‘Driven at the center [sic]of gravity’(DCG) technology is “the kind of

technological innovation that comesabout only once in every decade”,assertsMori Seiki. And it was unveiled at theopening of the company’s new ChibaCampus in October last year.

The Chiba Campus,located 20 km eastof Tokyo,is,in fact,the new home to manyof the staff from the former Hitachi SeikiCompany,which was purchased by MoriSeiki in 2002 and is the third Mori Seikimanufacturing site in Japan.

As president Masahiko Mori explains,the DCG machines were a driver forchange throughout the company.“Development of these machines[NH4000/6300DCG and NV4000DCG]meant revamping our company structure.To raise the reliability of the machines,wehad to improve the precision of each part.After that,we had to meet short deliveryschedules to accommodate the rapid start-up goals of our customers.To accomplishthis,we implemented innovations in theproduction process,includingincorporating cell production methodsand dynamic analysis which allowed us tobuild machines with an optimum balancebetween quality,cost,and delivery neverseen before.”

This revamping is encapsulated in anumber of individual themes.The first ofthese is the ‘Auto Camp Site System’.TheChiba assembly shop is divided up intoindividual ‘sites’where all parts arearranged around a work area and a singleoperator assembles them.Reducedwalking to search for parts has helpedslash delivery times.

A second theme is ‘Making the factorya showroom’,which is intended to turn a

traditional factory environment into onemore reminiscent of a semiconductor ormedical equipment plant. In a real test ofcleanliness,the factory floors have beenpainted white! Previously they were amore forgiving green.

“If you go to a plant that makes beer ormilk bottles,they show you how it allworks so that you can go home thinking,‘There’s nothing to worry about’. In thesame way,one of our goals inincorporating showroom functionalityinto the Chiba Campus was to raisevisitors’trust in our machines,”explainsMori Seiki.

Under the heading of ‘The 2-2-2-project’,the company is reducing

production lead times for machines fromsix months to two.More specifically,theproject sees raw material stocks reducedto two months’supply,machineproduction lead time reduced to twomonths,and finished product stock alsoreduced to just two months. Improvingcustomer satisfaction is key.

‘INSOURCED’ NOT OUTSOURCEDImportant in achieving this is the fact thatthe company is bringing in-house most ofthe parts that other competitor machinetool makers are outsourcing! Better pricingas well as shorter deliveries are claimed.

Away from Chiba at the company’s Igaplant,a new R&D centre has been

LOW VIBRATION IS GOOD VIBRATION

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In the frameLast year, Mori Seiki threw open the doors of its new Chiba Campus to reveal new production and

design philosophies. Machinery was there to see and hear all. Andrew Allcock reports

Factory and showroom.White floors reminiscent of a semiconductor plant

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inaugurated.This single department is theresult of drawing together three previouslyseparate activities: the DM Group,whichspecialises in mould and die machining;the engineering group,which makescustomer-specific proposals;and 200designers involved in the realisation ofnew products.Better information sharingis the key objective here,with applicationand market-facing knowledge helping toimprove new machine designs.Chibaclaims a further 100 development staff.

Finally,Mori Seiki has set up anautomotive parts-focused group at itsNagoya location.This new team willconcentrate on turnkey projects.

The Chiba Campus is,in fact,thecentre for the production of multi-functionmachine tools – what Mori Seiki is calling‘super process integrated machines’.Andthe newly remodelled environment isparticularly linked to the manufactureand presentation of these machines.“Multi-axis machines have been thefocus of a great deal of attention.As a plant specifically designedto handle production of thesemachines,the Chiba Campusis an industry-first,”says Mori

Seiki.“It represents an attempt on our partto put together an environment for makingproducts that will have greater addedvalue than those of any other company.”

And it claims “unmatched”levels ofprecision and productivity for its multi-axismachines,with the Campus’showroomenvironment an important tool inconveying the message.“It allows visitorsnot just to see,but also to feel what our

multi-axis machines are all about byviewing presentations.These presentationscan only be done on a production floor,and include cutting demonstrations usingreal machines and showing the actualprecision data,”underlines the company.

But the stars of the Chiba Campusopen day show were the DCG machiningcentres.According to managing director,development executive officer Dr EngKazuyuki Hiramoto:“The 1990s were atime of acceleration for machiningcentres.Since then,however,improvements in motor performance havenot brought about any significantincreases in speed,with the whole

industry growing stagnant inthis area.

“The factorpreventinggreater speed isvibration,generated bypushing

spindles,tables,and other moving

components in placesoutside their centre ofgravity.Unfortunately,it isimpossible to insert ballscrews right in the centre

of gravity by design.Toovercome this technicalbarrier,we

MACHINE TOOL TECHNOLOGY

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came up with the answer of creating avirtual centre of gravity using twoballscrews.This is the Mori Seiki approachto being ‘Driven at the Center of Gravity’.”

The company had two goals with itsnew machines: to give the company’sengineers “free reign to develop their‘dream machine’”;and keep the numberof new parts low to ensure a low-costmachine.

The construction of the verticalmachine (see page 11) sees the spindlesupported by an arch-like structure.Thisset-up allows the power created duringmovement to be absorbed in the centre ofthe construction.This approach is part ofthe company’s Force Loop AdvancedShape (FLASH) technique that allowsmachining forces to traverse across a so-called box-in-box structure and throughthe bed,forming a closed loop,andresulting in a more stable platform.

The NV4000DCG is also designed sothat the workpiece is always supportedabove the bed,so there’s no overhang,andthis reduces changes in the dynamiccharacteristics of the machine related totable position.The table itself is driven in yby ballscrews set either side and sittingoutside the linear guideways and,hence,itis ‘virtually’driven at the centre of gravity. Insimilar fashion,the z-axis is driven by twoballscrews,one either side of the spindle.Because the table can be driven throughthe centre of gravity for x-axis traverse,onlyone ballscrew is used:but that’s a total offive ballscrews for three axes!

COST AND DELIVERY CONTROLBut since the company makes its ownballscrews at the rate of 2400/month,it hascost and delivery under its own control.

In the case of the horizontal machines,the NH4000DCG and NH6300DCG,the

construction is more obviously seen to bebox-in-box.So within a rigid non-movingbox sits another box which moves in x –side to side.This box is driven by twoballscrews operating outside of theguideways and providing the ‘driven at thecenter of gravity’capability.On the movingbox is mounted the spindle carrier whichruns on two guideways located verticallyon the box’surface.Because the ballscrewcan be attached to the spindle carrier atthe centre of gravity,there is just a singleone driving y-axis movement.The pallet,however,is once again driven by twoballscrews to offer the DCG feature in the zaxis.Five ballscrews again.

In the case of both horizontal andvertical machines,Minimum Moving Mass(M3) has been achieved throughcomprehensive digital analysis,deliveringthe ideal mass and supporting improvedaccuracy and dynamic response,without

compromising strength or vibrationdamping.

In quantifying the degree to whichvibration has been eliminated,Mori Seikiclaims that – when compared to machinesfeaturing a single ballscrew in x,y and z –values for vibration magnitude arereduced from over 20 to less than 1 micronfor x,for y the reduction is from over 7 tounder 2 microns,and for z the change isover 14 reduced to under 1 micron.Thisallows both higher speed and more rapidacceleration,while delivering highestquality surface finish,says Mori Seiki.

The NV4000 DCG,for example,realises1.5x increased acceleration compared tothe existing NV5000.

In addition to the innovations of DCG,FLASH and M3 are added other designdetails such as an inclined machinecabinet roof that allows condensedcoolant to run to one side on the

horizontals,plus cabling and pipingattached to the spindle centre of gravity toreduce fatigue in these parts.And finally,says the company, with easy access to allkey components,simplified maintenance

schedules and reduced Mean Time ToRepair (MTTR ),there’s more time spentgenerating income.❐ See DCG in action on both vertical andhorizontal machines at MACH,stand 5350.

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MACHINE TOOL TECHNOLOGY

Award-winning technology

Mori Seiki's NV4000DCG vertical and NH4000DCG horizontal high-precisionvertical machining centres have won Japan's newspaper Nikkan KogyoShimbun's 46th Best 10 New Products Award for 2003. The Award is presented tocompanies that have developed and implemented the top 10 new productsduring the year.

Reasons for the award included the ability of Mori Seiki's 'Driven at the Centerof Gravity' (DCG) innovation to increase a machine's operating and machiningprecision, while improving surface quality and reducing machining time. DCG isa basic technology that can be extended beyond machining centres andincorporated into other types of machine tool.