We explore the potential of clamping technology in a process-optimised manufacturing operation. By Walter Frick
Bernt Ritz, consultant for technology, standardisation and clamping tools in the German Engineering Federation’s Precision Tools Association, outlines the trends that manufacturers of clamping technology currently have to address:
- Progressively increased machining of composites, lightweight components, thin-walled and miniaturised components,
- Individualisation of workpieces, and concomitantly smaller batch sizes,
- Higher concentricity accuracies and balance qualities for tool holders, Fully automatable manufacturing processes and reliable process monitoring,
- Automated workpiece placement,
- Networking and unambiguous identification of clamping technology components,
- Implementation of sensor technology for data acquisition and transmission, plus
- Online configurators for clamping components.
This list maps out the framework in which the sector’s innovative efforts are tackling.
Potentials Of Networked Clamping Technology
“Most customers have taken on board the importance and the potential of clamping technology in a process-optimised manufacturing operation. Whereas, for instance, the primary focus used to be on faster machine tools or longer useful lifetimes of the cutting materials, nowadays clamping technology has at least the same perceived importance,” said Jürgen Förster, sales manager at Andreas Maier Gmbh & Co KG (AMF).
Automation plays a major role in this context. Different retrieval options and concurrent seamless communication with the machine tool are nowadays considered standard features. Mr Förster said, “We see a very definite trend towards a combination of different clamping methods. Zero-point clamping technology often constitutes the basis, and is supplemented by hydraulic, magnetic or pneumatic systems to form a flexible modularised whole.”
Seamless networking and communication between the clamping devices and the machine tool are crucial factors for an optimised manufacturing solution in regard to Industry 4.0 and the associated components. Thus, the existing status in the customer’s manufacturing operation should be taken into consideration as the basis for planning and optimising the production processes. For instance, AMF has fitted the zero-point clamping modules with position sensors, thus enabling automated manufacturing with robot loading in a dependable process.
The company is also tackling the topic of affordable automation solutions for existing machine tools with low-cost automation, including loading, gripping, storing, clamping and identification.
Choosing The Right Clamping Device
Rofl Ehrler, product manager of clamping devices and milling tools, Guhring, observed that tool clamping devices are becoming more specific depending on the metal-cutting tools being used. This means that the development of high-precision tools is simultaneously seeing a parallel diversification of clamping devices.
However, Mr Ehrler is rather sceptical when it comes to the role of “smart” clamping devices in networked manufacturing operations: “Smart holders (both sensory and intelligent) are being researched, but due to the lack of networking, are not yet suitable for full coverage use.” Instead, he advocates “optimally dimensioned and selected clamping devices”, with which metal-cutting tools “can be used to significantly better effect and pushed towards enhanced machining performance and longer useful lifetimes”.
Additively Manufactured Slim Chucks
In a digitally networked manufacturing operation, clamping technology will play a crucial role, since for an optimal process the blade often has to be brought closer to the working point on the component than before.
For this purpose, chucks are required that are extremely slim in construction without any loss in performance. This stipulation is being met by Mapal with its slim-contour hydraulic expanding chucks, which enable hydraulic expansion clamping technology to be employed where shrink-fit chucks used to be the only option. This is made possible by additive manufacturing: the functional area is deposited on the conventionally manufactured main body using selective laser melting.
Since dry machining is accounting for a progressively larger share of the manufacturing processes involved (not least out of environmental considerations), the thermal stability of the chucks is crucial. Thanks to additive manufacturing, the temperature-critical solder joint between the clamping sleeve and the main body can be dispensed with. This means the chucks can be used in a reliable process at operating temperatures of up to 170 deg C.
Additive manufacturing, to quote Jochen Schmidt, product manager of clamping technology at Mapal, “creates entirely new concepts for clamping technology, offering an added value for the customer in terms of process reliability and costs. We are already using this technology for series production.”
Mr Schmidt concurs that mass production operations will increasingly demand chucks that can be integrated into intelligent manufacturing structures featuring a high degree of automation, adding that “all system components here have to be amenable to digital networking.” Tool chucks are normally used only in direct clamping applications—for small diameters. “With the aid of additive manufacturing,” Mr Schmidt said, “we have succeeded in offering precisely this kind of chuck: hydraulic expanding chucks with a slim contour for direct clamping of tools with diameters of three mm or more”.
Modularised Systems For Flexible Applications
A trend towards compatible modularised systems enabling each clamping task to be solved intelligently and affordably, while assuring a high level of consistency between different machines has been observed by Markus Michelberger, sales manager clamping technology, Schunk.
The factors of automation, flexibility and digitisation will in future become crucial for success in production operations. “With the aid of sensors, clamping devices will very soon be able to continuously monitor the clamping force. If this decreases, or if vibrations occur, the machining parameters will be automatically adjusted so as to assure a reliable process and maximised efficiency,” added Mr Michelberger.
For example, the Magnos force measuring system, which was on display at Emo Hannover 2017 as a technology study, enables the clamping force to be continuously acquired in the case of magnetic clamping solutions, and the process data to be responsively adjusted. In addition, the electrically controlled 24-V zero-point clamping module is reportedly a world-first according to Mr Michelberger, paving the trend towards a “fluid-free, highly networked machine tool”.
He believes that additively manufactured components will also be gaining steadily in importance during the years ahead. An example would be the company’s multi-purpose grippers. With their high gripping forces, they can also be used as clamping devices in some cases. Called the eGrip, users can use the licence-free, web-based tool to design individual gripper fingers in 15 minutes. The user can upload one of his own Step or STL files and specifying a series of variables, such as gripper type, weight, the gripper’s mounting position or the fingers’ length. Once the ordering procedure has been completed, the gripper fingers are additively manufactured and delivered within one week.
The general consensus is that tomorrow’s manufacturing systems will be completely networked, and will, not least with the aid of the clamping devices and gripping systems, continuously acquire both their own status and that of their surroundings.
“Our goal is to utilise the exposed ‘closest-to-the-part’ position of our modules in order in future to provide detailed monitoring of each individual step in the process, and to continuously supply the line’s control system and the ERP system with process data,” concluded Mr Michelberger.