Bolted connections are among the most frequently used, but often underestimated construction elements in mechanical engineering. Their reliability has a direct influence on the safety and availability of a system. If they fail, there is a risk of downtime, high maintenance costs and, in the worst case, production losses.

A medium-sized mechanical engineering company was faced with precisely this situation: in an automated production line, recurring screw breakages and loosening occurred over a period of months, particularly at highly stressed connection points between the drive housing and the bearing block. Despite regular maintenance and retightening of the connections, the problem persisted.

Analysis of the causes

The situation was systematically investigated as part of an optimization project. The first step was to evaluate the previous calculation and installation documents. This revealed that many of the existing connections had been dimensioned according to empirical values. Some were significantly oversized, others with insufficiently defined preload forces.

For an objective assessment, the bolted joints were then analyzed using a software-supported calculation, including in accordance with VDI 2230. The decisive factor here was the exact mapping of the load cases, including changing operating loads and temperature influences.

The path to optimization

The calculations provided a clear basis for technical adjustments:

• Geometric optimization: By adjusting the screw length and the contact surfaces, settling phenomena could be reduced.

• Material combination: The previous pairing of heat-treated steel and aluminum was replaced by a more suitable combination, which improved the flow behavior.

• Preload forces: Simulations were used to define optimum tightening torques in order to keep the preload force stable during operation.

• Assembly processes: The introduction of a documented tightening procedure with torque/rotation angle monitoring significantly improved assembly quality.

Calculations and simulations showed that many of the screws previously used were oversized. Targeted adjustments made it possible to increase the load capacity by up to 40 % while using less material.

The result

The implementation of the measures showed measurable results within a few production cycles:

• The failure rate of the screw connections fell by 81.1 %.

• The cost of materials fell by 23.8%.

• At the same time, assembly efficiency improved, as the clearly defined tightening values minimized scatter.

Overall, the optimization led to significantly higher system availability and a long-term reduction in maintenance costs.

Conclusion

The example shows how great the influence of a well-founded screw calculation can be on the overall reliability of a Design . By using modern calculation software, load distributions, preloads and material behavior can be precisely recorded. In other words, weak points can be identified before they become a problem.

Those who systematically analyze bolted connections and design them in accordance with VDI 2230 not only increase technical safety, but also the cost-effectiveness of the products.