Laser surface treatment machine for Ariane 6 Cryogenic Tanks 2019-01-1897
Surface treatment of cryogenic tanks (liquid oxygen and liquid hydrogen) for the Ariane 6 Space Launcher is a critical step for the adhesion of insulation materials. This operation is currently performed by the help of chemical products which are for some of them carcinogenic, mutagenic and repro-toxic. The large tank dimensions require using an important quantity of those products which generate massive recurring costs and health and environment problems.
ArianeGroup has previously qualified and patented the Laser Surface Treatment as a replacement solution to chemical process. The aim is to use energy provided by infrared laser beam to modify the top layer of the tank surface. The chosen technology is Nd-YAG pulsed laser. Electroimpact has been chosen to carry out the industrial application.
The main components of the laser system are a laser source, to generate the laser beam, an optic fiber to transport the beam and an optic with galvo mirrors to focus and move the laser on the part. The optic scan field is about 50 x 50mm, so it needs to be mounted on a machine to be moved over the part. To cover the overall tank dimensions (5.4m diameter by 16m length), we chose a long arm robot (Kuka Kr 120R3900), and a 20m linear axis to access either the cylinder part and bulkhead areas.
First challenge to correctly apply the Laser Surface Treatment is to respect the focal distance between the laser focalization lens and the part despite tank shape deviations. We implemented a 2D profilometer above the optic that measure the focal distance and provide the value to the machine controller that correct to robot trajectories in real time.
Second main challenge is to integrate in line inspection systems able to check to the treatment operation quality. To perform this function, we use 2 kind of sensors:
- An optical sensor looks at the part color and compare to the red-green-blue reflection to the value of a reference sample
- A plasma sensor measures the plasma intensity to detect a potential decrease that means a treatment failure.
By developing a custom end-effector with laser optic and sensors, we are able to match the part real shape and inspect the process quality which is mandatory for an industrial application.