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Cold water cleans machined parts.

Cold water cleans machined parts

According to a certain television commercial, clothes can be laundered in cold water when using Brand X detergent. Cleaning machined workpieces, however, is another matter. In metalworking operations, parts cleaning is traditionally done with heat and solvents. This can lead to environmental concerns and potentially increased energy use.

Cold water may not seem an effective cleaning medium, but when applied under very high pressure in a carefully directed discharge, cold water can clean very effectively. Automated washing machines can deliver cold water to part surfaces at pressures up to 10,000 psi.

Certain benefits accrue to well-engineered applications of machines such as those built by The Reiss Engineering Co Ltd, Elan Div, Coventry, England. These machines are of "machine-tool" type construction, with a frame mainly fabricated from 4" and 6" box section steel with 3/8" mild steel plate cladding.

The high-pressure water system comprises the pump, valves and various hoses, pipes, and fittings. The pump is selected on the basis of the individual application, but sized such that it will be under used by a minimum of 25 percent. Elan manufactures their own special pressure-balanced, servo-controlled valves capable of starting, stopping, and controlling the flow of water at high pressures without shock or "hammer".

Cold-water washing uses no chemical agents or heat to aid cleaning; only a rust inhibitor is added to the water in the amount of 1 percent by volume. The volume of water used in cleaning is relatively small, and is allowed to drain directly into a tank integral with the base of the machine. The tank has a succession of weirs, which, due to the low rate at which water is moving, allow contaminants to separate by settling. A drag conveyor lifts debris from the tank bottom, discharging it into a container.

Water is then pumped from the tank through special filters which remove residual contaminant prior to recycling. These filters are effective down to 35 particle size and are self-cleaning.

Cleaning cylinder heads

One application of an Elan Div machine in the automotive industry is a fully-automated system designed on inline transfer principles for the Swedish car maker SAAB. The machine delivers one clinically-clean cylinder head, dried and ready for assembly, every 48 sec.

When "dirty" cylinder heads arrive by conveyor at the cleaning station, they are in a fully-machined condition. Each has residual "sticky" aluminum swarf randomly distributed on some surfaces, and particularly in various pockets and recesses. Removing the surface swarf presents no serious obstacle to the high-pressure cold-water washing technique, but the camshaft bores are a tricky problem. These bores are finished-machined in line and their half-caps are bolted in position.

But one of the two bolts securing each half-cap is hollow, that is, it has small-diameter axial and transverse holes. These holes connect with others drilled in the head casting and the half-cap, and their function is to convey lubricating oil to the camshaft bearings. Special probe jets had to be provided to deal with these small-diameter holes to guarantee that no swarf remains within them.

The Elan installation, which has integral, fully-automatic work handling throughout, is modular in design and consists of four separate but inter-connected sections. The first section deals with receiving and orienting incoming cylinder heads, and with transferring them one at a time, on a lift and carry mechanism, to the working areas of the machine.

Here, high-pressure cold-water washing and air-knife drying are carried out respectively. In these sections, blocks are automatically manipulated through a series of different attitudes, to present them to various arrays of water and air-drying jets.

In the washing section, plain cold water at a pressure of 4000 psi is used, and leaves the jets at a velocity of some 500 mph. The water, which is delivered by a 175-hp main pumping set, contains a corrosion inhibitor and is filtered, and circulated for reuse.

Accurate positioning and manipulation of each cylinder head is critical for cleaning the oil transfer holes mentioned above. In fact, special jets are dedicated to this operation, and reciprocating movements are used so that the water is "lanced" into opposite ends of the holes alternately. (See sketch.) This alternating action continues for a preset number of cycles, as determined by the Siemens programmable controller controlling the entire installation.

Elan has specialized in the development and application of automated high-pressure cold-water washing for diverse industrial installations in general, and for post-machining cleaning in particular. For more information, contact The Reiss Engineering Co, Ltd, Elan Div, Unit 12, Herald Way, Binley Industrial Estate, Coventry CV3 2NY, England, or circle 364.

PHOTO : Automotive engine block in test bay at Elan's Coventry factory being test cleaned using a multi-jet manifold to reach several machined holes simultaneously.

PHOTO : High-pressure, cold-water part washing machine, designed to integrate with a number of machining cells forming part of a flexible manufacturing system, is installed at a US factory. The machine operates automatically by means of a "teach and learn" programmable control. A shuttle system in front of the machine, manufactured by Scharmann Machine Tool Corp, interfaces with the washing machine and other Scharmann machines being fed by an AGV.

PHOTO : Sketch showing cleaning of oil transfer holes in cylinder head and hollow bolts securing camshaft half-caps. Special jets use a programmed reciprocating motion to "lance" water under high pressure into opposite ends of the holes alternately.

PHOTO : Detail showing 3-axis arm for manipulating water jet head within the washing machine. Used in conjunction with a turntable for mounting workpieces, the three-axis arm gives full coverage of all areas of a range of components.
COPYRIGHT 1989 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1989 Gale, Cengage Learning. All rights reserved.

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Publication:Tooling & Production
Date:Jun 1, 1989
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