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All Rights Reserved. Log In. Paper Titles. Plasma-Particle Interaction in Spray Forming p. Electrical Discharge Grinding of Polycrystalline Diamond p. Recent Developments in Tool Materials for High Article Preview. Abstract: High-Speed Machining HSM is one of the emerging cutting processes, which is machining at a speed significantly higher than the speed commonly in use on the shop floor. Add to Cart. Materials Science Forum Volumes Main Theme:. Advances in Materials Manufacturing Science and Technology. Edited by:. Online since:. December Cited by. Related Articles. Lamikiz Fig. Ten years later the German firm Reickner introduced the hobbing principle using a worm-type cutting tool.

Figures 1. Ford manufactured the first mass produced car. The new mass production, along with tight dimensional and form requirements, led to improvements in the same types of machines known since the end of the previous century. However electrical engines fully introduced in were used instead of steam power. In L. Wilkie, working for Do-All, developed another basic machine tool, the metal cutting contour band sawing machine. Parson, an engineer at the Bendix Corporation, developed an automatism for controlling a 3D machining operation, improved by MIT over the following three years.

In those years, the programming binary code was supported by punched cards and later by perforated tapes. But the real spread of numerical control NC was in the s and s, when the microprocessor became the brain of the control mechanism and the CNC Computer numerical control concept was fully developed. In the s, the open architecture of controls based on PC buses and cards enabled the integration of machines in intelligent manufacturing systems.

The programmable controller is currently integrated in the same architecture of the CNC to make all machine operations automated and therefore programmable. In this group, the early types were lathes where an additional milling head was included now they are called turning centres , but recent developments are directly designed as complex multi-axis machines different of lathes and milling machines. Figure 1. Placed here, a turning, milling or drilling tool can be moved in a big workspace. Another main motion is provided by a power lathe headstock placed on a horizontal flat bed; if a turning operation is performing this headstock turns the workpiece, whereas if a milling operation is performing this headstock slowly moves the workpiece controlling its angle position.

At the same time a drum turret moves along the horizontal guides. Parallel kinematics is not a global solution for all machine tools; however, it can be applied to big ones. At present, the US industry classification class. Some types are disappearing, such as the planing or shaping machines, but others are more or less in use.

It is difficult to be strictly academic when defining the types Fig. It would be easier to classify machining processes instead of those machines which apply them.

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A very up-to-date classification, where the classical machine types are included along with new ones, is shown in Table 1. This book is focused on the general types, i. However the basic design and construction principles are common for all, even those only barely mentioned in this book.

The global scheme for designing, manufacturing and verification of a machine tool is summed up in Table 1. Table 1. Inputs and factors are related Definition of requirements Workpiece size Workpiece geometry Removal rate Precision Kinematic behaviour Batch size Price Features of the machine tool and systems Machine size Milling or lathe, other type Roughing or finishing machine Assembly, thermal aspects Element masses, drives Automation systems, ATC and APC Life cycle cost analysis Selection of the basic mechanism Machine degrees of freedom Definition of the main motion Main motor, workpiece or tool rotation Definition of the structure Configuration Bed Structural elements Guideways selection Definition of drive trains Knee, gantry, fixed or travelling column, etc.

Cast iron, polymer concrete, others Cast iron, cast steel, polymer concrete, welded steel Friction, roller bearings, hydrostatic Drive motors, ball screws or linear motors, couplings 1 Machine Tools for Removal Processes: A General View 9 Table 1. Users might be non-specific customers but included in typical sectors with common requirements, or an individual customer with highly defined specifications.

Small and medium machines are usually produced considering hypothetical customers, offering some options in catalogues, on the contrary to large machines which are usually designed to order. Machining would be needed at each point of the part, so the machine workspace must be larger than the workpiece size. In some machines modifications are done to be able to accommodate workpieces larger than the workspace, for example the gap-frame lathes, where the maximum swing diameter is larger than the maximum working diameter.

The global shape of the part is the key point to select one type of machine. If the part is cylindrical, the lathe is the first machine to be considered. If it is prismatic, a milling centre may be the most adequate. Only in some cases may there be a doubt, in the light of the capabilities of the new five-axis milling centres provided with high-torque rotary axes tables, which are able to make turning operations as well as milling. If the features are few and simple they do not contribute to the complexity increase i.

One example is again the five-axis milling centres, where two orientation axes are added to the basic three-axis Cartesian machine, making it possible to machine all faces of complex spatial forms in one setup. In this case, milling tools are integrated in a lathe to perform details like key-slots, polygonal faces or inclined planes in the same setup, at the same time adding additional DOF to the lathe such as the controlled rotation of the C-axis and the Y-axis linear movement out from the plain XZ.

In some applications the design driver is precision, but in others it is mainly to achieve a high productivity. However precision driveways, machine structures with both a high stiffness and a damping and tight toolpath control are highly recommended. Solutions for precision and productivity are conflicting. This the basic pattern for most of the current milling and turning machines. This is a commonly used word which really involves two different concepts: accuracy and repeatability.

Accuracy is the capability of being on target with a specification, quantified by the bias or difference between the obtained and desired result. However, repeatability is the ability to reach the same value over and over again. Therefore a machine may be repeatedly inaccurate in one extreme case, or imprecise yet very accurate at the other extreme. A somewhat related concept is resolution, the smallest difference between two following values that can be distinguished by measuring devices.

Accuracy and precision are the main objectives of machine tool constructors. The guidelines and methodologies for machine design and assembly, the machine elements manufacturing, the testing procedures and the use of auxiliary systems are inspired by this requirement [21, 24]. High precision is very expensive; it requires identifying, controlling and reducing all error sources. Good assembly practices, the tight adjustment of carriages to guides and the measurement of errors after assembly are the basic techniques to reduce them.

High stiffness is always desired. High damping ratios of machine frame elements and joints enable vibration reduction.


In machine tools there are five heat sources: the main motor-spindle, the drive motors, the process, material removed as chips and finally the temperature changes of the workshop. Errors in part shape and dimensions may occur if sharp or very rapid direction changes in tool movement are programmed.

Smoothing functions are offered to reduce these errors by moderns CNCs. A very illustrative picture about precision in machining was given by McKeown [16] after Taniguchi [22], lightly modified in [6]. As shown in Fig. Evidently, these good numbers are located in the segment of high quality and expensive machines; however they are a good indicator of the current technology level. A comparison with the boring machine by J. Some machines usually make a few but long operations on unique parts while others makes a lot of short operations on each workpiece. An example of the first case is the big milling centre for stamping die finishing.

Examples of the second case are milling centres for automotive iron cast parts. The latter cases are where rapid idle movements are much recommended. This is an important aspect in sculptured surface milling [13, 14] because the tool is constantly changing trajectories on the complex surfaces; therefore machine agility greatly depends on axes accelerations. The same can be said of machines for automotive components, where the tool must move quickly between the multiple machining points.

Generally, a universal CNC machine is able to process a wide range of different workpieces, only downloading another CNC program and with few changes in part workholding devices see example 1.

On the opposite, a transfer line see example 1. This is an important factor that depends on machine size in linear proportion and precision in exponential relation. Several software utilities for a correct life cycle cost analysis LCC are available. At present, the environmental impact of machine tools themselves is not a key factor; however that of their machining process is taken into account in several innovation projects.

In most cases, the aforementioned requirements lead to a definition of traditional common-sense solutions, because all applications look similar to the previous. However, as with other mechanism and machine problems, new solutions are launched radically rethinking all the design steps from the starting point, i. This fact has become evident in the development of multi-task machines, like those shown in Figs. See also Sect. Nowadays, the structure of these machines is absolutely different from the classic lathe.

In some ways it can be said that a second generation of multi-task machines has been born in the last four years, starting their design from the user requirements, which must be collected from the machine company sales departments. The function of this mechanism is moving either the tool or the workpiece, or both simultaneously [19]. Three references systems can be defined: 1. The three are very useful. Thus, the first is where all machining operations are defined and programmed. The second is that used by an external observer.

Finally, the last is used by machine control to move the tool tip. A conversion from the former into the latter must be always performed. In manual machines it is the user who does that, interpreting the workpiece drawings, but in CNC machines it is this control device which performs this function, known as the interpolation function. The machine reference i. The names of machine degrees of freedom are defined with respect to the main motion that provides torque and the power to remove material.

The nomenclature and positive and negative directions of axes are defined in the ISO standard [10], being the Z-axis which matches the main motion axis. The required movements lead to typical kinematics solutions and machine configurations [4, 24]. Thus, for cylindrical parts the basis is 2 DOF mechanisms, resulting in the lathe as the machine to be used. For a milling machine mainly three-axis mechanisms are used.

The three-axis movement is solved with a Cartesian configuration, with at least two of the axes mounted in serial. In some cases all the movements are applied to the tool, others are divided among the tool and workpiece, and on the odd occasion all are applied to the workpiece.

The five axes, like the machine shown in Fig. Lamikiz Three axes Two axes Fig. In this way the milling tool can be placed in a specific orientation with respect to each workpiece surface. This is really the best solution for milling, yet at the same time the complexity of the mechanism and its control has increased. Three configurations are common in five axes milling centres; the kinematic chain is going to be defined starting from the workpiece towards the tool tip, where L means a linear axis and R a rotation axis.

Thus, three types are defined in Fig. One axis rotates twists the head while the other tilts it. On the other hand, Cartesian motions may be produced either at the tool or machine table see diagram of Fig. This configuration is used in large gantry machine tools, usually for machining large moulds and dies. One rotation is a cradle-like movement whereas the other is around an axis perpendicular to the plate. This configuration is commonly used in small compact machines, or in three-axis machines provided with accessory rotary tables.

The three mean Cartesian axes can be solved by a travelling column configuration, but in other cases the cradle base is provided with one linear degree of freedom. These five-axis machines are very suitable for tall workpieces or for cylindrical parts with faced plates and holes around their perimeter. Current machines tools are really simpler in design than fifty years ago. For example, the mechanism of the gear shaper shown in Fig. Another example of a full mechanical solution is the hacksaw of Fig. On the other hand, a high damping ratio and low thermal distortion must be achieved.

The main body of the structure constitutes the machine frame. It can be built in one block or assembling several individual sub-frames see Fig. One important component is the bed, where all others components rest. It is the solid base of machine after construction, placed on the ground of the workshop using some kind of isolated supports. They are part of the mechanism, being linked with relative movement between them. The interface of those elements with relative movement must be very stiff and damped along the perpendicular direction to slide while allowing a smooth motion along it.

Two structure design concepts are used, the open-loop and closed-loop configurations. In the first case the process forces are conducted to the ground through just one structural way, whereas in the closed case forces are derived by 1 Machine Tools for Removal Processes: A General View 17 Fig. Obviously, in the first case the structure is weaker, therefore a higher error measured at the tool tip position is produced by machine deformation due to the cutting forces; in the second case, stiffness measured at the tool tip increases. On the other hand, and for the same machine size, the first type usually offers more workspace and workzone accessibility for part handling than the second.

The characteristic open-loop for milling machines is the C or G knee frames, very common in small machines. The access to the workzone is easy, but this structure is sensitive to thermal and mechanical charges torsion and flexion with an asymmetrical response. The frame overhang produces Abbe errors on the workpiece see Sect. In Fig. Lamikiz time; another advantage is that it allows the part to be set up in one zone while milling runs in the other if the machine table is sufficiently long. With respect to closed-loop frames, the bridge or gantry structure is used for medium and large machines, which usually perform heavy-duty work or finishing on big parts.

In some cases the bridge is fixed and table moves, in others the workpiece is fixed and all movements are by the bridge or a travelling beam placed on the bridge case c in Fig. Nowadays, there are also some new architectures using parallel kinematics, where stiffness, kinematic and dynamic principles are somewhat different. In these machines the use of isostatic structures prevents spatial distortion of machine bodies.

Chapter 10 is dedicated to this type of machine. As for lathes, structures are open-loop for horizontal models and closed-loop for the huge vertical ones also called vertical boring mills. In lathes cutting forces are translated into torsion to the bed through the carriage guideways.

For the last fifteen years horizontal CNC lathes have had slant beds in which the turret moves along; this fact makes the part handling and chip evacuation easy; however, at recent fairs some developments with a horizontal bed, traditional for engine lathes, and turrets placed under the workpieces have been shown e. For small and medium lathes and machining centres, isolation pads or blocks are usually enough to reduce vibration transmission to and from the machine tool. These supports have some simple height adjustment to make the alignment.

When vibration isolation is desired in a support-critical installation, an inertial block foundation system is often the best option. The machine is jointed to a concrete basement by anchor bolts, levelling screws or levelling wedges to adjust and align the machine bodies. This is the case with big milling or boring machines where the workpiece table rests on the ground and the column structure is a separate group resting on the ground as well. Another case is the long table milling machines with travelling column, where good alignment is required. Ductile cast iron can be an option to increase the stiffness of some components.

Cast steel is used in headstocks. The main disadvantage is the lack of damping. Some solutions use fillings, like sand or polymers, to improve damping and attenuate vibrations. Other problems are derived from the residual stresses and distortions typical of welding and the nonhomogeneous behaviour of the weld seams. Now it is used in some lathe or milling machine beds. The positive feature is its high damping, but its main drawback is the low thermal conductivity. Structural behaviour under static or inertial loads is currently carried out with the Finite element method see Sect.

Although cutting forces are variable, both in modulus and direction, the maximum values can be considered inputs for the 3D model. The structure equivalent tensions and deformations are mapped as a result of the analysis Fig. Currently, even the simplest software packages are able to perform a good calculus. In FEM, the most difficult aspect to define is related to contacts between structural components along the DOF, where stiffness, damping, backlash and other construction details are difficult to estimate.

Typical machine stiffness values, measured like the displacement of the spindle nose with regard to the machine bed due to force action, are as follows. For a vertical machining centre, stiffness values of approx. With respect to grinders, external cylindrical ones are in 20 L. With some variations depending on the machine tool type, the sources of flexibility are: the tool, ram and column, the spindle and toolholder interface, the axis carriages and rails, ball screws and finally the bed.

The analysis of natural modes and frequencies is easy to run see Fig. In finite element models damping is always an Fig. However, in real machines damping comes mainly from the contact in the guideways, where rolling bearings in one case or friction sliding ways in the others include uncertainty in the model. On the other hand, a careful experimental modal analysis can measure the natural frequencies and modes of a just constructed real machine with sufficient accuracy, and at the same time could be used for updating the FEM model used in design; however this latter is currently only used by research centres [9].

The usual procedure is to use the thermal capabilities of FEM packages, including some assumptions about the maximum heat sources as inputs. Some changes in design could be derived from this analysis. After machine assembly, the final analysis step is to check the real behaviour of the system formed by the machine and tool, in a test working under aggressive conditions.

Then, two vibration problems can happen. The first is the forced structural vibration under the action of the periodical cutting forces. This is a problem common to all mechanical systems, being studied using the FRF function response function. To prevent resonance, natural frequencies of the system must be far from force frequencies, which can be done varying the stiffness or mass of machine elements. Chapter 3 explains the basis of chatter in depth, due to its relation with spindle vibrations and damage.

With respect to the machine, excitation of the machine structural modes may occur when machining conditions are aggressive enough. Then, low frequency Fig. Lamikiz vibrations affecting machine life and workpiece roughness appear. In them, spindle speed is referred in the abscises and the depth of cut in the Y-axis, showing the borderline between stable and non-stable i.

An example is described in Fig. In the dashed square in this figure are the two most restrictive directions. Along them, an axial depth of cut less than 1 mm must be applied to avoid chatter. These factors have lead to a policy design based on different machine modules placed on common beds.

Three main advantages are achieved with this: 1. Beds for several machine models are produced using the same polystyrene model and making optimal use of each iron casting. The direct advantage, a better price, is obtained from the foundries. Some subcontractor companies reach a high specialisation producing elements and units that can be installed on different machines and for different machine manufacturers, such as rotary heads, tool changers, indexers, tables, rams, etc.

The elaboration of offers for customers in different areas of the world can be rationalised, with good customisation to user requirements yet at the same time avoiding special engineering for each case. Several options can be implemented on the same bed, like two turrets, milling heads, steady rests and different types of tailstock. Another example is the two rotary-axis machining unit shown in Fig.

Moreover, the concept used in this machine, the Multi-step XT, is based on individual-spindle modules. Guideways are sliding systems where two surfaces are in contact; the fixed is known as the guide whereas that placed on the sliding component carriage is known as the counterguide. But some deformation is inevitable and if it happens a constant deformation value or a symmetrical behaviour with respect to the guide length is highly recommended. The gripping of slides on guides due to either a low lubrication or a geometrical distortion coming from frictional heating must be taking into account when guides are designed.

To achieve that, usually the guide is hard but the counterguide is softer or more flexible. This is a key element to refit the guide along machine life, by compensating wear induced clearances. The opposition to sliding must be as low as possible. Machine movable components are 6 DOF spatial bodies; therefore the mechanical joints must restrict five of them while allowing the desired one, a rotation in the case of bearings or a longitudinal movement. Usually guides between structural elements are placed in parallel pairs, sufficiently separated to provide the correct support of one element on the other.

The use of the kinematic coupling concept, explained in Chap. For precision machines the couple V-shape and flat guide see the example in Fig. Usually one guide is the master in the assembling of elements whereas the other is adjusted to the final position. In the case of rotational joints, ball or roller bearings are the standard solution.

Hydrostatic bearings are only used for specific applications in grinders or rotary tables. Hydrodynamic bearings are used only in the wheel axis of grinders, because starting is problematic. For longitudinal movements the three main types of guideways now being used in machine tools for material removal processes are explained below see also Sect.

Although contact between roughness peaks cannot be totally avoided, reduction of the frictional work and friction coefficient is achieved. Oil must be periodically injected onto the counterguide to ensure this functional regime is reached. At the same time the counterguide has some small channels on its internal contact surface, called spider arms, to provide a uniform oil supply on the entire contact surface.

The main advantage of this classic guide type is the high damping ratio. As a main drawback, friction is too high at high speeds and friction heat can affect precision and even the guide life. The stick and slip phenomenon also occurs at low speeds. Guides can be machined and grinded directly on the structural material, or built on hardened steel and bolt on the machine structure, where they are finally ground to achieve the final straightness. Currently, a few millimetres thick polymer sheet type PTFE, polytetrafluoroethylene is bonded to the counterguide contact surface.

These materials greatly reduce friction with steel or cast iron. The final adjustment of the carriage on the guide is an important operation, being manually performed by skilled operators using chisel shape scrapers and tincture Prussian blue or vermillion. The surface pattern resulting from scraping is also beneficial for retaining oil along the carriage movement. This type of guide is used in lathes, likewise in high precision machines, because scraping is the way to achieve very good straightness and flatness.

In high speed machines the continuous inversions of movement with the consequent reversal and stick and slip problems do not recommend this solution. Balls are adequate for light loads and high velocities, and rollers for high loads but lower velocities, just the same as in the case of bearings.

This sliding system comprises a rail guideway, with one carriage with integrated elastic wipers on the end faces, sealing strips on the upper and lower faces of the carriage and closing plugs to close off the fixing holes in the guideway. The carriage and guideway of a linear recirculating ball or roller are matched and fitted to each other as a standard system due to their close tolerance preload. Rolling guides are stiffer than friction slides, with a lower opposition to displacement.

The 26 L. Lamikiz installation is easy, as well as the maintenance by the rapid substitution in case of damage to the guides or carriages. Usually machine tool manufacturers buy them just assembled with the required guide length, with the carriage mounted on the guide and preloaded to a specific value depending on the estimated load to move. The main drawback of this sliding system is its low damping due to the direct contact of metal-to-metal of the bed-to-guide-to-roller-to-carriage.


Some additional carriages specially designed for a high damping, using polymers or inducing an oil film, can be inserted among rolling sliders. The life of this type of guides is determined by the fatigue of the rolling elements or races, in the same way as the rolling bearings. To keep the film, an external pump continuously injecting the oil onto the bearing is required. When this technique is used on rotary joints, the result is an extremely stiff design with almost no radial error motion; the pressure exerted by the film automatically centres the spindle in the bearings. On the other hand, the stiffness of the bearing is proportional to supply pressure.

Therefore hydrostatic supported spindles are used in high-cost grinders. On the other hand, new linear guides designs based on the hydrostatic principle are currently under development. The problem is to inject and collect oil along the sliding of the carriage on the guide. In these designs, the carriage contains all the hydrostatic compensation and pockets on its internal surface shape. For large diameter rotary plates, hydrostatic support of the flange disk enables very heavy parts to be supported without friction on the external radius friction torque depends on the radius of the force application ring , whereas roller bearings are used on the plate central axis.

To do that a relative motion between the cutting edge or edges and the workpiece must be applied. Motor power derives from both figures, since this power is the product of torque and speed. In a few cases the tool is fixed on some sort of carriage and workpiece moves, as in lathes. Otherwise, in drilling, milling and most operations, a rotary tool is moved directly by an electrical motor.

Asynchronous induction motors are the most widely used, consisting of two components, an outside stationary stator having coils supplied with AC current to produce a rotating magnetic field and an internal rotor attached to the output shaft that is given a torque by the rotating field.

In machine design, a good selection of the motor torque and power is very important.

Effective approach to high-speed machining

For this purpose a simple calculation can solve the basic motor specifications. The following example shows how to define the torque and power of a lathe for large diameter workpieces. Rotation speed must be rpm for this cutting speed on this diameter. Two depths of cut are studied, 2 and 4 mm in diameter. Lamikiz Table 1. There is a high specific cutting force because this is a difficult-to-cut alloy.

Bearing these results in mind, a motor can be selected for this lathe applying a safety factor, for example a power of 17 kW and maximum torque of Nm are feasible values. Basically there are three types of main motion setup, as shown in Fig. The first is the conventional and more widely used, where the motor is connected to the spindle by a timing belt. This rubber belt is a good vibration insulator; besides, no special care must be taken in the assembly of the group. This solution is possible up to a 6, rpm rotational speed. The second type is the direct drive using a flexible coupling between motor and spindle.

Here, a more reliable and better torque transmission is achieved, 12, rpm and even 16, rpm in special cases being possible. At the same time the flexible coupling is an effective heat insulator between motor and spindle. Furthermore, with the correct spindle assembly to the machine structure, all its thermal growth is derived towards the coupling and the motor, with no influence on the tool position.

For this reason this is the most widely used configuration for precision machines. Finally, high speed machines with rotational speed higher than 18, rpm require compact electrospindles, where the electrical motor is embedded in the spindle. This mechanical solution provides a very good concentricity of the group, needed for high speeds. The angular bearings are hybrid, with steel races Fig.

On the other hand, the heat from the motor itself and friction in bearings is great, requiring an internal water circuit with external cooling. More details are in Chap. Today linear motors make longitudinal displacements possible without other transmissions, but ball screws are still a less expensive and at the same time efficient solution. There, the feed motor, usually a synchronous brushless motor, is coupled to the screw shaft by a flexible coupling, which at the same time is a good torque transmitter, a thermal insulator and eliminates the necessity of a perfect alignment of the motor with respect to the screw.

In other cases the connection of the motor to the screw is by means of a timing belt, with the same advantages and drawbacks that the case of use belts for the main spindle indicated in the preceding subsection. The screw is supported at both ends by angular ball or conical rollers bearings, in configuration double back DB in the former case to increase the rigidity of the axis. For this same reason the screw is usually pre-stressed. This fact also reduces the impact of screw thermal dilation. The sliding component is bolt to the nut; nuts can be square, round or with flanges for a stiffer adjustment to the machine component.

The screw diameter ranges from 6 to mm, whereas the screw lead does it between 1 and 60 mm, keeping a certain proportionality between these two features. If the lead is high, fast movements can be obtained but with a low mechanical advantage. Small leads imply slow movements but with a high mechanical Fig. Lamikiz advantage; at the same time small ones are more highly recommended to ensure precision and controllability of the drive train.

The calculation of screws is based on preventing two mechanical problems. First, buckling due to shaft working under compression when the nut displaces along the screw. Second, critical whirling speeds must be avoided, only in the case when the shaft rotates and the nut moves along the screw. The other case is when the screw is fixed and the motor rotates the nut; evidently the motor must be placed onto the carriage. See Chap. The thermal growth of the screw is a key aspect to be considered and reduced.

During the normal function of ball screws, heat coming from the friction of balls movement on the thread causes a significant longitudinal dilation of the screw. If the shaft has been placed with pre-stress, some dilation is absorbed by this good practice. However some microns always appear. To reduce dilation to a minimum, one solution in machines for high precision is the forced fluid cooling of the screw, internal to the hollowed out shaft, or even the forced cooling of the nut. This increases the price, but maintains thermal growth within machine requirements.

Nevertheless, if the axis position is measured by a direct linear scale, thermal growth becomes considerably less important, because CNC works to reach the desired axis position until it matches with that measured by the linear scale. Therefore, the thermal insulation of external measurement scales from machine heat sources is essential. This is the case of manufacturers of small and medium machines, who try to be flexible regarding user wishes. This is an important competitive factor for their businesses. However in the case of large machine tool companies, the use of their own controls and the need to simplify the production chain means this option is not suitable.

Big machine manufacturers usually sign an agreement with a CNC provider to develop specific CNCs for their machines, being commercialised with the machine tool trademark. Basic CNC functions are shown in Fig. The experimental results demonstrate that the proposed algorithm improves the machining speed in the program consisting of small line blocks without any hardware support. To investigate the performance of the introduced algorithm, the authors implemented it to the machining center equipped with Samsung SNC that consists of a 64 bit main processor and a 32 bit floating point DSP as the motion control CPU.

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