Renishaw hardware the key at Scots machine shop

Castle Precision Engineering (Glasgow) Ltd has become one of the UK's largest independent CNC machine shops, and is a firm believer in the benefits of Renishaw's probing systems

At Castle Precision Engineering (Glasgow) Ltd, quality is a company wide issue.

At every stage from administration and purchasing, to the project engineer and the team implementing a production run, there is support for the operator at the machine - the point at which component quality is determined.

Adopting such a philosophy has seen this progressive company become one of the UK's largest independent CNC machine shops, and a firm believer in the benefits of Renishaw's probing systems for pre-process, in-process and post process control.

The company now relies on post process inspection at the machine, using their co-ordinate measuring machines only when designated by the customer.

'We specialise in CNC production machining, progressing volume precision work with efficiency and accuracy.' states Works Manager, Alex Skinner.

'To excel in this, we invest in quality.

The key resource is quality people.

High calibre project engineers, managers and time-served engineers working together as an efficient team, constitute an unrivalled pool of experience and professionalism.

However, to improve our performance, we regularly invest in new technology with quality at the core - quality plant, quality tooling and quality systems.' Castle Precision Engineering retains an extensive toolroom facility with jig boring and conventional machining, for the design and manufacture of tools and fixtures.

However, its strength lies in the high tolerance work undertaken for companies in the automotive, defence, electronics, oil and aerospace sectors.

Through working with leading players in the Aerospace sector, where absolute precision and quality are more than added values, the company has developed its own unique software programme, linking SPC capabilities with Renishaw's probing solutions.

Throughout the machine shop, Renishaw probing has been fitted to a significant proportion of the company's machines, which includes nine horizontal and six vertical machining centres, nine lathes and a variety of borers.

However, it was an application on a Mori Seiki SL600 turning centre, fitted with Renishaw tool setting and inspection probes, that was used by Alex Skinner to illustrate Castle's quality principles.

Explained Mr Skinner: 'We have written our own software which records the probe's statistics.

If we put in a part/serial number, not only are the actual machining dimensions shown, but the required and actual dimensional tolerances are also displayed.

This allows us to statistically examine the performance of a given machine, knowing at all times we are within a tolerance of +/-11/2 thou', and therefore in control.

It also allows us to print out SPC data at the request of a customer.

The ability to probe a component and prove the dimensional accuracies have proved invaluable in securing certain contracts.' 'Typically, design data is taken-in as IGES of DXF files.

CAM programmes are produced in Textsoft Procam 3D and DNC linked to the relevant machine.

A 'critical component' from Rolls Royce will not allow any change to finished cutting data, but we can alter other data as befits the machining operation.' continued, Mr Skinner.

'A forged titanium ring, 'a spacer', part of a compressor assembly, is mounted on set fixtures in the Mori Seiki SL600 and 'trued up'.

A Renishaw HPA tool setting arm is then located on a fixed mounting base within the lathe, enabling the operator to datum the master tool, automatically correcting offsets and ensuring each tool is in position to start the machining sequence.

On securing the ring, we will carry out a finished machining operation and check it completely.' However, during this machining cycle, Castle also take a number of sizing passes, checking the diameter of the component with a Renishaw LT02 inspection probe system, correcting the offsets as necessary before further machining.

'This is repeated where tolerances are critical.' added Mr Skinner.

'After completing the programme, we probe the finished part, carrying out 23 dimensional checks.

This data is downloaded automatically to our server for future reference and drives our SPC system.

We print out the SPC data as a matter of course and although Rolls Royce doesn't require it, the component history will travel with a component around the factory, allowing us to verify the dimensions at any given time.' Alex Skinner has his next quality goal clearly in sight.

'We already have touch trigger tool breakage detection on the machines but this takes time and is only ideal for unmanned roughing operations and reduced feed rates.

I am under attack from all sides - the Eastern Block and China for example, all doing a certain quality of work, cheaper.

Often, work lost to the tiger economies will find its way back to us six months later when the required quality of work has not materialised, but that still means we have lost six months production - I can't afford that! The only way I can offset the cheap labour economies is to cost-effectively automate the machining process where possible.' Mr Skinner believes that Renishaw's new NC1 laser-based tool setting system for machining centres may be the answer to further improving competitiveness.

'The NC1 system will allow me to measure tool lengths and diameters at normal spindle cutting speeds, automatically updating offsets in the machine controller.

More importantly, NC1 should allow me to increase productivity on at least four high speed machining centres, and is especially suited to unmanned machining operations, where tool damage can cause costly scrap or re-work.

After each machining operation, tools can be passed through the NC1's laser beam at rapid feed rates to check for damage.' Pump bodies, engine components for Rolls Royce, Starfish and Chieftain Tank projects for the MOD, machined components for state-of-the-art Linn audio systems - all are testimony to Castle Engineering's guaranteed quality procedures, producing 'right first time', on time, every time.

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