Sound advice

As a result of LMT UK's milling advice, precision aerospace, marine, defence and specialist automotive tooling contractor Brinksway Tool reviewed its pocket milling strategies in the production of formers for composite panels – and claims it was able to slash processing times of up to five days down to just five to six hour cycles.

Following the LMT milling trials, the company can now produce three former plates complete in the time taken previously for one with the added bonus of a tool life increase for milling inserts approaching 25% and the use of one less insert per cutter.

According to Carl Nickerson, works director of the Audenshaw, Manchester-based company: “Although it was a relatively simple task of removing material to reduce weight by creating six pockets up to 170mm wide by 180mm long and 75mm deep in the underside of composite forming tools some 1.5m by 500mm, the time taken was totally unacceptable especially as it only involved roughing cycles.”

He describes the roll on effect of producing the formers on the company's Correa 3-axis Prisma 20 CNC machining centre as creating a ‘log jam' due to the drawn out nature of the process.

He suggested to CNC manager Simon Cornell that the company's principal tooling distributor, EW Equipment of Cheadle, may be able to help and in turn it recommended a joint survey of the process by LMT UK using the latest Fette MultiEdge cutters and new PVD coated inserts.

Explains Mr Cornell: “Before we even looked at the methods being adopted LMT's engineer was checking out the power and torque curves of the machine and he immediately suggested we reduce the size of the milling cutter from a five tooth to a four tooth, uneven pitch style cutter which has a positive rake angle. He also suggested that we change the method from plunging the spindle to depth to one that profiled the programmed forms.”

Mr Cornell outlines how LMT's engineer explained that the existing tooling and process had the effect of pushing the inserts into the job and consequently loading the spindle. This was not helped by the large radii on the circumference of the insert which ideally demanded higher torque from the spindle drive than was available.

Mr Cornell, in conjunction with the LMT engineer, formulated new cutter paths using the LMT Fette MultiEdge 4Feed cutter of 32mm diameter – developed specifically for roughing in mould and die applications requiring 25% less power to drive the tool. It also has a positive rake angle that helps lower cutting vibration with deep chip groove topography at the face.

When combined with the latest generation of Fette MultiC, PVD AlCrN coated thick ECP V07 insert – which has the advantage of high heat resistance due to a TiN layer on its circumference supported by a toughened carbide substrate – it gives high stability at both high and low cutting speeds. The insert can also be used without coolant and in the Brinksway application, an air blast was introduced to clear the rapidly growing volume of chips from the cutting zone.

Speeds and feeds were reprogrammed to run the cutter at 240m/minute with a 10m/minute rate of feed but just 1mm depth of cut. As a result, the process can be run for at least an hour before the inserts need to be changed – a 25% improvement over the incumbent tool supplier with the time taken to remove the stock material reduced to between five and six hours.

Brinksway Tool is the largest tooling company in the Hyde Group Tooling Division of the £200 million turnover aerospace contractor, Hyde Group. The Audenshaw operation employs 58 people, 20 of whom are highly skilled fitters, eight are apprentices and the balance provide competence for the high level of CNC machining often employed by the business.

The two bays are split into fabrication, assembly and rig build, which currently supports 80% of the business completing recent projects such as a £500,000 fixturing contract for the Chinese aerospace industry and the design and build of special tooling exported to India. Other recent projects have included the re-engineering of a military helicopter windscreen frame, the production of aircraft passenger door jigs, composite lay-up tools, wing jigs and modelling boards for autoclaves.

Brinksway Tool's installation and fitting teams have worked on aerospace projects in Sweden, South Korea and Taiwan and by meeting the call worldwide for the precision measurement and reverse engineering of aerospace structures, the company has the largest installation capacity in the UK for Leica 3D, LTD500 laser tracker systems which are constantly in demand for special project applications.

LMT
www.lmt-tools.com Brinksway Tool
www.brinksway-tool.com