AIOS Automotive Integrated Overhead Systems GmbH has been producing headliners at its headquarters in Überherrn, Saarland, since 1986. With around 350 employees and a turnover of over 79 million euros in 2024, the company focuses strategically on the mid-range, upmarket and premium markets.
The company, which was acquired by Callista Private Equity GmbH, Munich, in 2024, manufactured around 470.000 headliners in 2025, predominantly in batch sizes of between 500 and 1.000 units. The headliners are manufactured at the company's headquarters and delivered to two plants in Bremen and Maichingen in the Stuttgart area, where they are assembled into complete overhead systems with elements such as lamps, frames, sunroof technology and cabling. These components are then delivered just-in-sequence to the assembly lines of well-known car manufacturers.
Production on two presses
First, glass fibres, foam, nonwovens and films are processed into a composite material and then moulded into the support section of the headliner in a press. This is followed by fully automatic trimming of the edges and cut-outs for sunroofs and lighting. In the subsequent laminating process, the vehicle-specific decorative fabric is applied, which is coated with a hot-melt adhesive on the underside. After placing the support part on the lower die, both are heated and the decorative fabric blank, which has been cut to size in the meantime, is pulled in. Both are then bonded to the support part under pressure and heat. The die is then cooled. This speeds up the process and stabilises the component.
The clamping nuts are distributed across six units in the upper die – three each on the front and rear – and four in the lower die, two each at the front and rear.
The challenge: die fixation in confined spaces
The dimensions of the dies used correspond to the sizes of the headliners. The majority of the premium vehicles to be equipped are saloon cars and SUVs with large overheads and corresponding dies.
With total weights of 6 to 7 tonnes and sizes of around 2 x 3 metres, and in some cases even larger, the dies place high demands on the clamping technology.
Before switching to ROEMHELD technology, they were fastened with screws in T-slots. However, this solution proved to be problematic: employees had to tighten the large M20 screws manually with considerable effort – which was very difficult to do in the confined conditions. This was because there was no room for a metre-long wrench at the rear of the press, where space is limited.
"Even the strongest employees had great difficulty applying the required torque," explains Dirk Weikert, Team Leader Mechanics at AIOS.
Since October 2025, ten hydro-mechanical clamping nuts with through-thread and clamping force indicator have been in use on a laminating press. The M20 size is used with a nominal clamping force of 60 kN and a tightening torque of only 9 Nm.
Safety and quality risk
This led to screws being tightened to varying degrees depending on the employee, some of which were too tight and some too loose. This resulted in a considerable safety and quality risk: there was a danger that the upper and lower dies would shift, causing the components to be pressed unevenly. The result would have been rejects. In the worst case, an upper die that was too loose could even have fallen down – an unacceptable risk to employees.
"The focus was on employee and process safety," emphasises Weikert. The number of die changes was irrelevant – the priority was clearly on process reliability.
The solution: hydromechanical clamping nuts with force indicator
The team leader came across ROEMHELD's clamping nuts while searching the internet. AIOS has been using products from the clamping technology specialist since 1998: hydraulic push-in clamps have been in use ever since, as well as ball rails in machine tables of various presses.
The decisive factors in choosing the hydromechanical design were the visual clamping force indicator, the purely manual operation without an aggregate, and the very low force required for clamping. Weikert was also impressed by the ease of retrofitting, the adaptability to different clamping edge heights and the maintenance-free components.
Since October 2025, ten hydromechanical clamping nuts with through-threads and clamping force indicators have been in use on three laminating presses. The M20 size is used, with a nominal clamping force of 60 kN and a tightening torque of only 9 Nm.
The clamping nuts are distributed across six units in the upper die – three each on the front and rear – and four in the lower die, two each at the front and rear. An important advantage of the clamping elements is that the nuts are easy to retrofit and temperature-resistant up to 120 °C, which is important for use on the laminating press with its heating and cooling cycles.
They have a continuous thread and are therefore tolerant of different clamping edge heights and tolerances without the need to adjust the length of the tie rod. As all dies are standardised at AIOS, the elements can be used on any press.
The vehicle-specific decorative fabric is applied on the laminating press. First, an employee places the carrier part on the lower die. Both are heated, then the decorative fabric blank, which has been cut to size in the meantime, is fed in and bonded to the carrier part under pressure and heat.
Simple and reliable
The operating principle is as simple as it is effective: after manually adjusting the clamping nut to the clamping edge, the integrated hydraulic cushion is preloaded by turning an Allen key. The clamping nut converts a small tightening torque into a large clamping force. The indicator pin of the optical clamping force indicator rises when the full clamping force is reached – a clear visual signal for the operator.
"The mechanical operation with very little effort and torque makes work much easier for our employees," emphasises Ferit Acar, deputy production manager. "In the past, our strongest people had to use large levers. Today, a small Allen key is all that is needed – that is enormous progress."
Improved process stability
The constant clamping force helps to maintain the tight tolerances of five tenths. This prevents misalignment between the carrier part and the decorative fabric, even with seasonal changes in adhesive behaviour. In this way, the clamping solution helps to permanently ensure the dimensional accuracy and quality of the headliners and reliably meet the requirements of OEMs in the premium segment. Ferit Acar emphasises: “The uniform and reproducible clamping of the tools with the aid of hydromechanical clamping nuts contributes directly to process stability and thus to product quality.”
The indicator pin of the optical clamping force indicator at the top left of the clamping nut rises when the full clamping force is reached – a clear visual signal for the operator.
Highest product quality is the be-all and end-all
Weikert sums up that the expectations for the hydromechanical clamping nuts have been met. He particularly emphasises the punctual delivery, uncomplicated operation and reliability of the products. The latter is particularly important at AIOS, as the employees come from different professions with very different levels of prior knowledge and experience, which has an impact on their expertise and desire for ease of use.
“Highest quality is essential for the success of our headliners in the premium segment," emphasises Weikert, "and ROEMHELD clamping technology makes an important contribution to this."
Dirk Weikert, Team Leader Mechanics at AIOS (left), and Robert Rac, Technical Consultant at ROEMHELD
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