In December last year, Albany Pumps — a leading manufacturer of positive-displacement gear pumps, twin-screw pumps and rotary lobe pumps — bought its first wire-cut EDM machine. Installed at the company’s facility in Lydney, Gloucestershire, this is being used to machine a variety of high-precision parts — such as gears and rotors — as well as prototype and customised parts (see above).

Prior to buying the CUT 30P from Coventry-based GF Machining Solutions (www.gfms.com), Albany Pumps had sub-contracted its wire-cut EDM requirements; and while this arrangement was ‘satisfactory’ in most respects, it did create some issues regarding the sub-contractor’s ability to meet the company’s stringent quality requirements and lead times.

Design engineer Roy Allen says: “EDM is a precise, non-contact manufacturing technology ideal for machining high-accuracy parts and features to close tolerances. In the past, we used to sub-contract this work out, but in doing so we lost an element of control over our quality and delivery.

"Because we manufacture performance-critical equipment and components, and because our customers rely on us to deliver quality solutions on time every time, we decided to bring the EDM process in-house.”

Machine shop foreman Stuart George says: “The CUT 30P hasn’t replaced any of our existing machines, but it has given us additional capacity and increased flexibility. For example, we can use the machine during the day for one-offs and for our R&D projects; at night, it can be set to undertake small-batch production work, which includes cutting gear profiles.

“The investment in the EDM machine also means that we can now manufacture components from solid bar, as opposed to from castings. This has had a positive impact on part quality, as we are no longer at the mercy of variable casting quality. It has also had a positive effect on lead times, as we no longer have to wait for castings to be delivered.

"Although the EDM process is perhaps slower than that of our more conventional equipment, such as vertical gear-cutting machines, the fact that our EDM can operate ‘lights out’ means that an additional 16hr of production are potentially freed up every day. Moreover, to help liberate the CUT 30P’s unmanned operation still further, we had GF Machining Solutions retrofit a 25kg wire spool in place of the machine’s standard 8kg unit.”

Other advantages that the CUT 30P has delivered include improved part accuracies and surface finishes. For example, with just one pass using 0.25mm-diameter brass wire, Albany Pumps can meet its accuracy and surface finish requirements without, in many instances, the need for manual secondary finishing operations.

Mr Allen says: “The accuracies and repeatability we are now able to achieve have also helped us to improve the performance of our pumps. This has been particularly noticeable following our EDM machining of pump lobes. Moreover, gear pumps with EDM-cut profiles are quieter in operation — and the exacting tolerances we achieve mean that fitting time is significantly reduced.

“Another plus point is the fact that we don’t have to make any allow-ances in our designs for the limitations of our machines. The CUT 30P machines parts and features exactly to drawing, and that means that the ‘design-to-manufacture’ process is more effective.”

Gear production

Based in Stoke Mandeville, Gibbs Gears is another company that recently bought its first wire-cut EDM machine, in this case a CUT 300mS (pictured below) — also from GF Machining Solutions. Installed at the company’s 20,000ft2 facility in March this year, the machine was bought specifically to help Gibbs Gears exploit the growing market for low-volume non-standard gears, as well as provide a cost-effective and quick turn-round for prototype and pre-production gears and transmission components.

Established in 1954, Gibbs Gears manufactures high-performance high-precision gears for a diverse range of industry sectors in the UK and world-wide.These include aerospace, motor-sport, medical, marine, power generation, and oil and gas. In recent years, the company has experienced a steady increase in demand for low-volume non-standard gears and the production of prototypes.

Managing director Reece Garrod says: “More and more UK and international customers are approaching us to see if we can manufacture gears with non-standard pitches and pressure angles. In the past, such requests were problematic to us if the gears couldn’t be manufactured using our conventional gear-cutting tools.

"If the quantities required were low, the cost of producing bespoke tooling meant that these non-standard jobs were not economically viable. However, the new CUT 300mS means that we can wire-cut the gear form, negating the need for specialised and costly tooling.

“Prototype projects are also important to the future of the company. However, prototype production and development is often time-intensive and can impact on our production resources and capacity. Our ambition to provide customers with a world-class one-stop prototype gear design and development manufacturing service was a key factor in our buying the CUT 300mS machine.”

That said, Gibbs Gears had considered sub-contracting its wire-cut EDM requirements, as sales manager Philip Maurice explains: “Out-sourcing can appear attractive. There is no large capital outlay, and interruptions to existing manufacturing operations can be managed and kept to a minimum.

"However, sub-contracting has its dangers, with control over quality and delivery times effectively relinquished to a third party. We took the long-term view and decided that we would maintain control over all our means of production — and that meant that we were in the market for a new wire EDM machine.”

The CUT 300mS features GF Machining Solutions’ Taper-Expert system and Quadrax design (crossed double guiding of the X, Y, U and V axes) for machining large tapers, while automatic wire threading ensures trouble-free unattended and ‘lights out’ operations.

Since being installed at Gibbs Gears, the machine has been used to produce internal and external spur gears and helical gears, as well as standard and non-standard internal splines and keyways. It also allows the company to wire-cut rough gear forms in their pre-hardened state and finish the parts after heat treatment.

This is particularly cost-effective for small-batch work, as it negates the need to invest in grinding equipment and processes for post-heat-treatment operations. Gibbs Gears is currently carrying out a ‘gap analysis’ to achieve NADCAP approval for its EDM processes. Once this is accomplished, the company (which also has AS9100 Rev C and BS EN ISO 9001:2008 approvals) will be even better positioned to handle complex, high-precision aerospace contracts.