Dry stripping undercarriage doors

Citation

(2000), "Dry stripping undercarriage doors", Aircraft Engineering and Aerospace Technology, Vol. 72 No. 6. https://doi.org/10.1108/aeat.2000.12772fab.008

Dry stripping undercarriage doors

Dry stripping undercarriage doors

Keywords: USF Schlick, Paint, Blasting

Plastic and starch media dry stripping ("PMS" and "SMDS") systems are said to be progressively superseding wet chemical stripping for the controlled removal of paint from aircraft structures and components during maintenance, inspection, repair and overhaul procedures.

USF Schlick, part of the USF Surface Preparation Group, is a major pioneer of the of dry stripping technology, and has recently supplied a state-of-the-art robotic SMDS system employing wheat starch, to Boeing Asta, Australia, to remove paint from aluminium undercarriage main doors. USF Schlick is based in Metelen, Germany, and is a sister company to USF Vacu-Blast International, which has produced systems in the UK, including the supply of PMS facilities to the Royal Air Force and the Defence Aviation Repair Agency (DARA).

As well as eliminating the former need for potentially hazardous and time-consuming paint stripping solutions, the natural biodegradability of wheat starch is believed to provide an additional environmental benefit.

Fully automatic stripping of the components is carried out with a specially developed "flat" blast nozzle, guided by a programmable six-axis robot. The robot is attached to an overhead gantry – the linear axis – which traverses the part at a precisely controlled speed. The whole system is contained in an acoustically insulated 4m 8m 4m blast enclosure.

Used starch media is recovered by a closed-loop process, which employs a well-proven scraper conveyor mechanism and extraction ducting to feed the media, together with dust and debris, to a high-integrity media recovery and separation system. This comprises a cyclone separator, a magnetic separator, a large-mesh screening unit, and an additional high-performance, eight-stage cascaded air separator. Two integrated de-ionisation units are said to dissipate any residual static charges.

The recovered media is then fed to a storage silo for reuse. A specially designed, double- chambered pressure pot facilitates continuous blasting. The silo has large outlets which prevent "bridging" or clogging of the media and ensures complete evacuation of the silo. A belt-type dosing device guarantees a uniform, repeatable flow of media.

USF Vacu-Blast International, has also recently supplied a special automatic precision peening machine to the Italian company, Sicamb SpA, specifically for the fatigue life improvement of the wheels and associated wheel components fitted to the new Eurofighter "Typhoon" aircraft. Sicamb manufactures these aluminium alloy and steel parts as workshare partners of Dunlop Aviation.

Based on Vacu-Blast's "Ventus AXT" design and controlled by a PLC based system, the machine has a 1,500mm 1,400mm 1,200mm high processing enclosure and incorporates an array of four peening nozzles fitted to a two axis roof-mounted blast nozzle manipulator. Components are attached to special fixtures on a variable speed powered turntable, which rolls in and out of the enclosure to facilitate manual loading and unloading. The maximum component processing envelope is 700mm diameter by 700mm high.

The new machine can handle both steel shot and glass beads, depending on the type of part to be processed, and is equipped with the latest in-cycle magnetic media separation and classification system. This is said to ensure total segregation between the two types of peening media used and guarantees that only the highest grade media is recycled to the nozzles via the generator-reclaimer, thereby maintaining optimum process integrity and repeatability.

Details available from USF Vacu-Blast International, USF Surface Preparation Group. Tel: +44 (0)1753 526511; Fax: +44 (0)1753 538093; E-mail: info@vacu-blast.co.uk