Method of grinding the cams of a camshaft.

0001The invention relates to a method for grinding cams of a camshaft by means of a numerically controlled camshaft grinding machine, in which the camshaft is arranged in a workpiece holder with a predetermined angular velocity in predetermined angular increments around its longitudinal axis and a grinding slide with a grinding wheel in an axis perpendicular to the longitudinal axis can be delivered in predetermined steps, depending on the geometry, the material and the desired surface finish of the camshaft and the cams, a grinding wheel is selected for processing in its condition and the infeed of the grinding wheel is adjusted.

0002A method of the type mentioned above is generally known. For example, in DE-Z "Werkstatt und Betrieb", 1985, pages 443 to 448; 1986, pages 655 to 660; 1987, pages 269 to 274 and 1988, pages 201 to 206 described various processes with which production cam shape grinding machines are controlled depending on various parameters, including the geometry of the cams and the camshaft and the material used.

0003Finally, from the dissertation by Yegenoglu "Calculation of topography parameters for the design of CBN grinding processes", Faculty of Mechanical Engineering of the Rheinisch-Westfälische Technische Hochschule Aachen, 1986, a mathematical model is known to determine topography parameters of external cylindrical grinding processes and strategies for process design to derive.

0004In the initially mentioned methods, such as those used for cam shape grinding, attempts have been made to capture certain individual aspects of cam shape grinding using mathematical models and to derive process parameters from them, but the focus of these efforts was on the form accuracy, ie the dimensional accuracy of the ground cams, while economic criteria have been taken into account at most.

0005In the work of Yegenoglu, economic aspects were also taken into account, but that known model relates to general external cylindrical grinding processes and there is no closed system to convert the model ideas found into a production strategy.

0006The invention is based on the object of developing a method of the type mentioned in such a way that the physical mechanisms of the cam shape grinding with tool specifications and process parameters are brought into a closed cycle in order to economically, that is to say with a minimal grinding time, making the most possible use of the physical Possible to find an optimum.

0007According to the invention, this object is achieved by the following process steps: - Determining a minimum grinding time from the geometry of the cams and the maximum angular velocity; - Determining a maximum related chip removal volume as a function of the maximum drive power of the grinding wheel drive; - Determination of a maximum machined workpiece volume from the minimum grinding time and the maximum related chip removal volume; - Determining a maximum infeed from the maximum machined workpiece volume and the geometry of the cams; - Determining a grinding wheel type from a table of predetermined grinding wheel types depending on the predetermined roughness depth of the cam; - Grinding the cams by means of the specific grinding wheel while setting the maximum infeed.

0008The object underlying the invention is completely achieved in this way. For the first time, the two most critical parameters of the grinding process are assumed, namely the maximum possible angular velocity of the so-called C-axis on the one hand and the drive power of the grinding wheel on the other, in order to use the special geometry of the camshaft cams to be machined to achieve a maximum related chip removal volume as a critical parameter of the to determine the inventive method. This maximum related chip removal volume then in turn determines the maximum infeed via the geometry of the cams in such a way that when this infeed is set the grinding machine is operated at the limit of its possible performance data. The specification of a finite amount of actually available grinding wheels can then, depending on the desired surface quality, ie depending on the desired roughness, an associated grinding wheel can be determined in order to then allow the cam shape grinding process to run.

0009In a preferred further embodiment of the method according to the invention, the following steps are additionally used: - Determining the degree of chip filling from the maximum drawn chip removal volume; - Comparing the determined degree of chip filling with a limit value; - Reduction of the maximum amount of chip removal until the chip filling degree does not exceed the limit value; - Determining the associated maximum infeed from the reduced maximum time span volume obtained; - Grinding the cams using the specific grinding wheel while setting the maximum infeed.

0010These measures have the advantage that, in addition to the limit data for the maximum angular velocity in the C axis and the power of the grinding wheel drive, the physical process of chip removal by cutting the grains of the grinding wheel is taken into account in such a way that the chip filling degree , ie the ratio of the individual chip volume to the chip space volume, should not exceed a certain limit. Here, too, the topography of the grinding wheel via the chip space between the grains of the grinding wheel and the size of the material chips removed flow in again as physical processes.

0011In a further preferred embodiment of the invention, the following further steps are used: - Determination of the individual grain force from the maximum obtained chip removal volume; - Comparing the determined single grain force with a second limit value; - reducing the maximum amount of chip removal obtained until the individual grain force does not exceed the second limit value; - Determining the associated maximum infeed from the reduced maximum time span volume obtained; - Grinding the cams using the specific grinding wheel while setting the maximum infeed.

0012This measure has the advantage that the resilience of the grains of the grinding wheel is tightened as a further process parameter, in order to prevent premature excessive wear of the grinding wheel if the grinding power is too high. In this case too, a certain reduction in grinding performance is accepted in the interest of fulfilling this secondary condition.

0013In a further preferred embodiment of the method according to the invention, a maximum related chip removal volume is determined from a further boundary condition and the respectively larger chip removal volume is used to determine the maximum infeed for grinding the cams.

0014This measure has the advantage that, in addition to the boundary conditions already mentioned, further boundary conditions that result from empirically determined dependencies are taken into account again via the central process variable, namely the maximum amount of chip removal. In this case too, a certain reduction in the grinding performance, ie an increase in processing time is accepted in order to be able to meet additional boundary conditions depending on their expediency.

0015In further refinements of the method according to the invention, these additional boundary conditions can be the roughness depth of the cam and grinding wheel or the shape error of the cams or the cutting performance of the camshaft grinding machine or the wear of the grinding wheel or the peripheral zone temperature of the cams or the machined workpiece volume.

0016If all the above-mentioned boundary conditions are taken into account as the limits of the optimum grinding time that can be achieved, the result is a closed concept for cam shape grinding, in which the theoretically possible combination of cam shape grinding machine, grinding wheel, conditioning of the grinding wheel and workpiece, with regard to its geometry and material, is achieved . Individual boundary conditions can now be selectively neglected in order to achieve a further reduction in grinding time while accepting certain restrictions.

0017The method according to the invention is particularly suitable for the user-controlled operation of a cam shape grinding machine via a screen menu control with a graphic dialog, in which the user of the grinding machine is given screen masks one after the other in which he can insert the still missing characteristic values ​​of the respective processing task. The numerical control of the grinding machine then selects the respectively optimal grinding wheel from a stored catalog of actually available grinding wheels from the fixedly specified and a variably entered parameters and automatically sets the required process parameters of the cam shape grinding machine, in particular the movement of the C-axis, i.e. the axis of rotation of the Camshaft and the X axis, ie the travel of the grinding carriage.

0018It has been shown in practical tests that the optimization of grinding processes that can be achieved with the method according to the invention leads to a drastic reduction in grinding times, so that camshafts can be ground with a significantly increased output in the production process, the grinding wheel being exposed to optimally low wear and tear at the same time conditioning of the grinding wheel is also optimally integrated into the grinding process.

0019Further advantages result from the description and the attached drawing.

0020It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own without departing from the scope of the present invention.

0021Embodiments of the invention are shown in the drawing and are explained in more detail in the following description. Show it:<ul id="ul0001" list-style="none"><li>Figure 1 is a side view, extremely schematic and partly in section along the line II of Figure 2, a cam shape grinding machine, as it can be used to carry out the method according to the invention.</li><li>Fig. 2 is a plan view of the cam form grinding machine shown in Fig. 1;</li><li>3 shows a detailed view, on a greatly enlarged scale, of a cam in progress to explain various operating parameters;</li><li>4 shows a side view of a camshaft, as can be processed by the method according to the invention;</li><li>5 is an extremely greatly enlarged scale, a perspective view of an octahedral CBN grain, as used in modern grinding wheels;</li><li>6 is a partial view, in section and on a greatly enlarged scale, of a surface of a CBN grinding wheel;</li><li>7 is a perspective view for explaining a machined workpiece volume;</li><li>FIG. 8 shows a representation similar to FIG. 3, to explain the speeds of the grinding wheel and cam effective in the method according to the invention;</li><li>9 shows a diagram for explaining boundary conditions as they are taken into account in the method according to the invention;</li><li>10/1 to 10/12 a flow chart to explain an embodiment of the method according to the invention.</li></ul>

0022The aim of the method according to the invention is to implement the machining task, taking into account the material, the raw and finished part geometry and the surface quality, in a machining concept in which a prediction of the tool specification, the conditioning parameters, the technology parameters, the process sequence and the machining time can be made without to conduct experimental trials. The information determined for shape grinding of the camshaft is presented to the control of a cam shape grinding machine in a form which enables editing of the proposed numerical control program in accordance with DIN 66025.

0023The method according to the invention preferably relates to the field of CBN grinding, in which grinding wheels with an abrasive material made of CBN (cubic boron nitride) crystals are used. A quantitative connection is established between the physical processes of the CBN cam shape grinding as a closed circuit with the process parameters of the cam shape grinding machine.

0024To do this, the machining task is first defined. The workpiece with material, oversize and geometry is specified as the input variable. The criteria with vibrations and temperature are specified as the disturbance variable and finally the limit criteria, ie the shape error and the surface quality, are defined as the output variable.

0025The technology follows from the machining task, both with regard to the machining kinematics and the machining kinetics. The former means the process variables of the infeed, the machining volume, the angular velocity, the cutting speed, the contact length and the equivalent grinding wheel diameter as manipulated variables, while the second one includes the chip removal volume, the cutting force, the power, the process duration, the wear and the dynamic stiffness understood as process variables.

0026The tool is then determined from the machining task and the technology based on the design and conditioning. The former is understood to mean the state variables of the specification and the topography, while the second is to be understood as the core variables, ie the infeed and the speed strategy of dressing.

0027The technology and the tool then ultimately result in the machining concept, for which the result variables, namely the cutting value optimization for minimum grinding time and the control variables for the NC program according to the raw / finished part description, production data, machining sequence, conditioning strategy and execution instructions, are output as a protocol.

0028In summary, this means that in the method according to the invention, the workpiece characteristics (material, oversize and geometry) are initially specified as input variables and the limit criteria (shape error of the cam contour, surface quality, thermal boundary zone influence) as output variables in order to determine the machining strategy therefrom. As a result of the relationship between machining kinematics as manipulated variables with the numerical consideration of the design of a grinding wheel topography and machining kinetics as process variables, a machining concept is defined so that a minimal grinding time with optimal cutting values ​​is made possible, which determine the NC program as the control variable as the result variables. An essential part of the proposed method is the specification of the physical mechanism of action of the machining process with an analytical consideration of the cutting edge movement during grinding as well as the interaction of the individual components at the cutting point.

0029The method according to the invention is preferably represented as a graphic dialog on the cam shape grinding machine in a manner which is easy to handle for the user of the grinding machine. In this way, a group of materials can be specified in an advantageous manner, because experience has shown that the camshafts to be ground only consist of a finite number of materials. The user of the grinding machine therefore only needs to specify a certain standardized material by means of a code number. The geometry parameters of the cam contour are kinetodynamically analyzed by means of multiple derivation over time and represented as process parameters, as is known per se.

0030The tool paths in the X-axis and the perpendicular Z-axis are also shown graphically and can be specified by the user of the grinding machine depending on the application.

0031When considering the machining kinematics, it is assumed that the grinding wheel moves with its peripheral cutting edges relative to the workpiece on an orthohypocycloid, the path of which results from the superimposition of the peripheral speed of the grinding wheel and the workpiece speed. The successive othohypocycloids lead to material removal in the contact area during surface production, the size of which is determined by the infeed, the machining volume, the contact length and the equivalent grinding wheel diameter.

0032The specified roughness depth of the cam contour to be machined defines the grain size and thus the concentration of the CBN grinding wheel.

0033In summary, the theoretical grain protrusion is first derived and then the chip space volume is determined by means of the grain distance. It is assumed that the CBN grit is integrated in the grinding wheel bond by means of cylindrical tie bars, which give the grit a stiffness depending on the modulus of elasticity (2-10 x 10⁴ N / mm²), the bending strength (25-150 N / mm² ) and the compressive strength (100-1000 N / mm²) anchored in the binding. It is important here that ceramic bonds of CBN grains are preferably considered in the context of the present method.

0034In the underlying grain distribution model, it is assumed that the grains lie in a statistical cutting edge distribution in a square arrangement on concentric levels. This gives the possibility to calculate the area-related kinematic number of cutting edges, the grain density, the individual chip volume, the grain load, as well as the degree of chip filling, in order to then coordinate the characteristic parameters of the grinding wheel topography with the machining kinetics. Using the calculated tool data, a CBN grinding wheel with its name from the tool file is recommended.

0035The conditioning parameters are determined according to the theoretical grain wear and the theoretical removal ratio.

0036Overall, an optimization strategy is pursued with the aim of achieving a minimum grinding time under consideration of certain secondary conditions and thus accurately describing the cutting data.

0037Finally, the determined values ​​for the user of the cam shape grinding machine are displayed in the graphics dialog using a protocol.

0038Before the special peculiarities of an exemplary embodiment of the method according to the invention are described, the underlying physical model should first be briefly explained. In addition, reference is made to the aforementioned Yegenoglu dissertation, which contains further explanations about the physical processes involved in CBN grinding.

0039The parameters of a multi-stage grinding process, which determine the machine setting for cam shape grinding in the plunge process as a control variable, are the cutting speed v_C., the workpiece angular velocity ω_W and the infeed per value rotation a.

0040The cutting speed v_c can be regarded as a constant parameter, which is determined in a multi-stage process according to the respective grinding task. The cutting speed corresponds in a first approximation to the peripheral speed of the grinding wheel. The cutting speed v_c can be deduced from the relationship using the cosine rate: v_c² = √<o ostyle="single">v_s² + v_w² - 2 v_s v_w cosα</o> (m / s) [1] Where v_w = 2π r_i · N / 60,000 (m / s) [2] With n = ω_w / 360 (min⁻¹) [3] is. Values ​​of v_C. = 60-140 m / s. Compared to the cutting speed, the workpiece peripheral speed is v_w smaller by at least two powers of ten and the speed ratio is given by the equation q = v_c/ v_w      [4] given. The length of the engagement arc results from the curvatures of the grinding wheel and workpiece as well as from the radial feed. The radial feed corresponds to the infeed amount of the grinding wheel per workpiece revolution. The geometric length l_G, via which each cutting edge engages with the workpiece, is calculated l_G = √<o ostyle="single">ad_eq</o> (mm) [5] With<maths id="math0001" num=""><img file="EP0342528A2_D0001.tif" /></maths>

0041Contact lengths for cam shape grinding are usually between l_G = 0.1-5 mm. Larger values ​​result in particular on the cam flank.

0042The cutting volume is given by the cam geometry and the infeed per workpiece revolution:<maths id="math0002" num=""><img file="EP0342528A2_D0002.tif" /></maths> Where b is the cam width, φ_G the base circle angle, R_G the base circle radius, R_G the base circle radius, φ_F the flank angle, R_K the flank radius for an interval, φ_S the apex angle and R_S denotes the tip radius. The grinding time per cam revolution can be calculated using the equation t_H = (φ_G· 60) / ω_G + 2 (φ_F· 60) / ω_F + (φ_s· 60) / ω_S      [8th] to calculate.

0043The following applies to the machining kinetics: With the specified grinding allowance, it is important during roughing to remove as much material as possible in the shortest possible time without fear of thermal damage to the peripheral zone.

0044The chip removal volume can be calculated from the cutting volume and the grinding time per cam revolution:<maths id="math0003" num=""><img file="EP0342528A2_D0003.tif" /></maths>

0045Relative to a grinding wheel width of 1 mm:<maths id="math0004" num=""><img file="EP0342528A2_D0004.tif" /></maths>

0046Usual related chip removal volumes are in the range of Q ′_w = 0.1-5 mm³ / mms for finishing. Here, surface roughness depths R_Z. = 0.5 µm to 4 µm achievable. Extremely high chip removal volumes Q_w′ = 85 - 110 mm³ / mms are made possible. These values ​​depend on the material, the grain size, the concentration and the cutting edge load.

0047From the chip removal volume Q_w'The cutting performance can be calculated. The equation is: P_c = K · Q_wⁿ      [11] Herein, k means a constant and n an exponential coefficient, which takes into account the respective workpiece-related relationship between chip formation and friction energy.

0048A comparison of the constant k and the exponent n for the same material class, namely chilled cast iron, pearlitic ferrous cast iron and malleable cast iron, shows that the type of conditioning of the grinding tool represents a distinction in its sizes:

0049For example, k = 1.903 and n = 0.384 apply to synchronous conditioning without sharpnesses, k = 1.824 and n = 0.384 to synchronous conditioning with sharpnesses, while k = 1.869 and n = 0.36 to countercurrent conditioning without sharpnesses and to countercurrent conditioning with sharpnesses k = 1.754 and n = 0.36.

0050The reason for this phenomenon is to be found in the chip space formation and in the generation of the cutting edge geometry.

0051The specific cutting energy<maths id="math0005" num=""><img file="EP0342528A2_D0005.tif" /></maths> can be represented in a similar manner depending on the volume of chip removal.

0052The cutting force at a constant chip removal rate is given by the equation<maths id="math0006" num=""><img file="EP0342528A2_D0006.tif" /></maths> given. With constant cutting performance and increasing cutting speed, the cutting force decreases degressively. This connection is ultimately due to the reduction in the chip cross-section.

0053The cutting force is determined as the sum of the individual forces currently acting on the cutting edges in the cutting. The individual force components of a collective of cutting a grinding wheel for external plunge grinding are the cutting tangential force F_ct and the normal cutting force F_cπ.

0054The cutting force F_c can then be described by the context F_c = √<o ostyle="single">F_ct² + F_cn²</o>(N) [14]

0055The normal cutting force F_cn can be said about the relationship<maths id="math0007" num=""><img file="EP0342528A2_D0007.tif" /></maths> determine, where the proportionality factor µ represents the cutting force ratio<maths id="math0008" num=""><img file="EP0342528A2_D0008.tif" /></maths>

0056Since µm is determined by the chip formation mechanisms on the grain cutting edges, the cutting force ratio mainly corresponds to the shape of the cutting edge, the number of kinematic cutting edges, the chip cross section, the grain material, the workpiece material and the coolant conditions.

0057With CBN discs, a cutting ratio of µ = 0.36 to 0.45 is assumed and there is a loading angle of the cutting edge α_b = arctan µ = 19.8 ° to 24.2 °.

0058The greater the ratio of tangential force to normal force, the lower the friction, shear and separation processes taking place in the contact zone, which indicates a sharp cutting edge condition with coordinated chip spaces. With careful coordination of the grinding wheel specification and the conditioning to the grinding process, it is possible to create the topography of the grinding tool in such a way that only very slight deviations in the initial cutting force ratio occur before in the stationary area.

0059The following applies to the tool: In order to interpret the specification, the roughness must first be taken into account, which is generally prescribed for the respective grinding task. However, the roughness depends on the specification of the CBN grinding tool and on the other hand on the engagement conditions. The specification of the CBN grinding tool is selected according to the grain size and concentration in accordance with the process, so that the roughness requirement can be met under the kinematic and kinetic conditions to be explained. The specification of the grinding tool determines the initial effective roughness, with small grain sizes and increasing concentration the initial effective roughness decreases. A large grain and decreasing concentration increases the initial effective roughness.

0060The following table of corresponding parameters can be specified for CBN grinding wheels available today: <tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="3" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="52.50mm" /><colspec colnum="2" colname="col2" colwidth="52.50mm" /><colspec colnum="3" colname="col3" colwidth="52.50mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" align="center">Grain size</entry><entry namest="col2" nameend="col2" align="center">concentration</entry><entry namest="col3" nameend="col3" align="center">Initial effective roughness</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">B 64 / B 91</entry><entry namest="col2" nameend="col2" align="left">K (%) = 30 to 42</entry><entry namest="col3" nameend="col3" align="left">R_tse = 3.2 - 5.5 µm</entry></row><row><entry namest="col1" nameend="col1" align="left">B 126</entry><entry namest="col2" nameend="col2" align="left">K (%) = 30</entry><entry namest="col3" nameend="col3" align="left">R_tse = 5.2 - 6.8 µm</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">B 181 / B 252</entry><entry namest="col2" nameend="col2" align="left">K (%) = 30 to 18</entry><entry namest="col3" nameend="col3" align="left">R_tse = 8.8 - 12.4 µm</entry></row></tbody></tgroup></table></tables>

0061The grain size and the concentration of a CBN grinding wheel result in the surface quality of the grinding tool, so that there is sufficient space between the peripheral CBN grains for the chips to be produced.

0062The type and hardness of the bond exerts an influence on the grinding wheel topography and on the breaking out of the CBN grains from the formation (ceramic). With a harder bond, the CBN crystals remain in the bond longer, so that the edges in the grinding process are primarily blunted. This not only changes the grain shape, but also the number of cutting edges.

0063The type of bond in a grinding wheel specification depends on the grain density C_K, which is selected as the grain size to describe the number of grains per mm³ volume of abrasive coating. the equation<maths id="math0009" num=""><img file="EP0342528A2_D0009.tif" /></maths> with the value q_m = 1.41 for an octahedron represents the dependence on the mean grain diameter and the concentration. W_m³ is the theoretical volume of an octahedron.

0064In order to consider the grinding wheel topography, the area-related kinematic number of cutting edges, the cutting volume per cutting edge, the cutting space volume and the cutting space filling degree must be taken into account. This creates the possibility, using analytical parameters, to carry out a theoretical coordination between the volumes of the machining process, on the one hand, using the technology parameters and the tool, on the other hand, via the topography with a defined specification. At the same time, the workpiece wear is examined, which is caused not only by changed grain geometry, but also by the breaking out of the grains when the grain load is high and the strength of the binding material is not coordinated.

0065The following relationship can be described for the area-related kinematic cutting edge number:<maths id="math0010" num=""><img file="EP0342528A2_D0010.tif" /></maths> where K is the volume-related concentration, W_m the average mesh size for the grains, ie 1.42 times the grain diameter for an octahedron d_k and finally q is the speed ratio, as already shown above. The area-related kinematic number of cutting edges has the dimension mm⁻².

0066The individual chip volume can be determined by the equation depending on the cutting conditions and the grinding wheel specification<maths id="math0011" num=""><img file="EP0342528A2_D0011.tif" /></maths> determine. The single chip volume receives the dimension µm³ if you choose the exponents with m₁ = 0.598, n₁ = 0.201 and p₁ = 0.798 and W_m in µm, Q_w in mm³ / mms, d_eq in mm and v_C. in m / s.

0067To determine the chip space volume, the theoretical mean grain protrusion and the grain spacing should first be determined. The theoretical average grain supernatant between the peripheral grain tips and the binding material is given by the equation<maths id="math0012" num=""><img file="EP0342528A2_D0012.tif" /></maths> given, the exponents can be specified with m₂ = 0.05, y = 0.25, n₂ = 0.1 and p₂ = 0.4.

0068The mean grain protrusion is then due to the simplified relationship Z._r = 0.62 * Z_th (µ) [21] certainly.

0069The grain spacing can then be determined by the equation<maths id="math0013" num=""><img file="EP0342528A2_D0013.tif" /></maths> to calculate.

0070The chip space volume then results from the following relationship V_SR = (l_k - Z_r 1.41) Z_r2 (µm) [23]

0071The relationship between the individual chip volume and the associated chip space volume is defined as the so-called chip space filling degree<maths id="math0014" num=""><img file="EP0342528A2_D0014.tif" /></maths>

0072The degree of chip filling depends to a large extent on the material to be machined if one assumes that the specification and the topography are adapted to the requirements of the cutting conditions. Depending on the material and material condition, the chips have different shapes. In the real grinding process, the chips require a larger chip space volume than their own volume. From this it can be deduced that the chip filling degree must not exceed a certain limit value, for example 0.75, if an overloading of the abrasive coating is to be avoided.

0073In this regard, radial grain wear is permitted using the equation r_s = (0.75 - f_G) · Δ b_s · Z_r (µm) [25] is calculated, where Δb_s = 1.42 corresponds to the grain coverage factor.

0074The stability of the grinding tool is very important when plunge grinding. If the radial wear exceeds a certain permissible dimension, the required shape can only be created again by conditioning (dressing). The conditioning interval is often used to assess the grinding process. It is given as the ratio of the removed material volume to the radial grinding wheel wear by the so-called grinding ratio or referred to as stock removal ratio G. The total wear of the grinding wheel required to calculate the stock removal ratio obeys the relationship: V_vs = π · d_s · R_s · B · 10⁻³ (cm³) [26]

0075The machined volume of material within a conditioning interval can be calculated using the equation V_{Flat share} = V_w · N_w · T_s (cm³) [27] calculate, where V_W the machining volume per workpiece, N_W the number of machined workpieces per hour and day_s indicates the stand interval between two conditions.

0076With this, the transfer ratio becomes too<maths id="math0015" num=""><img file="EP0342528A2_D0015.tif" /></maths>

0077As a result of the dulling of the grain, the individual grain force F increases due to increased friction_K. On the other hand, the bond to the grain base is more strongly eroded at higher cutting capacities, which in turn decreases the grain breaking force F_Kmax has the consequence.

0078The load on the individual grain is determined by the number of cutting edges over which the cutting force is distributed as a result of the grinding wheel specification and the process parameters.

0079The individual grain force is calculated<maths id="math0016" num=""><img file="EP0342528A2_D0016.tif" /></maths> in which A_K = l_G · B (mm²) [30] the contact area is.

0080The effective cutting edge distance l_K and the length of the intervention are dependent on the infeed and the cutting speed in addition to other influencing variables. The effect of changing the kinematic quantities v_s and V_w on the chip thickness a_n is through the relationship<maths id="math0017" num=""><img file="EP0342528A2_D0017.tif" /></maths> shown.

0081If the grinding wheel peripheral speed is increased with constant intervention sizes, the chip thickness decreases. Due to the fact that fewer cutting edges are engaged, the total cutting force is reduced. The contact zone temperatures can be reduced by reducing the contact time between the abrasive grain and the workpiece while the grain has a high thermal conductivity. For example, the thermal conductivity of CBN grain is 700 W / m ° C and is significantly higher than that of conventional aluminum oxide.

0082The conditioning of the grinding wheel must be taken into account as a further process parameter.

0083As is well known, grinding wheels lose both their original starting profile and their cutting ability as a result of wear. There is a change in the grinding wheel topography as a function of the grinding time. The task of conditioning is to bring the topography of the grinding surface back to its original shape. Diamond form rollers or sharpening rods are used as conditioning tools.

0084The conditioning parameters with regard to the rotating diamond tool are the shape sizes: profile shape, specification (grain density, settlement pattern) as well as the setting sizes: infeed per conditioning process, peripheral speed of the roll, axial side feed and speed quotient.

0085You define the degree of coverage with V_d = a_pd / f_ad      [32] as a quotient of the effective width of the roller profile and side feed of the roller per grinding wheel revolution, these values ​​are for V_d between 1 and 6, so the theoretical axial ripple<maths id="math0018" num=""><img file="EP0342528A2_D0018.tif" /></maths> is minimal.

0086The speed quotient<maths id="math0019" num=""><img file="EP0342528A2_D0019.tif" /></maths> results from the peripheral speed of the diamond roller v_R and the grinding wheel v_S. Changing directions of rotation of the roller (co-rotation and counter-rotation), the speed quotient and the axial side feed influence the initial effective roughness.

0087Now that the underlying physical processes have been explained in a summarized representation, an embodiment of the invention will now be explained in detail, in which an average value optimization is carried out on the basis of the processes described above. The aim of this cutting value optimization is to compare the theoretically derived relationships between the processing technology, the tool and the work result by means of determined dependencies, taking into account the performance limit of the machine tool and the grinding tool. It should be used to calculate optimal chip removal volumes for any infeed workpiece speed combinations in order to enable a minimal grinding time.

00881 and 2, a numerically controlled cam shape grinding machine is shown in an extremely schematic manner, which is identified overall by the reference number 10.

0089A camshaft 12 is clamped in a workpiece holder 11. The camshaft 12 can be rotated about its longitudinal axis 13, the so-called C axis, in defined angular steps by means of the rotating workpiece holder 11, as indicated by an arrow 14. The angular velocity of the workpiece holder 11 is identified by ω. As a result of the actually existing drives, with the required precision of the rotation angle setting of the C-axis 13, only a certain maximum angular velocity ω_Max possible, which can vary in areas over the cam contour, as will be shown below.

0090A grinding carriage 17 carries a grinding wheel 18 which can be driven by means of a drive motor 19. The power of the drive motor 19 is denoted by P.

0091The grinding carriage 17 with grinding wheel 18 can be advanced along an axis 20, the so-called X axis perpendicular to the C axis 13 of the camshaft 12, in defined X steps.

0092As shown in FIG. 2 in dashed lines, the grinding wheel 18 can be moved toward the camshaft 12 for machining the surface of the camshaft 12 in this way.

0093The grinding wheel 18 rotates about its axis 21, which coincides with the so-called Z axis. The grinding slide 17 or the workpiece holder 11 can namely be additionally displaced in the direction of the Z-axis 21 so that the grinding wheel 18 can process the individual cams of the camshaft 12 one after the other.

0094It is understood that the above illustration is only to be understood as an example and the invention is not restricted thereby. The invention can of course also be used in grinding machines in which the axis of the grinding wheel is inclined to the workpiece axis and the grinding wheel has a conical grinding surface instead of a cylindrical one and the like. More.

0095In the cam form grinding machine 10 according to FIGS. 1 and 2, an NC control device 25 is provided, to which input parameters 26 can be supplied. The NC control unit 25 derives control signals therefrom, which are fed via data lines 27 and 28 to the drive of the workpiece holder 11 and to the drive of the grinding carriage 17. A distinction is made here between the so-called "delivery operation" and the so-called "rail operation". During infeed operation, the grinding wheel 18 is advanced along the X-axis 20 to the camshaft 12 in order to achieve a certain material removal during grinding. In contrast, in rail operation, the grinding wheel 18 is adjusted along the X-axis 20 depending on the respective rotational position of the camshaft 12 about the C-axis 13 so that the point of engagement or the line of engagement on the grinding surface of the grinding wheel 18 is always at a desired point on the cam contour of the camshaft 12. As a result of the superimposition of the infeed mode and the track mode, the cams of the camshaft 12 can be ground along a spiral grinding path that begins on the raw surface of the unprocessed cam and ends on the contour of the finished surface of the cam. These processes are known per se and should therefore not be explained again here.

0096Fig. 3 shows a cam 30 of the camshaft 12 with further details.

0097The cam 30 has a so-called base circle 31, a tip 32 and lateral flanks 33.

0098In a first point 34, the grinding wheel 18 engages with a surface line on the surface of the cam 30. In second points 35, the base circle 31 merges into the flanks 33. The second points 35 thus define the so-called base circle angle φ_G. The radius of the base circle is R_G designated.

0099Third points 36 mark the transition from the flanks 33 to the tip 32. They thus define the so-called flank angle φ_F and the tip angle φ_S. The radius of the tip is with R_S designated.

0100A fourth point 37 denotes an arbitrary point, for example on the tip 32, at which a tangent 38 is placed on the cam contour. If a parallel tangent to the base circle 31 is drawn to the tangent 38, the distance between the parallel tangents 38, 39 gives the so-called survey value E.

0101A fifth point 40 and a sixth point 41 denote any points on the contour of the cam 30, shown using the example of two points on the flank 33. The radii of curvature of points 40, 41 are R_Fi and with R_Fn designated. This is to say that the radius of curvature with R_Fi or R_Fn in the area of ​​the flanks 33, ie via the flank angle φ_F varies while the radius of curvature with R_G in the area of ​​the base circle 31 via the base circle angle φ_G is as constant as with R_S via the tip 32 or the tip angle φ_S.

0102Various forms of tables can be set up to analytically define the cam contour. The contour of the cam 30 can thus be represented, for example, as a table of polar coordinates, but forms of representation are also common in which a so-called survey value table is specified, which represents the survey value E over an angle Θ.

0103In both cases, the table specified is converted into control commands for the angle of rotation of the C-axis 13 and the drive unit for the X-axis 20 of the grinding carriage 17 to determine the rail operation, taking into account the grinding wheel diameter.

0104In FIG. 3, the oversize by which the raw contour drawn in FIG. 3 is to be removed in order to obtain the finished contour shown in dashed lines is also designated by a.

0105Finally, FIG. 3 shows the roughness depth R in a section 42 with a greatly enlarged representation_Z.that is to be generated on the surface of the cam 30 by grinding. In addition, the material used is symbolized in section 42 with W.

0106The material symbolized with W is not a continuously variable size. Rather, a limited number of materials can be specified for the practical applications of the method according to the invention, as are usually used as camshaft materials. These include, in particular, chilled cast iron, malleable cast iron, pearlitic cast iron and it must also be taken into account whether these materials are case hardened or inductively hardened. In practice, this finite number of possibilities can be symbolized by a finite number of code numbers which can be selected by the user of the method according to the invention.

01074 shows a camshaft 12 as it can be processed using the method according to the invention. In the general illustration in FIG. 4, the camshaft 12 has n cams 30/1, 30/2 ... 30 / n. Typically, camshafts 12 with a total of 8 cams can be ground using the method according to the invention.

0108At the start of the grinding process, the grinding wheel 18 should be set in the Z-axis so that it faces the first cam 30/1. The distance of the grinding wheel 18 from the first cam 30/1 in the X axis 20 is an initial value X_A. This value must be specified for the method according to the invention so that the cam shape grinding machine can travel through this initial feed path at the beginning of the method before the grinding wheel 18 comes into contact with the first cam 30/1.

0109Furthermore, the aforementioned initial setting of the grinding wheel 18 along the Z axis 21 must be specified for this, which is determined by the initial dimension Z_A is marked.

0110In the subsequent processing of several cams 30/1, 30/2 ... the so-called cam jump Z_s, ie the distance between the cams 30/1, 30/2 ... in the Z-axis 21 can be specified. Finally, after machining the last cam 30 / n, the grinding wheel 18 has its axial end position Z_E reached, which must also be specified.

0111The cam width b must also be entered to determine the process parameters.

0112In order to illustrate the grinding wheel parameters, a CBN grain 50, ie a crystal of cubic boron nitride, is shown in FIG. 5, which ideally has the shape of an octahedron. The diameter of the CBN grain 50 is d_K and its volume with V_K designated.

0113As FIG. 6 shows, several of these grains 50, namely grains 50/1, 50/2 ... 50 / n, are integrated in a ceramic bond 55 in a real grinding wheel 18. The concentration of the grains 50 is denoted by K.

0114The distance between two grains 50/1 and 50/2 is l_K and the theoretical grain supernatant is Z on average_t. The chip space volume V_SR determine between two grains 50/1, 50/2.

0115With F_K 6 shows the effective grain force which acts on the grains 50/1 ... during grinding.

0116FIG. 7 shows, in a perspective illustration, a machined volume 60 as is machined on a cam when an infeed a is set at a cam width b. As can easily be seen from FIG. 7, the volume V results_w as the product of infeed a, width b and circumference of the cam, as will be explained below in relation to FIG. 9.

0117Fig. 8 shows the relationships at the effective speeds during the cam shape grinding.

0118As indicated by arrows 62, 63, the cam 30 and the grinding wheel 18 rotate in opposite directions. At the point of engagement 34, the workpiece speed v_w and the grinding wheel speed v_S, each represented as peripheral speeds, effective. The directions of the velocity vectors v_W and V_S result from the respective radii R_S the grinding wheel 18 and R_n of the cam 30, as has already been explained above for FIG. 3 for the cam 30.

0119The cutting speed v_C. results from the geometric addition of the vectors v_W and V_S and can be calculated according to the amount using the cosine rate.

01209 finally shows a diagram in which the grinding time t_H for a cam above the obtained chip removal volume Q ′_W is applied.

0121As is known, the grinding time t_H equal to the quotient of machined workpiece volume V_w (see FIG. 7) and the related chip removal volume Q_w'. The circumference of the cam 30 is calculated as the sum of the products of circumferential angles φ and radii R, as in FIG. 9 with the relationship<maths id="math0020" num=""><img file="EP0342528A2_D0020.tif" /></maths> is specified. Since the cam width b is constant, the machined volume V depends_w thus only from the variable oversize a. The relationship between grinding time t_H and related chip removal volume Q_w'Thus expresses itself in a hyperbolic curve, which is parameterized according to a, as shown in Fig. 9 for two examples a₁ and a₂.

0122However, one is in the choice of the obtained chip removal volume Q_w'Not free, because the adjustable related chip removal volume Q_w'Is limited by various process parameters.

0123These additional boundary conditions can be explained as follows - without claiming complete mention - on the basis of empirically obtained functions: A first boundary condition is the achievable roughness r_t of the workpiece and r_to the grinding wheel 18. With these two sizes and the concentration K of the grinding wheel 18 and the cutting speed v_S can be a first relationship for a limit value of the referenced chip removal volume Q_w'Represent as follows<maths id="math0021" num=""><img file="EP0342528A2_D0021.tif" /></maths>

0124The second boundary condition is the formal error f_m of the cam, which is known to be the quotient of cutting force F_C. and system rigidity C_G is. Then, taking the cam width b into account, the following relationship results:<maths id="math0022" num=""><img file="EP0342528A2_D0022.tif" /></maths>

0125The third boundary condition is tool wear r_s depending on the chip filling degree f_G, the grain coverage factor Δ b_s and the theoretical grain protrusion Z_r specify as follows:<maths id="math0023" num=""><img file="EP0342528A2_D0023.tif" /></maths> where Z is an auxiliary variable and the relationship<maths id="math0024" num=""><img file="EP0342528A2_D0024.tif" /></maths> obey.

0126The fourth boundary condition is the temperature T_M specify, and the relationship is:<maths id="math0025" num=""><img file="EP0342528A2_D0025.tif" /></maths>

0127As a further boundary condition, taking into account a drive power P of the motor 19 of, for example, 22 kW and taking into account maximum angular velocities ω_Max of 10000 ° C / min in the survey area and 3000 ° / min on the base circle the relationships Q_w5′ = 1131,183 · <maths id="math0026" num=""><math display="inline"><mrow><mfrac><mrow><mtext>1</mtext></mrow><mrow><mtext>b</mtext></mrow></mfrac></mrow></math><img file="EP0342528A2_D0026.tif" /></maths>      [42] depending on the cam width b as well as the relationship Q_w6′ = 0.694 · V_w′ [43] depending on the machined workpiece volume.

0128In the illustration in FIG. 9, a hatched area is a range of the permissible values, with straight lines 65/1 ... 65 / n being the boundary conditions Q explained above_w'Play and their intersections 66/1 ... 66 / n with the a-hyperbolas lie on a straight line.

0129Depending on which and how many of the above-mentioned boundary conditions are to be taken into account, the limiting boundary condition is the one with the lowest related chip removal volume Q_w'To be taken into account in order to then determine the infeed a as the minimum but optimal value, which is then at the minimum grinding time t_H min leads.

0130The control provided for carrying out the method according to the invention will now be explained on the basis of the flow chart of FIGS. 10/1 to 10/12.

0131In a first block 70, a determination program is started by first entering the input data either individually in block 71 or calling it up from machine-specific files.

0132The maximum power P_Max of the drive motor 19 of the grinding wheel 18 of, for example, 22 kW. Next, the maximum angular speeds of the workpiece holder 11 of the C-axis 13 are called, which can be between 10,000 and 30,000 ° / min. Finally, the stiffness is C_G the machine.

0133Material W is first called up as cam data using the table of typical camshaft materials already mentioned. Furthermore, the overall oversize A and the number of cams n of the camshaft 12 are specified. With regard to the cam contour, the base circle radius R_G and the contour itself, for example in the form of the data collection table E already mentioned_(Θ) specify. The cam width b must be entered as well as the adjustment path X_A the grinding wheel 18 in the direction of the X-axis 20 and the starting position Z_A the grinding wheel 18 in the direction of the Z axis 21 and the end position Z_E in this axis 21 and the cam jump Z_S.

0134The roughness depth R_Z. and the formal error f_m given. Regarding the thermal edge zone influence, symbolized by ϑ_RZ the user can make a yes / no decision by Y / N, with the effect that the further determination of the parameters is carried out either with or without taking into account the thermal boundary zone phenomenon.

0135The grinding wheel data are also specified in tabular form for a finite number of CBN grinding wheels available in practice. For each of these grinding wheels, the grinding wheel diameter d_S and specify the grain size B and the concentration K in the known manner. A polyhedron constant q_m, which in the case of an octahedron is 1.4, is also specified, as is the theoretical polyhedral volume W_m, which can also be specified in tabular form according to the type of polyhedron, provided that different polyhedra are provided for different grinding wheel coverings.

0136Furthermore, the grain coverage factor Δ b_s, the permissible maximum grain force F_Kzul for the grinding wheel and as a conditioning parameter, the dressing step a_d and the speeds of the dressing roller V_fd, V_{fd ′}to specify in the opposite direction.

0137The grinding wheel peripheral speed v_S, the number of workpieces to be machined per hour N_w and finally the conditioning interval of the grinding wheel T_s specify.

0138Finally, numerous constants are required in the course of the method according to the invention, most of which were obtained empirically and can therefore fluctuate within certain limits. In the following explanation of the method according to the invention, these constants are each given as specific numerical values, but it goes without saying that these numerical values ​​can also be subject to certain fluctuations for the reasons mentioned.

0139From the input variables specified in block 71, the cam geometry is first calculated in block 72 according to further characteristic values. So the workpiece diameter d_W, the flank radius R_F in the form of a table, the tip radius R_S, the maximum survey value E_Max and the base circle angle φ_G, the flank angle φ_F and the tip angle φ_S determined.

0140Depending on the elevation table and the maximum angular velocity of the C axis 13, the cam peripheral speed v_W calculated in block 73.

0141In block 74, the cosine theorem is used to add the vector circumferential speed v_W and the grinding wheel speed v_S the cutting speed v_C. the grinding wheel 18 determines.

0142The values ​​R_G, R_F, R_S, E_Max, φ_G, φ_F, φ_S, b, X_A, Z_A, Z_E and Z_S output and in the menu technology already mentioned in the form of a graphic dialog with the user of the method according to the invention. For this purpose, the camshaft can be represented in two side views in a mask, the values ​​listed in block 75 being illustrated graphically.

0143Parallel to the output in block 75, the ratio of cutting speed v_C. and workpiece speed v_W calculated as the quotient q.

0144In block 77, an effective diameter d_eq from the diameters of workpiece d_W and grinding wheel d_S determined.

0145In block 78, the cutting force f_C. using an empirical formula from the maximum power P_Max of the drive motor 19 determined.

0146With the help of the relationship already indicated and explained in FIG. 9, the theoretically minimum grinding time t is now in block 79_H min determined from the cam geometry and the achievable angular velocities ω.

0147From this, in block 80, as the central parameter of the method according to the invention, the maximum amount of material removal Q ′ obtained_wmax using an empirically derived formula from the maximum power P_Max of the drive motor 19 of the grinding wheel 18 is determined.

0148From the two values ​​of blocks 79 and 80 thus obtained, the maximum machined workpiece volume V ′_Wmax determine.

0149With the help of the complete relationship shown and explained in FIG. 9, a maximum infeed a is now set in block 82 as an output variable for the method according to the invention_Max the grinding wheel 18 determines.

0150This maximum delivery a_Max The next step is to check whether it is permissible with regard to various restrictions of the system used.

0151In order to accomplish this, the maximum drawn time pan volume Q ′ is again used as the central calculation variable in a block 83 ._wi as maximum value Q ′_wmax given.

0152As indicated at 84, this maximum output value Q ′_wmax can be decremented in the following procedure by various loop passes, as will be explained in more detail below.

0153In the first process loop, the predetermined roughness depth R_Z. For the finished cam surface, a specific type of grinding wheel is selected using the grinding wheel table, with which the specified roughness depth R_Z. can be achieved. As a result, the grain size B and the concentration K and thus also the grain diameter d_K firmly. The determined type of grinding wheel is output in block 86 and in turn is shown in the graphic dialog of the menu control.

0154The further process is now carried out using equations (1) to (42), which were explained in detail above. These equations are referred to below.

0155In block 87, the grain density C_K calculated.

0156In block 88, the area-related kinematic cutting edge number N_kin determined using equation (18).

0157In block 89, the individual chip volume V_IT calculated.

0158In block 90, the theoretical grain protrusion Z_th certainly.

0159With the help of equation (21), the real grain protrusion Z follows_r in block 91, with the aid of equation (22), the grain spacing l follows from this in block 92_K and finally, using equation (23) in block 93, the chip space volume V_SR.

0160With the help of equation (24), the chip filling degree f can finally be found in block 94_G determine.

0161In decision block 95 it is now checked whether the chip filling degree f_G is less than or equal to a predetermined limit value of, for example, 0.75. If this is not the case, then if the chip space volume V_SR is not large enough to match the individual chips with their individual chip volume V_IT to record, the output variable of this process loop, namely the related chip removal volume Q ′_wi decremented by a predetermined amount ΔQ ′_w. With this decremented value, the method returns to the already explained point 84 behind block 83 in order to carry out the above-described method steps until the obtained chip removal volume Q ′_wi has been decremented to such an extent that the chip filling degree is sufficiently dimensioned.

0162As soon as this is the case, the method continues its steps and calculates the grain wear factor r in block 97 using equation (25)_S.

0163With the help of equation (26) the total closure V_VS calculated and with the help of equation (27) in block 99 the machined material volume V_{Flat share} certainly.

0164This results in block 100 with the help of equation (28) and in block 101 with the help of equation (5) the contact length l_G.

0165In block 102, the contact area A_K and finally in block 103 with the aid of equation (29) the single grain force F_K calculated.

0166In decision block 104 it is now checked whether the single grain force F_K less than or equal to a permissible single grain force F_K perm is. If this is not the case, in other words if the load on the individual grain is too high, the central process variable, namely the obtained chip removal volume Q ′, is again in block 105_wi by the amount ΔQ ′_wi decremented, the decrement amount ΔQ_wi may be the same as that of block 96 or different. In this case too, the program returns to point 84 via the loop in order to use the decremented value for Q ′_wi continue to be calculated until the individual grain force F_K to the permissible value F_kzul has sunk.

0167It should be added at this point that the two process loops explained above are to be understood as options by which the process can be operated. Thus, as already mentioned, it is entirely possible to abort the method described above with block 85 and to proceed using the grinding wheel determined there, but then neither the chip space filling ratios nor the individual grain load ratios are taken into account. If, on the other hand, the method is continued, the chip filling ratios up to block 95 are first taken into account, upon reaching which the method according to the invention can alternatively be terminated. The related chip removal volume Q determined at the yes output of block 95_{w ′} can then with the help of blocks 81 and 82 in a maximum delivery a_Max the grinding wheel 18 can be converted, which is then naturally smaller than the amount that was determined at the exit of block 82 when the method according to the invention was run through for the first time.

0168If you now grind the camshaft 12 with the grinding wheel 18 while adjusting the infeed a, which has been reduced once, then on the one hand the restriction in block 80 with regard to the maximum power P is_Max of the drive motor 19 of the grinding wheel 18 as well as the restriction with regard to the chip space filling ratios of the block 94.

0169If, on the other hand, the method according to the invention is also allowed to run through the second loop up to block 104 and is determined on the basis of the twice decremented related chip removal volume Q present at the output of block 104_w'A correspondingly twice reduced oversize a, its specification leads to a grinding process during real grinding of a camshaft 12, which additionally takes into account the restriction of the individual grain load.

0170It goes without saying that as restrictions continue to be taken into account and the progressive reduction in the amount of time span Q_w'And the infeed a also an increase in grinding times t_H entry.

0171Corresponding considerations apply to the restrictions specified below, which can be taken into account individually or in any combination.

0172In block 106, the roughness depth is used as a restriction criterion with the aid of equation (36), and a value of the related chip removal volume Q ′ is derived from this._w1 calculated. In decision block 107 it is now checked whether the value Q thus determined_w1'Greater than or equal to the currently applied process value Q'_wi which has been determined after going through the method up to block 83 and possibly up to block 95 and / or up to block 104.

0173The result is that the newly determined value Q_w1'Is smaller, then this new value Q_wi'Via block 108 as a new process parameter for Q_wi'Should be specified if the roughness depth is to be taken into account as a restriction criterion.

0174However, it turns out that the newly determined value Q_wi'Is greater than the currently pending value Q_wi', The restriction criterion of the roughness depth can be ignored because its effects lie within the already considered range of the process parameters.

0175To take into account the next restriction criterion of the shape error f_m this must first be calculated in block 109 using equation (38). The next restriction criterion is then set in block 110 with the aid of equation (37) and a decision is again made via blocks 111, 112, as was explained above for blocks 107, 108.

0176In block 113, the next restriction criterion is tool wear r_s with the aid of equation (39) and in turn a decision is made via blocks 114, 115.

0177In block 116, the temperature T is the next restriction criterion_M taken into account with the aid of equation (41) and the corresponding decision made in blocks 117, 118.

0178Block 119 determines the next restriction criterion with the aid of equation (42), the machine data with subsequent decision in blocks 120, 121, and in a corresponding manner block 122 uses equation (43) to calculate a further restriction criterion based on machine data with subsequent decision in the blocks 123 and 124.

0179In the following block 125, the grinding wheel-specific values, i_S, W_m, K, d_K, Z_th, l_G and V_SR displayed in the graphics dialog of the menu navigation.

0180The same applies in block 126 to the output of values ​​from the grinding wheel conditioning, where, for example, the values ​​a_d, V_fd, V ′_fd, q, r_s, T_s, G, N_kin, V_IT, F_G and f_K be displayed in the graphics dialog.

0181Finally, in block 127, the selected material W and the values ​​V for the grinding wheel type are also used as machining parameters_C., ω, V_{Flat share}, Q ′_wimax and t_H or taking into account the travel of the grinding wheel in the Z and X direction (without machining) of the total grinding time.

0182The determination of the process parameters to be taken into account then ends in block ₁28 and the values ​​determined are now transferred as operating parameters for the cam shape grinding machine 10 into the NC control unit 25 or its output interfaces of the data lines 27 and 28, in order to now cam the camshaft 12 in to grind the determined shape.