Product category:
CNC automatic lathes
News Release from: Citizen Machinery UK | Subject: CNC sliding head mill/turn centre
Edited by the Manufacturingtalk Editorial
Team on 15 June 2007
CNC sliding head lathe fits automation
ideal
Pump manufacturer is making maximum use of automation to maintain competitiveness, and said a CNC sliding head mill/turn centre fits exactly into what the company is trying to achieve.
Employing 105 persons, privately-owned Stuart Turner produces more than 120,000 pumps a year and generates sales in excess of GBP 17 million The same attention to detail as was applied to the company's model engineering products ancestry is now being maintained today in its modern production and assembly areas
This article was originally published on Manufacturingtalk on 26 Feb 2004 at 8.00am (UK)
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The company is certainly enjoying the benefits of keenly applied automation to hold off the competition - especially from overseas.
According to Stuart Turner's machine shop supervisor, Craig Geeson: "We are mindful of making the maximum use of automation to maintain competitiveness and develop the business, and our Citizen M32 - III CNC sliding head mill/turn centre fits exactly into what we are trying to achieve." This he qualified in the production of more than 620,000 parts - one every 47s, which also includes all non-productive time - that have been produced on the machine in the 23 months following installation.
In keeping with the automation mindset of the production team, Geeson maintained very detailed comparisons of the 17 different parts produced in quantities that vary between just 12 and 170,000 per year, where the CNC sliding head mill/turn centre has decimated previous floor-to-floor times.
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In a subcontrator's view, its latest mill/turn centre stands out for its powered tooling ability to mill and drill and in particular, through the added flexibility from its two Y-axis cross feeds.
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When Target Sports bought its first Citizen B12 Type V, CNC sliding headstock lathe, it wanted to machine high quality brass dart bodies - it was quickly followed by a second machine.
Sliding heads raise productivity by two-thirds
To help meet growing demands for torque control tooling, MHH invested in two Citizen sliding head lathes from NC Engineering, and is now achieving an average 65 per cent higher productivity.
For instance, a drive spindle is now produced in 120s complete in a single operation against 406 s previously, a saving of 238%.
The time to completely machine a plug has been slashed from 71.2s to 22.5s - a 216% saving - and a hose end coupling is now produced 74.8% faster.
This record of the machined coupling reflects a massive return on investment against the previous automated fixed-head lathe method saving 18.7s on each component - especially when 170,000 couplings were produced in the last 12 months.
Geeson said: "Overall, the Citizen has shown a cycle time saving of 117.69%." Such is the rate of production, for which 16h/day are under 'lights-out' conditions, that the machine will normally deposit 900kg of brass into the swarf cart every 24h.
The Citizen M32 - III CNC sliding head mill/turn centre and its supplier, NC Engineering of Watford, UK, were introduced to Stuart Turner by a local Sandvik Coromant technical sales engineer, Gary Wilson.
Subsequently, Stuart Turner has a very close relationship with NC Engineering and Sandvik, which has led to the development of advantageous methods, introducing new tooling and the reduction of cycle times.
The previous fixed-head, six-axis gantry loaded mill/turn machine with twin-turrets and subspindle was not slow.
It had been progressively improved with Sandvik's help but it was suggested that the type of parts produced would be better served by sliding head technology.
To this Geeson was quick to add: "We had a learning curve because we had to evolve a different approach to programming the parts, but it has certainly paid off." The Citizen M32 has a 7.5kW main spindle delivering up to 8,000 rev/min and a 3.7kW subspindle having a top speed of 7,000 rev/min.
The vertical gang tool post has four driven tools and five turning tool positions and an independent back tool post has three driven positions.
Combined with the turret, these three toolholding areas enable three tools to cut simultaneously.
The 10-station turret can accommodate multiple tool holders and driven tools that bring the total tool carrying capability to 72 tools which are put to good use by Stuart Turner's setters.
As a matter of course, they leave a common set of tooling permanently on the turret and by using effective pre-setting, can change the tool post tooling in a matter of minutes.
Quite often, two changeovers are made in a day.
The machine was specified from NC Engineering with an Iemca TS560P barfeed system that comprises multiple bar racks with a total capacity of 56 bars of 32mm diameter material up to four metres long or 224 bars of 8mm diameter.
Added Phil Horsley, general factory manager: "This helps us to extend our unmanned running and minimises bar end wastage.
The company tends to run 32mm, 25mm, 15/16in, 13/16in and 8mm bar sizes, of which 98% is CZ121 brass, the balance being stainless steel.
As part of the automation package that enables a direct 'bar to wash' scenario to be maintained, Stuart Turner utilises the NC Engineering unload gantry on the Citizen to transport the parts from the subspindle of the machine for placement onto a slatted conveyor for feeding to a longer conveyor that runs the length of the barfeed.
From this conveyor the parts are deposited into plastics boxes ready for washing and the plastics boxes are fed to the unload point on a separate conveyor that also runs beside the barfeed.
Due to the amount of unmanned running and the volume of swarf produced, a higher output LNS Microfine II swarf conveyor was retrofitted.
Stuart Turner was very complimentary over the stability of the Citizen machine: "Our general tolerances are 0.1mm but we have some requirements of 20 micron," said Geeson.
"Once set, it is rare to change an offset at the control and we are confident to leave the machine running over the weekend without fear of problems.
We have people willing to come in and re-bar and check parts through this period.
Even if we turn the machine off for a day it will immediately go back to the sizes set, whereas our other machines in the shop tend to need a while to stabilise after a long break in production." Typical of the type of component produced is a shuttle valve from 32mm C2121 brass that is machined to 30mm diameter by 130mm long.
This part previously took 122.8s which was cut to 75s on the Citizen M32 III.
Altogether 25,500 of these components are produced a year.
The process involves step diameter turning to 25mm diameter, deep hole drilling, cross drilling and tapping, the milling of flats, internal and external grooving, the cross drilling of three holes followed by the tapping of two with 1/8in BSP and 3/8in BSP threads and the chasing of a 3/8in BSP on the end spigot.
Said Geeson: "We try to balance main and subspindle operations and have found that by overlapping parts of the cycle we have been able to virtually eliminate any dead time." Meanwhile, with the focus on production, the Citizen has also proven its worth on prototype components and for machining items of tooling and fixturing where some cycles involve very intricate milling and profiling.
"These parts would probably have been made outside - but our policy is to machine and assemble everything in-house under our control.
This means the Citizen has proven to be a very flexible and essential piece of equipment to us," summed up Horsley.
* About Stuart Turner - Anyone interested in model engineering will be familiar with the Stuart Turner name.
On display in the company's museum are more than 100 working models, all in impeccable condition, of engines, pumps, generators, boats and even a Stuart Turner motorcycle - glowing testimony to the glorious early 1900s heritage of this Henley-on-Thames, UK business.
Today, still privately owned, Stuart Turner is a re-focused business.
It sold its models division to a Guernsey, Channel islands-based company.
The sale allowed Stuart Turner to concentrate on three key areas of pump design, development and manufacture for customers in the building services, commercial products and leisure markets. Request a free brochure from Citizen Machinery UK ...
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