in Vol. 2 - November Issue - Year 2001
Dramatic Time Savings with switch to Wet Blast Cleaning of Transmission Systems
A cleaned transmission unit is pictured here after being processed in the Vaqua(r) machine at ZF Great Britain.

A cleaned transmission unit is pictured here after being processed in the Vaqua(r) machine at ZF Great Britain.

In the Spotlight

USF Abrasive Developments is a manufacturer of wet peening and blasting equipment. It is located in England and a member of the USF Surface Preparation Group.

Nottingham-based, ZF Great Britain - the UK centre of the ZF Group, Europe's largest independent manufacturer of transmission systems, axles and steering units - specialises in the remanufacture of transmission sets from cars, buses and trains to agricultural equipment and huge earthmoving plant.

Exhausted gearboxes and transmission sets are sent to the company for complete refurbishment to "as new" condition and resold into the replacement market through transmission specialists or directly to transport and original equipment manufacturers.  ZF Great Britain remanufactures some 10,000 gearboxes a year at its purpose-built facility which was established in Nottingham in 1981 and has been steadily expanding since to cope with continually growing demand.
As part of its ongoing programme of process and quality improvement, the company recently introduced a semi-automatic Vaqua(r) wet blast machine, to streamline the cleaning and degreasing of incoming transmission units prior to remanufacturing operations.   As a result, cleaning times have been slashed by 30 minutes for smaller units and up to two hours for larger gearboxes, with obvious benefits in times of increased throughput.  

Parts cleaned in their fully assembled State

Previously, cleaning was carried out manually, with gearboxes having to be stripped down into their sub-assemblies.  Now, using the Vaqua machine - custom designed and manufactured by USF Abrasive Developments, part of the USF Surface Preparation Group - units can be thoroughly cleaned in their fully assembled state.
The cleaning operation in the Vaqua machine is a three-stage process and follows a pre-wash in an ultrasonic cleaning unit (supplied by CC Hydrosonics).  The first stage is blasting with a special water-based chemical and glass bead media mix.  This is followed by a clean water rinse and then dry air blasting to removes residual water.  Since the process operates at 60oC there is also an inherent drying effect.
The machine has a 2000mm x 2000mm x 2000mm processing enclosure and is equipped with nine process nozzles.  Eight of these are mounted on a vertically oscillating unit, controlled by servo drives. The additional gun is available for manual operation, if required, through a conventional external operating position and viewing window.

Programmable to suit different Gearbox Types

The parts are positioned on tailored jigs on  a powered turntable. Two  integral "roll-in" turntables are installed and  the enclosure has vertically sliding doors at each side to allow "pass-through" loading and off-loading by powered overhead hoist to streamline handling.  Nozzle oscillation speed, turntable speed and blasting and rinse cycles are programmable to suit different gearbox types via the machine's Mitsubishi PLC process control and monitoring unit.
Full cyclone separation ensures that all fines and contaminants are removed from the system during operation, and an oil removal unit is also fitted to dispose of excessive amounts of oil and grease.
Chris Adcock, Production Engineering Manager at ZF Great Britain, responsible for specifying the Vaqua machine, commented on its operation:  "The time savings achieved by the machine are tremendous in terms of increasing our production throughput, but I have to admit that we did have some reservations initially about the use of a wet blasting approach based on glass bead media, because of the potential risk of component contamination.  However these were unfounded and I'm more than pleased with the effectiveness of the rinsing side of the cycle.  Thorough inspection has shown that externally we don't have any glass bead left in blind holes where, historically, we have experienced problems with other  blast cleaning systems, which have led to the need to re-tap out contaminated internal threads."

For information: 
Paul Mitchell
USF Abrasive Developments,
USF Surface Preparation Group Ltd, Norman House, Henley-in-Arden, Solihull, West Midlands, B95 5AH
Tel: +44 (0)1564 792231 
Fax: +44 (0) 1564 795479