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FROM LATHES TO LASERSThe last quarter century has seen extensive changes to the way that wemake our products. New materials, new production processes and theadvent of computer technology and robotics have all added grist to themill of manufacturing. Ray Billingham of the Process EngineeringDepartment of Lucas Engineering and Systems Ltd charts a coursefrom lathes to lasers.

The methods used to shape andprocess materials are normallysubject to on-going development,which widens their application

and improves their performance or costeffectiveness. Whilst this traditional'evolutionary' progress in the technologyhas continued over the last 25 years(with some noteworthy developments tobe discussed later), the attention of mostmanufacturing businesses over the lastdecade has been focused on the'revolutionary' approach to themethodology of manufacturing.

It was realised in the early 1980s thata step change in manufacturingperformance was required, and that thiscould not be achieved solely byimprovements and innovations inprocess technology. A strategy builtlargely around the enabling technologyof the computer, but with the initial aimof simplifying and restructuring shopfloor systems, was necessary to providefor the integration of all the previouslyindependent manufacturing activities.Such an approach was necessitated byboth severe competition and changingmarkets which were now demandinghigh variety, small batch volumeproducts of high quality, often madefrom non-traditional materials at muchlower costs. This is in stark contrast tothe market demands, for which manymanufacturing systems were originallydesigned, in the 1960s and 1970s, whenthe call was for high volume, low varietyand medium quality.

The role of process engineering inachieving this step change improvementin manufacturing, continues to be thedevelopment of machine systems whichintroduce flexibility, automation, controland reliability into existing processes. Itis also of paramount importance that anynew process should incorporate the latterprinciples as early as possible.

Processing technology trendsLucas Industries is a company with

manufacturing operations in theautomotive, aerospace and industrialequipment sectors. A few years ago,working groups with representativesfrom all these sectors producedtechnology forecasts for both materialsand manufacturing processes, with theobjective of identifying the most probablemajor developments over a ten yearperiod. Table 1 highlights the processingtechnologies which were seen as offeringmajor opportunities. Many of theseprocesses have been actively pursuedand some have been introduced intoproduction. In the following sections,some of the developments are reviewedin more detail, highlighting advanceswhich are seen as offering majorpotential for improving thecompetitiveness of manufacturing.

Advances in processing technologiesShaping operations

Cutting and Grinding - Cuttingmethods will continue to progress, usingcomputerised control systems, anddevelopments in tool materials andcoatings have permitted increasedcutting speeds and feeds to be appliedwith ever increasing tool life.

Developments in grinding operationsare seen as of major importance, with thepotential to replace other cuttingoperations. The main reasons for theemergence of grinding as a primary metalremoved method are the improvementsin grinding wheel quality, coupled withthe ability to change and dress wheelsautomatically, the evolution of CNC andadaptive control and the improvedmachine structures now available. Creepfeed grinding (CFG) is worthy of mentionin the above context. CFG is a slow-feedsurface grinding technique which usesfull depths of cut to achieve high metal

removal rates. Depths of cut varybetween lmm and 40mm and feed ratesof 0.1-1 mm/min are used. The machinetools employed are similar to aconventional surface grinder, but whenthe operation requires large amounts ofstock removal, the machines are severaltimes greater in size and performancethan a conventional grinder. The processis both a stock removal and finishingtechnique, competing directly withmilling and broaching by eliminatingoperations from the manufacturingcycle. CFG can do this by:• Eliminating intermediate annealing

stages required on fine tolerancedcomponents which would have beenmilled or broached.

• Grinding components to full form inone pass, which previously wouldhave required two or three grindingoperations.

• Finished through hardenedcomponents to form in the hardcondition, thereby eliminatingvirtually all the previously requiredsoft stage cutting operations.Recent development work on CFG with

unhardened nitralloy steel has shownthat coolant application needs to beoptimised for the process to workeffectively but that considerableimprovements are possible eg:Manpower productivity increased by 345%Machine productivity increased by 168%Cost savings on wheel usage of 50%Non-contact metal removal - Themethod of metal removal involvingelectro-chemical and electro-dischargetechniques, although used extensivelyfor tool-making for a number of years, isprogressively being improved by bettercontrol systems, sensors, robotics, andthe like, and by hybrid machinedevelopments. Electro-chemical arcmachining (ECAM) combines theprinciples of ECM and EDM to give faster

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The forebear of today's high technology CNC lathes looks clumsy by comparison (left), while gear testing (right) has come a long way, too.(Pictures by kind permission of Machinery)

removal rates, smoother surfaces and apotential for long hole drilling. CNC lasercutting machines are now availablewhich involve minimal tooling costs andare ideally suited for low volume batchwork.

Cold forming- Mechanical pressesavailable now are capable of up to 2000strokes per minute, compared with atypical rate of 50 strokes/min 25 yearsago, but require high volume productionto take advantage of the increased speedof operation. Hydraulic presses ofimproved design and with CNC controloffer an ideal flexible machine tool forpresswork.

Opportunities exist to support coldforming techniques by the developmentof computer-based modelling systems, toencapsulate specialist knowledge andtheoretical considerations. Such expertor knowledge-based systems couldultimately enable the process design fornear-net-shape complex forms to becarried out by designers, who have anunderstanding of deformation mechanicsbut little metalforming experience.However, the development of theseknowledge-based systems is only likelyby high investment, collaborative, long-term programmes and would requireconsiderable computing power.

Casting- Casting processes aimed atimproved dimensional control, reducedmachining requirements andconsistently good quality have emergedduring the last decade. One examplewhich is receiving much interest atpresent is Thixoforming; semi-solidmetal forming. This is a hybrid betweencasting and forging in which semi-solidalloys with the stiffness of butter can beformed in complex die cavities, under lowpressure, in a single operation and attemperatures substantially lower than

used for casting. The process offers highquality near-net-shape parts withimproved properties and few defects.Manufacturing advantages include thehigh level of automation that can beapplied to the material handling, heatingand forming operations.

The key to the technology, which wasdiscovered at the MassachusettsInstitute of Technology in the early1970s, is the production of a startingmaterial which has a unique, fine,non-dendritic structure and is in asuitable form for re-heating. Althoughseveral routes are available for suchmaterial, the first to achieve commercialapplication is the magnetohydrodynamic(MHD) casting system developed byAlumax Inc in the USA (1). The MHDtechniques provides a non-contactmethod of controlling the structure of thealloy during the solidification process.Current applications are predominantlyusing aluminium alloys to produceautomotive wheels and brakingcomponents in the USA and WestGermany. The technology can be appliedto a wide range of commercial alloys andalso offers an excellent route for formingmetal matrix composites to near-net-shape components. Thixoformingdevelopment in the UK is being led by theUniversity of Sheffield (2).

Powder metallurgy - Althoughmainly applicable to high volumeproduction because of the tooling costs,powder metallurgy probably offers themost precise, high quality metal formingprocess. Improvements in powder qualityand methods of compaction haveextended the application to more criticalcomponents and to tooling. For example,techniques such as hot isostatic pressinghave made it possible to remove theweakening effects of porosity, and

achieve almost theoretical density inpowder metallurgy components.

Plastics processing- Polymer matrixcomposites (PMC's) are often dividedinto two categories: reinforcedplastics and advanced composites.Although there is no clear-cut lineseparating the two, the distinction isusually based on the level of mechanicalproperties. Advanced composites will bediscussed further on.

Reinforced plastics have been in usefor 30-40 years in applications such asboat hulls, automotive panels andsporting goods, using relativelyinexpensive low-stiffness glass fibres inpolyester resin matrices. The area ofapplication has been considerablywidened by the Reinforced ReactionInjection Moulding (RRIM) process. Inthe RRIM process, two liquid componentsmixed with the reinforcing fillers arechemically reacted in the mould toproduce a solid thermoset type polymer.Compared with conventional injectionmoulding techniques, this is a lowpressure, low energy alternative withpotentially reduced cost for productssuch as car lamp reflectors and fasciapanels.

Developments of the structural foammoulding process by Cinpress Ltd hasresulted in the elimination of sink marksand much lower moulded-in stress,resulting in mouldings which are moredimensionally stable and free fromdistortion.

The process is operated by theinjection of gas into the flow of plastic asit enters the mould to form continuoushollow channels within the moulding,assisting the transfer of pressure fromthe point of feed to the extremities of themoulding. More design freedom results,enabling mouldings with different wall

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Today, high tech wizardry is the name of the game,such as this laser cutter from Rhodes Pierce-All Ltd

thicknesses to be adjacent to each other,and webs and bosses to be producedwithout surface sink marks.

ProcessesFabrication - Laser technology is seen

as a growth area because, in addition towelding, it offers other process optionssuch as cutting and surface treatments.Laser equipment can be accuratelycontrolled and readily automated. It ishowever, relatively expensive, comparedwith conventional welding equipmentand applications require carefulconsideration to obtain high utilisationby taking advantage of the versatilityand multi-station working ability.

Adhesive joining technology is arapidly developing field, with thepotential to replace many existingfastening methods and it provides anexcellent example of product-processinteraction. Sales of engineeringadhesives are showing an annual growthrate of 5-10% in the UK. There has been afailure to recognise that the adhesivealone is not enough and that designersand engineers need to ensure that thejoint design, surface preparation,dispensing technology, curing processetc are optimised to ensure consistentjoint quality. Development of computer-

based knowledge systems are again seenas an important aid to the successfulselection and application of adhesivesand Lucas Engineering has produced anexpert system (3), which will eventuallybe marketed.

Adhesives offer a number of verypositive advantages:• Greater load bearing capacity results

from a larger bond area• The bonding of totally dissimilar

materials is possible• The joint is usually more aesthetically

pleasing; localised distortion andburning which may occur withwelding are avoided •

• Reduced local damage maysubsequently result in less corrosion

• An adhesively bonded structure isoften stiffer than a similar weldedstructure

• A change to adhesive bondingfrequently results in a reduction invibration and noise (in vehiclestructures)

• Some adhesives can also act assealants against fluids by gap filling

• Adhesive bonding can be a more costeffective process than manytraditionally used joining techniques.Heat treatment — With few

exceptions, heat treatment processes areseparated from the main manufacturingarea, because they usually involve longcycle times, large batch working andoften heat and smoke. Although thispattern is likely to continue in manyinstallations, with new and re-locatedoperations, careful attention to material,process and equipment selection maymake it possible to integrate heattreatment more successfully into themanufacturing flow line - for example,through the use of medium carbon steels,selectively hardened by a short cycle,single shot induction heating process.

Plasma processes for nitriding andcarburising continue to find applicationswhere improved fatigue resistance,control of the surface properties andpenetration into deep holes and recessesis required. They also have theadvantages of reduced cycle times andimproved environmental conditions.

Surface engineering- This iscurrently a high technology growth areain the UK, mainly because it providesopportunities to design the surface of acomponent or product to meet operatingneeds, usually without the need tochange the material or properties of thebulk product. A wide range of processesare covered under this genericgroup: physical and chemical

vapour deposition techniques; ionimplantation; spraying and painting;electrolytic and electroless plating. Apartfrom the engineering applications toprovide enhanced corrosion, wear andscratch resistance and so forth, muchpotential exists for thin films in a widerange of material compositions forelectronic devices.

Assembly - Much can be done to easeassembly, and indeed manufacturingcomplexity and problems, by the use ofDesign-for-Assembly and Design-for-Manufacture systems (4) (the IBM desktop Pro printer provides a classic exampleof the power of these techniques inachieving product improvement and costsaving). It has been demonstrated byLucas workshops that the use of thesetechniques can yield reduction in partcounts of 33-45%, and an averageassembly cost reduction of 44%.

It is now recognised that, to remaincompetitive, most major manufacturingbusinesses need to integrate automaticassembly into their manufacturingsystems. In many companies the use of asingle system dedicated to one producttype is not cost effective. In order toobtain the flexibility required for largeproduct families and small batch sizes itis necessary to undertake extensivein-house development of assemblysystems, making use of standardequipment, such as computers, robots,vision and transport systems, whereverpossible. The effectiveness of suchsystems is highly dependent on thequality and consistency of the piecesbeing assembled, placing an additionaldemand on downstream processes.

General developments in processengineering

There are a number of areas whereconsiderable advances have taken placewhich will have an impact on processengineering to improve efficiency,flexibility and quality of manymanufacturing operations,i) Materials handling and partsidentification:• Transportation of materials and parts

between manufacturing cellsinvolving container technology andflexible routing systems.

• Robotic handling for loading/unloading process equipment,assembly and test cells.

• Automated identification ofcomponents and products, egbarcoding, to provide completetraceability through themanufacturing route.

MANUFACTURING ENGINEER JULY/AUGUST 1990

SILVER JUBILEEii) Equipment control and processsensors:• Use of programmable control systems

for machine tools and processequipment.

• Component geometry monitoring withadaptive control by CNC.

• Performance monitoring to providefault diagnostics.

iii) Quality Engineering Methods:• Statistical process control.• Failure modes and effects analysis.• Process capability assessment.• Process optimisation using techniques

such as those developed by Taguchiand Shainin.

• Poka Yoke, or foolproofing devices.• Quality Function Deployment,iv) Databases:• On-line computer databases to aid

selection of equipment, process andmaterials.

v) Tool Management:• Standardisation and rationalisation of

tool geometries and materials.

Advanced Composite MaterialsAlthough not strictly under the remit

of this article, it is not possible to omitreference to advanced compositematerials because of inevitableconsequences on processingtechnologies.

Remarkable advances in structuralmaterials technologies have taken placeduring the past 25 years. New compositematerials offer superior properties - suchas high temperature strength, highstiffness and light weight - comparedwith traditional metals such as steel andaluminium. The additional feature ofsuch materials is that they can be tailoredto have the properties required by a givenapplication. Use of such application-designed materials can lead to higherfuel efficiencies, lower assembly costsand longer service life for manymanufactured goods.

Composites consist of fibres orparticles of one material held together bya matrix of second material. They areclassified according to their matrixphase; ceramic matrix composites(CMC's), polymer matrix composites(PMC's) and metal matrix composites(MMC's). The level of maturity of thethree groups differ greatly; PMC's are byfar the most developed, whereas CMC'sare still in their infancy and MMC's, witha few exceptions, remain primarily ofmilitary interest. Production of advancedPMC's in the USA is projected to grow by15% annually for the remainder of thecentury, increasing from £820 million to

nearly £7 billion by the year 2000.Current production in the USA shows thefollowing pattern:Aerospace -50%Sporting Goods - 25%Automobiles &Industrial Equipment - 25%

Advanced PMC's currently comprise3-6% of the structural weight of thecommercial aircraft such as the Boeing757, the fraction could eventuallyincrease to 65% plus in new transportdesigns.

Experimental MMC's have beendeveloped for use in aircraft, missiles andthe NASA space shuttle. The mostsignificant commercial application ofMMC's to date is an aluminium dieselengine piston produced (300 000annually) by Toyota, which is locallyreinforced with silicon carbide fibres,allowing increased combustiontemperatures. This latter development issignificant, as it suggests that MMC's canbe reliably mass-produced to becompetitive in a very cost-sensitiveapplication.

Advanced composite materials maycost as much as 100 times more thansteel and aluminium on a unit weightbasis, therefore their first use hasgenerally been in the less cost-sensitiveapplications, such as military aerospace.However, because military productionruns are typically small, there is littleincentive to develop low-cost, highproduction rate manufacturingprocesses, which would make thematerials more attractive for commercialapplications such as cars. The lack ofsuch processes is a major barrierpreventing more widespread commercialuse of these materials.

The reinforcing materials alsorepresent a high cost burden oncomposites and it is predicted, forexample, that the current cost of siliconcarbide fibre at£680/kg could fall to£27/kg when production reaches 18 144kg annually.

The two key goals of processtechnology should be: To support thedevelopment of new manufacturingmethods where the capital equipmentand labour cost burdens are compatiblewith commercial applications ofcomposites; To ensure the processes arecapable of producing large numbers ofcomponents to closer specification limits.

Additional factors related toincreasing the commercialisation ofadvanced composites are centred aroundthe tailoring of the material to suit theapplication. This necessitates a closer

relationship between researchers,designers, manufacturing engineers andproduction personnel as well as newapproaches to material costs.

ConclusionsAlthough the major performance

improvements in manufacturingcontinue to come from the application ofa total systems engineering approach,using computer technology asappropriate, certain evolutionarychanges in metal shaping and processinghave been indentified as ready forexploitation eg; grinding, lasers, semi-solid forming adhesives, surfaceengineering and assembly.

Manufacturing equipment and controlsystem developments are seen to belargely compatible with increasedproduct variety and reduced batch sizes.Processes traditionally associated withlarge batch processes eg; heat treatment,require special attention.

Design for manufacture and assemblyis of critical importance and a closercollaboration (simultaneousengineering) between designers andmanufacturing engineers is necessary.

There are many areas of processtechnology which may still be regardedas a black art, and a start is now beingmade to encapsulate the experience ofmany specialists into knowledge basedand expert computer systems to ensure acontinuity within industry.

Advanced composite materials are ripefor commercialisation, but require anintegrated design and manufactureapproach, to ensure that materials aretailored to applications. New low cost,high production rate, reproduciblemanufacturing methods are the goal. 133

References1. Semi-solid Metal Casing and Forging MP Kennedy et al. Metals Handbook, Vol15,9th Ed.2. How to become perfectly formed. TheEngineer, 6th July 1989.3. Choosing the Right Adhesive - Review.Assembly Automation, November 1989.4. Design for Assembly - a key elementwithin Design for Manufacture. B LMiles. Proceedings Institution ofMechanical Engineers, Vol 203,1989.

AcknowledgementsThe author wishes to thank the

Directors of Lucas Engineering &Systems Limited for permission topublish this article and colleagues in theProcess Engineering Department for theircontributions to its preparation.

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