Product category:
CNC automatic lathes
News Release from: Star Micronics GB | Subject: Star CNC sliding head automatic lathes
Edited by the Manufacturingtalk Editorial
Team on 07 February 2003
Ease of use and high reliability sold
the autos
The appeal of these sliding head CNC automatics was based on their comparative ease of use and the promise of high reliability and has been borne out in practice, says the user.
Ever since its foundation in 1989, Dundee-based subcontractor, Bonspiel Engineering, has specialised in manufacture using CNC sliding headstock lathes Throughout that time the company has relied exclusively on Star machines with FMB bar magazines supplied by A and S Precision Machine Tools
This article was originally published on Manufacturingtalk on 14 Jul 2000 at 8.00am (UK)
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Rapid growth in the last few years has seen its plant list grow to 21 Star lathes, the latest acquisitions being four high-speed SA-12/16s.
Sales director Steve Bruce outlines the company's approach to manufacturing.
"Right from the start we elected to concentrate on sliding head work.
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Magazine feeds small diameter, full-length bars
Designed for feeding sliding-head and fixed-head automatic lathes with bar in the diameter range 2 to 16 mm, the new Turbo 2-16 has been added to the lower end of FMB's standard bar magazine range.
As a result we have accumulated a lot of expertise and are willing to tackle jobs that other shops would probably turn away.
A recent example of this is a connector pin for a sub-sea application, which we produce from super duplex stainless steel alloy.
Additionally, a lot of the components that we make are required in fairly small volumes, say tens or twenties.
However, to do that requires reliable, flexible, easily set machine tools which is why we have continued to purchase Star lathes." Bonspiel was established on the back of a rapidly expanding requirement from Scotland's electronics industry.
Studs and shafts for cash machines provided a ready source of work and by 1995 the company had moved from its original premises to make space for additional plant.
In August 2000, a second move doubled the available factory space and the company added one machine per month for the following seven months.
Along the way the mixture of work had altered to become much more wide ranging.
Bonspiel is now a major supplier of pin-type connectors for specialised electronics applications in addition to shafts and studs of various types.
Components are produced from a huge range of materials including aluminium, brass, copper alloys, stainless steels and engineering plastics.
Cycle times range from tiny dowel pins produced at the rate of 2,000 per hour to the super duplex connector pin which takes six minutes.
Many of the pin-type components are sent for gold plating while other components are subject to straightforward assembly or forming operations.
"We began operating with a Star RNC-16," Steve Bruce explained.
"Bonspiel was founded by Paul Carver, me and my father, Eddie, who had prior experience of CNC sliding head operation.
The Star machine's appeal was based on its comparative ease of use and the promise of high reliability.
This has been borne out in practice as the average downtime on our machines is less than one day per year per machine." He continued, "Over time the technology has improved; all of our more recent machines have sub-spindles while the productivity of the latest SA-12/16 machines is highly impressive, particularly on smaller sized components like connector pins where he 12,000 rpm spindle and overlap machining facilities offer a real advantage.
We make one female connector pin where a crimped end is required; as well as producing the slot using a slitting saw we are able to do the forming work in-cycle by nudging the closed end of the connector with a turning tool." All of the company's machines are equipped with FMB bar magazines to enable unmanned operation.
Because of this, every lathe is operated unmanned for at least 40 hours per week.
As with the Star machines, there have been noticeable improvements in bar feed technology over the last decade.
The latest FMB systems are easier to set, allowing quicker bar changeover, which is important to Bonspiel as on some shaft jobs it is only possible to produce ten components per bar.
Likewise, on shorter batch work there can be three or four set-ups per day, so any improvement in re-set time is highly valued.
The largest capacity machines in the factory are four Star SR-32s.
These are used largely for telecommunications work where the 32mm bar capability is needed for connector bodies.
It also allows parts up to 24mm square to be produced from round bar.
The company is a practiced exponent of the art of producing polygonal components from round stock, reasoning that the extra time spent machining the flat features is more than outweighed by the disadvantage of trying to handle pre-formed bar.
"A lot of the alloys that we buy are not available in non-round sections anyway," said Bruce.
"Moreover, some of the alloys that we machine are only available in a restricted range of bar diameters so we often find ourselves having to remove a lot of material.
This is where the high rigidity of the Star machines comes into its own, as they can support some quite severe plunge cuts without compromising finish or accuracy." A recent example was the connector manufactured from super duplex stainless steel.
The component is about 100 mm long and in basic form it resembles a lance of the type used for jousting.
However, along its length are a series of reliefs used to locate the part within a plastic moulding so that the finished component looks like a lance that has been threaded through a series of rings.
"We already make a similar component for the customer from beryllium copper but super duplex is more of a challenge," Bruce remarked.
"This is made more so by the restricted availability of bar sizes.
We have to begin with a 12.7mm diameter bar and produce a component with a minimum diameter of 1.5mm along a substantial proportion of its length.
In addition we have to cross drill a 0.5mm diameter hole at one end.
Added to this, we need a very good standard of finish as two of the diameters are used to shut off within the mould." The machining sequence to produce the steel component is similar to that used for the beryllium copper equivalent but with necessary adjustments to the cutting data, resulting in a cycle time approximately double that required for the more machinable material.
They were produced on one of Bonspiel's Star SR-16/20 machines.
Using the lance analogy the component is machined from the handle to the point.
The 'handle end' of the lance is turned to diameter, end drilled and cross drilled, then the conical boss is turned, followed by grooving and back turning of the shaft and 'doughnuts'.
The head is then back turned and the component supported in the sub spindle for parting off, which produces a conical point.
"This is a very good demonstration of the Star machine's capabilities as the machine made no 'complaining noises' throughout the batch and the components were within tolerance," Mr Bruce concluded.
"Our customer is very pleased with the results.
In essence, pleasing our customers is what our Star machines have enabled us to do for the past 14 years.".
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