who really is ahead?
GUIDO BORN (Product Manager Workpiece Clamping Systems at ROEMHELD's Hilchenbach site): The theme of this year's EMO 2013 held by the VDW was "Intelligence in Production", so it required intelligent solutions for production technology that are sustainable into the future so that they can cope with the enormous pressures on costs and the ever-increasing demands for efficiency and environmental sustainability. I think that we in Europe have a certain leadership role to play here in all of these aspects, and that we are ahead of the global competition.
QUESTION: What does that mean for your particular sector - clamping technology?
GUIDO BORN: We are constantly striving to reduce clamping and set-up times for our customers in the machining of their workpieces. At EMO 2013 in Hanover we once again demonstrated some innovative automation solutions for workpiece clamping, and these were very well received. Shorter clamping and set-up times, longer machine runtimes, greater accuracy of workpiece machining and precise repeatability of every clamping force and positioning routine are the most significant advantages of this automation solution and they were a clear focus of our design work.
QUESTION: What effect do the new clamping systems have?
GUIDO BORN: Every step of the process - from inserting the workpiece into the clamping device, the machining process and removing the workpiece is automated. If workpieces need to be turned during the machining process, and the clamping jaws require changing, or the clamping area altered, these processes can also be automated. It means that several clampings and different work processes can be carried out without manual intervention.
QUESTION: To what sort of workpieces are the new automation solutions suited?
GUIDO BORN: Our innovative clamping solutions are suitable for components of varying sizes, dimensions and geometries, enabling machining on up to six sides with no operator intervention. Of course the restrictions on dimensions and mass are imposed by the available machine space and the type of freely selected robot used.
QUESTION: To develop the automated mechanical clamping elements you chose DEPRAG, the renowned screwdriving experts from Amberg, to join the team.
PETER GNÜCHTEL (DEPRAG): Our range includes a convincing selection of EC-Servo screwdriver system and pneumatic screwdrivers. In this scenario these screwdriver spindles are the drive that opens and closes the relevant clamping fixture.
GUIDO BORN: But screwdriver systems from DEPRAG offer much more than this. Our automation partner DEPRAG has comprehensive expertise in control technology. And that is what makes this collaborative venture so valuable for us.
QUESTION: Can you go into a bit more detail?
GUIDO BORN: Willingly. Besides a hydraulic solution we also now supply a pneumatic and fully automatic version. These new variants are based on standard DEPRAG components. A 280W DEPRAG ADVANCED LINE air motor drives the pneumatic clamping fixture. With it the operator can use both hands to insert a heavy workpiece into the clamping element, while pressing a foot pedal to start the air motor to set the spindle in motion to clamp the component. But for the fully automated solution we opted for DEPRAG EC screwdriving systems.
PETER GNÜCHTEL: The screwdriving process control system sets the required speed and revolution rate. There is no need to fiddle around with a torque wrench. The result is a repeatable and steady frictional connection to ensure the high quality of the machining processes, such as machine cutting or polishing. It is easy to control the function directly on the device.
QUESTION: The new mechanical HILMA clamping fixtures that you presented at EMO 2013 used EC screwdrivers with the appropriate control system as the automation module. Do you use single and dual spindle units?
PETER GNÜCHTEL: Yes indeed. For the HILMA MC self-centering clamping system we recommended a single spindle unit with a DEPRAG MINIMAT ® EC-Servo integral screwdriver (straight design). This allows free programming of the clamping force and thus guarantees maximum flexibility and process reliability. It is possible to individually adjust the torque, speed, waiting time and direction of rotation within a torque range of 50 to 270 Nm. The integral sensor-controlled torque and rotation angle measurement system precisely regulates the clamping process, and also records the important process parameters, guaranteeing maximum and repeatable accuracy.
GUIDO BORN: The spindle unit with the EC-screwdriver is controlled by a DEPRAG AST30 process controller, on which it is possible to freely program the processes on our clamping system. Specific system processes can be compiled by means of the stored basic programs supplied. We input the necessary parameters for the order in hand onto the screwdriving module via a central control unit (robots, logistics and screwdriver technology). An easy-to-read display provides fast access to the user programs, selected by their numbers.
PETER GNÜCHTEL: Communications interfaces are of vital importance for stationary deployment within an automated production facility. The AST30 communicates via Ethernet, Profibus, SPS interface and RS232. The results of the last 1400 clamping procedures are stored and prepared for output. Additional software modules include graphical display of screwdriving curves, integral SPC functions and comprehensive analysis options on a PC.
QUESTION: The automation module is also suitable for retro-fitting existing clamping systems. Is that not an expensive operation?
PETER GNÜCHTEL: Absolutely not. With the compact modular structure of our screwdriver units, they can be incorporated into any machine.
GUIDO BORN: The DEPRAG screwdriving function module with its straightforward interfaces considerably reduced the work involved in system integration for our customer. We received the screwdriving module from DEPRAG as a ready-to-integrate functional component that had been specifically and comprehensively tested on our sample parts.
PETER GNÜCHTEL: Another of the priority aims of our design engineers is to minimise servicing and maintenance costs. That way the integral standard software is able to connect quickly, easily and cost-effectively with the basic LC156 control system selected for the self-centering systems, with 30 inputs and 26 outputs. The menu navigation is already fully available within the standard program: communications TP-CPU, error handling, limit switch monitoring, touch panel (TP) menu, error output, oils, parts counter and cycle time, sliding tables, manual operating functions.
QUESTION: The automated HILMA MC self-centering clamping system is suited ...
GUIDO BORN: ...particularly well for workpieces on vertical and 5-axis machining centres. On the other hand the dual spindle module, which DEPRAG developed in collaboration with our company, is used on our TS 125 range of tower clamping systems. This now also enables us to automate secure, multiple clampings with low set-up times on horizontal machining centres. Our HILMA TS tower clamping systems are the universally deployed base element for a wide variety of positioning and clamping tasks in a flexible manufacturing environment.
QUESTION: Does the dual spindle unit differ essentially in structure from the single spindle module we talked about before?
PETER GNÜCHTEL: No, not very much. Of course it requires two MINIMAT® EC-Servo screwdrivers (torque range 25 to 140 Nm) and two AST30 process control systems. Our screwdriving function module has been extended with the addition of a slightly larger basic control system with 38 inputs and 34 outputs. However, to keep the distance between axes on the screwdriver spindles inside the TS tower clamping system as small as possible, we developed a new top offset gearing especially for the HILMA products. That way it is possible to achieve a high level of workpiece density and keep travel distances to a minimum.
GUIDO BORN: That was a major advantage for us. The DEPRAG automation experts have a huge range as standard, but when the automation solution you are looking for is not in that range ...
PETER GNÜCHTEL: ...we always come up with good ideas and solutions.
Many thanks for such an interesting discussion.
The interviewer was technical journalist and editor, Trixy Schmidt. She was interviewing Workpiece Clamping Systems product manager Guido Born at the ROEMHELD site in Hilchenbach, and DEPRAG's applications specialist Peter Gnüchtel.
As a world market and quality leader, ROEMHELD designs and develops, manufactures and markets components for fast, automated and economical manufacturing, assembly, clamping and drive technology. Its core sectors are international machine tools, the automotive, aerospace and agricultural industries, as well as the medical technology sector. ROEMHELD also supplies a comprehensive range of elements for the manufacture, testing and maintenance of large components for wind power generation installations. The wide range of products consists of some 16,000 catalogue items, and ROEMHELD's technicians and design engineers are constantly developing customer-specific solutions. In 2012 the 450 employees at the company's three sites in Laubach and Hilchenbach in Germany and Götzis in Austria achieved a sales turnover of around €90m. With its own sales and servicing companies ROEMHELD is represented in more than 50 countries on every continent.
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