Better quality control with digital assistance systems

A digital assistance system developed by Fraunhofer researchers will enable significantly more workers to ensure the quality of crankcase honing at Volkswagen.

Every manufacturing operation, be it in the automotive industry or another sector, has to run flawlessly. If errors can be spotted early by making it possible for many individuals to share knowledge, then resources can be saved.

If even the smallest tool is worn, finished parts may have to be rejected. Cost and resource efficiency make it essential to eliminate sources of defects and thus ensuing rejects. Since this is Volkswagen’s mission in Salzgitter too, the company aims to optimise the process control of honing machines.

A honing machine hones crankcases — one of the most complex and expensive parts of a vehicle — before they can be installed in an engine. It finishes piston ring faces so that the parts meet specified tolerances and shapes exactly and fit well in engines. Cylinder bores are honed to obtain the required surface quality of the crankcases, which minimises frictional losses in an engine later. Workers are unable to see how this massive machine concealed behind its housing does this, so staff have difficulty assessing and analysing the machine’s relevant parameters.

Researchers at the Fraunhofer Institute for Factory Operation and Automation IFF in Magdeburg are helping the company improve control with a digital assistance system. The system makes it possible to share knowledge about the machine among several individuals. Anybody working on the machine should be able to assess crankcase quality and to inspect the honing machine — and to take appropriate action whenever necessary. Until now, quality control has been in the hands of a single expert.

The digital assistance system guides workers step by step through the daily quality check on the machine. A digital checklist, as well as virtual models and the expert’s know-how, is stored in the system. The user interface has been kept simple: staff see a complete virtual model of the equipment to the right on a large monitor and the checklist to the left. Any tool up for inspection on the checklist is marked by the system on the virtual model of the equipment.

“The experts are informed which tool they have to inspect and where the tool is located,” said Tina Haase, a researcher at the Fraunhofer IFF. The system also provides assistance during inspection itself — images show the user what the tool ought to look like ideally and what signs of wear preclude further use.

The system also assists staff with measured parameters, especially when they are assessing and evaluating collected data. The system compares measured values entered in the checklist with stored tolerances.

The car maker aims to use the digital assistance system to enable every employee to analyse and correct the process themselves. Employees should be intervening preventively and rectifying errors long before rejects are produced, rather than merely reacting to defective manufacturing.

The virtual model of the honing machine explains step by step what requires attention during visual inspection. ©Photo Fraunhofer IFF.

The system is currently a prototype. The researchers at the Fraunhofer IFF intend to expand the assistance system in another stage. Workers have to correct the manufacturing process whenever a defective product — in this case, a crankcase — is produced. The researchers now intend to virtually remove the housing enclosing the machine in the assistance system in order to visualise the causal relationships. This will enable staff to view the honing process and test the effect of individual parameters on manufacturing in the system.

“We expect the use of a digital assistance system to disseminate previously pooled knowledge in order to control complex processes preventively and improve them sustainably,” said Jörg Rudolph, an engineering specialist at VW’s engine plant in Salzgitter.

Top image: The honing machine at VW’s plant in Salzgitter ©Fraunhofer IPT.