N° 40 - March 2004

T H E C N C A N D S E R V O M O T O R S + D R I V E S M A G A Z I N E

informationnum

PRODUITSNew for gear cutting

SOLUTIONWooden mold

machining

Num : CNC Complete Solutions

New PC panelsNew PC panelsHall 5 - Stand B158

Hall 11 - Stand M16

num information No 402

CORPORATE NEWS

automatic control systems.In parallel, our plant inArgenteuil France wasno longer suitable and wasrelocated to Colombes,another Paris suburb.In Germany and the U.K.,we also relocated to havepremises better suited toour sales business, especiallyservices. Last but not least,our subsidiaries now havenew guidelines givingthem more operationalindependence, whichallows them to be moreresponsive and closer totheir customers. That is quitea lot for one year. But asClaude Mandil, Executive

Several changes weremade to Num’s orga-nization in 2003. Whatis the situation today? It is true that the reposi-tioning of Num withinSchneider Electric andmore specifically within theMotion Control activity hasgiven rise to severalchanges. The CNCs arenow manufactured in theSouth of France in Carros,Schneider Electric’s worldproduction center for

“ For 2004, we have doneeverything to ensure success”

Director of the Interna-tional Energy Agency,said, to be efficient is tokeep changing. I definitelybelieve that to improve, onemustn’t be afraid of callingoneself into question.

How do you see2004?We have set up flexibledynamic structures with theaim of improving addedvalue for our customers.For instance, we areorganizing both ourservices and our productlines to have a global,relevant approach. We arealso enriching and adapting

our product line to be evenbetter attuned to customerrequirements. We havetherefore done everythingto ensure success. Themain trade fairs such asIndustrie 2004 (Machine-outil 2004) in France,Xylexpo in Italy, Grindtecin Germany, etc. that willbe held during the first halfof the year will be a goodtest to see whether ourinnovations are bearingfruit. As could be expected,we will be exposing ourlatest graphic functions(see box) that were alreadyvery popular at their previewat the Milan EMO and our

new PC panels (see box).Finally, we will reassert ourambition to approach themarket from a job-orientedangle, as is demonstratedby our gear cutting package(see opposite).

Philippe Toinet, Sales and Marketing Manager, explains what Num did to prepare 2004.

Philippe Toinet,Num Sales andMarketing Manager

With their depth behind the front of 95mm (front 5 mm), these new PC panelsare very compact.

Num Provides EnhancedGraphic Functions

Previewed at the Milan EMO and Machine-outil 2004,Num's new graphic functions are the result of apartnership with DPTechnology aimed at integratinggenuine milling and turning CAD/CAM capabilities inAxium Power CNC systems. Three levels of service willbe available. The first, basic on PC panels, gives accessto an especially user-friendly and tutorial 2D editor. Thesecond provides 3D simulation of the machiningprogram using the CNC's G functions. This level allowsa genuine test to be made of the program, because theoperator sees exactly how the machining operationswill work, including special cycles. The third opensthe CNC system to all the CAD functions of Esprit. Thistotal integration ofthe CAD functionsin the CNC gives ito u t s t a n d i n go p e r a t i o n a lflexibility and takesinto account allthe engineeringdata.

Num Expands Its Line of PC Panels

Shown for the first time at the Industrie 2004 trade fair in Paris, the latest NumPC panels boast an excellent price/performance/size tradeoff. Called iPCsCompact, they come with two different microprocessors: Pentium 4 1.7 GHzfor SCADA type applications and Celeron 667 MHz for more conventional HMIapplications. Their communication specifications - one Ethernet port, four RS232 ports, two USB ports, two PCMCIA ports and one PCI port - allow themto adapt to almost any situation. The openness plus their computation powerand their large memory will be particularly appreciated by OEMs looking for apanel to meet multiple needs, especially for job-oriented approaches.Their 15" screen provides astonishingly good display quality under all envi-ronmental conditions. In addition, there are those who will appreciate theuser-friendliness of a touch screen providing the function keys.With their depth behind the front of 95 mm (the front itself has a depth of 5mm), these new PC panels are very compact. In addition, all the ports are

located underneath the case, facilitating their installation and not takingup any extra depth in the cabinet.Last but not least, end users will certainly notice how rugged these newPCs are, making them capable of withstanding the bumps and jolts

commonly encountered in industrial environ-ments.

3num information No 40

It is easy to imagine the quality disruption caused by a manufacturing flaw in a gear.That is why gear cutting fully deserves special attention. Mindful of this, Num engineershave developed complete solutions to meet all basic needs.

PRODUCTS

Gear Cutting

Cost-effective solutions withhigh performance!

T he mechanicalkinematics ofa gear-cuttingmachine almost

always has the sametype of design (see Fig. 1).A spindle equipped withinthe tool head, along witha set of linear axessynchronized to the workpiece, the machine has anexceptional ability toorchestrate tool headspindle and work pieceaxis movements with highprecision. The number ofsynchronized axes differsaccording to the requireddegree of machiningcomplexity.

PackagesEngineered to FitYour ProcessRequirement!Supplementing it’s millingfunctions, Num now offerstwo software packagesdedicated to gear cutting,within the Num Power

1000 and Axium PowerCNC families. Each packageincludes a complete setof G functions for geargeneration by grindingwheel or hob cutters, aswell as tool change andretraction macros.

With the basic package,the CNC synchronizescutter rotation and axial toolmotion (Z axis) with therotation of the work piece(C axis). This configurationis therefore principallydesigned for the simplestmachines with three axes(X, Z and C) plus a spindle.

With the second package,the CNC adds tangentialtool movement (Y axis) tothe synchronization of theZ and C axes. In additionto covering applicationswith up to 6 axes (X, Y, Z,A, C, and W) plus a spindle,this solution also extendsthe range of manufacturing

of bevel gears and helicalgears with straight orconical cutting tools.

To these two new packagesis added the gear alignmentfunctionality, giving the fol-lowing capabilities: • Re-cut a previously

machined gear.• Setting the angular

alignment of correspon-ding teeth, when multiplegears are generated onthe same shaft. (seephoto).

• Automatic gear alignment:Built-in cutting tool andgear re-synchronization,

X axis – radial feed of the hob with respectto the gear; Y axis – tangential movementof the hob to cater for tool wear or generationof gears with tapered teeth; Z axis – axialmovement of the hob thru the gear duringmachining; A axis – tool head swivel to matethe hob angle to the gear tooth angle;C axis – work piece rotation; S – tool headspindle rotation.

To program themachine, the user isguided by a series of

questions andanswers plus graphic

views.

(end page 4)

via a non-contact sensor,allowing for automatic“tool-work piece” timingpickup, when reintro-ducing a precut orhardened gear into themachine.

Job-OrientedGraphics Empo-wer the User!Faithful to its job-orientedapproach, Num has alsodeveloped an interactivegraphic user interface(HMI).

fig. 1

Photo BK

num information No 404

SOLUTIONS

Building Europe around machine tools

Swift had a strongneed for flexibility

because of the largenumber of variants in

its production.

Gear Cutting (end)

Number ofaxes

Min/Max

3/43/53/8

3/324/32

Basicpackage

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Advancedpackage

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CNC System

Num Power 1020Num Power 1040Num Power 1060Num Power 1080Axium Power

Summary of the capabilities offered by the new gear cutting packages (available/unavailable)

Examples ofseveral gears

on the same shaft.

This HMI allows the userto create complex gearmachining programs simplyby answering a number ofquestions concerning thecutting tool and the gearto be generated (seephotos). There is no needto know the ISO language!This operation is simplifiedeven more by the graphicview of the different elements(work pieces and tools).

The user interface alsoprovides tool wear mana-gement, which contributesto optimizing the life of anoften costly, cutting tool,by automatic shifting overthe tool’s working length.This tool managementapproach is especiallyadvantageous in helpingto avoid process sizevariations and therebyallows high part quality tobe preserved over time.

The aim of these newfunctionalities is to providea cost-effective solutionfor the most commonapplications for new orreengineered machines.For more special needs,Num does not hesitate toput its experience to useto find a suitable solution(see article, page 11).

S ince 1960, Cosmec has been makingspecial wood- and plastic-workingmachines.This Italian manufacturer hasa catalog of several basic machines that

can be customized and tailored to meet the needsof each customer. Cosmec works in a great varietyof fields,but they all share one common requirement:flexibility.

An Italian OEM, A British User and aFrench ManufacturerSwift is a leading British manufacturer of trailersand recreational vehicles known in particular for thequality and elegance of its interior wood furnishings.Swift recently decided to restructure its furnitureproduction. It finally chose an Italian Cosmecmachine because of its speed and accuracy, and thesupport of their import agent,VWM woodworking,who are one of the UK’s leading suppliers of newand used CNC machining centers.

The system chosen was a NR machining centerwith fixed gantry and moving beds. Two 3-axistoolheads with a power rating of 10 kW each,include a 12-position tool changer.Two separateworktables allow loading and unloading to becarried out in masked time while machining conti-nues on the other table.The machining center is controlled by a NumPower 1050 CNC system. “We needed accuracyand computational power to control the entiremechanical system of the machine simultaneously toguarantee maximum time optimization,” explainedDott Dimitri Tansini, owner of Cosmec.“And Swiftwanted a machine that was compatible with itsexisting machines.”This pan-European operationwill continue, since Swift has ordered othermachines!

5num information No 40

T he French company Aquarese specializesin the integration of ultrahigh pressure(2000 to 4000 bar) applications of thistechnology for a wide variety of uses such

as cutting, pickling, deburring, etc. “Our servicesrange from feasibility studies to equipment supply,”explains Bruno Galiot, head of the AutomaticControls R&D Department at Aquarese.“We tailorour services exactly to the customer’s needs soas to develop a long-term partnership which allowsus to build on joint know-how.” In this context,Aquarese had to meet a real challenge from SnecmaMoteurs to demonstrate the economic advantagesof 5-axis waterjet cutting over rough milling oftitanium aviation parts more than 100 mm thick.

Challenge met…… even if some problems remain to be solved tomake the process fully reliable, several difficultieshave already been overcome. First, the thicknessand nature of the material.Water-jet cutting canbe pictured as wire cutting, with one end of thewire left free. It is then easy to understand thatthe longer the jet, which is the case for thicker parts,the harder it is to control the jet’s reactions as itmoves across the part. Moreover, this is the firsttime this technique has been used in the aviationindustry for such thicknesses, and the results arequite satisfactory for thicknesses up to 160 mm!At the same time, titanium is the metal with thehighest strength-to-weight ratio of all the knownstructural metals. That is why it is so hard tomachine, especially in this case, which involvesmore than ordinary cutting and is much morelike machining.”The machine includes a 5-axis gantry and a rotarytable.The axis system is controlled by an AxiumPower CNC. The use of the RTCP (Rotationaround Tool Center Point) function improves controlof the water-jet’s trailing angle, dependant on thedirection of movement. Because the Axium Powersystem is so open, it was easy to integrate pagesdedicated to this application in the system HMI.

Process Monitoring Integrated in the HMIFor reasons of safety, reliability and traceability,it is mandatory to continuously record the water-jetflow rate, abrasive flow rate, etc. during machining.Any undue drift in these parameters can be precursorsof manufacturing defects. It is therefore essentialfor this data to be continuously accessible.

How to cut through 160 mmof titanium with water ?The advantages of a pressurized waterjet for cutting cotton, food and certain metals are well known butuntil now, these techniques have been used only for materials of reasonable hardness and thickness. AtSnecma Moteurs, Aquarese have designed a machine to cut through titanium parts more than 100 mm thick.

“We developed two new contexts that we addedto the existing ones of the CNC,” says Bruno Galiot.“The first context is a ‘process monitor’ whichshows a graphic view of the parameters beingmonitored by the PLC.This view allows true qua-lity monitoring since all the events that occurredduring production can be related to a specificpart serial number. A second context key, labeled‘Aquarese’, gives access to maintenance functions.”The data is saved on the hard drive of the PC paneland is accessible via the data network. Similarly,part programs can be transferred directly fromCAD/CAM.“This machine has undeniable economic andtechnical advantages,” concludesBruno Galiot. “Moreover,we haveother contacts in the aviationindustry for similar needs.”

Waterjet Machining

Screens developedby Aquarese for thisapplication andintegrated in theAxium Power HMI

Line of turbojets produced by Snecma Moteurs (Snecma Photo)

Machine controlpanel

num information No 406

W ith the appearance and rapidgrowth of power steering systems,the role played by such systems inthe success of a model has greatly

increased.The gains in reliability, size, cost, etc. areassets which benefit the automotive manufactureras well.When it purchased PSA Peugeot Citroën’s Dijonplant in 2000, the Japanese Koyo group, secondmanufacturer in the world for steering systems,was well aware of the advantages of acquiring aproduction unit that had already been a leaderin this area for several years. For KSDSE (KoyoSteering Dijon Saint-Etienne), the induction quenching know-how has given rise to specialdevelopments for producing the inductor nowsold by the company to other plants within thegroup. It was therefore understandable for KSDSEto pay particular attention to the maintenanceof its production tool by retrofitting a three-axisinduction quenching machine.

Induction Quenching, A Specialist’s JobThis process, used especially with steels, consistsof almost instantaneously heating the surface ofa part to around 900°C, then cooling it very rapidly.The part is heated by induction or eddy currentscurrents.The quality of the results depends on two

factors, the frequencyand the shape of theinductor.The first processgives the steering rackexcellent hardness pro-perties. But if it wereleft as is, it would be likeglass: both hard andbrittle. In 2003, as itwas starting on newproductions, KSDSEdecided to re-engineera steering shaft induc-tion quenching machine.“Induction quenchingis not a fast process.”explains Jean-Pierre

Retrofitted with anAxium Power, thisinduction quenchingmachine is used forprocessing steeringrack shafts.

Automotive Subcontracting

KSDSE is a specialist in the production of steering systems for automobiles who havechosen Axium Power to retrofit several of its machines.

Rzeczynski of the induction quenching shop.“Ouroutput is around one part per minute. However, itis essential to control the space between the induc-tor and the part very accurately, because the qualityof the result depends on this.These measurementswill allow the inductor to be positioned flawlesslywith respect to the part.” It is the CNC that makesthe measurements and moves the inductor alongthe part.In addition to the usual advantages of retrofitting,such as extending the life of a machine and/orobtaining a more user-friendly and powerful HMI,the replacement of the old system with an AxiumPower makes settings more flexible, especially formeasurements. “We no longer have to measurepositions at a specific number of fixed points,”continues Jean-Pierre Rzeczynski, “which allowsus to consider using this machine for smallerproduction runs.”

When Reliability and Optimization AreCombined!“First we want to ensure the operational reliabilityof our tool changer, which supports 56 tools.”says Michel Lambert, of the MaintenanceDepartment,“This 6-axis machining center allowsthree steering boxes to be assembled simultaneously.To machine them, we make approximately 12 toolchanges per cycle. Before the retrofit a relativelycomplex sequenced control regularly led to errorsin tool changes and thus to machine stoppages.Now, by controlling this function as an axis, theposition of the tool changer is much more accurateand the arm that comes to get the tool is correctlypositioned in front of the next tool.”This operation required re-writing the PLC program,which is now in Ladder, making it much easierto understand and maintain. However, only a fewminor adaptations were required to the part programs,necessary to benefit from newly available functions,such as rigid tapping.

SOLUTIONS

An induction quenching machine,a huron machining center …KSDSE is renovatingits equipment

Inductor movementrelative to the partmust be flawlessly

controlled.

This retrofit wasespecially beneficial

by making the toolchanger control more

reliable andoptimizing it.

7num information No 40

Five Num 1080 CNCs control the systemmachining stations. They are integratedin a TCP/IP network and communicatewith a special server program.

Entrance doorsmade to order onthe production line

T he Dutch manufacturer Kegro Deurenis capable of making any and all externaldoors simply by measuring the opening.External doors are much more varied

and complicated to manufacture than internaldoors. However, Jan Hermanussen, ProductionManager at Kegro, is not complaining about thisdiversity. “For many years, we have been makingmade-to-order external doors, but we needed toautomate production to become cost-effective.”The German company MKM won the contract.For major projects like this, Klaus Baumann, MKMmanager, called on longstanding partners suchas Num. “We used five Num Power 1080 CNCsallowing us to control up to 32 axes divided intoa maximum of 8 groups.”

Three Major Assets: Flexibility, Quality and SpeedThe system includes five machining stations, afeed robot at the head of the line, the stackingsystem at the end and a roller conveyor totransport the doors. The head of the lineconsists of a gantry milling machine for profilingthe doors. All the data relative to the door profileis communicated to the milling machine by a barcode.When both straight and curved doors have beenprofiled, a transfer conveyor loads it onto a rollerconveyor which brings it to the next station, andso forth.“ The main challenge was to accuratelyposition doors of different shapes,” continuesKlaus Baumann. ”To do this, we installedtotally flexible stops at each station. The doordimensions and possible radius of curvatureare known, so that Y axis stops can be adjustedaccordingly. We can thus position, clamp andmachine the profiled doors accurately at eachstation.”Deadlines were of course an additional challenge.“We are renowned for three major reasons: flexibi-lity, quality and speed,” explains Jan Hermanussen,“and this system contributes a lot to that success.”This is obviously due to the mechanical systemsbut also to a large extent to the electronics andthe software written by the German companyTechni-Soft. Each of the five machines equippedwith CNCs, the feed robot, the roller conveyorand the stacking unit are independent units.

This allows the components on the machiningstations to be controlled separately. A PC com-municating with the CNC is connected to eachstation.A client program specific to each station collectsdata such as “door on conveyor”, “failure”, etc.It transmits this data to a specially developedserver program via a TCP/IP network.The serverprogram analyzes the data received from theclients and sends back instructions. These areinstructions like “finish machining” or “preparemachining”, etc.The system is very flexible because the CNCprograms for the different machines are notgenerated until the bar code has been read.Changes remain possible up to that point. Inaddition, the CNCs have 3D macros allowing themto produce curved parts.The only programmingrequired is interactive data entry into templatemasks for variants of flat parts. Similarly, poly-nomial interpolation optimizes path following,allowing flawless smoothing.This networking concept has the enormousadvantage of simplifying the wiring. And it waspossible to do away with quite a few hardwarecomponents. For instance, the exact thicknessof the door is measured on the first machineand communicated to the server program.As soonas the door reaches one of the other machines,the measured thickness is communicated to itsclient program which then sets it in a PLCparameter. The parameter is then used by thatCNC’s program.

With its new MKM machining center controlled by a NumCNC, Kegro is fully equipped to produce one off doors ofvarious shapes.

Woodworking

The main challengewas to accuratelyposition doors ofdifferent shapes.

num information No 408

SOLUTIONS

M any standard and special tools are indaily use for machining metals.Whenthey become blunt, these valuableitems are not scrapped straight

away, because they can be re-sharpened severaltimes. However, this can become a difficult jobwith complex tool geometries.Hubert Haller, Manager of Hawema Werk-zeugschleifmaschinen GmbH located in Trossingen,is a tool grinding expert. Hawema, the companyhe created in 1993,works mainly on developing andmanufacturing grinding machines equipped withnumerical controls, and it has been very successful.The 5-axis Hawemat 2000CNC grinding machineintroduced in 1997 has won several awards forits innovative design.This machine was used asthe basis for the Hawemat 3000 and 2001 grindingmachines.The Hawemat 2001 specializes in toolsharpening and the production of small tools.The Hawemat 3000 grinding machine is speciallydesigned for manufacturing new and special purposetools.

Only Num!In parallel with the development of the Hawemat2001CNC grinding machine, Hubert Haller tooka new step in innovation: a strong partnership withNum as the single source for all the electrotechnicalparts and software. “We already had Num CNCsand the NUMROTOplus‚ software alongside othermakes.A year ago, we decided to work with Numalone. In effect, Num proposes software that is

Tool grinding encompasses the production of new tools andtool re-sharpening. The second activity is much moreprevalent and the work is often more difficult. The associationof new HAWEMAT grinders equipped with Num CNCs andNUMROTOplus‚ software, the world leader in this specialty,provides a complete and effective solution.

an international benchmark for tool grinding,combined with the new Axium Power Level 1 CNCand MBLE axis drives, a drive system that is justright for our machines. For our production wethus have all the electronic circuitry and softwaregrouped in a single package.” Another advantageis that Num provides service all over the world.Some of Hawema’s licensees are located in Americaand Asia where they produce for their local markets.They also use complete Num packages.

The Rolls Royce of Grinding ProgramsMetzmeier Werkzeugservice GmbH located inVillingen-Schwenningen is one of Hawema’s loyalcustomers. This specialist tool grinding servicecompany invested at the end of last year in aHawemat 2001, as explains their manager, KlausMetzmeier.“We are increasingly receiving requestsfor special tools and we have to be able to satisfythem. But that is only possible with a machineequipped with software that is easy to use andcapable of producing complete tools. In our opinion,NUMROTOplus‚ is the Rolls Royce of grindingsoftware, and that is exactly what we want forour customers.”In addition to the reliability of the machine, theCNC and the software,Klaus Metzmeier appreciatesthe system’s great flexibility.The programs can beassembled like the tiles in a mosaic, then simulatedfor appraisal. Klaus Metzmeier adds, “What I likemost is the possibility of calculating the entiregrinding operation. Approximations are replacedby exact calculations supplied by the system inrecord time,which allows me to give my customersrealistic information.”Among its customers, Hawema counts Gühring,DaimlerChrysler,HAM,Aescu-lap and many other renownedcompanies specialized ingrinding. Currently, more than250 Hawemat grinding machinesare in use around the world.

Tool Grinding

Facilitate toolsharpening

The Hawemat 2001CNC grinding machine is themost sophisticated of the Hawema 5-axisgrinding machines equipped with a CNC.

Hubert Haller,manager of Hawema:“With its worldbenchmark toolgrinding software,its new Axium PowerCNC and its MBLEaxis drives, Num is theideal partner for me.”

Because of therequirement todetermining theircontour, sharpeningtools accurately is avery complex jobwhich can be evenmore difficult thanthe production ofnew tools.

NUMROTOplus® – Some of its advantages

• A wide range of tools from simple drill bitsto special complex cutters

• Tool manufacture and sharpening• 2D and 3D simulation• Interfaces with the measuring system

and CAD/CAM• Networking• Software, CNC and drive included in

a single unit• Individual training for beginners and

experienced users

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The five-axis headof the Routech-CTCmachining centercontributes to themachine’sproductivity.

Examples of products

Good workmanship patterns

M Modelteks.r.l. is adynamicI t a l i a n

company specializing inwoodworking and lightalloy metalworking formolds.The company was crea-ted in 2002 and rapidlygained a reputationamong mold manu-facturers and thermo-formers through itsknow-how and its capa-bility to satisfy specialrequirements, particu-larly in the area of tyresfor large machinery(earthworking machi-nery and agriculturalimplements).Among itscustomers it countsrenowned Italian manu-facturers.

From Designto Machining“Because of our expe-rience in this field,”begins MassimilianoSalvarani, TechnicalManager, “Modeltekis capable of handlinga complete project.

Sometimes without even knowing exactly howthe final part will look.We make a sketch of thepattern and after a 3D analysis of the machiningprocess simulated by CAD, we produce apreproduction run with the different phases ofadjustment, assembly and testing of molds andmasks, supplemented by cutting programs forfinished plastics.”The patterns can have geometries with simpleor complex contours, up to maximum dimensionsof 4000 x 1360 x 1300 mm.The design and manufacture of the part surfacerequire many hours of study, programming andcutting, since a certain degree of smoothnessand precision are required for the pressurethermoforming process.The plastic film is heatedand adheres to the mold by a combination ofcompressed air pressure and vacuum, allowingdeep recesses and cavities to be made.A latest generation Routech-CTC machiningcenter is used to make the patterns as it can

handle different types of materials, such as woodand aluminum. An impressive productivity isobtained on this machining center, with highinstalled power and a strong mechanical structurecombined with precise movement on five inter-polated axes with a high dynamic range.“Because of its simplified programming usingmachining cycles, the Num Power 1050 contri-butes to optimizing the work of the peopleresponsible for designing and making thepatterns,” continues Massimiliano Salvarani.“The digital technology of the CNC-feedbacksystem also allows us to achieve relatively highmachining precision.”

Maximum Collaboration“The qualities of the Num Drive CNC andfeedback systems,” explains MassimilianoSalvarani, “proved to be essential for makingcertain patterns, as the complexity of the profilesand machining difficulties were reduced by thisHMI adapted to our job.Because of its architecture and the high perfor-mance of the drives (axes and spindles), theNum Power 1050 system is a very flexiblesophisticated instrument for us mold makers,as we machine all sorts of patterns, using bothby external CAD and onboard programming.“Integration of the PC panel in the CNCincreased the system’s potential by providingan HMI configurable for any application, thepossibility of communicating with the mostwidely used graphic programs, compatibilitywith the most common operating systems andconnection to the most widespread networks.“So you see,” concludes Massimiliano Salvarani,“these strong points of Num give us all theguarantees we need to meet the expectations ofour customers and prevail over increasinglyfierce competition.”

An new Italian company has selected Num’s numerical control technology formachining its thermoforming patterns.

Thermoforming

The qualities of theNum Drive CNC and

feedback systemsproved to be essential

for making certainpatterns, as the

complexity of theprofiles and machining

difficulties werereduced by this HMIadapted to our job.

num information No 4010

APPLICATION

W hen you start looking into gears, youcannot fail to be impressed by theirdiversity and complexity. First youneed to choose the geometry according

to the required transmission characteristics, thento use mathematical formulas to calculate themechanical specifications of the parts, based onthe feed rate, torque, material, etc. For instance,a helical gear train with parallel axes provides agradual meshing with a large number of teethin contact, giving a continuous drive with a smooth,quiet transmission. If, in addition to having helicalteeth, the gear and pinion are tapered instead ofcylindrical, then you have a spiral bevel gear (seephoto) or even hypoid gear if the axes of the gearand pinion are not in line.So, if designing a gear is job for specialists, whatabout manufacturing them?

A Special Trade!Gear cutting machines are so special that whenRenault Véhicules Industriels planned to re-engineertwo Oerlikon S30 gear shapers (4 digital axes and6 measured axes for positioning the cutter and

A job-oriented approachmakes all the difference !Experience reduces risk. This was especially true when it involved putting a finger in a pie and that piewas a spiral bevel gear! That is what Num and Arielec did when re-engineering gear cutting machines at RVI.

workpiece spindles), replacement of the CNC wasa real problem. How could they retain functionsspecially developed for machining hypoid gearsand essential for guaranteeing the same level ofservice as before, while at the same time increasingcutting speeds?These machines used dedicated gear cutting CNCsdesigned exclusively by their OEMs, but thesemanufactures had ceased trading years ago.Therewas practically no documentation on themachines; in other words, what they did was wellknown but how they did it was a mystery.Replacement of this “black box” and the axis driveson these machines was a real challenge.That iswhy Renault VI decided to rely on the know-howof Arielec and Num, and to contract the entirere-engineering to them.“The first step in the process was to make an

analysis of the old drivechain in order to modifycertain mechanicalratios and yet staycompatible with theoriginal design concept.”explained Denis Castangfrom Num, with thehelp of Jean Merlin andPhilippe Ollier fromRenault VI and MarcelBastide from Arielec.On this level, Num’sexperience with gearcutting proved veryuseful, because from anexisting base, it allowedNum to tailor the CNCexactly to the needs ofRenault VI with Numdigital reference feedbacksystems whose torquecapabilities are especiallywell suited to ensuringthe mechanical stabilityneeded to guarantee thequality of machining.Four functions werespecially developed for

this manufacturer. They were designed usingdynamic operators in C. The first function canautomatically calculate the synchronizationcoefficients between the workpiece spindle, thecutter spindle and the Y axis, which greatlysimplifies the operator’s job.

Spiral Bevel Gears

Oerlikon S30 machine

11num information No 40

The second function consists of programmingthe cutting pass with different start and end feedrates. By moving an axis this way, chip removalis improved and machining generally proceedsunder better conditions.The third function, switching the cutter spindleto become an axis or a spindle (change to C axis)allows accurate reworking and several passes ona given tooth.Finally, the fourth function developed is animportant enhancement over what existed before:emergency retraction of the tool in synchronizationwith the workpiece, even in the case of a powerfailure.This is achieved by intelligently managingthe available dying resources between the axesso as to allow hob retraction without breakage.Hobs are very expensive tools and any safety systemthat preserves them is a major asset.One more advantage: the openness of the AxiumPower system made it possible to give the HMIthe same look and feel as the original one. Hereagain, this is advantageous for the user, who can

resume production as though nothinghad changed… well, almost, exceptfor the huge gains in productivity!

Speed Doubled!!The new CNC associated withNum HP Drives and Num Drivemotors really boosted the performanceof these two machines.The spindle speedis now nearly 250 rpm, up from around130 rpm,which has real advantages for productivity;in addition, it was possible to preserve the manygear cutting tools designed over the years to meetspecial needs!In conclusion, it is often possible to re-engineera machine, even a very complex one that is old andrelatively undocumented, subject to choosing anopen, high performance system and a CNC manu-facturer with the expertise necessary to understandthe application, plus the special know-how of thecustomer and the OEM.

Hypoid gearsWhat is a bevel gear pair?There are two types:

Spiral bevel gear Hypoid gear

In the case of a spiral bevel gear, the gear axis is aligned with the pinion axis and the pinion andgear have the same helix angle. In hypoid gears, the pinion axis is offset from the gear axis. Thepinion and gear have different helix angles and the pinion angle increases with the offset.All the gear pairs made by RVI are hypoid because the offset increases the load capacity and thisdesign allows a larger pinion diameter for a minimum gear diameter. That is one of the reasons RVIgear pairs are smaller than those of the competitors.

The teeth can have two types of profile: As a general rule, the gear pairs manufactured by RVI have ungenerated teeth. The gear toothprofile is straight (formate) and the pinion tooth profile is curved. (the gear cutting time is shor-ter when the teeth are ungenerated).

Gear cutting is carried out in two modes:- Continuous division (Oerlikon)All the teeth are machined simultaneously, the tooth edge is epicycloidal and cannot bereground.- Intermittent division (Gleason)The teeth are cut in succession, the tooth edge is an arc that can be reground.RVI gears are cut by continuous division as this technique is more capable of withstanding ben-ding stresses because of the tooth shape, allowing a more stable bearing surface under load.

P. Ollier of RVI

Spiral bevel gear

PINION

GEAR

PINION

GEARUNGENERATED TEETH(FORMATE GEAR)

GENERATED TEETH

GearPinion

Published by Num SAImmeuble “Les Courlis”46 avenue Kléber92700 ColombesTel.: +33 (0)1 34 23 66 66Fax: +33 (0)1 34 23 65 49www.schneider-num.comUnited StatesNum Corporation (USA)603 East Diehl Road,Suite 115,Naperville, IL 60563Tel.: +1 630/505-7722Fax: +1 630/505-7754sales@num-usa.comwww.num-usa.comUnited KingdomNum (UK) LtdUnit 43 & 44, CentenaryBusiness Centre,Hammond CloseNuneaton CV11 6RYTel.: +44 (0)2476 387306Fax: +44 (0)2476 387316sales@schneider-num.co.ukwww.schneider-num.co.ukEditor: Laurence PetitguyotRealized by: AVANAOrléans (France)33 2 38 77 88 88ISSN 0248-73061st quarter 2004

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