Good quality machine tools operate reliably and hold tolerance for two decades or more. The problem is that technology moves ahead so quickly over such an extended period that the productivity of older machines cannot match that of their newer counterparts.

This was the situation Redruth-based sub-contractor DP Engineering Ltd found itself in until it purchased three new Cincom lathes from Bushey-based Citizen Machinery UK Ltd. They are an L20-XLFV installed three years ago, an identical machine that arrived in the autumn of 2021 and an M32-VIIILFV bought at the end of last year. The latter two machines were direct replacements for equivalent 20mm and 32mm capacity sliders of similar type and made around the turn of the millennium — several machine generations ago.

Philip Anthony, DP Engineering’s sales and marketing director (pictured below), said: “The faster rapid traverses and higher power and speed of the main and sub spindles as well as of the driven tools on the new lathes have increased our capacity considerably. One stainless steel aerospace part we previously turn-milled in one hit on an L20 that is 20-plus years old now takes half that time to produce on its modern replacement.

“It is a similar story on the 32mm machine, which is more user-friendly than the former generation lathe and has better access and visibility into the machining area. Moreover, the addition of a rotary B-axis on the gang tool post enables us to machine more complex parts than was previously possible on our sliders.”

A notable technological advance from Citizen since DP Engineering purchased the earlier Cincoms was the introduction five years ago of its proprietary LFV (low frequency vibration) chip breaking software running in the Mitsubishi control. It has resulted in a significant increase in productivity when machining malleable materials such as titanium and stainless steel.

It is particularly beneficial for the sub-contractor, as one-third of its turnover is derived from the aerospace sector in which the use of such materials is commonplace, as it is in the medical industry, which has also generated more work since the start of the pandemic. Normally during machining, stringy swarf often entangles itself around the tool and component, risking damage to both and necessitating lathe stoppage to clear it from the machining area.

Mr Anthony continued: “The first L20 we bought in 2019 has LFV. We knew about the technology and sent a team of engineers to Citizen Machinery’s Brierley Hill centre of excellence to see demonstrations of the chip-breaking function in action.

“For certain parts of cycles, it is very effective at ensuring that what usually becomes a bird’s nest of swarf is broken up into shorter chips, avoiding having to stop the machine to remove it and the consequent loss of production.

“The best part is that LFV can be programmed to stop during a cycle when it is not needed by inserting a G-code, minimising the slight reduction in metal removal rate during the periods when the tool oscillates away from the component's surface to break the chips.

“On some jobs, even when cutting stainless steel, we don’t have to use LFV at all. It depends on the component design, the tolerances that have to be held and the tooling used. However, it is fantastic to have it there for when we need it.”

He added that, in practice, LFV is particularly effective at controlling swarf on the L20s during turning and drilling operations, while on the M32 it speeds roughing and also plays a role when thread cutting. Overall, having complete control over swarf generation ensures that processes are more reliable and repeatable, added to which tool life is noticeably increased.

Another attribute of the latest three Cincom lathes that increases their versatility, apart from the extended periods of spindle uptime and unmanned running made possible by the LFV chip-breaking software, is the ability to turn-mill shorter components in fixed-head mode without the guide bush, which can be removed and replaced within 30min.

This allows lower quality, unground bar to be used, increases by several millimetres the maximum diameter of stock that can be accepted and also reduces bar wastage due to much shorter remnant lengths. Consequently this mode of operation is frequent in the Redruth factory, especially for the significant amount of kanban production fulfilled by DP Engineering for its customers.

Mr Anthony pointed out that overall, taking into account the higher speed of machining, the LFV chip breaking function and the option of guide bush-less operation, the latest three lathes give DP Engineering not only considerably higher productivity but also a lot more flexibility when allocating jobs to the 18 turning machines around the factory, including the current tally of five Cincoms.

A couple of dozen jobs have already been transferred from multi-turret fixed-head lathes to the new sliding-head models for ‘one-hit machining’, freeing up the former for other production duties. Such versatility is ideal for a subcontracting environment, leading to faster deliveries to customers, enhanced reputation and more orders.

Mr Anthony said that as space on the shopfloor in Redruth is fairly limited, replacing machines with models that are much more productive is an ideal way to grow the business without the expense and disruption of having to move to larger premises. This is especially important in respect of his turned parts production, which accounts for three-quarters of throughput.

DP Engineering is a cog in the wheel of Cornwall’s £732 million manufacturing industry. It was the brainchild of a keen motorcycle rider, the late David Paull, who was frustrated at not being able to obtain engine parts for his motorbike and decided to machine his own. In 1952 he started a motor reconditioning business, David Paull Motor Cycles, which led him into sub-contract machining and was the forerunner of the current firm.

In 2008, DP Engineering gained AS9100 accreditation in addition to ISO 9001: 2000 and established itself as a supplier to the aerospace industry. Due to business expansion, in 2014 the company purchased a purpose-built, 17,000ft² premises in Redruth, where the sub-contractor operates today under the watchful eye of CEO Martin Legg.

Major sectors served include aerospace, defence, oil and gas, marine and renewables. The company is known for being a low-to-medium volume shop, producing parts typically from 10- to 50,000-off. Lean manufacturing principles allow cost effective production, from prototypes through to batch work, and over 500 kanban items can be produced for next-day delivery.

Other capital investments made by the sub-contractor within the past 12 months, apart from the two Cincom lathes, include a Matsuura five-axis, 10-pallet cell for automated machining of prismatic components, an Aberlink coordinate measuring machine to inspect them, and a ViciVision optical, non-contact measuring machine for quality control of rotational parts.