New sandblasting process: Removing aircraft paint with corn

Sandblasting processes can be very costly. Aircraft parts such as engine cowlings are repainted during maintenance work. To do this, the existing paint layer must first be removed. Until now, this has been done by chemical means or manually with a sanding machine. A newly developed sandblasting process from Sappi uses corn starch that is blown through a nozzle onto the painted surface by means of compressed air.

However, this process requires the nozzle to be guided over the surface at a constant speed and always at the same distance. This is because, especially in the case of parts made of fiber composites, only a few micrometers lie between clean paint removal and costly damage to the synthetic resin surface. In the Eurostars project "Ecostrippair", researchers from the ZHAW School of Engineering have therefore developed a semi-automatic solution for this precision work.

Collaboration instead of programming
"The required precision naturally calls for a robot," says project manager Marcel Honegger from the ZHAW Institute for Mechatronic Systems. "However, we didn't program a fully automated robot, but created a system in which the workers use the robot as an intelligent tool - a high-precision extended arm, so to speak." The robot is controlled by human hands at all times.

For this purpose, the ZHAW researchers have developed a compact operating console based on a tablet computer. The user manually brings the robot arm with the attached sandblasting nozzle into the starting position. The robot independently regulates both the alignment and the distance of the nozzle to the surface and precisely controls the speed.

To the explanatory film of the ZHAW School of Engineering:

Protect surfaces and personnel
The robot moves the sandblasting system evenly along the top of the aircraft. Equipped with force and distance sensors, the robot also masters curved surfaces without any problems. "Thanks to its high precision, the system removes only the paint while protecting the underlying surface of the component," says Marcel Honegger. "In addition, the process is more efficient and also more ecological." No chemicals are used in the process, only corn starch. This is in a closed circuit and passes through the nozzle several times. "Last but not least, the users will also benefit from the newly developed system, as it reduces the physical workload immensely," says the ZHAW researcher.

Robot ready for field test
To ensure safety in the work area of the industrial robot at all times, the system has a second control system that is used exclusively for monitoring. "Sensors check all angles and speeds," says Marcel Honegger. "If irregularities occur, the system is immediately stopped automatically." Initial tests in the ZHAW robotics lab have been successful. Now the system is to be tested at Air France. For Marcel Honegger, applications in the railroad industry, for example, would be conceivable in addition to the aircraft industry.

www.zhaw.ch