If such changes go undetected, the production quality suffers without being noticed. Particularly in critical components for medical technology, but also with safety-relevant parts for the aerospace industry, even the tiniest differences can put the stability of the entire system at risk. Therefore, close examination of the laser beam should be integral to each and every stage of the manufacturing process. But which parameters should be measured, and which measurement methods are practicable for this purpose?
These are the parameters used to evaluate a laser beam:
- Power and energy
- Spatial intensity distribution
- Focus position
- Beam quality
- Divergence
- And: the stability of these parameters over time
Often, in order to detect changes in the laser beam, one measures its power or energy. The measurement technology for this is long established, and – depending on the laser type, power level or energy – there is a wide range of thermal, pyroelectric and photodiode sensors available. However, when it comes to LPBF applications, there are several limiting factors to consider:
- The power or energy density in LPBF applications is often so high that thermal sensors would require additional cooling
- Since the build chamber is always very dusty from the metal powder, the delicate sensor surfaces must be shielded from it
- The build chamber is cramped, so there is no room for any extensive measuring setup
- To operate the laser, the door to the build chamber must be closed frequently, which makes cables problematic
These limitations, along with the ever-growing number of applications for AM technology, are driving the manufacturers of measuring instruments to develop individual metrological solutions for LPBF systems. MKS Instruments has now introduced a new, ultra-compact power gauge that was specially developed for measuring high powers in confined spaces. The footprint of the Ophir Ariel measuring device is about the same size as a standard playing card and fits comfortably on the palm of your hand. The battery-operated device shows the measurements directly on its display, saving them internally or sending them via Bluetooth to a receiving device outside the build chamber. Not only does it meet the dust protection requirements, the system is self-contained and splash-proof. In order to cover a wide measuring range from 200mW to 8kW without requiring additional air or water cooling, the Ariel power gauge combines two operating modes: (a) brief measurements of the energy for high-power lasers up to 8kW, and (b) continuous power measurements for lower powers up to 500W. Due to the system's high thermal capacity, several consecutive pulses with an accumulated energy of 14kJ can be measured before it has to cool down. For laser beams with high power but a smaller diameter, the removable diffuser (included) enables safe power measurement.