PROCESS DESCRIPTION

 

In our view, vapour blasting is suitable for cleaning external surfaces of aluminium coatings but it does not provide an attractive finish for long periods of time. Blast cleaning internal surfaces may cause shards of glass media to impregnate the surface that under the influence of engine harmonics may pass from the casting to the oil. For this reason we finish the castings using a barrel process. As a result, the inside shines as much as the outside.

Plastic plugs ranging from 2mm up to 150mm are inserted into blindholes, oilways and bores. The castings are lightly vapour blasted and dipped in chemicals to remove resins, oxidation and smut. A further vapour blast with fresh media results in a silk white casting which does not resemble the original finish and soon goes off.

The exceptionally clean castings are placed into another machine containing ceramics and detergent. The ball bearings cascade over the surface of the casting gently burnishing it and changing the finish from white to lustrous aluminium. The finish is uniform and the small media size ensures that nooks and crannies are similar to the main surfaces.

The eighteenth century technique for polishing objects is easier to understand than its modern day equivalent. Imagine a rotating cement mixer full of pebbles into which rough castings are inserted. Eventually the casting will be smoothed by the pebbles, resulting in a shine.

POLISH

Aluminium castings viewed through the microscope show a mountainous landscape of peaks and troughs. Brilliant reflective surfaces are achieved when the distance between the peaks and troughs is reduced. This is termed contour lean average (CLA). The CLA can be reduced on flexible belt sanders and scurfing mops. Fine finishing is possible using varying grades of soap after the first two processes.

The rates quoted for polishing include a pre-clean and ceramic burnish of the internal surfaces. Thorough cleanliness ensures that the polisher's fingers do not transfer oil or grease to the polishing mop.

PREPARING CASTINGS

In order that we can complete your job within two weeks it is essential that all steel components be removed. Exceptions to this are cylinder liners and valve guides that remain in position and are protected.

SENDING CASTINGS

Most household named couriers will collect from your door subject to credit card payment. Some rates also include insurance against loss or damage in transit. Weight restrictions may apply so the maximum weight of one box should not exceed 30Kg. Also bear in mind that the box containing castings will be used to return the finished items, therefore, the more substantial the better.