The Finnish aluminium extrusion specialist, Purso Oy, has recently installed a Vapormatt automated wet blast system on its latest advanced-technology extrusion line in Siuro, Finland – one of the most modern of its kind in Europe. Extrusion force of the new line is 27MN (megaNewtons). The company also operates two other lines, with extrusion forces of 35MN and 16MN.
Modern aluminium extrusion technology has resulted in continuing growth in the use of aluminium profiles across Europe, not only to produce aluminium profiles for use in the building industry but also extruded components for an increasing number of applications in the transportation engineering, electrical engineering and electronics sectors. Purso Oy produces aluminium extrusions to order for all these sectors and exports to many countries throughout Europe and the rest of the world.
An integral and vital part of aluminium extrusion production is to effectively clean extrusion dies between manufacturing runs to eliminate surface contamination. Following their removal from the extrusion press, dies are usually first treated with a caustic solution to clean off surplus aluminium and then undergo a water rinse. With wet blasting dies can be processed immediately after rinsing – still in a wet condition, thereby saving time.
Wet blasting also offers other significant advantages. The process has been found to provide a more gentle cleaning action than conventional dry shot blasting, with less potential substrate damage, which helps to extend die life and minimise the risk of damaging delicate edges – there is no edge burring or excessive “rounding”. In addition, because the process creates a finer surface, dies can be utilised for longer periods before re-cleaning becomes necessary due to the build-up of surface contamination.
Surface defects, such as micro-cracks, are also more easily identified following wet blasting as the process produces a fine-grained surface. Wet blasting also continually washes the surface to remove trace elements of caustic materials that can remain in cracks. As dies are often nitride or PVD coated following cleaning, this can help to ensure better coating adhesion.
Innovative concept in automated wet blast processing
Purso Oy has successfully employed a Vapormatt ‘1010’ manually operated wet blast machine for this application for a number of years. However, with the introduction of its latest extrusion line, the company has now significantly streamlined extrusion die cleaning by installing the recently developed Vapormatt ‘Cougar Radial’ machine, which features an innovative (patent pending) concept in automated wet blast processing.
Dies are normally loaded onto the Cougar Radial machine by overhead hoist through a safety-interlocked door and are retained in a specially designed radial fixture attached to a special 1100mm diameter roll-in turntable. The turntable fixture is easily adjustable to suit different die sizes and can accommodate dies weighing up to 250kg of up to 500mm in diameter.
During automatic processing in the machine’s 1550mm x 1300mm x 1180mm high sealed processing enclosure, a four-gun blast gun array traverses radially across the turntable at a closely governed speed as the turntable and fixture rotate. This combination of movement, coupled with the inclined angles of the four separate wet blast streams, ensures a high degree of surface penetration and the consistent processing of bores, orifices and other difficult to access surface areas.
The machine is programmed with a pre-defined sequence of gun array movements linked to turntable rotation speed – different programs are employed, depending on the design of the dies being processed. Adjustment of the turntable speed governs process duration.
Following blasting, the automated sequence is repeated at high speed using dedicated rinse nozzles, with the blast guns turned off, to provide initial component rinsing and remove residual traces of the blast media. Final rinsing is then carried out by hand when unloading the cabinet with a manual rinse gun. A manual process station is also provided to allow immediate processing of individual “urgent” parts or to enable areas needing only a small amount of additional processing to be dealt with.
Other features of the new Cougar Radial machine include closed loop operation: media filtration using a batch elutriation technique and an external liquid filtration system
allows process debris and dirt removed from the component surfaces to be collected to facilitate easier disposal via established in-house waste streams.
The Purso Oy machine was supplied via Vapormatt’s specialist distributor in Scandinavia: