Parallel Kinematic Machine Tools – Current State and Future Potentials

M. Weck (1), D. StaimerLaboratory for Machine Tools and Production Engineering, Chair for Machine Tools

Aachen University of Technology, Aachen, Germany

AbstractParallel kinematics have recently attracted attention as machine tools because of their conceptualpotentials in high motion dynamics and accuracy combined with high structural rigidity due to their closedkinematic loops. This paper, prepared with input from CIRP colleagues as well as of machinemanufacturers and end-users involved in PKM, attempts to review the development of parallel kinematicsfor machine tools, their practical application and their performance compared to classical machine tools.

Keywords:Manufacturing Equipment, Parallel Machines, Performance

1 INTRODUCTIONParallel mechanisms, well established as handling andpositioning devices, have recently attracted attention asmachine tools because of their conceptual potentials inhigh motion dynamics and accuracy combined with highstructural rigidity due to their closed kinematic loops.Starting with the public presentation of the first parallelkinematic machines (PKM) on the IMTS fair in 1994,extensive research has been conducted both in univer-sity laboratories as well as in machine tool industry.During the last decade, more than 200 different parallelmechanisms, mostly as prototypes or academic studies,have been build [1].In spite of this high interest and research efforts, themarket response to PKM was quite poor and mostmachines have been evaluated in university laboratoriesrather than in a production environment [2]. In addition,there are highly antagonistic opinions about PKM tech-nology; the concept is claimed to be inferior to serialmachines and practically not useful [3] on the one handbut called the innovation focus on the Metav fair 2000 [4]on the other hand. This paper attempts to review thedevelopment of machine tools based on parallel kine-matics and their characteristics compared to classicalmachine tools.

2 BACKGROUNDParallel mechanisms are studied since around 1800 bymathematicians, e.g. Cauchy, since they provide inter-esting mathematical problems, e.g. the singularity analy-sis. More recently, Gough [5] and Stewart [6] used“hexapod” type parallel mechanisms for tire testing andas actuated flight-simulator, Figure 1. Even in the 60’s,the application of such structures as machine tools hasbeen discussed but rejected due to the lacking controltechnology. Parallel structures have been re-discoveredin the 80's in the robotics community. The most populardesigns are the Delta robot [7] and the Tricept [8]. Bothstructures have been commercialised and can be foundin different industrial applications [9].The first prototypes of parallel machine tools have beenintroduced to public at the IMTS show 1994 Chicago.The machines were intended for complex 5-axis millingoperations and were realised as Gough-platform [5].Within the following years, many new prototypes formilling and other processes have been developed inindustry and research institutes, often mainly intended tostudy the fundamentals of this new technology ratherthan as market products. In addition, a large number ofpatents related to PKM has been applied [10].

2002‘60

Industrial Parallel Robots

‘50 200019941985

Industrial Parallel Machine Tools

Gough’s Tire Tester Delta Robot Variax Z3-Sprint

Figure 1: History of PKM as production systems.

Nowadays, PKM are entering the commercial marketand are already established in niche applications. Thus,the implementation activities are now mainly carried outby machine manufacturers in collaboration with researchinstitutes.

3 CLASSIFICATION OF PKM“A parallel manipulator is a closed-loop mechanism inwhich the end-effector is connected to the base by atleast two independent kinematic chains. A fully-parallelmanipulator is a closed-loop mechanism with an ndegree of freedom end-effector connected to the base byn independent chains which have at most two links andare actuated by a unique prismatic or rotary actuator”[11].Combinations of fully parallel mechanisms and additionalserial axis are often referred as hybrid systems. Withrespect to this definition, a close to infinite number ofmechanisms with parallel structure can be synthesised.

Combination of basic elements

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Figure 2: Design Methology for PKM [12].

A systematic methodology for the design of PKM topolo-gies as proposed in [12] is illustrated in Figure 2. Thebasic idea is to subdivide the mechanism into simplefunctional units. The kinematic substructures for thegeneration of the platform joint movements are chosenfrom a list of predefined solutions. A valid combination ofthese basic elements as well as the number of drives isthen enumerated with respect to the required DOF of the

end-effector. The geometric configuration of the jointconnections is finally chosen from a list of pre-existingsolutions.Many different topologies of PKM have recently beenstudied in detail [11, 13, 14]. A widely used classification[15] subdivides them into planar and spatial mechanismsand classifies by the degree of freedom (DOF) of theend-effector and the actuator and joint arrangement. Theterminology is illustrated in Figure 3 for the well knownGough platform, a fully parallel mechanism introduced inthe 50’s as tire testing machine, Figure 1. The end-effector is connected by six kinematic chains to the base,where each chain consists of a universal-joint (RR), adriven prismatic joint (P) and a spherical joint (S) at themoving platform. Thus, the kinematic structure isdenoted as 6-DOF 6-(RR)PS.

Planar/Spatial

DOF

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(c)

RR

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S

6 DOF, 6-(RR)PSGough Platform

Figure 3: Terminology for classification [15].The same end-effector movement can also be realisedwith legs of constant length but actuated footpoints, e.g.the Hexaglide [16], Figure 4 (c), as 6-DOF 6-PRRS orthe Hexa robot [17], Figure 4 (d), actuated by rotarydrives. By grouping the individual chains into pairs with acommon drive, three DOF can be locked which results inmechanisms with 3 DOF of the end-effector, e.g. theDelta robot [7], Figure 4 (a) or the Linear Delta designs,Figure 4 (b).

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6 DOF, 6-P(RR)SHexaglide

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(c) (d)

Figure 4: Classification of PKM key designs.It has to be noted, that often used terms as “hexapod”and “tripod” are less precise to characterise a parallelstructure since they do not give any information aboutthe kinematic topology and the realised motions.

4 STATE OF THE ART

4.1 Realised PKMWithin the recent years, many PKM for milling and otherprocesses have been realised. Table 1 in the annex givean overview about realised machines and their specifi-cations according to a questionnaire sent to researchinstitutes and companies involved in PKM technology.The majority of these machines is intended for millingprocesses either as 3-axis or 5-axis systems. Morerecently, also other processes such as riveting, formingand turning are established with PKM.

Milling 3-axisMotivated by physical and commercial limits of conven-tional serial machining centers (MC’s), different machinetool manufacturers are currently investigating the capa-bilities of PKM as kinematic structure for high speed 3-axis machining centers.The Specht Xperimental [18], Figure 5, is a hybridsystem where the x-y movements are realised by aparallel scissors architecture whereas the z-axis islocated in the table. The kinematic concept enables areduced machine width of less than 1500 mm for a x-travel of 630 mm. The machine is equipped with lineardirect drives for the scissors kinematic which enables avelocity of the TCP of 120 m/min and an acceleration of15 m/s2. The machine is currently investigated by a pilotcustomer.

Figure 5: Specht Xperimental MC (Source: Cross Hüller).

A different kinematic approach is realised in theSKM 400 [19]. The machine is realised as a fully parallelsystem based on three extensible legs which are linkedby universal joints both at the platform and the machineframe. The spindle carrier is supported by an additionalpassive chain, to lock the rotational d.o.f., Figure 6.Thus, the machine is free of linear guidings and tele-scopic guiding guards.The machine is characterised by a good relationbetween workspace and required floorspace which isclaimed to be similar to conventional machines. Theprototype machine has been presented on different fairs.Pilot customers will test the machine within the course of2002 [19].

Figure 6: SKM 400 3-axis parallel MC [19].

Milling 5-axisMany machine concepts based on parallel kinematicshave been realised for 5-axis machining. While in thepast fully parallel concepts have been dominant, a trendtowards hybrid solutions can be observed.The Ecospeed [20] by DS-Technology is intended for themanufacturing of structural aeronautic parts in aluminumalloys. The machine is realised as a hybrid system wherethe rotary tool axes and the z-movement are realised asa fully parallel structure which is carried by serial x- andy-axis as cross-slide, Figure 7 .

y

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B

Workspace X = 4m - 30 m Y = 1000 - 2000 mm Z = 650 mm

Spindle Tilt Amax = +/- 40° Bmax = +/- 40°

Max. Velocity/Acceleration vmax = 50 m/min amax = 10 m/s2

wmax = 15 U/min amax = 12 1/s2

Spindle 75 kW 24000 rpm

Figure 7: Ecospeed: Fully parallel head for A-, B- and z-movements in serial x- and y-axis [20].

The parallel kinematic swivel head can be handled as amodule, thus enabling the machine manufacturer toscale the x- and y-axis travel according the workpiecerequirements, e.g. small y-travel and long x-travel foraircraft stringers. Additional information about the

machine and application are given in section 5. A similarconcept Hermes, also intended for the machining ofaerospace monolithic parts has been exhibited on the2002 BIEMH fair in Spain by Fatronik [21].

Figure 8: Dynapod for the machining of large moulds anddies [22].

The idea of combining serial axis for large travels withparallel kinematics for the rotary axis has also beenimplemented by the company Mikromat within theGerman research project ACCOMAT. The Dynapod,Figure 8, consists of a gantry design for the x- and y-movements which carries either a 3-axis or a 6-axis PKMas satellite. The latter concept allows redundant use ofthe x- and y-movements by means of high dynamicmovements of the satellite with overlapping slowermovements of the gantry axis [22].A different target application is established by thecompany Deckel-Maho. The TriCenter is intended asuniversal 5-axis milling machine with special focus onthe tool dexterity. Thus, the rotary axis are realised as aserial fork head. Based on the kinematic of the Tricept[8], the TriCenter is a complete redesign to improve themachine’s rigidity. A pre-series prototype has beenshown on the EMO 2001, Figure 9. The rigidity of themachine has been improved with respect to formerTricept designs to allow high chip removal rates both inaluminum alloys and steel [23].

Figure 9: TriCenter as universal 5-axis MC [9].

Figure 10: Metrom Pentapod [24].

To overcome the orientation limits of classical kinematictopologies, i.e. the classical Gough-platform, the com-pany Metrom recently developed a Pentapod machinewhich is based on five extensible legs carrying the mainspindle, Figure 10.The kinematics have been configured so that in onerotary tool axis inclination angles of 90° are possible. Incoorporation with a rotary table as redundant axis, themachine is capable of full 5-sided machining. A specialcontrol strategy is implemented within the machinecontroller which handles the redundancy of tool andtable movements. Thus, the programming can beperformed in a classical way without constrained toolorientations [24].A mobile machine concept based on PKM has recentlybeen developed at the University of Hannover for thequick repair of large stamping dies. The Dumbomachining unit, based on a parallel kinematic with addi-tional serial head, can be brought to the press withouttaking the die out for the repair work, Figure 11. Themachine is currently investigated under practical dierepair conditions within a German research project [25].

Figure 11: Mobile milling machine for die repair [25].

Non-Milling ProcessesRecent PKM developments also focus on other proc-esses than milling, e.g. turning, riveting, forming as wellas wood machining.The company Index developed a vertical turningmachine V100 based on linear delta kinematics. Themachine combines workpiece handling and manufactur-ing task, thus reducing the nonproductive time. Moredetails about the machine as well as its application aregiven in section 5.For additional non-milling application, it is referred to thereferences. [26] describes the development of a 5-axismachine for woodworking application. Main target arecost benefits caused by the fact, that all slides of thekinematic use the same secondary drive of the linearmotor. In [21], the application of parallel end-effectormodules for automated drilling and riveting operations inaerospace manufacturing is addressed. They areconsidered as compact modules easy to be adopted intoscalable travelling columns with fast assembly andreadapting capabilities. [27] describes the developmentof a parallel structure for flexible bending application asbasic development tool for part and process research.

4.2 Conceptual advantages and drawbacks of PKMThe conceptual capabilities of PKM are discussed in [2,3, 28, 29]. Figure 12 summarises often mentioned bene-fits and drawbacks. It has to be remarked, that some ofthese conceptual characteristics are only valid forparticular topologies of PKM.Within the following section, we attempt to review, inwhich way these conceptual capabilities affect theperformance of machines and which technologies areeither available or needed to be investigated to imple-ment conceptual benefits and avoid drawbacks.

Simple frame design

High stiffness due to closedkinematic loops

Use of repetition parts

Traction-compressionstress in the links

High dynamic due to lowmoving mass

Modular design

More complex control

Limited dexterity

Poor ratio of system sizeto workspace

Very susceptible to thermal load

Performance is pose dependant

DrawbacksBenefits

Complex Key-Components

Linear drives used forrotary movements

Figure 12: Conceptual advantages and drawbacks ofPKM.

4.3 PKM characteristics

DesignPKM are characterised by their non-linear transmissionof movements and forces from joint- to task-space.These transmission characteristics are influenced by thekinematic topology of the mechanism and its geometricconfiguration. Thus, during design the following twosteps are most important [30]: • Choosing the appropriate kinematic topology • Choosing the right geometric dimensionsThe second step is most important since the perform-ance is highly influenced by the geometric dimensions ofa PKM. As example, changing the platform radius of aclassical Gough-platform by 10% may modify the worst-

case stiffness by 700%. Thus, a poor topology but opti-mally designed may perform better than a mechanismwith appropriate topology but poor design.To choose the right dimensions for the design parame-ters with respect to a given application is a difficult task:a) There are many performance values which have to

be taken into account and which are often antago-nistic to the design parameters, i.e. kinematic stiff-ness vs. workspace.

b) There is a nonlinear relation between designparameters and performance.

c) Many performance values are of the type "best case- worst case" over an up to six-dimensional work-space.

Since the performance characteristics vary within aworkspace of complex shape a simple and uniqueperformance comparison of either parallel with serialkinematics or different parallel mechanisms becomesmost difficult. To get an optimal kinematic configurationin a short time, the designer has to be supported bysuitable analysis- and optimisation tools.A classical way of finding the required design parame-ters is to define a cost function as the weighted sum ofthe performance values as function of the design pa-rameters. A numerical procedure is then used to find thedesign parameters which minimise the cost-function withrespect to an initial guess. This strategy is limited duethe definition of the weight factors, e.g. in terms ofpriority [30]. In addition, due to the complexity of theoptimisation problem, no guarantee can be given to findthe global optimum.To avoid these limitations, different approaches areproposed. The parameter space approach [31] estimatesfor each performance requirement all satisfying solutionswithin a multidimensional design-space. The intersec-tions of these individual solutions contain the sets ofdesign parameters which will meet all requirements.Thus, the optimal solution is either chosen by thedesigner intuitively or estimated by the classical cost-function approach.An approach based on pareto-optimal design isproposed in [32]. The idea is to estimate all sets ofdesign parameters with genetic algorithms, where theindividual performance values can only be maximised bya weakening of another performance requirement.Within the resulting sets of pareto-optimal designparameters, the optimal configuration for a given taskcan be chosen.It can be observed, that the development of design toolsfor PKM is still open research. While tools for theperformance analysis are widely established, theestimation of an optimal layout for a given applicationhas to be automated to establish conceptual capabilitiesin terms of modularity and reconfigurability.

Stiffness AspectsThe stiffness of PKM is mainly influenced by thegeometric configuration of the kinematics and thecomponents stiffness.Thus, one design target during geometric configurationhas to be a homogeneous transmission of forces fromjoint to task space as prerequisite for homogenouskinematic stiffness over the workspace. The joints arethe key components of a PKM with respect to stiffness.Their design has to be refined to optimise the antagonis-tic characteristics stiffness and orientation capability andto provide a homogeneous stiffness over the rotationangle, Figure 13.A general statement about the stiffness characteristics ofrecent PKM is not feasible. On the one hand, it has beenproven, that the conceptual advantages of PKM

regarding high stiffness can be implemented into realmachines as illustrated in Figure 14 (B) and (C). On theother hand, geometric configuration as well as the keycomponents are complex but of major importance, thusoffering gaps for inferior performance, i.e. Figure 14 (D).

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Figure 13: Stiffness vs. orientation angle of a joint [33].

When comparing serial kinematik machines (SKM) andPKM regarding stiffness, two points have to be consid-ered. On the one hand, the spindle/holder/tool system isthe most critical element in the compliance chainbetween tool and workpiece [3]. Thus, the inhomo-geneous kinematic stiffness of the manipulator islessened by the serial arrangement of machine andspindle/holder/tool system. On the other hand, anonlinear stiffness over the workspace can also be seenon many serial machines, e.g. in ram configurations,where the stiffness depends on the ram travel or forkheads, where stiffness also depends on the orientationof the rotary axis.

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Figure 14: Measured relative stiffness of different PKMand SKM. All machines are measured with the same

setup between table and a dummy tool. Data is the worstcase stiffness within the workspace with 0° spindle

orientation.(A) 5-axis serial MC for structural aerospace

components, horizontal spindle(B) 5-axis hybrid MC for structural aerospace

components, horizontal spindle(C) 5-axis MC, fully parallel, horizontal spindle(D) 5-axis MC, hybrid kinematic, vertical spindle

In addition to the static stiffness characteristics, thedynamic stiffness is of major importance as prerequisiteof booth high chipload and drive dynamics such asadjustable velocity gain and jerk. Comparing thefrequency response function and modal analysis ofdifferent PKM, it can be observed that in general vibra-

tions of the legs are dominant but with low amplitude andphase shift, thus having low influence on the stability ofthe cutting process. On the other hand, vibrations in thelegs can seriously affect the drive dynamics if they arecoupled to the drive control.

Accuracy AspectsPKM are as accurate as the transformation model in thecontroller describes the actual behaviour of the machine.Similar to serial machines, the accuracy of PKM isaffected by many error sources, which are illustrated inFigure 15. Due to the parallel structure, the errors of theindividual axis are coupled, e.g. a single axis error willcause errors in all DOF of the end-effector. Thus, theerror sources are more complex to separate than inserial machines, where the individual axes are calibratedone by one [34].

Nominal kinematic model:• Joints have one center for

all d.o.f• Joint locations are known• Actuators move with one

d.o.f• Actuators pass exactly

through joint centers• All measurements are

without errors

Errors due to:• Manufacturing and

assembly• Kinematic errors (joints,

actuators)• Deformations by gravity

and inertial forces• Thermal growth• Limited sensor accuracy• Control uncertainty• ...

Com

pens

atio

nC

alib

ratio

n

Figure 15: Error effects in PKM [35].

To achieve the required accuracy, the transformationmodel in the controller has to be fit to the machine’sbehaviour by calibration and compensation. Differentstrategies are used: • Kinematic calibration by means of identifying the

geometric parameters of the machine, i.e. joint loca-tions. In general, indirect strategies are used whichrely on external measurements of the end-effectorpose. The kinematic parameters are then identifiedusing nonlinear optimisation algorithms to minimisethe error between predicted and measured pose. Themeasurements can either be in one DOF, e.g. with adouble-ball-bar [35, 36] or probing [37], in three DOF,e.g. with a laser tracker [19, 38] or double-ball-bartriangulation [39], as well as in six DOF with a specialdevice based on inductive sensors and levelmeters[40].

• Spatial error compensation by means of a threedimensional matrix of measured errors over theworkspace, which are compensated for within thecontroller [19].

• Functional compensation of predictable errors, i.e.sagging due to gravity forces. The leg forces areeither calculated [35] or established by the motorcurrent in the controller [19]. The resulting deforma-tions of the kinematic chains are then compensatedfor.

Within actual prototypes, in general a combination of theabove listed strategies is used. To decrease thermaldeflections, either compensation methods [40] are usedor the affected components are stabilised by cooling[19, 35].For 5-axis PKM, positioning errors in cartesian axis in therange of 10-20µm have been reported [35, 40, 41].Taking into account, that a straight movement in onecartesian axis of a PKM requires a multi-axis interpola-tion, the accuracy of multi-axis motion in cartesian spacecan be assumed to be roughly the same.

The contouring accuracy in multi-axis interpolation (x, y,A, B) of a Ecospeed [20] PKM has been evaluated atcustumer tests. A 5° cone with 175mm diameter hasbeen machined in aluminum at a feed rate of 5m/minwith a roundness of 10µm. Booth surface quality androundness error are better than on conventional serialhead designs according to the custommer.Recent 3-axis PKM achieve positioning errors between10µm and 15µm [18, 19]. In contrast to 5-axis machines,where errors in all DOF can be compensated in thecontroller, these machines need additional mechanicaladjustments to align two rotary movements of the tool.With respect to the requirements of automotive power-train manufacturing as target market, the accuracy ofthese machines still needs further improvement to fulfilthe high acceptance standards [42]. To guarantee a highlevel of machine availability, the customers service andmaintenance practice has to be taken into account. If themachine’s accuracy drops down as a result of a collisionor wear, the customers service staff must be able toeliminate these errors in an efficient manner. Thus, themachine supplier has to provide measuring equipmentand methods for shop-floor recalibration.

Motion ControlPKM are in general programmed in cartesian spacesimilar to conventional machines. The transformationfrom cartesian space to joint space is computed in thecontroller at least each interpolation cycle. In recent PKMin general commercial control systems are used, seeAnnex, Table 1. The specific transformation functions areeither implemented on external processor boards ordirectly within the NC via original equipment manufac-turer (OEM) interfaces. For safe and efficient machineuse, the controller has to make available additionalfunctionality, such as look-ahead function in joint spaceand a monitoring of the workspace limits of themechanism [43, 44] as well as accuracy relatedfunctions as error compensation and a support for thecalibration of the machine [19, 35, 40].The drive control of PKM is usually realised in joint spaceby independent linear axis controllers designed similar toclassical machines as cascaded P/PI controller. It hasbeen observed, that on higher velocities, the trackingerrors increase drastically [44] thus the usable velocityhas to be limited in favour of path accuracy [42]. Theselimitations are induced by the nonlinear behaviour inher-ent with PKM such as variable inertia as well as dynamiccoupling effects of the individual drive axis.For a better exploitation of PKM’s dynamic behaviour,different approaches are investigated. In [45], the limitedresolution of the velocity feedback, calculated by time-discrete differentiation from the actual position feedback,is identified as limiting factor for the control parametersof the Linapod PKM with linear direct drives. Byintegrating acceleration feedback of an additionalFerraris sensor, a velocity feedback of higher quality isderived which enables both higher control parameters aswell as increased tracking bandwidth and disturbancebehaviour.Other approaches incorporate the nonlinear behaviour ofthe parallel mechanism into the control laws, e.g. [37, 45,46]. It is shown in [44], that the tracking errors cangreatly be reduced by applying a model-based controlscheme, that computes the actuator torques for a giventrajectory. The feedback controllers then only need tocorrect unmodelled effects, e.g. friction. The parametersfor the dynamic model can be identified and optimisedonline by the controller with adaptation algorithms. In[46], the active inertia is calculated within the interpola-tion cycle with respect to the actual workspace positionand the velocity gain of the axis controller is adjustedaccordingly. Since the damping of the velocity can be

held constant within the workspace, higher position gainscan be adjusted.Nonlinear control strategies require high computationalefforts for the calculation of the dynamic properties onthe one hand and fast interfaces to the drive controlleron the other hand. Thus, their implementation into com-mercial machine tool controller is still an open issue.

Cost benefitsPKM have the potential of low machine costs due to thereduced mechanical complexity. This statement hasbeen confirmed by machine manufacturers, who aresuccessful with PKM on the market. On the other hand,at present the high costs for PKM specific componentssuch as joints prevent any benefits on the market. Thus,to be competitive on the market, recent PKM must havea higher customer’s value by means of machineperformance. Future improvements with respect to costsare expected by higher production volumes and a higherlevel of components standardisation [47].

5 PKM APPLICATIONS

5.1 AerospaceModern aircraft engineering is characterised by anintegral design which results in most complex compo-nents to be machined from monolithic blanks. The partsare characterised by a high amount of material to beremoved which as a rule is higher than 80%. Approx.80% of the parts in the military aircraft sector are to bemachined in 5-axis mode and it is expected that thistendency will become accepted also within the civilsector.The current bottleneck in 5-axis high speed machining(HSM) is the limited dynamics of the rotary tool axis andthe required compensation movements of the linear axis[20].Against this background, the company DS-Technologiedeveloped a machining system based on a parallelstructure where the rotary tool axes and the z-movementare realised as a fully parallel structure which is carriedby serial x- and y-axis.

Figure 16: Ecospeed PKM for machining complexmonolithic aerospace parts (Source: EADS).

The parallel structure as substitution of a classical fork-or swivel head implements two main advantages. On theone hand, a high swivel rate of the tool of 15 rpm isachieved in all angular positions without compensationmovements in the linear axis of more than 50 m/min. Onthe other hand, a mass reduction of the head of about

50% was achieved compared to conventional swivelhead which enables higher dynamic of the x- and y-axis.The first 2 machines have been handed over to thecustomer in May 2000, currently four machines areproducing in four shifts around the clock, Figure 16.From the customer’s point of view, the investment inPKM technology enables the following enhancementscompared to conventional 5-axis machines [49]: • Reduction of processtime (-42%). • Higher part quality due to better surface. • Improved reliability of the machine • Improved availability of the machine • Improved flexibility compared to conventional multi-

spindle systemsFrom the machine tool manufacturer’s point of view, thePKM technology offers the following advantages [20]: • Lower complexity of the head design compared to

swivel or fork heads. A weak point of these conven-tional concepts are the media supplies to the spindlewhich have to be realised through the rotary axis viaslip rings and transmission couplings which aresusceptible to failure. The media supply on theparallel head can be realised via simple and reliablehoses and cables.

• Less maintenance efforts, e.g. spindle change within2 hours.

• Use of standard components.Until today, 10 machines of Ecospeed type have beendelivered to customers in Germany, United Kingdom andCanada.

5.2 Automotive

Powertrain manufacturingIn the field of high-volume powertrain manufacturing, theuse of flexible and semi-flexible manufacturing systemshas become more and more important. Thus, theperformance as well as investment and operational costof the incorporated machining centers have a decisiveinfluence on the economic viability of flexible manufac-turing systems [42].An analysis of operations to be machined on typicalpowertrain components such as gearbox housings,crankcases and cylinder heads, reveals that about 40%of the machining time are used for drilling, reaming andtapping operations while approx. 5% are related tomilling operations. 55% of the machining time arenonproductive for positioning and tool changing.Thus, one target is to reduce nonproductive positioningtime. From theoretical considerations, it is assumed thatup to 12% of the total machining time can be reduced bythe use of PKM technology [49].On the other hand, a comparison of different PKM andSKM has shown, that these improvements can not yet berealised in practical applications, Figure 17.The following observations have been made [42]: • To reduce nonproductive time, also peripheral com-

ponents must be optimised to the whole system.Most significant are tool and pallet changer as well asthe axis for workpiece positioning as well as a propersynchronisation between interpolating and position-ing axis.

• Due to jerk limitation in favour of path accuracy, thespecified accelerations of PKM can not yet realisedwithin the process.

Machine 1 Machine 2 PKM 1 PKM 2 PKM 3

Proc

ess

time

Conventional PKM

Tool change time Positioning time Productive time

Figure 17: Machining time of a cylinderhead (56operations, 6 tools): Conventional MC vs. PKM [42].

A different approach to reduce nonproductive time isproposed by Renault Automation Comau. The strategyassigned to the Urane SX, Figure 18, is to move a singletool with high agility to enable circular milling strategiesfor machining holes and threads of different diameterand thus eliminating tool changes and spindle stops.The lightweight design of the machine enables accelera-tions of 35m/s2 and a jerk factor of 1500 m/s3. Thus, hightraversing speeds are realised even during shortpositioning distances. The agility of the system has beendemonstrated in a drilling operation of 16 fixing holes ina gearbox flange face. The cycle time was 5,8scompared to 6,3s on a conventional multi-spindle head[50].

Figure 18: Urane Sx as drilling, tapping and spotfacingunit (Source: Renault Automation Comau).

Figure 19 illustrates a study for machining cylinder heads(1600/day) and compares a cell of linear direct drive(DD) MC’s with a cell mixed of Urane SX PKM and lineardirect drive MC’s. Within this cell configuration, theUrane Sx machines perform the drilling, tapping andspot-facing operations, while the conventional MC’s areintended for more complex operations, e.g. reaming. Theinvestment for the mixed PKM/SKM cell is 60% of theconventional solution and requires lower floor space.

Conventional: 11 MC (DD), Invest 100%

PKM: 3 MC (DD) +5 Urane Sx, Invest 60%

Figure 19: Case study cylinder head, 1600/day: InvestPKM vs. SKM (Source: Renault Automation Comau).

Automotive supplierSimilar to powertrain manufacturing, the reduction ofnonproductive time currently offers the main potential forincreased productivity for the high volume production inthe automotive supplier area. With this focus, thecompany Index developed a vertical turning machineV100 based on a linear delta structure, Figure 20. Allaxis motions are allocated to the workpiece.

Figure 20: Turning machine based on a linear deltakinematic [51].

The spindle unit is capable of 3-axis movements, thusenabling both the feeding motion for machining as wellas the part handling. Mainly intended for turning applica-tion, additional milling and grinding operation can beperformed with optional available driven tools. The high

motion dynamics (f=50 m/min, a=10 m/s2) enable fastpositioning movements for the workpiece change andthus a short chip-to-chip time.The machine has proven high accuracy and highstiffness which enables high chip removal on the onehand and the capabilities of machining hardened steelon the other. During customers tests, a diameter D=15 ±0,02mm has been machined in hardened steel (HRC 58-62) with a machine capability of Cmk=2,8 and surfaceroughness of Rz=2µm. This high accuracy level has alsobeen proven in interpolation mode by machining asphere, Figure 21.

Slider shoe (bronze):Demands on accuracy: machining result: Shape sphere (´D=19mm): ± 6 µm ± 3 µm

Diameter bore (D=20mm): ± 50 µm ± 2 µm

Figure 21: V100: Machining results (Source: Index).

6 GENERAL OBSERVATIONS AND FUTUREPOTENTIALS

Since the first parallel kinematic machines have beenestablished in industrial applications with customerbenifits, they have been proven to be a feasibleapproach to improve machine tool’s performance.However, the development of parallel structures formachine tools is rather “young” compared to the longexperience with classical serial machines. Thus in someapplication fields, where conventional machines aredeveloped close to the economic and technical limit, e.g.standard MC’s, PKM’s performance has not yet reacheda competitive level.The PKM machines which are successful on the markethave been designed towards a special bottleneck of theapplication of conventional machinery, thus making mosteffective use of conceptual capabilities of PKM whileavoiding possible conceptual drawbacks either by aconceptual approach or by advanced technologicalsolutions.Nevertheless, it must be clearly stated, that furtherresearch and development is needed to enable a morewide practical use of PKM. The following needs can beobserved. • Since the design and performance prediction of PKM

is more complex, it is essential to provide effectivetools to choose the appropriate kinematic topology onthe one hand and to optimise the design towards aspecial application task, thus making effective use ofthe conceptual capabilities such as modularity orreconfigurability.

• PKM consist of rather new machine componentssuch as joints, which are simple repetition parts onthe one hand but a key for the overall performanceon the other. Further improvements of components,e.g. joints with linear high stiffness, are essentialwhile also taking into account the components cost.

• It can be observed, that dynamic performance oftendoes not meet the expectations. To enable thedynamic capabilities by means of high path velocitycombined with high path-accuracy, both the nonlineardynamics of PKM as well as coupling effects have tobe considered in commercial motion controllers.

• Maintenance topics, such as machine calibration andgeometric accuracy evaluation have to be developedtowards shop-floor oriented use thus enabling themachine user to handle these topics an accordanceto his experience with classical machines.

7 ACKNOWLEDGMENTSThe authors wish to thank all those colleagues andindustrial companies who sent valuable informationmaterial.

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[14] Rey, L., Clavel, R., 1998, A General Overview andHistory of Parallel Robots, 1. InternationalesParallelkinematik-Koloquium IPK 98, ETH Zürich,Switzerland.

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[18] Stengele, G., 2002, Cross Hüller SpechtXperimental, a Processing Center with new HybridKinematic, Proc. 3rd Chemnitz Parallel KinematicsSeminar, 23.-25.5.2002, Verlag WissenschaftlicheScripten, Zwickau, pp.609-627.

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[20] Hennes, N., 2002, Ecospeed – An InnovativeMachinery Concept for High-Performance 5-Axis-Machining of Large Structural Components inAircraft Engineering, Proc. 3rd Chemnitz ParallelKinematics Seminar, 23.-25.5.2002, VerlagWissenschaftliche Scripten, Zwickau, pp.763-774.

[21] Saenz, A., Collado, V., Gimenez, M., SanSebastian, I., 2002, New Automation Solutions inAeronautics trough Parallel Kinematic Systems,Proc. 3rd Chemnitz Parallel Kinematics Seminar,23.-25.5.2002, Verlag Wissenschaftliche Scripten,Zwickau, pp.563-578.

[22] Neugebauer, R., Ihlenfeld, S., Kirchner, J., Adam,F., 2000, Redundante Hybridkinematik für denGroßwerkzeug- und Formenbau, Proc. 2rd

Chemnitz Parallel Kinematics Seminar, 12.-13.4.2002, Verlag Wissenschaftliche Scripten,Zwickau, pp.153-168.

[23] Gronbach, H., 2002, TriCenter – A Universal MillingMachine with Hybrid Kinematic. 3rd ChemnitzParallel Kinematics Seminar, 23.-25.5.2002, VerlagWissenschaftliche Scripten, Zwickau, pp.595-608.

[24] Schwaar, M., Jaehnert, T., Ihlenfeld, S., 2002,Mechatronic Design, Experimental PropertyAnalysis and Machining Strategies for a 5-Strut-PKM, 3rd Chemnitz Parallel Kinematics Seminar,23.-25.5.2002, Verlag Wissenschaftliche Scripten,Zwickau, pp.671-682.

[25] Tönshoff, H.-K., Friemuth, T., Urban, B., 2001,Increased Availability of Large Stamping Dies,Proc. Of the 2nd International Conference on Designand Production of Dies and Moulds, June 21-23,Kusadasi, Turkey.

[26] Czwielong, T., Zarske, W., 2002, Pegasus –Incorporating PKM into Woodworking, 3rd ChemnitzParallel Kinematics Seminar, 23.-25.5.2002, VerlagWissenschaftliche Scripten, Zwickau, pp.843-856.

[27] Neugebauer, R., Putz, M., Drossel, W.-G., Lorenz,U., Blau, P., 2002, Application of the ParallelKinematic Principle in a New Hydraulic Powered,Flexible Bending Machine for Tubes and Profiles,3rd Chemnitz Parallel Kinematics Seminar, 23.-25.5.2002, Verlag Wissenschaftliche Scripten,Zwickau, pp.629-638.

[28] Zirn, O., Treib, T., 1998, ParallelkinematischeWerkzeugmaschinen – Wachstumsgesetzeparalleler und serieller Kinematiken imWerkzeugmaschinenbau, Konstruktion, 50(1-2):31-36.

[29] Weck, M., Giesler, M., Pritschow, G., Wurst, K.H.,1996, Den hohen Anforderungen gerecht – NeueMaschinenkinematiken für die HSC-Bearbeitung,Schweitzer Maschinenmarkt, 45, pp.28-35.

[30] Merlet, J.-P., 1998, The Importance of OptimalDesign for Parallel Structures, Proc. First

European-American Forum on Parallel KinematicMachines, 31.8.-1.9.1998, Milano, Italy.

[31] Merlet, J.-P., 1997, A Design Methology for theConception of Robots with Parallel Architecture,Robotica, 15:367-373.

[32] Kirchner, J., 2001, Mehrkriterielle Optimierung vonParallelkinematiken, Dissertation TU Chemnitz,Verlag Wissenschaftliche Scripten, Zwickau.

[33] Cobet, M., 2002, Designing PKMs: WorkingVolume, Stiffness, Frequencies, 3rd ChemnitzParallel Kinematics Seminar, 23.-25.5.2002, VerlagWissenschaftliche Scripten, Zwickau, pp.83-105.

[34] Patel A. J., Ehmann K. F., 1997, Volumetric ErrorAnalysis of a Stewart Platform Based MachineTool, Annals of the CIRP 46-1, 287-290.

[35] Weck, M., Staimer, D., 2000, On the Accuracy ofParallel Kinematic Machine Tools: Design,Compensation and Calibration, Proc. 2rd ChemnitzParallel Kinematics Seminar, 12.-13.4.2002, VerlagWissenschaftliche Scripten, Zwickau, pp.73-84.

[36] Ota, H., Shibukawa, T., Tooyama, T., Uchiyama,M., 2000, Forward Kinematic Calibration Method forParallel Mechanism Using Pose Data Measured bya Double Ball Bar System, Proceedings of the Year2000 Parallel Kinematic Machines InternationalConference, September 13-15, 2000, Ann Arbor,Michigan, USA, pp. 57-62.

[37] Schwaar, M., Neugebauer, R., Kirchner, J., 2000,Steuerung von Parallelkinematiken 2rd ChemnitzParallel Kinematics Seminar, 12.-13.4.2002, VerlagWissenschaftliche Scripten, Zwickau, pp.195-201.

[38] Heisel, U., Hestermann, J.-O., Böhler, H., Plischke,N., Thaysen, O., 2000, Realisierung großerSchwenkwinkel für die 5-Seiten-Bearbeitung mitPKM-Werkzeugmaschinen, 2rd Chemnitz ParallelKinematics Seminar, 12.-13.4.2002, VerlagWissenschaftliche Scripten, Zwickau, pp.125-140.

[39] Weikert, S., Knapp, W., 2002, Application of theGrid-Bar Device on the Hexaglide, 3rd ChemnitzParallel Kinematics Seminar, 23.-25.5.2002, VerlagWissenschaftliche Scripten, Zwickau, pp.295-310.

[40] Neugebauer, R., Krabbes, M. Kretzmar, W.Schönitz, J., 2002, Improvement of the CalibrationAccuracy by a New Measurement Process,Frequencies, 3rd Chemnitz Parallel KinematicsSeminar, 23.-25.5.2002, Verlag WissenschaftlicheScripten, Zwickau, pp.443-454.

[41] Powell, N., Whittingham, B., Gindy, N, 1998,Parallel Link Mechanism Machine Tools:Acceptance Testing and Performance Analysis,Proc. First European-American Forum on ParallelKinematic Machines, 31.8.-1.9.1998, Milano, Italy.

[42] Hertel, A., 2002, Requirements for ParallelKinematics for Powertrain Manufacturing in theAutomotive Industry, 3rd Chemnitz ParallelKinematics Seminar, 23.-25.5.2002, VerlagWissenschaftliche Scripten, Zwickau, pp.753-762.

[43] Meylahn, A., 2001, Effiziente Algorithmen für dieSteuerung von Werkzeugmaschinen mit Hexapod-Kinematik: Transformation, Kollisonsüberwachungund Freifahrunterstützung, Dissertation RWTHAachen, Shaker Verlag, Aachen.

[44] Honegger M., Codourey A., Burdet E., 1997,Adaptive Control of the Hexaglide, a 6 dof ParallelManipulator, Proc. Int. Conf. on Robotics andAutomation ICRA'97, Albuquerque NM, USA.

[45] Pritschow, G., Eppler, C., Garber, T., 2002,Influence of the Dynamic Stiffness on the Accuracyof PKM, 3rd Chemnitz Parallel Kinematics Seminar,

23.-25.5.2002, Verlag Wissenschaftliche Scripten,Zwickau, pp.369-378.

[46] Weck, M., Krüger, P, 2000, Adaptive Regelung fürMaschinen mit paralleler Kinematik, Proc. 2rd

Chemnitz Parallel Kinematics Seminar, 12.-13.4.2002, Verlag Wissenschaftliche Scripten,Zwickau, pp.73-84.

[47] Dürschmied, F., Hestermann, J.-O., 2002,Achieving Technical and Economic Potential withINA Components, 3rd Chemnitz Parallel KinematicsSeminar, 23.-25.5.2002, Verlag WissenschaftlicheScripten, Zwickau, pp.263-276.

[48] Lilla, A., 2001, Herstellung komplexer integralerFrästeile für die Luft- und Raumfahrt mitParallelkinematiken “Ecospeed”, 1. InternationaleFachtagung über Parallel-kinematische Werkzeug-maschinen, 21.-22.6.2001, Messe Stuttgart.

[49] Stave, H., 2001, Bearbeitungszentren für dir flexibleGroßserienfertigung prismatischer Teile, Tagungs-band 3. Chemnitzer Produktionstechnisches Kollo-quium, Chemnitz 2001.

[50] Passemard, J. R., 2001, Possible PKM Applicationsin High Volume Production, 1. InternationaleFachtagung über Parallel-kinematische Werkzeug-maschinen, 21.-22.6.2001, Messe Stuttgart.

[51] Walker, T., Haberkern, A., 2001, Anwender-erfahrungen für Drehteile mit PKM V100, 1.Internationale Fachtagung über Parallel-kinematische Werkzeugmaschinen, 21.-22.6.2001,Messe Stuttgart.

9 APPENDIXTable 1 gives an overview about specifications of recentPKM’s. Data is based on a literature survey and aquestionnaire sent to CIRP-members and industryinvolved in PKM technology.

Tabl

e 1:

PKM

dev

elop

men

ts (s

ourc

e: li

tera

ture

sur

vey

and

ques

tionn

aire

sen

t to

CIR

P m

embe

rs a

nd in

dust

rial c

ompa

nies

).

Man

ufac

ture

r/Lab

orat

ory

Mod

elAp

plic

atio

nTy

peD

OF

Wor

kspa

ce [m

m]

Orie

ntat

ion

[Deg

.] (m

ax/m

in)

Velo

city

lin.

axi

sVe

loci

ty ro

t. Ax

isAc

c. li

n. A

xis

Acc.

rot a

xis

1C

hiro

nV-

Con

cept

Mill

ing

Hyb

rid3

450*

300*

300

%12

0 m

/min

%30

m/s

2%

2C

MW

Hex

apod

e 30

0M

illin

gPa

ralle

l6

700*

700*

300

N.A

.50

/50/

20 m

/min

N.A

.10

m/s

2N

.A.

3D

ecke

l Mah

oTr

icen

ter

Mill

ing

Hyb

rid5

630*

630*

600

180/

-95

120/

90/9

0m/m

in30

U/m

in20

/15/

15 m

/s2

N.A

.4

DS-

Tech

nolo

gie

Ecos

peed

Mill

ing

Hyb

rid5

4000

*100

0*50

0±4

0/±4

050

m/m

in15

U/m

in10

m/s

212

rad/

s5

ETH

Zür

ich

Hex

aglid

eM

illin

gPa

ralle

l6

600*

500*

xN

.A.

N.A

.N

.A.

35 m

/s2

N.A

.6

Fatro

nik

Her

mes

Mill

ing

Hyb

rid5

x*y*

400

±30/

±30

z=80

m/m

in50

U/m

inz=

10m

/s2

1500

°/s2

7Fa

troni

kU

lyse

sM

illin

gPa

ralle

l3

500*

500*

500

%50

m/m

in%

5 m

/s2

%8

Fook

eTr

iom

axR

apid

Pro

toty

ping

Para

llel

650

0*50

0*40

0N

.A.

30 m

/min

N.A

.10

m/s

2N

.A.

9G

eode

ticG

500

Mill

ing

Para

llel

650

0*50

0*50

0N

.A.

9 m

/min

N.A

.N

.A.

N.A

.10

Gid

ding

s&Le

wis

Varia

xM

illin

gPa

ralle

l6

700*

700*

750

±25

66 m

/min

N.A

.10

m/s

2N

.A.

11H

ecke

rtSK

M 4

00M

illin

gPa

ralle

l3

630*

630*

630

%10

0 m

/min

%10

m/s

2%

12H

exel

Cor

p.To

rnad

o 20

00M

illin

gPa

ralle

l6

600*

600*

600

N.A

.N

.A.

N.A

.N

.A.

N.A

.13

Hita

chi S

eiki

PA 3

5II

Dril

ling

Para

llel

335

0*35

0*20

0%

100

m/m

in%

15 m

/s2

%14

Hon

daH

VS-5

00M

illin

gH

ybrid

365

0*50

0*40

0%

60 m

/min

%10

m/s

2%

15H

ülle

rHille

Spec

ht X

perim

enta

lM

illin

gH

ybrid

363

0*63

0*75

0%

120/

120/

60 m

/min

%15

/15/

10 m

/s2

%16

IFW

Han

nove

rD

umbo

Mill

ing

Hyb

rid5

480*

480*

480

180/

-95

N.A

.N

.A.

N.A

.N

.A.

17IF

W H

anno

ver

Geo

rgV

Lase

r pro

cess

ing

Hyb

rid5

Ø19

00, H

=950

±115

/±11

570

m/m

in18

0rad

/min

N.A

.N

.A.

18IF

W H

anno

ver

PaliD

APi

ck&P

lace

Para

llel

640

0*40

0*40

0±4

5/±1

515

0 m

/min

N.A

.25

m/s

2N

.A.

19IF

W S

tuttg

art

Hex

act

Mill

ing

Para

llel

620

0*20

0*10

0±1

5/±5

30 m

/min

N.A

.5

m/s

2N

.A.

20In

dex

V100

Turn

ing

Para

llel

328

0*28

0*28

0%

50 m

/min

%10

m/s

2%

21In

gers

oll/W

ZL A

ache

nH

OH

600

Mill

ing

Para

llel

660

0*60

0*80

0±3

0/±1

540

m/m

inN

.A.

3,5

m/s

2N

.A.

22IS

W S

tuttg

art

Lina

pod

Mill

ing

Para

llel

660

0*60

0*60

0±2

0/±1

512

0 m

/min

N.A

.40

m/s

2N

.A.

23IT

IA-C

NR

Mila

noC

eler

usM

illing

Stu

dyPa

ralle

l6

600*

600*

300

N.A

.60

m/m

inN

.A.

10 m

/s2

N.A

.24

ITIA

-CN

R M

ilano

Dra

gonf

lyD

ebur

ring/

Wat

er C

uttin

gN

.A.

%N

.A.

%N

.A.

%25

ITR

I/MIR

L, T

aich

ung

HL-

5VM

illin

gH

ybrid

565

0*85

0*65

0±4

532

m/m

in10

0rad

/min

6,5

m/s

2N

.A.

26IW

U C

hem

nitz

Hex

aben

dFl

exib

le F

orm

ing

Para

llel

6N

.A.

N.A

.N

.A.

N.A

.N

.A.

N.A

.27

Jian

gdon

g, C

hina

XNZ

2010

Mill

ing

Hyb

rid4

1200

*800

*630

A=+9

0/-2

060

m/m

in30

U/m

in5m

/s2

7,6

1/s2

28JS

C L

apik

TM 1

000

Mill

ing/

Prob

ing

Para

llel

6N

.A.

N.A

.N

.A.

N.A

.N

.A.

N.A

.29

Krau

seco

&Mau

ser

Qui

ckst

ep H

S500

Mill

ing

Para

llel

363

0*63

0*50

0%

80 m

/min

%20

m/s

2%

30Ku

nmin

g/Ts

ingh

hua

Uni

vers

ityX

NZ

63M

illin

gPa

ralle

l6

400*

400*

300

±35/

±25

15 m

/min

N.A

.0,

5m/s

2N

.A.

31M

etro

mP

800

Mill

ing

Para

llel

5(6)

800*

800*

500

±90/

±90

w. T

able

N.A

.N

.A.

N.A

.N

.A.

32M

ikro

mat

/IWU

Che

mni

tz6X

Mill

ing

Para

llel

663

0*63

0*63

0±3

0/±1

540

m/m

inN

.A.

10 m

/s2

N.A

.33

Mik

rom

at/IW

U C

hem

nitz

Dyn

apod

Mill

ing

Hyb

rid3

to 8

N.A

.N

.A.

N.A

.N

.A.

N.A

.N

.A.

34M

ikro

nTr

iagl

ide

Mill

ing

Para

llel

317

0*12

0*25

0%

N.A

.%

15 m

/s2

%35

MTC

, Chi

naQ

uiqi

haer

Mill

ing

Hyb

rid5

4000

*145

0*12

00A=

±95/

±30,

C=±

200

30 m

/min

30U

/min

2 m

/s2

N.A

.36

Neo

s R

obot

ics

Tric

ept T

R80

5M

illin

gH

ybrid

5Ø

2500

, H=8

0018

0/-1

090

m/m

inN

.A.

10 m

/s2

N.A

.37

Oku

ma

Cos

moC

ente

r PM

600

Mill

ing

Para

llel

642

0*42

0*40

0±2

512

0 m

/min

N.A

.15

m/s

2N

.A.

38R

eich

enba

cher

Pega

sus

Woo

dwor

king

Para

llel

350

00*1

400*

250

%12

0 m

/min

%10

m/s

2%

39R

enau

lt Au

tom

atio

nU

rane

SxD

rillin

g/Ta

ppin

gPa

ralle

l3

500*

500*

250

%10

0 m

/min

%35

m/s

2%

40Se

naEc

lipse

Rap

id P

roto

typi

ngPa

ralle

l5

Ø15

0*17

0±9

010

m/m

inN

.A.

N.A

.N

.A.

41SM

E Ti

anjin

Uni

vers

ity3-

HSS

Mill

ing

N.A

.3

Ø50

0, H

=400

%20

m/m

in%

10 m

/s2

%42

Tekn

iker

Seya

nka

Mill

ing

Para

llel

540

0*40

0*40

0±3

0/±1

560

m/m

in20

0rad

/min

10 m

/s2

50 1

/s2

43To

yoda

Hex

aMM

illin

gPa

ralle

l6

500*

500*

350

±40/

±20

100

m/m

in15

0rad

/min

15 m

/s2

N.A

.44

Tsin

ghua

Uni

vers

ityVA

MT1

YM

illin

gPa

ralle

l6

500*

400*

600

±35/

±25

15 m

/min

N.A

.0,

5m/s

2N

.A.

45W

ZL A

ache

nD

ynaM

Mill

ing

Hyb

rid3

630*

630*

500

%90

m/m

in%

10/1

5 m

/s2

%46

ZFS

Stut

tgar

tPa

ralix

Mill

ing

Para

llel

650

0*40

0*40

0A=

-30/

+90,

B=±

2090

m/m

inN

.A.

20 m

/s2

N.A

.

Tabl

e 1

cont

inue

d: P

KM d

evel

opm

ents

(sou

rce:

lite

ratu

re s

urve

y an

d qu

estio

nnai

re s

ent t

o C

IRP

mem

bers

and

indu

stria

l com

pani

es).

Man

ufac

ture

r/Lab

orat

ory

Mod

elSp

indl

e sp

eed

Spin

dle

pow

erTo

ol in

terf

ace

Driv

e ty

peSe

nsor

type

Con

trol

ler

Rep

eata

bilit

yPo

sitio

ning

acc

urac

y

1C

hiro

nV-

Con

cept

2700

0rpm

3,7k

WH

SK-A

32Li

near

dire

ctLi

n. E

nc.

Siem

ens

840D

N.A

.N

.A.

2C

MW

Hex

a pod

e 30

024

000r

pm24

kWN

.A.

Balls

crew

Lin.

Enc

.PC

-bas

ed±1

µm8µ

m/3

00m

m3

Dec

kel M

aho

Tric

ente

r24

000r

pm19

kw(S

1), 2

6kW

(S6)

HSK

-A63

Balls

crew

Rot

. Enc

/Lin

. Inc

.Si

emen

s 84

0DN

AS P

art <

10µm

N.A

.4

DS-

Tech

nolo

gie

Ecos

peed

2700

0rpm

75kW

HSK

-A63

Balls

crew

/Rac

k&Pi

nion

Lin.

Incr

.Si

emen

s 84

0DN

.A.

N.A

.5

ETH

Zür

ich

Hex

a glid

e42

000r

pm10

kWN

.A.

Line

ar d

irect

Lin.

Incr

.Po

wer

PC

, VM

Ebus

N.A

.N

.A.

6Fa

troni

kH

erm

es40

000r

pm27

kWH

SK-A

63Ba

llscr

ewLi

n. In

cr.

Siem

ens

840D

N.A

.N

.A.

7Fa

troni

kU

lyse

s30

000r

pm15

kWN

.A.

Balls

crew

Rot

. Enc

.Fa

gor 8

070

N.A

.N

.A.

8Fo

oke

Trio

max

N.A

.N

.A.

N.A

.Ba

llscr

ewR

ot. E

nc.

Andr

onic

400

N.A

.N

.A.

9G

eode

ticG

500

2800

0rpm

10kW

N.A

.H

ollo

w s

haft

Rot

. Enc

.Si

emen

s 84

0D±5

µm±2

5µm

10G

iddi

ngs&

Lew

isVa

riax

2400

0rpm

17kW

?H

SK-A

50Ba

llscr

ewLa

ser

Gid

ding

s&Le

wis

N.A

.12

µm

11H

ecke

rtSK

M 4

0015

000r

pm31

kWH

SK-A

63Ba

llscr

ewR

ot. E

nc.

Siem

ens

840D

N.A

.<1

5µm

12

Hex

el C

orp.

Torn

ado

2000

1800

0rpm

20kW

HSK

-A50

Balls

crew

N.A

.PC

bas

ed

N.A

.N

.A.

13H

itach

i Sei

kiPA

35I

I20

000r

pm2,

6N

T 15

Rac

k &

Pini

onR

ot. E

nc.

Fanu

c 18

i-MN

.A.

N.A

.14

Hon

daH

VS-5

0020

000r

pmN

.A.

N.A

.Ba

llscr

ewN

.A.

N.A

.N

.A.

N.A

.15

Hül

lerH

illeSp

echt

Xpe

rimen

tal

2000

0rpm

60kW

HSK

-?63

Line

ar d

irect

/Bal

lscr

ewLi

n. In

cr.

Siem

ens

840D

N.A

.<1

5µm

16

IFW

Han

nove

rD

umbo

3000

0rpm

9kW

HSK

-E32

Balls

crew

Rot

. Enc

.Si

emen

s 84

0DN

.A.

N.A

.17

IFW

Han

nove

rG

eorg

VN

.A.

N.A

.N

.A.

Balls

crew

Rot

. Enc

.Si

emen

s 84

0DN

.A.

N.A

.18

IFW

Han

nove

rPa

liDA

N.A

.N

.A.

Sele

noid

H

all

PC (d

Spac

e)N

.A.

N.A

.19

IFW

Stu

ttgar

tH

exac

t42

000r

pm12

,5kW

SK30

Balls

crew

Rot

. Enc

.Si

emen

s 84

0D±5

µm<2

0µm

20

Inde

xV1

0010

000r

pm14

kWTu

rnin

g to

ols

Balls

crew

Lin.

Incr

.Si

emen

s 84

0DN

.A.

4-15

µm/2

50m

m21

Inge

rsol

l/WZL

Aac

hen

HO

H 6

0010

000r

pm27

,4kW

(S1)

HSK

-A10

0Ba

llscr

ewLi

n. In

cr.

Siem

ens

840D

6µm

25µm

22IS

W S

tuttg

art

Lina

pod

2400

0rpm

27kW

HSK

-A63

Line

ar d

irect

Lin.

Incr

.IS

G-N

CN

.A.

N.A

.23

ITIA

-CN

R M

ilano

Cel

erus

2400

0rpm

20kW

HSK

-A63

Balls

crew

N.A

.Si

emen

s 84

0DN

.A.

N.A

.24

ITIA

-CN

R M

ilano

Dra

gonf

lyN

.A.

N.A

.N

.A.

N.A

.N

.A.

N.A

.N

.A.

25IT

RI/M

IRL,

Tai

chun

gH

L-5V

1200

0rpm

8kW

BT 4

0Ba

llscr

ewN

.A.

Siem

ens

840D

N.A

.15

µm

26IW

U C

hem

nitz

Hex

aben

dN

.A.

N.A

.N

.A.

Hyd

raul

icN

.A.

N.A

.N

.A.

N.A

.27

Jian

gdon

g, C

hina

XNZ

2010

1000

0rpm

10kW

BT40

Balls

crew

Lin.

Incr

.PC

-bas

edN

.A.

±20-

30µm

28JS

C L

a pik

TM 1

000

N.A

.N

.A.

N.A

.Ba

llscr

ewR

ot. E

nc.

PC-b

ased

N.A

.N

.A.

29Kr

ause

co&M

ause

rQ

uick

step

HS5

0015

000r

pm28

kWH

SK-A

63Ba

llscr

ewLi

n. In

cr.

Siem

ens

840D

N.A

.N

.A.

30Ku

nmin

g/Ts

ingh

hua

Uni

vers

ityX

NZ

6320

000r

pm10

kWBT

40Ba

llscr

ewR

ot. E

nc.

PC-b

ased

N.A

.N

.A.

31M

etro

mP

800

3000

0rpm

9kW

N.A

.Ba

llscr

ewR

ot. E

nc.

Andr

onic

200

0N

.A.

<20µ

m32

Mik

rom

at/IW

U C

hem

nitz

6X30

000r

pm16

kWH

SK-E

50Ba

llscr

ewLi

n. In

cr.

Andr

onic

400

N.A

.10

µm33

Mik

rom

at/IW

U C

hem

nitz

Dyn

apod

N.A

.N

.A.

N.A

.Ba

llscr

ew/L

inea

r dire

ctN

.A.

N.A

.N

.A.

N.A

.34

Mik

ron

Tria

glid

eN

.A.

N.A

.N

.A.

Line

ar d

irect

Lin.

Incr

.In

dram

at M

TC20

0±1

µmN

.A.

35M

TC, C

hina

Qui

qiha

er10

000r

pm12

kWH

SK-A

63Ba

llscr

ewLi

n. In

cr.

PC-b

ased

N.A

.N

.A.

36N

eos

Rob

otic

sTr

icep

t TR

805

up to

300

00rp

mup

to 4

0kW

N.A

.Ba

llscr

ewR

ot. E

nc. /

Lin.

Incr

.Si

emen

s 84

0D20

µm50

µm37

Oku

ma

Cos

moC

ente

r PM

600

3000

0rpm

7kW

HSK

-E32

Balls

crew

Rot

. Enc

.O

kum

a O

SP-U

100

N.A

.N

.A.

38R

eich

enba

cher

Pega

sus

N.A

.N

.A.

N.A

.Li

near

dire

ctLi

n. In

cr.

Siem

ens

840D

N.A

.N

.A.

39R

enau

lt Au

tom

atio

nU

rane

Sx40

000r

pm12

kWN

.A.

Line

ar d

irect

Lin.

Incr

.Si

emen

s 84

0DN

.A.

N.A

.40

Sena

Eclip

se40

000r

pmN

.A.

ISO

20

N.A

.N

.A.

PC-b

ased

N.A

.N

.A.

41SM

E Ti

anjin

Uni

vers

ity3-

HSS

8000

rpm

6kW

N.A

.N

.A.

N.A

.IP

C+P

MAC

N.A

.25

µm42

Tekn

iker

Seya

nka

3000

0rpm

8,5k

WN

.A.

Balls

crew

Rot

. Enc

.Fa

gor 8

070

N.A

.N

.A.

43To

yoda

Hex

aM42

000r

pm15

kWH

SK-A

40Ba

llscr

ewR

ot. E

nc.

Fanu

c 15

i-MA

N.A

.12

-29µ

m/3

00m

m44

Tsin

ghua

Uni

vers

ityVA

MT1

Y30

00rp

m2k

WN

.A.

Balls

crew

Rot

. Enc

.PC

-bas

edN

.A.

N.A

.45

WZL

Aac

hen

Dyn

aM16

000r

pm15

kWH

SK-A

63Ba

llscr

ewLi

n. In

cr.

Siem

ens

840D

3µm

20µm

46ZF

S St

uttg

art

Para

lixN

.A.

N.A

.N

.A.

Balls

crew

Lin.

Incr

.Si

emen

s 84

0DN

.A.

N.A

.