Sliding-head turning

OEM brings specific production in-house to ensure that parts are machined to specification

Posted on 29 Oct 2015 and read 2793 times
32 J Allen main
When waste disposal and sewage treatment equipment manufacturer Haigh Engineering Co Ltd introduced a new product line, the company found that it had a precision, quality and capacity issue to deal with. It solved this by
buying a new sliding-head turning centre.

An OEM manufacturer with an extensive range of waste disposal solutions for the health-care sector and the water utilities, Haigh developed its Quattro Pulp disposal unit to reduce running costs for customers, as well as to cut its own carbon footprint.

At its 60,000sq ft facility in Ross-on-Wye, the 94-employee business operates 24/5 and manufactures over 4,000 different turned parts — in diameters ranging from 4 to 300mm — to support the assembly of its product range.

The quality issue in question related to new small-diameter components that fit into Haigh’s Quattro product line. The parts demanded tighter tolerances and surface finishes than previously required — specifications that could not readily be achieved by the company’s larger machines.

With regard to its capacity issue, Haigh was placing work worth more than £15,000 per annum with local sub-contractors that were having difficulty obtaining the tolerances and surface finishes required. This situation prompted manufacturing manager David Brown to look for an appropriate turning centre.

Mr Brown says: “We looked at a number of sliding-head machines before trialling a series of parts with two vendors. We wanted a machine to manufacture a variety of parts up to 25-26mm in diameter.

One vendor offered a 20mm-capacity machine that could be pushed to a limit of 25mm. Their only other option was a 32mm-capacity machine. The 20mm machine was too small, while the 32mm machine was too large — and its price was beyond our budget.”

33 Assembly part small
In August, Haigh bought a Tornos ST26 from Coalville-based Tornos UK Ltd (www.tornos.com) to produce 40 of the 50 families of small parts required for its new Quattro Pulp machine. “The inability of the other machine supplier to fit with our 4-26mm-diameter requirement instantly made the Tornos ST26 our primary choice.

Additionally, it was apparent that Tornos has invested in the aesthetics of its machines — not just the technology inside. Tornos has also addressed machine access, as the ST26 has a sliding door that gives the operator access from the front and rear of the machine.”

Also favoured by Haigh was the fact that the ST26 has a Fanuc control similar to the company’s existing machines, thus considerably reducing the operators’ learning curve.

Furthermore, the ST26 is particularly rigid, allowing it to achieve high levels of tolerance and surface finish, as senior technologist Jeremy Allen confirms: “We produce spring rod components that are part of an intricate spring assembly.

The 303 stainless-steel rods have a 7mm shank with a tolerance of +0/-0.036mm and a surface finish of 0.2Ra. Our larger machines couldn’t achieve the surface finish, and neither could our sub-contractors. Our only option was to turn the parts then roller-burnish the finish, which ironically was too good. The Tornos ST26 gave us the desired finish within the right tolerance band without secondary finishing.

“It was a similar situation with an aluminium bush housing that forms part of the same spring assembly. The bush housing has a 40mm-deep bore, within which are 7.25, 11.38 and 16.09mm diameters in the H7 and H9 range. With high-pressure through-coolant, the ST26 comfortably produces these parts, whereas our sub-contractors tooling left a spiral score in the bore.”

33 sliding door small
Unlike many of Haigh’s other machine tools, the Tornos ST26 can run ‘lights out’, as Mr Brown highlights: “On each shift, we run batches of 100-500 parts and then set the machine to run overnight unmanned. This means that it has very little down-time — and it produces parts up to 75% faster than our other machines, thanks to the ability for simultaneous front-end and back-end working.”

When questioned about Haigh’s choice of machine tool vendor (the company has bought some £1 million worth of new machines in the last five years), Mr Brown says: “We are not under the same pressures as sub-contractors
who are looking to shave fractions of a second off production times. We are a prestigious OEM with a recognised brand.

“While we invest in the latest production technology to support our product design department and maintain production schedules, our ethos is to invest in high-quality plant that will stand the test of time.”

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