Angst+Pfister Sensors and Power, Zürich, Switzerland, has developed a new type of oxygen sensor for the metal, ceramic and polymer Additive Manufacturing processes. The new long-life digital oxygen sensors and sensor modules for AM offer ppm signal resolution and no cross influence from most other gases.
A complex combination of long exposure times at low oxygen concentration, together with process generated gases that influence the response of the oxygen sensor, can cause problems, explains Angst+Pfister. While the build chambers are gas tight in order to reduce argon or nitrogen, consumption, this means that certain process-generated gases cannot escape the build chamber. Humidity control – be it for the powder bed itself, powder canisters and/or the chamber walls – is another parameter influencing the performance of certain types of oxygen sensors.
Angst+Pfister’s new sensor is a weak acidic electrolyte electrochemical sensor, which enables a long operational lifetime and less cross influence from other gases such as, but not limited to, hydrogen and other reducing gases. Two versions of the sensor are available, one is a 0-25% O2 type with a signal resolution < +/-30 ppm O2 and the other sensor is a 0-10,000 ppm O2 sensor with a signal resolution of +/- 1 ppm O2. The sensors have a M16 x 1 mm thread for process integration.
The combination of the 0-25% O2 PO2ES-103PD oxygen sensor and the 0-10,000 ppm O2 P-41AGWD oxygen sensor makes process and safety control in various Additive Manufacturing processes.
The signal output is controlled by specially designed electronics that are protected in an enclosure with EMC and IP65 protection. The output signal from the conditioning electronics is RS485 Modbus (optional 4-20 mA), enabling easy integration into a central PLC unit. The cable length between the electronics and the PLC unit can be chosen arbitrarily long, the cable length between the sensor and the conditioning electronics is 50 cm (maximum 100 cm).