To enhance the manufacture of technically challenging moulds from hardened stainless steel, Leicestershire-based Ledwell Plastics has invested in a new Sodick AD35L spark erosion machine supplied by Warwick-based Sodi-Tech EDM.

This advanced die-sink EDM machine provides the speed and accuracy required to reduce costs and enhance precision, while also offering low electrode wear and the necessary reliability to facilitate unmanned overnight operations.

Ledwell Plastics is an injection moulding and toolmaking specialist that serves many different industries, including agriculture, food packaging and electric vehicles. Founded in 1969 by Paul Simms, father of current managing director Benn Simms, Ledwell can mould parts weighing from 1g up to 1.5kg, while the largest moulding produced to date measures 900mm long x 450mm wide x 90mm deep.

Operating around the clock from two factories in Leicester, negotiations are currently in progress to acquire a third premises for this progressive 36-employee business.

Mr Simms said: “Our toolroom makes moulds from many different materials, everything from aluminium through to hardened stainless steel. Recently, however, we were working almost exclusively with the latter material in the production of very small and intricate moulds, a trend that looked set to continue for some time.

“Our problem was our existing die-sink EDM capability, which was somewhat antiquated, meaning we had issues with accuracy and breakdowns that were impacting project timescales and costing a lot in repairs.”

As a result, Ledwell Plastics sought a new die-sink EDM that could work to tolerances of less than 0.025mm. In addition, the highly technical, hardened stainless steel moulds require a large amount of sparking, so fast processing speed was another factor high on the wish list.

He continued: “The Sodick AD35L fitted the bill nicely, especially as it was also the perfect size. We looked at other spark eroders, but after undertaking some research and speaking to other Sodick users, we settled on the AD35L. During an on-site demonstration at Sodi-Tech EDM we could see that the machine’s performance was particularly impressive with its high-speed linear motors.”

Mr Simms cites the 10-year warranty on positioning accuracy, excellent surface finish and low amount of electrode wear as further factors supporting the purchase of the Sodick machine. “The AD35L was installed at the end of January 2021, with Sodi-Tech EDM delivering a full training programme here at Leicester. Sodi-Tech was also great at providing advice on things like optimum electrode selection.”

Along with the hardened stainless steel moulds, the ISO9001-accredited company uses its new AD35L for jobs involving materials such as aluminium, steel and hardened tool steel. As Ledwell works extensively on the design and development of moulded parts for its customers — often involving patent applications — non-disclosure agreements (NDAs) are in place for almost all projects.

Although the company can say little about the moulds it machines, the benefits offered by the Sodick AD35L are clear to see.

High-speed linear technology
Mr Simms continued: “Our new Sodick allows us to run overnight, unlike our previous machine, which we could never trust in that regard, particularly with blind components/features that are difficult to flush. The high-speed linear technology of the AD35L evacuates the cavities much better with its enhanced flow of dielectric fluid.”

Notably, investment in the new machine has boosted the production of sliding cores for the company’s range of injection moulding machines, which extend in capacity from 60 to 440 ton capacity. Previously, the company would cut entire sliders (six impressions per slider set) with a single large copper electrode. But this process was time consuming and expensive regarding the amount of copper required.

Mr Simms explained: “With the AD35L we spark just three cavities at a time, before indexing the slider over. However, we double up on the amount of sliders we spark – loading two at once for machining with a single electrode. As the cycle time is quicker and electrode wear is low, we are manufacturing fewer electrodes and buying less copper. In addition, accuracy and repeatability are better.”

As part of its structure, the Sodick AD35L features optimised rib arrangements which increase rigidity by approximately 70% to support enhanced workpiece precision. In addition, because machine deformation is minimised, users can enjoy the full performance potential of Sodick high-speed linear motors.

Mr Simms concluded: “Our operators love the machine as it’s streets ahead of where we were before. Furthermore, the AD35L will help drive more work through the tool room, upholding our tradition of cost-effective solutions with excellent quality. All of our tooling is guaranteed for a minimum life span cycle, which is bespoke for each individual component.”