After receiving a contract from a multi-national medical firm to machine multiple variants of two types of endoscopic-device parts from 303 stainless steel bar, Shannon-based medical-component manufacturer Smithstown Light Engineering installed 24 Cincom sliding-headstock CNC bar autos between last summer and the beginning of this year.

The annual quantity required is currently 18 million parts (to make nine million assemblies).

Managing director Gerard King identified the business opportunity in 2017 and machined sample parts on a 20mm bar capacity Cincom L20 installed three years earlier to fulfil a contract that is still running (turning a 316 stainless-steel spindle for a medical delivery device).

Discussions progressed, and to develop the process further, he decided to buy — on spec — a 12mm bar capacity Cincom L12 from Citizen Machinery UK Ltd (www.citizenmachinery.co.uk).

This lathe, which is of a more appropriate size for producing the endoscope parts in short cycle times, was installed in August 2017 in a second (newly acquired and extensively refurbished) unit on the same industrial estate in Shannon.

An extension currently being built at this unit will bring the sub-contractor’s total factory space to 80,000ft².

Further successful trials continued with the assistance of applications engineers at Citizen Machinery UK’s Bushey and Brierley Hill technical centres, where programs were optimised and early samples were turn-milled.

In April 2018, the medical-equipment OEM was ready to award the contract.

Sound support

Mr King said: “The first of the L12s started arriving here in July 2018, and the last ones were on site by January this year; all are operating 24/7.

“The lead time from the customer signing the contract to our shipping the first parts in production quantities was five months, and Citizen supported us well during this ramp-up phase.

“A lot of the success of the project was down to the partnership that has developed between our engineers and those at Citizen Machinery UK, which incidentally has two applications and service engineers in Ireland dedicated to this market.

“Before delivering the machines, Citizen set them up at its technical centres, complete with high-pressure coolant, mist extraction and full tooling packages, so they were production-ready when they arrived.”

He added that the Cincom L12s are so accurate, being easily able to hold dimensions to within 5µm, that with the relatively open tolerances on the endoscope component drawings, a process performance in excess of Ppk 2 is being achieved — better than the Ppk 1.33 specified.

This means that there is never a need to ‘chase tolerance’, so the 24 bar autos are attended by fewer operators than would otherwise be needed.

All of the latest sliding-head lathes are equipped with Citizen’s patented LFV (low-frequency vibration), which is activated by programming special G-codes at the control to impart the ideal size of chip required to offset problems such as the ‘bird-nesting’ of swarf.

The technology can also improve tool life, and it often allows an increase in the depth of cut, while achieving improved surface finishes.

These advantages are achieved by ‘vibrating’ the servo axes in the axial direction, while synchronising this vibration with the rotation of the spindle.

The ‘air cutting’ introduced by this technique is characterised by the intermittent expulsion of fine chips, along with the elimination of problems such as chip entanglement and built-up edges.

In conclusion, Mr King said: “More than one third of a billion endoscopies are performed every year around the world, and we are currently manufacturing about 2.5% of the associated consumables at the premium end of the market.

“There are many medical contracts that involve these sorts of numbers.

“Now that we have proved ourselves to be capable of developing a mass production facility in a very short timeframe, we are hopeful of winning more high-volume business.

“While medical devices for endoscopy constitute around two-fifths of our turnover, we are also very active in machining coronary delivery devices and cobalt chrome implants, with trials in titanium currently in progress.

“Future projects could involve any of these.”