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Vol. 8
March Issue
Year 2007
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in Vol. 8 - March Issue - Year 2007
Wet Blast Cleaning Of Aluminium Extrusion Dies Achieves Important Production Benefits



The Vapormatt

Further information: Robin Ashworth Vapormatt Ltd Monarch Centre Venture Way, Priorswood Industrial Estate Taunton, Somerset, TA2 8DE, UK Tel. +44.1823.257976 Fax: +44.1823-336446 E-mail: robin.ashworth@vapormatt.com www.vapormatt.com

Vapormatt’s 'Cougar 15' wet blast machine has been shown to provide a highly effective means of cleaning aluminium extrusion dies between manufacturing runs to remove surface contamination. Use of the machine can achieve important benefits and significantly streamline the die cleaning operation.

In particular, substantial time savings can be made over the alternative process of dry blasting. Following removal from the extrusion press dies are usually first treated with a caustic solution to remove surplus aluminium and then undergo a water rinse.  With wet blasting the dies can be processed immediately after rinsing – still in a wet condition.  With dry blasting, a lengthy drying-off period is necessary in order to avoid the risk of water contaminating the blast media and clogging the machine.

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". Added to this, because the process creates a finer surface, dies can be utilised for longer periods before re-cleaning due to the build-up of surface contamination becoming necessary.

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.

Dies are normally loaded onto the Vapormaster machine by overhead hoist and are retained vertically in a specially designed fixture attached to a roll-in turntable mechanism. The fixture is easily adjustable to accommodate different die sizes.

Once in the sealed processing enclosure, accessed through a safety-interlocked door, the 1350mm diameter turntable can be rotated to facilitate all-round cleaning using the manually operated blast nozzle. The 2200mm wide x 1350mm deep x 1330mm high enclosure has two external operator positions to provide optimum access, and is constructed in grp with an abrasion-resistant lining.  The machine can handle dies weighing up to 250kg and up to 500mm in diameter.

The Wet Blast Process

Vapormatt wet blasting (or 'Vapormatting') is a solvent- and dust-free simultaneous cleaning and degreasing process that employs an operator-safe cleaning solution comprising a special mix of water, detergent and media – a glass bead mixture is normally used. This is projected at the component through a special blast nozzle. The operating pressure of the process is highly controllable and effluent from the machine is processed through a filtration system, which separates out solid waste for safe disposal and allows the water to be recycled.  Because no solvents or other potentially hazardous chemicals are used by the wet blast process, it is not subject to stringent EU solvent emission, VOC or dust emission legislation.

Vapormatt manufactures a wide range of wet blasting cleaning and degreasing systems, extending from small manual cabinets suitable for automotive workshops to large automatic machines used for special applications such as the surface preparation of wire products and the de-painting of aircraft wheels.