Innovation and efficiency

Bernhard Grobusch GmbH, which currently has 28 employees, has developed over the years into a highly sought-after specialist for blow mold manufacturing and for gauge design and manufacturing. In addition to its strong technical expertise, the company’s success is also due to its high-performance manufacturing machines and Tebis AG's CAD/CAM software.

The company specializes in manufacturing gauges (image: Bernhard Grobusch GmbH, Inden).

The primary customers of Bernhard Grobusch GmbH, which is located in the municipality of Inden between Düren and Aachen, are companies in the automotive supply industry that have come to appreciate Bernhard Grobusch GmbH's experience, flexibility and reliability. "We're not planning any extreme growth in personnel, but we’ll continue to expand our expertise and our technical capabilities with machinery and software solutions that enable us to meet the customer's requirements even more successfully," stresses Peter Grobusch, who, together with his brother Bernd, directs the company founded roughly 40 years ago by their father, a master model manufacturer. Initially, models for foundries began to be manufactured in the 1960s, and blow molds and injection molds, including bottled molds for the packaging industry, starting in the ‘70s, while the automotive industry has come to be an increasingly important customer since the mid-‘80s.

"We have repeatedly specialized in specific application areas so that we could hold our own against the major competitors as a small company with 20 to 30 employees," explains Grobusch. "That’s why we are currently focusing almost exclusively on molds and devices for blow molding as well as the manufacture of measurement and test gauges for quality assurance."

The product spectrum includes blow-molded parts for the air passages in engine compartments and in vehicle interiors – although complete ventilation systems are also produced as well as liquid containers and tank fill nozzles. The gauges developed and produced include testing and measuring devices for vehicle windows, headlight systems, interior trim parts, automobile door seals and the blow-molded parts mentioned above.

Grobusch adds: "We supply every gauge with a comprehensive measurement record; this is provided for the blow molds only on customer request. However, we’re changing over to more intensively testing all blow molds in order to provide the customer with optimal quality and reliability." A high-performance 3D CAD/CAM system is absolutely essential for this process. Grobusch explains this using the example of an injection mold for plastic bottles that was previously produced by model manufacturing and then digitized. However, the problem that repeatedly arose was that the two bottle halves were never precise mirror images.

But this could be very easily implemented with a 3D CAD system. That’s why Bernhard Grobusch GmbH decided to implement the Tebis CAD/CAM software in 1988, after having first acquired their initial CAD experience using AutoCAD. "The Tebis software with the AutoMill module was the first system we learned about that could mill across an entire series of surfaces," says Grobusch. "The other systems could only machine two or three sections of a surface together, which is unacceptable for manufacturing steel molds."

Complete ventilation systems are also implemented in mold manufacturing (image: Bernhard Grobusch GmbH, Inden).

  • Expanding the number of CAD/CAM workstations step by step

    After the initial good results with Tebis software, the number of CAD/CAM workstations has been expanded step by step. Today Bernhard Grobusch GmbH has six CAD workstations used for designing molds and gauges. There are also four CAM workstations for generating the CNC programs and four Viewer stations right at the machines for viewing the design data and making small changes.

    Gauge manufacturing first became interesting to Bernhard Grobusch GmbH with five-axis machining, because the gauges for automobile windows, for example, have to be milled simultaneously in five axes. The sophisticated Tebis solution is even more effective for this process. Overall, a total of seven CNC milling machines with a milling area of up to 4,000 mm x 1,200 mm x 1,600 mm are currently used for manufacturing, where holes with a depth of up to 1,500 mm can also be made. Along with the Tebis Measure module, a Zett-Mess manually guided measuring machine has also already been in use at Grobusch for 10 years. A new Brown & Sharpe CNC measuring machine with an operating area of 3,300 mm x 2,000 mm x 1,600 mm was also procured this year. The parts or gauges are measured based on the specifications of the input data using PCDMIS and TebisMess measuring software.

    Peter Grobusch explains the company's collaboration with its customers: "We only accept orders when we receive 3D CAD models of the products to be manufactured, because only then can fast and efficient mold manufacturing be ensured. Efficient collaborations cannot be achieved with only 2D CAD data or drawings; these entail too many possibilities for interpretation and the resulting errors lead to delays and unnecessary costs." That’s why care is taken to ensure the greatest possible consistency in the internal use of the data at Grobusch.

    In most cases, the customers provide the product data in the form of CATIA files or in IGES or VDAFS format. The Tebis system has a high-performance direct interface to CATIA V4, which imports aspects including layer and filter structures, color attributes and most element information. "Unfortunately, it’s not yet possible to import and drawing information," Grobusch complains, "to account for the tolerance information that is so important to us.” The CAD models from the Tebis system can also be easily transferred back to CATIA V4, because the data structure is very similar in both systems.

    Cost-effective and flexible solutions can be implemented using flat-desk blow molds, as these don’t require a clamp in the blow-forming machine (image: Bernhard Grobusch GmbH, Inden).

  • The Tebis Viewer has replaced drawings for the company

    If the customer also requires drawing data in addition to the 3D CAD model, Grobusch employees resort to an AutoCAD LT installation, with the Tebis data transferred in DXF format. The Tebis Viewer workstations have eliminated the task of drawing for the company, with the result that all information is available in digital form and can be taken directly from the 3D model. The Bernhard Grobusch GmbH specialists distinguish three categories of blow molds. In conventional blow molding, such as for water containers, filling lines and normal air passages, the parison is initially extruded in the blow-forming machine. The machine then brings the mold together, and the parison is then blown out and cooled. In contrast, in suction blow molding, the parison is extruded and simultaneously drawn by suction into the closed mold. The 3D and flattened desk blow molds, developed together with a partner company, work with a robot that places the parison in the mold. This enables the implementation of cost-effective and flexible solutions, because no clamp is required in the blow-forming machine and the hydraulics are directly integrated in the molds.

    The area around the parting lines is often difficult to design in the blow molds. The Tebis system has been offering the designers useful functions to automatically generate the parting lines for the last several years. According to Grobusch, this was another argument for expanding the company’s CAD/CAM workstations. The colleagues who had previously worked in model manufacturing found 3D modeling with the Tebis system very easy. They were able to directly apply their extensive manual skills to CAD design.

    A total of seven CNC milling machines with a milling area of up to 4,000 mm x 1,200 mm x 1,600 mm are currently used for manufacturing (image: Bernhard Grobusch GmbH, Inden).

    Grobusch also mentions the Feature Technology as yet another advantage of the Tebis system, with which bores, threads and toleranced fits can be clearly defined in the CAD model with all manufacturing information to enable the subsequent implementation of automated CAM machining. Although this entails more effort in design, it also results in significant simplification, reliability and time savings in NC programming and manufacturing. "We’ve put a lot of effort into establishing clearly structured libraries for features, for corresponding NC sets and for tools to optimize our design and manufacturing processes," explains Grobusch. "This required that we break up some heavily used routines and establish a common internal company standard that is now mandatory for all personnel."

    Last-minute changes to molds that have already been completed are sometimes necessary. In this case, the Grobusch designers receive new 3D CAD models from the customer and have to adjust the molds accordingly. This time-sensitive work cannot be done using 2D data, and so, according to Grobusch, high-performance and consistent 3D CAD/CAM solutions are absolutely necessary.

    This combined measurement gauge for windows was designed using the Tebis CAD/CAM software (image: Bernhard Grobusch GmbH, Inden).

  • Deadline-driven work can only be completed with 3D solutions

    Grobusch mentions the new roughing module as an example of the capabilities of the Tebis software, in which the simulation not only performs more than just a visualizing task. In addition, a new intermediate geometry visible to the operator and corresponding to the machining result with the selected milling tool is generated during NC calculation. This minimizes idle travel, and the system also knows exactly how much residual stock is still present. The user can display this information and define the ongoing machining steps accordingly.

    Previously, although a visual simulation of the NC paths was possible, the user did not know very much about the intermediate result, could not define it as a new blank and did not always have the correct parameters for subsequent machining. This often resulted in unnecessarily long machine run times with many idle toolpaths.

    Grobusch concludes: "The comprehensive support from the Tebis software for five-axis machining has given us enormous flexibility. The current version of the software plays an important role here, as do two new five-axis machines from Deckel-Maho with which we recently expanded our machine shop. This has improved our efficiency in five-axis machining as well as 2.5D machining, which is now possible from five sides. This simplifies processing and also reduces the effort required by the operator."



Tebis software with the AutoMill module was the first system we learned about that could mill across an entire series of surfaces.



Cost-effective manufacturing throughout the process


  • Automated programming
  • Standardized processes
  • High process reliability


Mold manufacturing


Bernhard Grobusch GmbH


Inden near Aachen, Germany


Peter Grobusch


Managing director



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