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workpiece clamping technology

Frank Scheurer

November 6, 2023
10 Min.

The picture shows a small selection of Dürr Systems AG's clamping devices with the typical precision parts that are complex to machine and made of different materials.

The technology company Dürr Systems AG is widely known as an international market leader in the field of painting and final assembly systems, as well as the machine and robot systems required for this purpose.

The main markets include the global automotive industry and its suppliers. Dürr Systems AG also offers high-performance systems for exhaust air purification and paint finishing technology for numerous industries. At the main plant in Bietigheim-Bissingen, Germany, about 2,000 employees work on about 70,000 m² of factory space. A central position in this plant is occupied by the "Machining Production" department, which is responsible for machining both components for production and parts for development and testing.

Consequently, it is not only necessary to cope with a high variety of parts, but also to make the parts available to the respective internal customers in a timely manner. In addition, this requires a correspondingly wide range of technological equipment, as well as efficient and flexibly usable production capacities and, of course, the highly qualified specialist staff required for this.

Martin Bulling, Application Technology Manufacturing at Dürr Systems AG, gives a few key figures:
"For ongoing production and spare parts supply, as well as for development and the testing department, we manufacture about 200,000 workpieces per year. This is done both in single-part and in small and medium-series machining. These involve around 2,000 different active articles, of which in turn around 800 are machined cylindrically and cubically by 3-, 4- or 5-axis milling."


In order to cope with this variety of milling operations, as well as the highly varying quantities, in a performance-oriented and timely manner, the milling operations are carried out on 4- and 5-axis CNC machining centres, which are all equipped with pallet automation or with larger pallet/workpiece magazines. Depending on the workpieces, which are made of aluminium, titanium, stainless steel and POM, and whose dimensions range from a few millimetres to 80 x 80 x 130 mm, the machine running times range from a few minutes to 3 hours.

Another challenge is posed by the 800 workpiece variants mentioned and the strongly fluctuating numbers of pieces between 1 and 200 per batch. For example, there are workpieces that have to be machined in 60 planes with up to 70 different tools. From this, in turn, it quickly becomes apparent what high demands the workpiece clamping technology must meet in terms of optimum accessibility for multi-axis complete/simultaneous machining. Depending on the complexity of the workpiece, the company therefore relies on special clamping devices developed in-house as well as increasingly on standardised clamping technology from efficient suppliers for precision machining.

For years and on a larger scale, this has included the Swiss company GRESSEL AG in Aadorf, a specialist in workpiece clamping technology and automation. Starting in 2006 with centric vises of the Zentros series, the obviously good experiences led to successively equipping further machining centres with new centric vises centrinos, various system jaws and further with the mechanical zero-point clamping system gredoc.

left: A selection of the clamping technology equipment at Dürr Systems AG based on the modular system from GRESSEL AG for workpiece clamping systems. Right: Shows four C2 centric vises, all of which are fixed and clamped "round" on the machine pallet by means of the gredoc mechanical zero-point clamping system.

workpiece clamping technology for (almost) all situations

Martin Bulling comments:

"By using Gressel's modular clamping technology on all machining centres, we have achieved extensive standardisation of our clamping equipment. The highlight for the time being is the equipment of our latest 5-axis CNC machining centre with pallet changer and pallet magazine. Here alone, more than 50 clamping solutions are installed, again based on the mechanical zero-point clamping system gredoc and gredoc consoles in round and square. Based on these, C2 centric vises in the sizes C2 80 L-130, C2 125 L-160 and D2 double vises D2 125 L-320 are used for parts of all conceivable dimensions, as well as solinos clamping towers of the type 65-4V for multiple small part clamping. Depending on the machining requirements, the C2 and D2 centric and double vises for the OP 10 and OP 20 are equipped with various system jaws that can be changed very quickly if necessary."

But the consistent use of standard clamping technology goes much further, because in the meantime other machining centres and a measuring machine have been equipped with the mechanical zero-point clamping system gredoc, which enables the individual use of different clamping devices with one and the same interface. Or to put it another way: now it is feasible in practice to use the most diverse clamping solutions on different machining centres in a highly flexible manner.

consistent use of standardised clamping technology

Frank Scheurer, the GRESSEL AG distribution engineer responsible for the customer Dürr Systems AG, commented:
"This is where the universal system concept of our strictly modular clamping technology kit comes into its own. The mechanical zero point clamping system gredoc as a standardised basic interface on various machines plus the measuring centre, various centric and double vises in jaw widths and sizes, the clamping towers solinos for multiple clamping of small parts and finally coordinated jaws for the OP 10 and OP 20 - all in all we are talking about around 90 installed zero point clamping systems in various designs as well as more than 40 centric and double vises plus clamping towers with small part vises including accessories."

The fact that the investment in the multifunctional workpiece clamping technology based on the Gressel modular system proved to be highly beneficial for Dürr Systems AG is made clear by the fact that, to date, a good 350 of the 800 workpieces to be milled have been precisely and, above all, reproducibly machined with the help of the standard clamping equipment listed. In addition, the competence and performance of GRESSEL AG, which has now been proven over many years, brings further advantages, as Martin Bulling explains below:

"In order to make a decision regarding the choice of supplier for the standardisation of the workpiece clamping technology, we carried out extensive tests with various products on the basis of a workpiece made of aluminium that was very difficult to machine and was characterised by, among other things, 60 mm deep pockets and very high machining volumes.
We were convinced in every aspect not only by this, but also by the active support of Mr. Scheurer and the experts at the Swiss headquarters, the system capability of the GRESSEL modular system and the variety of equipment provided by the jaw programme, which is valuable in practice, as well as the minimised set-up/changeover times and the very simple handling. Furthermore, the really low maintenance effort and, last but not least, the possibility of downloading the 3D data of the clamping technology components from the GRESSEL homepage, convinced us in every respect. Therefore, further clamping technology projects are already being implemented, with which we will ensure the performance readiness and productivity of our department now and in the future."

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