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ROEMHELD Gruppe collaborating with partner AUGUST WENZLER MASCHINENBAU GmbH on new sensory clamping device concept.

For machining of workpieces to perform efficiently, the focus is often on optimizing the machining equipment and the clamping device used with its clamping elements. There are many influencing variables, but the initial situation is largely determined by the blank of the workpiece to be clamped.

The problem is customers have trouble producing a consistent high-quality blank and maintaining the correct clamping, which must be continually monitored. To overcome this, ROEMHELD could detect these defective blanks and monitor production more closely. In the process, it would be decided at an early stage whether further machining is possible and beneficial. If a part is detected as defective, the workpiece will be rejected at an early stage and does not pass through the entire process chain, saving valuable resources and machining costs.

Partnership with Wenzler

Based on this theory, Römheld GmbH Friedrichshütte and AUGUST WENZLER MASCHINENBAU GmbH, an inventor and manufacture of 5-axis machining centers, have developed an innovative clamping concept utilizing new sensory clamping elements from ROEMHELD which enables the measurement of various component states in the machining process. From loading and unloading via machining, the quality can be monitored continuously and documented without gaps. This is particularly important for lightweight vehicle components, which are becoming increasingly thin-walled and intricate.

The core of this highly engineered concept consists of ROEMHELD’s clamping elements, also known as swing clamps, equipped with sensors to detect the condition of structural blanks made of cast aluminum so that defective workpieces can be rejected before machining. In the innovative project of Wenzler Maschinenbau and ROEMHELD, the intelligent clamping technology checks the parts for casting defects and contour variations. It detects insertion errors and continuously provides information about the clamping position and clamping force on the component during machining.

To begin the project, the partners defined the information that is useful for state detection.

The result: by monitoring the clamping and support forces at two selected clamping points and by stroke measurement, it is possible to determine the following:

– whether casting defects or contour variations affect the dimensional quality of a blank beyond the tolerance range,

– whether the workpiece is correctly inserted, and the clamping position is correct

– whether the applied clamping force reaches the desired value

– whether the contact force of the workpiece is within the specified limits

– whether the clamping pressure on the fixture corresponds to the specifications.

Next, standard clamping technology equipped with sensor technology and stroke measurement is trialed.

Two modified hydraulic standard swing clamps equipped with sensors, a pressure sensor from ROEMHELD, and two contact sensors are used on the fixture to collect this data. The clamping and support forces are recorded directly at clamping point “1”. A swing clamp with integrated stroke measurement is used at clamping point “2” to determine the clamping arm’s position. Two sensors determine the direct contact force. An additional pressure sensor positioned close to the swing clamp indirectly measures the clamping force.

Lastly, contactless energy and data transmission communicate between fixture and control.

The energy for the sensors and their supplied data are inductively transported between the fixture and the machine control. All components are encapsulated and, therefore, less susceptible to interference. The ACTUAL data are visualized on the display and compared with the TARGET values. If they are OK, the machining process starts. If there are deviations, the system refuses to start.


About August Wenzler Maschinenbau GmbH:

August Wenzler Maschinenbau GmbH, based in Spaichingen, Baden-Württemberg, develops and manufactures 5-axis machining centers. The majority of their customers come from the automotive industry, and they use the machine tools primarily to machine chassis and suspension components made of aluminum. These include, for example, structural components such as front and rear axle frames, side members, and battery holders. The family business, managed in the third generation by Wolfgang Wenzler, was founded in 1954 and currently employs 41 people. It has been part of the Heller Group since 2009.


About ROEMHELD Gruppe:

Whether for aircraft, automobiles, machine tools, or cases for smartphones: ROEMHELD technologies and products have been used to manufacture numerous industrial commodities and goods for end users for more than 60 years.

Efficient clamping technology solutions for workpieces, as well as for dies in forming technology and plastics processing, form the core of our ever-increasing portfolio. This is supplemented with components and systems for assembly and handling technology, drive technology and automation, and locking mechanisms for rotors on wind energy systems.

In addition to a constantly growing range of more than 30,000 catalog items, ROEMHELD also specializes in developing and realizing customized solutions and is internationally regarded as one of the market and quality leaders.

Innovation through tradition: ROEMHELD was established in 1707 with a foundry in Friedrichshütte, which still belongs to the ROEMHELD Group today and counts as one of Germany’s oldest active industrial businesses.

The owner-managed group of companies employs approximately 560 workers at the three locations Laubach, Hilchenbach and Rankweil/Austria and is represented in over 50 countries by service and sales organizations. With customers from the mechanical engineering sector, and the automobile, aviation, and agricultural industries, ROEMHELD generates an annual turnover of more than 110 million Euro.


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Photo 1:

With the new concept “Innovative condition detection increases process reliability”, castings can be inspected before machining. Also, their quality can be continuously monitored and seamlessly documented during the entire production process. Mounting of a test fixture on a machine in Wenzler’s TechCenter. (Photo: Wenzler).


Photo 2:

Two modified hydraulic standard swing clamps equipped with sensors and a pressure sensor from ROEMHELD are used on the fixture to collect the required data. Mounting of a test fixture on a machine in Wenzler’s TechCenter. (Photo: Wenzler).


Photo 3:

One modified hydraulic standard swing clamp directly queries the clamping and support forces at clamping point 1. (Photo: Wenzler).


Photo 4:

A swing clamp with an additional integrated stroke measurement is used at clamping point 2 to determine the clamping arm’s position. Furthermore, the contact force is determined directly via a sensor. An additional pressure sensor (bottom left) indirectly measures the clamping force (Photo: Wenzler).

Photo 5:

The display shows the system status “Loading/unloading workpiece released”, all elements are in a defined position (Photo: Wenzler).


Photo 6:

The display shows that all ACTUAL data match the TARGET values. Machining can start (Photo: Wenzler).