Product category:
Miscellaneous machine tools, gear cutting machines and equipment
News Release from: RK International Machine Tools | Subject: Europa Jainnher JHC-12S centreless grinder
Edited by the Manufacturingtalk Editorial
Team on 03 June 2002
Centreless grinding to very tight
tolerances
The need to hold roundness tolerances within one micron and surface finishes of 0.2 micron Ra on aluminium spools sparked a search for the most cost-effective centreless grinding process.
The need to hold roundness tolerances within one micron and surface finishes of 0.2 micron Ra on aluminium spools used on pneumatic control valves, which vary in diameter between 6.2mm and 25mm, meant the investigation into the most cost-effective centreless grinding process became quite detailed for KV based in Crown Hill, Milton Keynes As Production Manager Larry Byrne outlined: "The complete project involved a turnkey type supply package where the machine was self-contained with the appropriate extraction so as not to contaminate the workshop and included process and wheel development to suit the grinding of aluminium." The whole project involved the evaluation of numerous new and rebuilt centreless grinding machines and their suppliers which led to RK International of Erith in Kent winning the order with its Europa Jainnher JHC-12S machine
This article was originally published on Manufacturingtalk on 1 Jul 2005 at 8.00am (UK)
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As Larry Byrne explained: "RK was able to take on the complete project, develop the thru-feed process and conduct process capability trials.
Twelve months on, we look back and agree that we had excellent service and support." The through grinding of valve spools was not straight forward due to the number of process variables.
Aluminium is not a simple material to grind and involved wheel and synthetic coolant development as well as dressing frequency in order to achieve the high orders of surface finish and roundness demanded.
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In addition, the clause to maintain a clean environment and avoid misting, which is a common problem with the centreless process, had to be met without restricting access to the machine for setting.
KV was established in 1988 following the merger of Kay Pneumatics and Vento Solenoids and has since become a leading supplier of pneumatic and fluid control systems and components with sales of some GBP 15 million derived from an international customer base.
The company has offices and factories in Milton Keynes with additional manufacture and distribution in Europe, America, India, Eastern Europe and the Far East.
Due to the nature of the product produced, the company is certified to BSENISO 9001 with a strong Total Quality Management system driving the high levels of performance attained by the products.
As Larry Byrne maintained: "The performance of our systems is related to our production capability and this is why we were so stringent in the centreless grinding machine meeting our specification." He described how the company designs and manufactures pneumatic systems for controlling an extensive variety of applications over a wide array of industry sectors including machine tools, transportation, safety systems and specialist areas such as those involved with pharmaceutical processes.
The machine shop at Milton Keynes produces all the components for actuators, cylinders, manifolds and control valves including circuitry which he described as critical.
"If a customer has a problem, we are able to look at the different elements and engineer the right solution and not just focus on one single part because that is all we are involved with," said Larry Byrne.
The Europa Jainnher JHC-12S is able to grind components up to 40mm diameter.
It has a 305mm by 150mm by 120mm grinding wheel size and 205mm by 150mm by 90mm control wheel.
Grinding wheel speed is 30m/sec and the control wheel is servo controlled in order to precisely tune through-feed rates in conjunction with the wheel tilt angle which is between +5 deg and -3 deg.
The Europa Jainnher is used to rough and finish grind the actuating spools at a rate of around 100,000 a year.
These are produced in typical batches of between 200 and 300 with the occasional large contract which can lead to around 5,000 spools being ground.
As the spools have to operate and service either three or five ports to accommodate the compressed air circuitry, the spool length can vary accordingly.
In addition, KV also produce bespoke solutions for customers which adds further variants to the process.
One area to which Larry Byrne praised the RK International operation was the ability to co-ordinate and accommodate the machine builder's knowledge with different suppliers to create the most suitable A12 C80L wheel specification, dressing frequency and synthetic coolant and integrate KVs own in-house grinding and product expertise to 'perfectly meet our needs'.
This in-house knowledge was important.
For instance, Trevor Perkins, the Europa operator has some 30 years of precision grinding experience and he is responsible for setting and operation of the machine.
He said: "We are not a big batch producer and we can effectively deal with batch sizes as small as 10 on the new machine because it is so easy and quick to set.
Most changeovers just involve resetting the control wheel, but for large size variations we change the work blade and this is still easy because it is so accessible even with the fume extraction in place." Trevor Perkins monitors the grinding process and dresses the grinding wheel as required.
But so stable is the process that this tends to be around 10,000 components.
Work samples are checked using non-contact gauging and a surface measurement device.
Prior to grinding, the spools are turned on Citizen CNC sliding headstock lathes to ensure consistent stock removal and following grinding, they are burnished and polished using a barrelling process under the control of the Europa operator.
Prior to assembly, each spool is then ultrasonically cleaned and tested.
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