Product category:
CNC automatic lathes
News Release from: Citizen Machinery UK | Subject: Citzen M32 CNC sliding head automatic lathes
Edited by the Manufacturingtalk Editorial
Team on 29 October 2001
CNC sliding head autos do the jobs in
one hit
When a company produces one million power tools a year, cycle time and lead time reduction is the name of the game to improve productivity, which is why it chose two Citizen M32 sliding head autos.
When a company produces one million power tools a year, cycle time and lead time reduction is the name of the game to improve productivity So when Makita, based in Telford, installed two Citizen M32 CNC sliding head automatic lathes, it was looking for substantial improvements to replace its well-proven semi-automatic line production techniques for families of drive spindles and electric motor armature shafts
This article was originally published on Manufacturingtalk on 27 Apr 2004 at 8.00am (UK)
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In changing over to the Citizen machines, supplied by NC Engineering of Watford, Makita now has a single hit operational process.
Previously the production methods involved six-stage machining processes on eight machine tools with three people per shift to operate the line.
Batches were produced in two day cycles with long changeovers between the different types but lead times are now less than 12 hours and operator levels have been reduced from 45 man/days a week to less than eight.
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Look in the toolbox toted around by any professional plumber, electrician, kitchen or shop fitter and you'll almost certainly see the distinctive blue form of a Makita cordless drill or power screwdriver.
Like Hasselblad, Mercedes, or Rolex, the Makita brand has earned its association with quality and reliability in the minds of its customers and tends to be the preferred choice of those who earn their living from its use.
Though the privately owned Japanese company was founded in 1915, Makita's power tools business only started in the 1950s.
It was the concentration on quality and some innovative product developments that turned this once obscure electrical equipment supplier into a global organisation with a network of factories around the world.
The UK operation Makita Manufacturing Europe, based in Telford, employs 500 people to produce one million hammer drills, circular saws, jig-saws, grinders and belt sanders a year.
Each requires up to 100 components to complete the assembly and around 95 per cent of output is exported from the UK.
One of the guiding principles in Makita's considerable success has been the concentration on fitness for purpose of the original design matched by the quality of the end product.
At Telford, which is a dedicated production operation, investment has been high to achieve flexibility in its manufacturing systems specified to meet current and future requirements.
Paul Harris, general manager explains the company philosophy: "We have a policy of continuous improvement to our batch machining practices which range from 2,000 to 10,000 units processed against Kan Ban style order driven production.
The two Citizen M32s are prime examples of significant productivity increases which also have the capacity to cope with larger, more complex components if the future need should arise." In-house manufacturing at Telford is geared to 'core' components which means the internal working of the company has a major influence on performance and quality.
It manufactures its own motors which even includes fine blanking of the laminations for the armatures and stators and it machines castings for the various transmission casings.
All shafts and spindles are produced in house and a new winding line is currently on order to provide a further major increase in productivity and flexibility.
The armature shafts produced on the new Citizen machines are turned from hardened material while Makita's output spindles are produced from heightened speed steel.
Both are free-cutting materials.
There are currently 12 shafts in all with diameters from 6 mm to 18 mm and lengths up to 150mm.
Around half the shafts produced require milled flats, knurls or hobbed gears while all are heat treated and cylindrically ground.
A general machining tolerance is +/-0.05mm.
"The shafts were previously manufactured on a semi-automated line comprising eight machines which needed three people each shift," outlines Paul Harris.
"The production sequence involved saw to length, face and centre and machine one end.
The part was then turned around, and other end produced on a side-by-side twin spindle lathe.
Any milled flats and knurls were then produced and gears hobbed.
However, batch lead time was up to two days and changeover times were lengthy," he reflects.
"We can now achieve the same output from the two Citizen M32s with a lead time of under 12 hours," he maintains and follows on the explain: "The two M32s have been installed beside a pair of older citizen E25Js and all four are overseen by one person.
This means our direct labour content has shrunk from nine men for each three shift day, to just 1.5 man days.
As we work 24 hours over five days, we have saved 37.5 man days a week plus occasional weekend overtime which has a real positive effect on production economics.
In addition, the 'single-hit' process has improved our levels of quality as all machining is referenced to a common datum position," he insists.
In practice, 95 per cent of throughput on the Citizen M32s can be machined using a standard kit of 20 tools which are permanently resident on each machine.
Bearing in mind the M-Series Citizen can accommodate up to 80 tools on its 10 station turret means there are still spare positions.
Likewise, all 12 component types can be machined from four different bar diameters - though material specification differs.
This provides Makita with a swift changeover time between different components; which can be easily achieved within 10 minutes and includes the first-off inspection.
Neil Pike, Makita's manufacturing manager, comments on the Citizen purchase: "Everyone who would be affected by the investment in these mac hines was involved in their selection.
Ultimately, we went with NC Engineering because we were confident in the machine capability and NC's ability to support them in the field which is proven by the two existing machines." Both the new Citizen M32s are equipped with C-axis on the main and sub-spindles and have an integral gantry-style off-load device.
This was specified to ensure smooth off-load without damage and also allows immediate availability of the part for inspection.
Typically, components are machined in about 60 seconds which is some 10 per cent faster than the original semi-automatic system of manufacture and adds to the economics tally of the investment.
The two machines are also linked to a three-stage filtration system to extract cutting oil vapour from the machining area and reduce airborne contamination.
In Makita's case, this has proven to be important due to the heat creation running higher speeds and feeds on the hardened material.
This provides a double advantage of higher productivity and tool performance.
Neil Pike follows on to explain: "The machines give the capability to simultaneously rough and finish and maintain high stock removal which has proven to be an important time saver.
"We run the machines at maximum speeds and feeds where possible," says Neil Pike.
"In practice this gives us excellent tool life and we also achieve very consistent surface finish and accuracy.
We have found it is normal to go through a day without any off-set adjustment whereas we used to stop and retune settings up to four times a day." For the manufacture of armature shafts, Makita has to produce a 'key' finish to locate the moulded armature core.
"We machine this at 4,500 revs/min with 0.3mm/rev feed and 3.0mm depth of cut. Request a free brochure from Citizen Machinery UK ...
With this method he concludes that the Citizen M32s are well able to sustain heavier cuts and have proven to be stable enough to immediately follow with a pre-grind fine finishing cut.".
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