Roller burnishing in the press shop

The first thing we see of a vehicle is its body. Regardless of the type of drive, it is always present and is a decisive design feature for car manufacturers. The design of a vehicle is a brand message and sales argument in one and a key USP of each individual manufacturer. Around 80 million vehicles are produced worldwide every year. Each of these vehicles consists of a body with around 300 parts. Each part in turn is manufactured with the help of several pressing and deep-drawing tools. One of these unique tool sets per vehicle type can therefore cost up to € 150 million. 

As these investments are so high, there is usually only one set of tools for the entire production period of a vehicle series. The tools therefore have to be adapted and repaired during production, resulting in additional direct and indirect costs.

Together with Picum MT, ECOROLL AG presented the design of a new and innovative process chain for these repairs at the VDI conference "Innovative Sheet Metal Processing 2025". 

On-site repair shortens throughput time

Usually, a tool has to be removed from the press shop to be repaired. It has to be delivered to the tool shop and then repaired there. According to figures from Dr. Dominik Brouwer, Managing Director of Picum MT, such a repair can take up to approx. 110 days. During this time, the tool cannot produce, and as it is the only tool for this type of vehicle, no body parts can be manufactured. 

Picum is already addressing this challenge with a mobile machine tool unit. The fact that this unit is delivered to the tool in the press shop, eliminates long transportation times, and repairs can be carried out much faster on-site. In one Picum customer example, the throughput time until the tool could be used again was around 35 days; in other words, that is a throughput time reduction of around 75 days and therefore a conservative cost saving of around 50%. 

Another major cost driver in the repair of deep-drawing tools is the finishing of the surface. This is usually done in a manual polishing process, which is time-consuming and cost-intensive. Together with Picum, ECOROLL AG has already tested the use of roller burnishing and machine hammer peening in this context. The tools can be integrated into the existing Picum machines and thus enable automatic finishing directly in the press shop. 

Roller burnishing as an alternative to manual polishing

A hydrostatic roller burnishing tool type HG is used for burnishing free-form surfaces. With these tools, a rolling ball on one half of the ball is subjected to a hydraulic medium and a pressure of up to 600 bar. Due to the hydrostatic bearing of the ball on the rolling medium, the ball can move freely in all directions. The entire surface is then burnished with a raster approach. 

As with all roller burnishing processes, the result is a significant reduction in surface roughness. At the same time, the surface becomes harder due to work hardening in the subsurface and high residual compressive stresses are introduced. 

For example, the manual polishing time for a cutting tool made from a standard material 1.2358 with a hardness of 56 HRC was significantly reduced by finishing the tool fully automatically on a machine tool using roller burnishing. 

An HG6 tool was used for the burnishing process, with which polishing could be completely substituted in this case. With a surface roughness after burnishing of R_z= 1.4 µm, a sufficiently good surface was produced, which also showed no quality differences to the manually polished tool in the cutting process. 

In addition to the higher reproducibility achieved by roller burnishing, the significantly shorter processing time should also be emphasized. Thanks to the fully automatic burnishing process, the machining time was reduced by 95% and now only takes a few minutes instead of several hours. 

Innovative process chain for repairing tools

These two technologies combined create a completely new and innovative process chain for repairing pressing tools. Local repair in the press shop can reduce throughput times and production downtimes significantly. 

The Picum MT's mobile processing system brings the machine to the workpiece and thus significantly shortens the overall throughput times for the repair. Combined with the innovative mechanical surface treatment, the time-consuming and expensive finishing process can also be automated, so that overall costs for repairing tools can be more than halved.