Many companies shy away from using 3D printing processes in series production, as deficits in process stability lead to quality fluctuations and make their use in mass production unprofitable. In order to overcome the weaknesses of the process, the Laboratory for Manufacturing Systems at TH Köln has developed a sensor-supported print head that monitors the process and corrects it if necessary.

"Standard 3D printing systems on the market only have rudimentary process monitoring, such as temperature control of the heating element. Quality fluctuations in the raw material can therefore not be compensated for and immediately lead to errors in the components. The desired print result cannot be reliably reproduced, which is why series production is only possible if a very high level of rejects is accepted," says Tilmann Spitz from the Laboratory for Manufacturing Systems, explaining the initial situation.

Process monitoring during the printing process

The laboratory has therefore developed a print head that monitors the properties of the filament. If deviations occur in the parameters examined, such as feed speed, feed resistance or wire cross-section, the system automatically initiates process optimization or triggers a production stop in the event of serious errors. As the print head calibrates itself, the complex and error-prone adjustment by the operator is not necessary. "Our print head is a cost-effective retrofit kit that can be installed on all standard industrial robots on the market. This means that additive manufacturing is possible with existing machines and there is no need to purchase an expensive complete system," says Laboratory Manager Prof. Dr. Ulf Müller.

Extruder inspects material before printing

Filament is a significant cost factor in production. Many manufacturers offer their own cartridge systems and printing materials that are optimized for the respective printers. Manufacturer-independent raw materials reduce costs, but do not work on all production systems in terms of temperature and cross-section. "Our newly developed extruder adapts the process to the specifications of the respective filament. This means that printing materials from other manufacturers can also be processed in high quality," says Spitz.

The new print head was developed as part of a research project and student work. The first demonstrator was the result of the "IntelliExtruder" project, which the laboratory carried out together with Grip Handling Technology until the beginning of 2018, proving the feasibility of the concept in principle. "On this basis, students from the laboratory optimized the mechanical structure, programming and algorithms in a total of seven Bachelor's and three Master's theses, so that we now have a system that is close to market maturity," says Müller.

The research project "IntelliExtruder - 3D print head with automatic calibration and adjustment" was funded by the Central Innovation Program for SMEs (ZIM) of the Federal Ministry for Economic Affairs and Energy. At the TH Köln, it was based in Prof. Dr. Ulf Müller's Laboratory for Manufacturing Systems at the Faculty of Plant, Energy and Machine Systems.