An ageing, in-line washing system has been replaced by a batch cleaning machine that is proving much more versatile in operation at the Poole factory of Thompson Valves, a manufacturer of high quality valves and flow control products.
Called Elba, the aqueous machine is supplied in the UK by Turbex (01420 544909) and has a number of advantages over the previous installation. While the old unit was also water-based, it processed components on a continuous belt and could not rotate them. As a result, water could be retained within components, causing staining and oxidation while they were in storage. Other problems were the system's large footprint and difficulty in obtaining spares.
In contrast, the programmable Elba can employ three types of cleaning cycle for any batch of parts. First, to prevent components clashing together, the basket is held stationary in its home position while jets run around it, spraying water from every angle. This is said to be ideal for cleaning light, simple parts, possibly those with turned diameters that need to be protected.
A second cleaning program involves rocking the basket through ±10°, offering improved access to components for better cleaning, while still avoiding contact between them and potential damage.
Third, one or several larger parts are fixed into a basket, which is rotated through 360°.
Image: Turbex provided a clean solution for Thompson Valves
A patented feature of the machine is its ability to adjust the movements of the holding basket and spray jets individually, allowing them to rotate in the same or opposite directions. Such cycles, says Turbex, provide excellent penetration into the most awkward areas of particularly complex valve components for the removal of oil, coolant, tapping grease, swarf and other contaminants from the previous machining processes.
Components at Thompson Valves range from 25 to 500 mm long and are produced from a variety of metals; mainly stainless steel, carbon steel, aluminium and brass. Stainless steel parts are put through a detergent wash and rinse cycle at 50 °C, followed by compressed air drying at 70 °C within the machine. Processing of the other materials omits the rinse stage for speed, as all components are, in any case, cleaned ultrasonically before assembly.
Richard Betts, production engineer at Thompson Valves in charge of the cleaning section, says: "We chose the Elba for a combination of reasons, based on its compactness, functionality and competitive price, which was a full £30,000 less than another model we looked at.
"The machine is quick to install, as the integral condensing system avoids having to fit extraction.
"It is also easy to operate, using our suite of nine installed programs, each of which takes typically five minutes.
"Overall, it supports the effective cleaning of components for the manufacture of valves used for safety-critical applications in the nuclear, oil and gas, petrochemical and marine markets, which are the sectors that we mainly serve."
Cleentek (0844 567 2950) designed and commissioned a robot cleaning line for aircraft fasteners, used in the manufacture of wings at Airbus's Broughton factory, near Chester. The system, which employs aqueous and solvent cleaning, uses a Yaskawa Motoman robot to support a six-stage cleaning process, thought to be the most automated and efficient aircraft parts cleaning line anywhere in the world. All the cleaning chemicals, including a replacement solvent, were custom-developed by Cleentek. The system is installed at J&P Group, near Chester.
"The aircraft fasteners were previously cleaned using an ultrasonic cleaning system, which used two different solvents for removing sealant from the fasteners," says Cleentek's managing director, Kevin Whittle. "Following research and development over a two-year period, Cleentek has devised a new robot cleaning process, utilising an aqueous cleaning processes and eliminating one of the solvents." Contaminated fasteners arrive at the line in plastic boxes, which are then emptied by the robot into cleaning baskets, with the dirty boxes put into a box cleaning machine. Working four baskets per batch, the fasteners then undergo a six-stage cleaning process: pre-wash, dry, ultrasonic cleaning (using the solvent – N-methyl-pyrrolidone), post-wash, rinsing with corrosion inhibitor, and dry.
Image: Cleentek's robot cleaning line for aircraft fasteners
The pre-wash system is a Cleentek Frontloader cleaning machine, which sprays a heated water-based chemical on to the fasteners at high pressure to remove swarf and other loose contaminants. After the drying process, the fasteners are picked and moved by the robot to the next machine – one of two Cleentek ultrasonic cleaning units fitted with an agitation system.
The ultrasonic unit heats the cleaning solvent solution to 60 °C and immerses the fasteners for 20 to 30 minutes. The cleaning solution and the scrubbing action of the cavitation process break down and remove the sealant from the fasteners.
The baskets of fasteners are then picked by the robot and moved to a post-wash system in another Cleentek Frontloader with three stages. First, the same water-based chemical used as a pre-wash removes any sealant not totally removed in the ultrasonic unit. The second-stage rinse then deposits a small amount of rust inhibitor before the fasteners are dried in a warm air blower.
Each full cycle lasts 30-40 minutes, after which the baskets of clean dry fasteners are taken to a filling station to be put into their now clean boxes. They exit the line as they arrived, on a roller conveyor, and are then stacked and returned to the wing assembly lines, ready for re-use.
AQUEOUS ANSWER AGAIN
MecWash Systems (01684 271600) has completed the installation of a further aqueous-based component cleaning system at Mahle Powertrain, in Wellingborough.
The new MecWash Midi offers both environmental and performance advantages, and features one of the most comprehensive, integral jetting arrangements it has ever designed, says MecWash.
The Midi is dedicated to cleaning aluminium V8 engine blocks and heads for a prestige automotive manufacturer and has the capacity to clean 30,000 individual machined 'engine sets' per year.
Image: The Midi is dedicated to cleaning aluminium V8 engine blocks and heads
"Each set, which comprises two cylinder heads and a block, features a wide range of machined elements, all of which have to be cleaned of machining oil and metal swarf to meet the customer's specifications," explains Phil Knightley, production engineer at Mahle Powertrain. "Clearly, this places great emphasis on the capability of the cleaning station, which fulfils a vital role between machining, and both leak and porosity testing procedures, ahead of packing and despatch.
"The decision to work again with MecWash, who have supplied a number of units for Mahle in recent years, was centred on the company's ability to meet this complex cleaning requirement in the required time-frame, and to do so in an environmentally responsible way, as a result of the aqueous-based design," he adds. (Mahle Powertrain operates an environmental management system in accordance with the international management standard, ISO 14001.)
Engine sets are loaded into purpose-designed fixtures and then onto individual trolleys that incorporate a steel roller system for ease of handling – both were also supplied by MecWash Systems. These trolleys are brought to the front-loading unit and latched into position before an operator rolls each set into the 800 mm deep drum. The wash chamber rotates the components in accordance with a six-minute wash programme, which can be tailored using the PLC. Each cycle subjects the components to a flood wash, external and internal jetting, as well as hot air and vacuum drying.
"As the fixtures are loaded into the drum, they locate on a central spigot, through which the wash solution is distributed to no less than 200 individual nozzles," explains John Pattison, managing director at MecWash Systems. "This not only delivers the optimum amount of cleaning solution, but also directs it at critical areas, to achieve the highest possible level of cleaning performance.
"We used a series of CAD drawings to overlay the three different components – blocks and cylinder heads – into the wash space, so that jet positioning could be determined."
Adds Mr Knightley: "We assessed a number of alternative systems during the specification phase, but concluded that the MecWash design optimised both our performance and environmental objectives – particularly given the high quality and high profile application within which the unit operates. Moreover, the company's ability to supply the machine, the fixtures, the trolleys and the chemical, meant there was an automatic interface between each of these key elements."
Layton Technologies (01782 370400) has worked with a major US aerospace firm on the specialist cleaning of precision mechanical and high value electronic components used in the manufacture of vision system, for military applications.
The company turned to Layton, which has offices in the USA, after the Santa Barbara Air Pollution Control District imposed stricter levels of compliance for solvent emissions.
The team from Layton designed and developed a system and cleaning process that not only meets the emissions requirements, but also reduced solvent usage by an impressive 60% after just a few months. Further, Layton Technologies introduced systems that are compatible with inexpensive, non-proprietary cleaning solutions previously qualified for parts that are also compatible with Class 10,000 Clean Rooms.
The company has also produced a design and process that is more economically viable, avoiding the labour-intensive methods of solvent emission reduction that are traditionally employed.
Operators can perform much of the day-to-day maintenance tasks themselves, meaning that costly down-time is avoided and the need for complex vacuum system technology, thermal oxidisers and carbon absorbers is avoided.
Further benefits were realised by the new system's ease of use, with clear touch screen functionality that provides simple control and process status.
And along with legislative compliance, safety and operational cost savings, the project has also helped to improve service levels to the customer's own clients as a result of maintained production rates and improved efficiencies.
At a leading British seal and bearing manufacturer, a Guyson Multiblast RSB blast machine and Guyson Orbit 600 rotary basket washer (01756 799911) are being used to blast etch, and then wash clean and rust preserve a series of mild steel seal rings. The system replaces time-consuming manual operation, which was a bottle neck in production.
Blast etching the seal ring surface on to the inner face of around 150 of the 400 mm diameter seal rings, to improve surface friction, could take an entire 8-hour shift. Dramatic productivity improvements have been gained since the introduction of the automated Guyson finishing equipment.
Now one operator can blast etch the same quantity, wash them clean with a rust inhibitor solution and stack them ready to be bonded, in just three hours. In addition, there has been improvement in surface roughness consistency, avoiding the previous constant manual labour attention. The operator now only has to load and unload 10 of the rings at a time into both machines and press the start button; the rest is automated.
NEW PROCESS SLASHES CYCLE TIME
The Multiblast machine is fitted with a driven turntable and two vertically traversing Guyson Model 400 suction fed blast guns, which can now undertake the blast etching process in a fraction of the time per unit, compared to the manual blasting, and to a more consistent, uniform standard, with 10 components processed simultaneously.
Image: The Guyson Orbit 600 rotary basket washer is being used to blast etch, and then wash clean and rust preserve a series of mild steel seal rings
The washing process uses a modified Orbit 600 spray wash cabinet having a central vertical spray bar fixed to the roof of the 'clam opening' cabinet that lowers down inside the circular seal rings when the lid is closed, matching up with a similar spray bar on the outside of the circle of rings.
These both deliver a high impact cleaning curtain of hot aqueous wash solution to remove any traces of blast abrasives. The spray washing takes only a matter of minutes and is undertaken using 5% wash solution of Guyson Formula 10 Plus that has a built-in rust inhibitor, so the parts can be safely shelved after processing for later usage.
First published in Machinery, May 2012
Author: Andrew Allcock