Manufacture of mill/turned components has become much more profitable at Staffordshire Precision Engineering (SPE), Newcastle-under-Lyme, since the subcontractor invested in a Star SR-20J sliding head CNC lathe. 

SPE’s joint managing directors, Phil and Gary Smith believe that the company’s improving profit margins are due directory to the reduction of cycle times on existing components and bringing work in-house that was previously subcontracted. Most importantly, however, the Star lathe gives the company the opportunity of attracting new business that they would not otherwise have won.

When Phil Smith joined the company in 1997, half of the company’s turnover came from truck manufacturers, but that type of open tolerance work has largely disappeared overseas and very little remains at SPE.

During the course of this decade, the company has targeted the medical, petrochemical and instrumentation sectors to reduce its reliance on the automotive industry. Furthermore, in May 2009 it received AS9100 registration and has moved aggressively into supplying aerospace parts.

In the past four years, SPE has spent £500,000 on new CNC plant including the Star multi-axis lathe, which has made a significant impact on the subcontractor’s shop floor.

For example, there has been a 35% saving in the time taken to turn a family of titanium aerospace components. Manufactured by SPE for a global aerospace customer, the components were previously machined in a longer cycle on a fixed head CNC lathe. In addition, subsequent operations were needed on a centre lathe to de-pip the reverse end after part off or to deburr inside diameter edges.

Comments Mr Smith: “The savings on this family of parts alone are substantial, as we can produce them in one hit on the Star and achieve a better leadtime.”

Manufacturing misconceptions

There were several factors that convinced SPE to invest in sliding head technology. The most significant was that the company was often 30% too expensive when quoting to produce certain volume turned parts, especially those of smaller diameter. It implied there was plant being used by competitors that, for certain work, was far more efficient than SPE’s fixed head mill/turn centres.

As Mr Smith reveals, the company had considered investing in sliding head technology in the past but held reservations about set-up times. “We knew of the process but had been put off due to fears about how long it would take to set up work. People said it could take five hours to change over a CNC slider to make a new part and then, with batch runs becoming smaller these days, the machine would run for only a day or so.

“On the contrary, we find the Star quick to set-up and programming a new part on the Fanuc control is straightforward, particularly if it is a variant within an existing family of components, and we are back into production rapidly.”

Clinically cost-effective

The contract that clinched SPE’s purchase of the sliding head lathe was not aerospace related but for the manufacture of a medical instrument – a device used in shoulder repair operations. Tolerances on the surgical component are tight, but the repetition achieved on the Star to hit the correct sizes continually has been impressive, according to Mr Smith.

The quality of the instruments is better than previously, when they were made on other machine tools. Shortly after SPE started machining the component on the Star, a quality control engineer from the customer visited with a digital micrometer to measure the width of the bit. He noted that on every part he tested, the measurement fell right in the centre of the 20µm tolerance band, which was not the case before.

This was the first job to be put on the SR-20J after it was delivered. Star wrote the program (as well as those for a number of aerospace components) as part of a turnkey supply agreement, which also included fitting high pressure coolant delivery to assist when processing stainless steels and other ‘difficult’ materials. Trial production of a number of components at Star’s Melbourne technical centre was included in the package, as well as a suite of training, which was important as the subcontractor was new to sliding headstock technology.

The price is right – but only if it goes down

Any subcontractor serving the aerospace sector knows that cost down is imposed year on year by the OEMs, passing from the Tier 1s down the supply chain and squeezing profits. It is virtually impossible to increase the price of an aero component.

Mr Smith cited an example of when he approached a customer asking to re-quote for a particular job. The contract was automatically put out to tender again. Another subcontractor offered to do the job for the original price and SPE lost the business. Some companies will take a job just to pay the wages, but the absence of profit means that they will not be able to invest in modern plant and in time will probably go out of business.

That, however, does not help SPE or, in the long run, the companies further up the supply chain. In Mr Smith’s opinion, the solution is to find more efficient ways of manufacturing components by installing machines like the 7-axis Star lathe, with its counter spindle and numerous live and static tools for in cycle cross and end working.

Savings of up to 35% – more in some instances – makes the difference between earning a decent profit and losing money, and helps to retain work that would otherwise be uneconomic.

Star Micronics
www.stargb.net