Just the job

A European research project aims to automate low volume production of workholding equipment, says Sue Stuckey

Europe is full of jobbing shops – small groups of highly skilled subcontract machinists that are the backbone of manufacturing industry. But a jobbing shop producing precision parts in small batches or one-offs is an unlikely setting for an unmanned machining cell, with its ability to churn out components in medium to high volumes.

For Robert Johnson, managing director of precision workholding equipment maker Craftsman Tools, the opportunity to develop such a cell should provide important commercial benefits. These include a 40% reduction in lead time between order and delivery and a 20% cut in production costs. Less obvious is the ability to depreciate machinery cost over a longer period. A machine that runs for 24 hours rather than 16 is one-third more productive.

The Yorkshire-based company is the lead industrial partner in a three-year, Ecu2m-plus (£1.33m) European collaborative research project to design and build a fully automated, computer numerically controlled (CNC) machining environment capable of producing a random mix of standard and custom products in lot sizes as low as one.

Emphasis is on automated machining of parts for workholding equipment, but the project will include development of handling equipment and a novel laser-based cutting tool monitoring system as well as laptop-based order processing software. This must be able to deliver product information from the customer to the machining cell using a direct numerical control link between the cell and the CAD/CAM program used to generate the machining data for the part.

Johnson will not say what form the cell will take, but a single CNC turn-milling centre could fulfil the requirement for turning and milling the parts with minimum handling between operations.

One of the project’s industrial partners is Spanish special-purpose milling machine maker Anayak. Apart from the company’s interest in developing a low-cost method of producing modular tooling packages that can be sold alongside machines, it is certain to have a strong influence on the design of the cell itself.

As the project’s proposer, Craftsman Tools will want first to fulfil its own need to automate production of workholding devices known as expanding mandrels through to, but excluding, final assembly.

Production engineers use these devices, which are designed to exact customer requirements, to hold parts firmly and accurately in place while machining external surfaces. The expanding mandrel fits into a bore already machined in the part. The job requires the mandrel to maintain precise concentricity between internal and external diameters during secondary machining such as turning, milling or drilling. When machining a gear blank, for instance, it is essential to maintain precision between the internal bore for a driveshaft and the external gear profile which transmits power to another part of a machine.

Under the new system, customers would be able to place their orders with a Craftsman sales engineer who will download the part’s specification to the machining cell using a laptop computer.

Mandrel assemblies have diameters from 25mm up to 300mm made up typically of 12 parts but that can extend to 60 parts for special assemblies that include protection, for example, for the windings of an electric motor.

The ability to machine parts in a variety of part and batch sizes puts a heavy demand on automated production. Machining tolerances must be good enough for final assembly without further finishing. The laser tool monitoring and failure prediction system will be a vital part of the process with its heavy demand on cutting tools – mandrel parts are made from hardened tool steel.

Craftsman will also want to use the new cell for machining parts for toolholders. Italian special tooling supplier Agint will also focus on this aspect.

Industrial partner Graham Engineering will focus on developing robotic welding and manipulator systems and has already identified potential partners with experience of heavy-duty manipulators for companies such as JCB Excavators. Graham Engineering makes metal containers for storing nuclear waste. They come in different shapes and sizes from some that look like a pillbox to others, in stainless steel, resembling a large oil drum up to 4m3. An order might be for a one-off. Another might be for 10,000 containers a year over 10 years.

Two machine tool research bodies – Amtri of the UK and Fatronik of Spain – will share funds of around Ecu1m, equivalent to half the second phase project costs, to provide basic research while the industrial partners will supply mainly equipment and services. The project is funded under Craft, the small firms’ scheme which is part of the Brite-Euram funding for industrial and materials research.

Andrew Rhodes, Graham Engineering’s design manager, sees the project as a think-tank which provides an opportunity to share ideas. More than that, a truly flexible unmanned production cell will allow the company to meet cost and delivery targets that Rhodes says would otherwise be impossible.

A year or so ago Derek Taylor, a partner with consultancy Beta Technology, presented a paper to a seminar organised by the Leeds Development Agency which first inspired and then helped Craftsman’s Johnson to carry out the gruelling task of putting together a project proposal and finding European partners.

Taylor says Craftsman Tools is the perfect case study of a company operating in a relatively low technology area which has grasped the opportunity to take a big step forward.

He also describes the move as brave. For small firms with limited resources, he says, three or more years is a long time to see a return on investment. For them the commitment to a project like Craft is a huge undertaking.