The combination of strict cleanliness requirements and demanding environmental legislation has transformed manufacturing in recent years. Steed Webzell assesses the industry's switch to 'clean and green'
Most production engineers will recall the days of open-top solvent degreasers, stacked barrels of trichloroethylene (trike) and somewhat questionable disposal methods. But over the course of the past decade, things have changed. Those able to make the switch to aqueous-based systems have done so, while others who remain reliant on solvent have traded in their open top tanks for enclosed systems, with many also switching to a less harmful solvent. Furthermore, environmental legislation means that all waste from such processes must be disposed of in a manner that protects Mother Earth.
Among the recent manufacturers to minimise solvent usage is Basildon-based Selex Galileo (a Finmeccanica company), which specialises in precision components for electronic systems used in the defence industry. The new aqueous-based Midi parts washing and drying machine from MecWash (01684 271600), installed at the company's Essex facility, acts as a focus for parts used at four UK locations – Luton, Edinburgh, Portsmouth, Basildon – together with Finmeccanica sites in Italy.
Image: MecWash is solving cleaning problems for Selex Galileo
ALREADY A KEY ELEMENT
The new MecWash Midi has already become a key element of the company's commitment to operating a 'machining centre of excellence' and now acts as the final cleaning stage for the vast majority of manufactured components. Following production and machining, parts are processed by the Midi before being despatched for assembly or further manufacturing processes, some 20% of which are centred on 'clean room' activity.
"The range of components – mostly aluminium – that we manufacture in the UK call for the cleaning facility to be highly versatile," says Mel South, manufacturing manager at Selex Galileo. "Stainless steel baskets with nylon dividers, nylon baskets or dedicated fixtures measuring up to half a metre in length can all be accommodated by the MecWash system. Importantly, the single unit is able to provide high quality cleaning on standard components, as well as highly complex, thin-walled investment castings."
The MecWash design sees cleaning processes centred on a rotating drum, in which baskets or fixtures are loaded from an adjacent roller conveyor and then subjected to spray/flood washes and drying processes to achieve high quality results. Mr South also points out that the introduction of the MecWash Midi has underpinned the company's commitment to improving its shopfloor cleanliness procedures and, significantly, made a direct contribution to the company's reduction in solvent usage.
In fact, the recommendation of a MecWash system was also the conclusion of consultancy firm Markham Anti-Contamination Specialists (01604 871119), which was commissioned to assess product cleaning procedures at site. A post-project statement from the company reads: "The significant volume of solvents that were being used across the manufacturing processes has now been reduced, in line with statutory requirements, while the quality of the cleaning process is still of the highest order, as a result of MecWash technology."
The story is similar at energy storage and clean fuel company ITM Power (which manufactures hydrogen energy systems at Sheffield for decarbonising transport and the built environment), where an aqueous, ultrasonic cleaning line from Turbex (01420 544909) is being used to wash many of the production components and fittings.
HIGH LEVEL OF CLEANLINESS
"A high level of cleanliness of the constituent parts of a hydrogen generator is paramount," says project and test manager at ITM Power, Alex Shields. "Oil or particulates on machined parts can cause valves and pumps to stick, while any grease on electrolyser components would pollute the catalyst and shorten its operational life."
During the R&D phase, the company cleaned components by hand, using solvents. But for subsequent batch manufacturing, it wanted to avoid the hazards of a large, solvent-based system. So an aqueous cleaning line, Versa 120, was ordered from Turbex. The line comprises three 120-litre tanks placed side by side, served by an overhead gantry that transfers baskets of components weighing up to 35 kg automatically between each stage.
The first, ultrasonic, tank contains heated tap water and soap, which is rinsed off by deionised water in the second, non-ultrasonic tank. The third operation is ultrasonic rinsing in a tank of heated, deionised water. At all three stages, baskets are dunked several times into the tank before proceeding to the next stage, creating agitation to help removal of soils. Two baskets can be processed simultaneously in successive stages along the line.
"Turbex managed the project from start to finish, including modifying the second tank to include a skimmer for removing any soap remaining on the surface water," says Mr Shields. "The supplier also produced the washing programs, which included determining the duration for each cleaning stage and setting ultrasonic power in the first and third tanks for best results. We've now had the machine for six months and, in my opinion, the aqueous line achieves equivalent levels of component cleanliness to a solvent system."
The Turbex installation at ITM Power depicts a clear preference for automated cleaning and degreasing, an emerging trend at many manufacturing sites. Automated washing is particularly prevalent at large OEMs…such as Airbus. This year, Cleentek (0844 567 2950) has undertaken a project at the aero giant's Broughton site, near Chester, to supply an automated cleaning line for washing aircraft fasteners. However, rather than deploy a conventional overhead gantry, this installation uses robots as the transfer mechanism. The line has been designed by Cleentek, working closely in conjunction with robotics specialist Yaskawa UK (01295 272755).
Image: The automated Turbex installation is a three-stage system
The aircraft fasteners were previously cleaned using an ultrasonic cleaning system, which employed two different solvents for removing sealant. Following R&D over a two-year period, Cleentek devised a new cleaning process, using aqueous cleaning techniques and eliminating one of the solvents.
Contaminated fasteners arrive at the line in plastic boxes. The robot picks the boxes up and empties the fasteners into cleaning baskets, with the dirty boxes placed in a box cleaning machine.
The fasteners initially enter a front-loading cleaning machine that sprays them with a heated, water-based chemical at high pressure to remove swarf and other loose contaminants. This system is also fitted with a drying process, so the fasteners are dry before the robot transfers them to the next process, an ultrasonic cleaning unit fitted with an agitation system. Here, the cleaning solution is heated to 60°C and fasteners are immersed for 20-30 minutes. The cleaning solution, together with the scrubbing action of the cavitation process, breaks down and removes the sealant from the fasteners.
Subsequently, the baskets of fasteners are again collected by the robot and taken to the final post-wash system (again front-loading), which has three stages. The first stage uses the same water-based chemical used in the pre-wash system. This removes any sealant not totally removed in the ultrasonic cleaning units. The second stage rinses the fasteners and leaves a small amount of rust inhibitor on the fasteners that helps extend their working life. Finally, the fasteners are dried using an integral warm air blower. When the cycle is complete, baskets of clean and dry fasteners are taken to the next station where they are filled into the now clean boxes.
It's interesting to note that the cleaning of boxes/tubs/trays used for the transportation of parts is becoming just as important as degreasing actual components. This theory is supported further by the recent installation of a customised cabinet washer for this very purpose at a prominent turbocharger manufacturer. The supplier, Industrial Washing Machines (0121 459 9511), says that keeping the component transportation tubs scrupulously clean ensures there is no risk of these critical precision-engineered parts becoming contaminated or soiled.
Approached by the manufacturer to develop a machine for this application, engineers at IWM faced the challenge of having to deal with soiling on the tubs that could include oils of various types and, in some cases, heavy grease.
They determined that the best and most economical solution would be provided by a highly customised version of the company's EDi 13 cabinet washer.
IWM modified its standard design to include a fine particulate filter system and a skimmer to remove oil residues from the wash water. The control system was also customised to meet the user's requirements, including provision for the wash water to be pre-heated automatically prior to the start of a shift, so that the machine is ready for immediate use.
The system employs a hot wash cycle using a low-foam detergent specifically formulated for use in the automotive industry, followed by a hot rinse. After the tubs have been rinsed, they are retained in the machine for an adjustable dwell period to allow them to dry naturally before being returned to use.
As a non-value added activity, no manufacturer will admit any fondness for spending money on cleaning and degreasing. But, in truth, everyone benefits from such investment – the manufacturer, its employees, its customers, and the environment. Some would say that's priceless.
Cold washer saves energy
A new, entry-level, aqueous cleaning machine that is both cost-saving and energy-efficient has been introduced by Dürr Ecoclean. Called EcoCBase W3, it has two modes of operation; instead of using the system for washing components at 65ºC, at the touch of a button it may alternatively cold-clean at 35ºC to save energy.
Of front-loading design, the equipment has a single process chamber with flood washing, spray cleaning and vacuum drying. The latter employs a technique that consumes half the energy required by conventional systems, leading to further cost and energy savings, yet is able to dry components fully, even after a cold wash.
Image: The new, Dürr entry-level, aqueous cleaning machine
Available from Geo Kingsbury Machine Tools (023 9258 0371), the basic configuration may be retrofitted with optional second and third immersion cleaning and rinsing stages within the same enclosed cabinet. Ultrasonics can also be supplied, consuming only 13 W of energy per litre, while the system can also incorporate chemicals for component preservation.
The new machine, which processes loads up to 100 kg, joins two further EcoCBase entry-level systems introduced last year for cleaning parts using non-halogenated hydrocarbons (C2) and polar, or partially polar, solvents (P2). The latter is aimed at machine shops that use a combination of coolants, including neat cutting oil and high additive oils comprising a mixture of solvent-based and aqueous constituents. Furthermore, the P2 model is suitable for paint stripping and adhesive removal.
First published in Machinery, November 2011