WO2017005577A1 - Procédé de meulage d'une pièce à travailler ayant une surface de portée cylindrique et procédé pour déterminer des paramètres de traitement - Google Patents

Procédé de meulage d'une pièce à travailler ayant une surface de portée cylindrique et procédé pour déterminer des paramètres de traitement Download PDF

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Publication number
WO2017005577A1
WO2017005577A1 PCT/EP2016/065153 EP2016065153W WO2017005577A1 WO 2017005577 A1 WO2017005577 A1 WO 2017005577A1 EP 2016065153 W EP2016065153 W EP 2016065153W WO 2017005577 A1 WO2017005577 A1 WO 2017005577A1
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Prior art keywords
grinding
workpiece
grinding wheel
feed
cylindrical bearing
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PCT/EP2016/065153
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English (en)
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Peter KRAJNIK
Roope ROININEN
Radovan DRAZUMERIC
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Scania CV AB
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Scania CV AB
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Priority to JP2018500580A priority Critical patent/JP2018525235A/ja
Priority to CN201680039935.8A priority patent/CN107735218B/zh
Publication of WO2017005577A1 publication Critical patent/WO2017005577A1/fr
Anticipated expiration legal-status Critical
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B5/00—Machines or devices designed for grinding surfaces of revolution on work, including those which also grind adjacent plane surfaces; Accessories therefor
    • B24B5/36—Single-purpose machines or devices
    • B24B5/42—Single-purpose machines or devices for grinding crankshafts or crankpins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B51/00—Arrangements for automatic control of a series of individual steps in grinding a workpiece

Definitions

  • the present disclosure relates in general to a method of grinding a workpiece by means of a grinding wheel, the workpiece comprising a cylindrical bearing surface, a radially extending sidewall extending outward from the cylindrical bearing surface, and a curved transition portion connecting the cylindrical bearing surface with the sidewall.
  • the present disclosure also relates to a method for determining processing parameters of such a grinding method.
  • a crankshaft 1 has a rotational axis A and comprises a plurality of crankpins 2 or journals, as shown in Figure 1 a.
  • Figure 1 b illustrates a cross sectional view of a part of such a crankpin 2.
  • the crankpin 2 comprises a cylindrical bearing surface 3, a radially extending sidewall 4 and normally a curved portion 5.
  • the cylindrical bearing surface 3 has a centre axis which is parallel to the axis of rotation of the crankshaft.
  • the sidewalls are arranged at opposite axial ends of the cylindrical bearing surface and connected to the cylindrical bearing surface via a respective curved portion 5 having a radius in a plane coinciding with the plane in which the axis of the cylindrical bearing surface is arranged.
  • the sidewalls each extend around the whole circumference of the cylindrical bearing surface and thus have a form of a cylindrical surface around the centre axis of the cylindrical bearing surface.
  • Forged steel crankshafts are sensitive to grinding-induced thermal damage which may result in inferior quality of the crankshaft.
  • the common types of thermal damage to the workpiece are grinding burn (oxidation burn), metallurgical phase transformations, softening (tempering) of the surface layer with possible rehardening, unfavourable residual tensile stresses, cracks, and reduced fatigue strength. This has for example been reported by Malkin and Guo, CIRP Annals - Manufacturing Technology, Volume 56, Issue 2, 2007, Pages 760-782.
  • crankpin is critical since it affects the dimensions, the surface quality, and the fatigue life not only of the cylindrical bearing surface but also of the curved portions and the sidewalls. Furthermore, grinding of crankpins often result in non-uniform grinding wheel wear, which in turn also may affect the quality of the crankshaft.
  • Another method for grinding of crankpins is a combined radial-plunge, axial-grinding method wherein for the majority of the process the grinding wheel plunges radially into the crankpin, followed by angle-plunge grinding during finishing.
  • the grinding wheel width is smaller than the distance between the two sidewalls.
  • This combined radial-plunge axial- grinding method may suffer from certain drawbacks inter alia because the grinding wheel is plunged radially. For example, if the grinding parameters are selected such as to avoid grinding burn the grinding cycle times become long. If shorter grinding cycle times are desired, the risk for grinding burn increases greatly. Furthermore, such grinding involves a high aggressiveness number and high, non-uniform, grinding wheel wear.
  • Yet another grinding method is the so called angle-plunge grinding method, wherein the grinding wheel plunges into the crankpin both radially and axially at an angle, typically to carry out grinding at an angle of the grinding wheel feed selected so that the sidewall grind will be completed ahead of the grind of the cylindrical bearing surface.
  • EP 1 635 989 B1 discloses an example of such a process.
  • US 4,603,514 A discloses a method of grinding a workpiece having a cylindrical portion, two sidewall portions and curved portions connecting the cylindrical portion with the respective sidewalls, such as crankshaft pins or journals. Grinding is performed by means of a grinding wheel having a width smaller than the space between the two sidewalls of the workpiece. During grinding, the grinding wheel and the workpiece are simultaneously moved relative towards each other in two perpendicularly intersecting directions such that one sidewall and part of the cylindrical portion of the workpiece are shaped by oblique feed grinding, followed by a similar grinding operation on the other side wall and the reminder of the cylindrical portion.
  • Such angled-vector grinding is essentially cylindrical grinding utilizing a rotationally symmetrical grinding wheel of an arbitrary profile, where the rotational axes of the wheel and the workpiece are parallel.
  • Angle-plunge grinding is a fundamentally better process compared to radial-plunge grinding, giving shorter grinding cycle times and less risk of burn.
  • a serious drawback of angle-plunge grinding is the possibility of large surges in material removal rate when there is a large degree of run-out in the incoming crankpin dimensions.
  • angle- plunge grinding is an inherently better process, where the fundamental grinding parameters are not explicitly understood or quantified. On the contrary, grinding parameters are chosen arbitrarily based on trial-and-error, resulting in regions of the crankpin with high temperatures and other regions with low temperatures.
  • grinding of a crankpin is not easy to control.
  • Sidewall grinding experiences extreme variation of aggressiveness number along the wheel profile as well as a longer cutting-path length compared to grinding a cylindrical surface. Therefore, one portion of the grinding wheel experiences a high aggressiveness number, causing excessive wheel wear and poor surface finish (high surface roughness) of the workpiece, while another portion of the wheel experiences a low aggressiveness number, causing high temperatures which can lead to thermal damage of the workpiece.
  • Oliveira et al. CIRP Annals - Manufacturing Technology, Volume 54, Issue 1 , 2005, Pages 269-272, discuss axial- or radial-grinding strategies employed to grind a crankpin sidewall. In the axial feed the grinding wheel is moved axially relative to the crankshaft, whereas in the radial feed the wheel is plunged perpendicularly towards the crankshaft rotating axis. Oliveira et al. concluded inter alia that it is possible to determine the most affected areas of the wheel profile according to each of the grinding strategies applied and based on said information selecting the most suitable grinding strategies and grinding conditions in order to reduce the thermal damage and wheel wear.
  • a crankpin is eccentric to the shaft main rotational axis, which requires moving the rotating grinding wheel (wheelhead) in a direction of the crankpin according to a rotation phase of the crankshaft.
  • Such accommodation of a radial feed can be done by traversing a grinding spindle in the radial direction towards the workpiece (X-axis) by means of CNC.
  • the axial feed is realized by a CNC-controlled Z-axis, independent of X-axis. This is for example disclosed in US 6,878,043 B1 .
  • a crankshaft rotates with a constant rotational speed the relative workpiece speed is changing according to a rotation phase of the crankshaft continuously as the grinding wheel passes around the circumference of the workpiece. While the problems associated with crankpin grinding has been disclosed above, the same applies to other workpieces comprising a cylindrical bearing surface, a sidewall and a curved transition portion.
  • the object of the present invention is to enable a grinding method of a workpiece by means of a grinding wheel, the workpiece comprising a cylindrical bearing surface, at least one sidewall extending radially outwardly from an axial end of the cylindrical bearing surface, and a curved transition region connecting the cylindrical bearing surface with said at least one sidewall, wherein the grinding method results in high productivity rates and controlled quality of the workpiece in terms of avoiding thermal damage, and which grinding method can be industrially implemented.
  • the object is achieved by a grinding method according to claim 1 and a method for determining process parameters of a grinding method according to claim 6. Exemplifying embodiments are defined by the dependent claims.
  • the workpiece may for example be a crankpin of a crankshaft, but is not limited thereto.
  • the workpiece may be any workpiece comprising a cylindrical bearing surface, a curved portion, as well as a sidewall extending radially outwardly from an axial end of the cylindrical bearing surface and connected to the cylindrical bearing surface by means of the curved portion.
  • the present invention is based on grinding the workpiece by controlling the depth of cut during each increment such that the points on the grinding wheel profile causing the highest surface temperature of the workpiece remain below or at a pre-set maximum surface temperature of the workpiece.
  • the surface temperature of the workpiece can never be higher than the pre-set maximum surface temperature threshold and thus thermal damages of the workpiece are avoided.
  • by controlling the depth of cut for each increment of the grinding cycle in accordance with the set surface temperature results in the lowest number of increments needed to grind the workpiece and thus inherently also the lowest grinding cycle time. Thereby, grinding can be performed in a controlled manner at high productivity rates without any risk for thermal damage of the workpiece caused by the grinding and hence controlled quality of the workpiece is achieved.
  • a method of grinding a workpiece by means of an essentially rotational symmetrical grinding wheel wherein the workpiece comprises a cylindrical bearing surface, a radially extending sidewall extending outward from the cylindrical bearing surface, and a curved transition portion connecting the cylindrical bearing surface with the sidewall, and wherein the grinding wheel has an axial extension less than the axial extension of the cylindrical bearing surface.
  • the method comprises grinding the workpiece in a plurality of grinding increments together defining a grinding cycle, each grinding increment performed with a respective feed of the grinding wheel in relation to the workpiece. In each separate grinding increment, the feed is selected so as to achieve a preset maximum surface temperature of the workpiece at a point of the grinding wheel resulting in the highest surface temperature of the workpiece.
  • the feed may suitably comprise an axial feed and a radial feed, which are independently selected so as to achieve said pre-set maximum surface temperature of the workpiece at the point of the grinding wheel resulting in the highest surface temperature of the workpiece.
  • the grinding method may suitably be an angle-plunge grinding process. This has the advantage of giving shorter cycle times compared to for example a process wherein, for the majority of the process, the grinding wheel plunges radially into the workpiece.
  • the axial feed and radially feed are preferably set so as to achieve a maximum material removal rate in each grinding increment.
  • the grinding wheel may suitably be rotated with a constant rotational speed.
  • the workpiece may suitably be rotated with a constant rotational speed throughout the grinding cycle in order to achieve an easy control of the process. It is however also possible to rotate the workpiece with a constant rotational speed within each increment, but with different rotational speeds in two of each other following increments. Depending on the apparatus used, it may also be possible to vary the rotational speed within an increment if desired.
  • the present invention also provides a method of determining processing parameters of a grinding method for grinding a workpiece by means of an essentially rotational symmetrical grinding wheel having a grinding wheel profile.
  • the workpiece comprises a cylindrical bearing surface, a radially extending sidewall extending outward from the cylindrical bearing surface, and a curved transition portion connecting the cylindrical bearing surface with the sidewall, and wherein the grinding wheel has an axial extension less than the axial extension of the cylindrical bearing surface.
  • the method comprises, based on a pre-set maximum surface temperature, determining a number of increments and the respective axial feed and radial feed of said increments, and comprises the following steps:
  • step b) based on the axial feed and the radial feed determined in step b) determining the resulting grinding wheel position after completion of one increment with said axial feed and radial feed,
  • step d) based on the grinding wheel position obtained in step c) determining a corresponding contact portion with a corresponding lower limit and upper limit of the grinding wheel profile;
  • step d) in case the lower limit of the contact portion is less than the upper limit of the contact portion obtained in step d) repeating steps b) to d) until the lower contact limit of the contact portion is not less than the upper limit;
  • Determining the axial feed and radial feed necessary to keep the pre-set maximum surface temperature at a point of the contact portion of the grinding wheel resulting in a highest surface temperature of the workpiece in step b) may suitably be performed such as to achieve a maximum removal rate in the increment. This further ensures a shortest possible grinding cycle without any risk for thermal damage.
  • the axial feed and the radial feed may be determined in step b by calculating a limit depth of cut function of the grinding wheel position in order to match the pre-set maximum surface temperature, and further comprising selecting two critical points of the limit depth of cut function in the current contact interval. Said critical points are then used to determine the corresponding axial feed and radial feed. Thereby the pre-set maximum surface temperature is matched only in two points of the contact interval and everywhere else, the actual depth of cut will be lower.
  • the limit depth of cut function may be given as:
  • ⁇ * is the pre-set maximum surface temperature
  • k is the thermal conductivity of the workpiece material
  • p the density of the workpiece material
  • c p is the specific heat of the workpiece material
  • e w is the specific energy into the workpiece
  • v s is the grinding wheel speed
  • aggr is the aggressiveness number.
  • the total specific energy characteristic, e tot may for example be obtained from grinding power measurements (i.e. experiments) performed in a first step comprising only sidewall grinding wherein only axial feed is used, and a second step comprising only cylindrical bearing surface grinding wherein only radial feed is used, and wherein the total specific energy in the transition region is obtained by exponential interpolation.
  • the specific energy into the workpiece characteristic e w (aggr) is then determined by calculating energy partition ratios and applying them to the total specific energy characteristic for each grinding type (i.e. grinding of sidewall only and grinding of cylindrical bearing surface only) separately, and wherein the specific energy in the transition region is again obtained by exponential interpolation.
  • a computer programme for determining processing parameters of a grinding method comprises programme code for performing the method steps of the method for determining processing parameters as disclosed above.
  • a computer programme for determining processing parameters of a grinding method comprises programme code stored on a computer-readable medium for performing the method steps of the method for determining processing parameters as disclosed above.
  • the computer programme may further be arranged to provide the determined processing parameters to an electronic control unit or another computer connected to or adapted to communicate with the electronic control unit.
  • the electronic control unit can for example be an electronic control unit of a grinding machine adapted to control parameters such as the axial feed and radial feed, as well as the number of increments.
  • a computer programme product is provided containing a programme code stored on a computer readable medium for performing the method of determining processing parameters of a grinding method as disclosed above when said computer programme is run on an electronic control unit or another computer connected to or adapted to communicate with the electronic control unit.
  • Fig. 1 a schematically illustrates a side view of a crankshaft.
  • Fig. 1 b schematically illustrates a cross sectional view of a portion of crankpin.
  • Fig. 2 schematically illustrates kinematics of grinding of a workpiece, such as a crankpin.
  • Figs. 3a and 3b schematically illustrate a two-dimensional view of crankpin-grinding geometry.
  • Fig. 4 illustrates a first exemplifying embodiment of a method for determining grinding parameters according to the invention.
  • Fig. 5 illustrates a second exemplifying embodiment of a method for determining grinding parameters according to the invention.
  • Fig. 6 schematically illustrates a device comprising a computer programme according to an embodiment.
  • the workpiece is in the following sometimes exemplified by a crankpin.
  • the workpiece and the grinding method is however not limited to grinding of a crankpin and the workpiece may be any workpiece having a cylindrical bearing surface, a radially extending sidewall and a curved transition portion having a radius and connecting the cylindrical bearing surface with the sidewall.
  • the workpiece comprises two radially extending sidewalls extending outward from the cylindrical bearing surface and each connected to the cylindrical bearing surface by a curved transition portion.
  • the present disclosure relates to grinding of a workpiece by means of a grinding wheel.
  • the workpiece comprises a cylindrical bearing surface arranged around a centre axis.
  • the workpiece comprises a radially extending sidewall which extends radially outward from the cylindrical bearing surface around the whole circumference of the cylindrical bearing surface.
  • the cylindrical bearing surface is connected to the sidewall by means of a surface constituting a curved transition portion having a radius.
  • Figures 1 a and 1 b illustrates an example of such a workpiece.
  • the grinding wheel is essentially rotationally symmetrical around a rotational axis thereof, and is rotated around said rotational axis.
  • the rotational axis of the grinding wheel is essentially parallel to the centre axis of the cylindrical bearing surface. Therefore, the radially peripheral surface of the grinding wheel will grind the cylindrical bearing surface whereas the axial peripheral surface of the grinding wheel will grind the sidewall of the workpiece.
  • the grinding wheel has a width, i.e. axial extension, which is smaller than the axial extension of the cylindrical bearing surface.
  • the present invention is based on an in-depth investigation to understand the complex mechanisms that arise at the interface between the grinding wheel and the workpiece at the cylindrical bearing surface, the sidewall and the curved transition portion connecting the cylindrical bearing surface with the sidewall, in terms of fundamental grinding parameters.
  • These fundamental grinding parameters are: contact length between the workpiece and the grinding wheel (/ c ), specific material removal rate (Q ), aggressiveness number ⁇ aggr), grinding power (P g ), and maximum surface temperature of the workpiece (6> m ).
  • a strategy of the grinding method has been developed. The strategy is provided to achieve an essentially constant-temperature process that yields the shortest cycle time that can be achieved within temperature thresholds to avoid thermal damages of the workpiece.
  • the temperature limit to avoid thermal damage, of the workpiece depends on the material of the workpiece and the heat treatment process.
  • the temperature limits may be determined via measured Barkhausen noise signals, measured residual stress values versus depth into the material, thermal softening from hardness measurements versus depth into the material, and rehardening burn by sectioning and examining for "white layer” (consisting of untempered martensite and retained austenite, resulting from phase transformations in the material of the workpiece) in order to "calibrate" Barkhausen noise signals to determine the thresholds for grinding without thermally damaging the workpiece.
  • these Barkhausen noise threshold values may be correlated with the simulated temperatures by the model, which will be further disclosed below, to determine processing parameters for grinding needed to avoid risk for thermal damage of the workpiece.
  • an optimal strategy for the grinding method is a unique version of angle-plunge grinding (also known as vector grinding), utilizing the inherently better approach of angle-plunge grinding, and avoiding the problem of selecting inputs based on trial-and- error.
  • the model developed may also be used if utilising other strategies for grinding, for example grinding methods utilising radial plunge followed by axial plunge.
  • the model developed in accordance with the present invention may be embedded into a simulation tool, i.e. a computer programme for determining processing parameters, that is used to visualize the fundamental grinding parameters, i.e. contact length between the workpiece and the grinding wheel, specific material removal rate, aggressiveness number, grinding power and maximum surface temperature at all points on the grinding wheel profile for a selected grinding increment.
  • the aggressiveness number and specific energy i.e. the energy per unit volume of material removal
  • the aggressiveness number and specific energy change not only along the contact length from the cylindrical bearing surface, through the curved transition portion and up the sidewall, but the actual instantaneous contact length changes throughout the process as well.
  • what the grinding wheel "sees” changes due to the changing three- dimensional surface along the radius of the curved transition portion and through the arc of contact.
  • This complex geometry has not previously been modelled and analysed, and trying to analyse all three portions (the cylindrical bearing surface, the curved transition portion and the sidewall) can prove very difficult as the conditions change drastically just a short distance between points of the grinding wheel surface in contact with the workpiece.
  • Figure 2 schematically illustrates how the relative workpiece velocity, v w , which constitutes the fundamental kinematical grinding parameter needed for modelling, is derived. More specifically, Figure 2 schematically illustrates a generalised case of workpiece grinding kinematics, where the workpiece angular speed, ⁇ , is modelled around the workpiece (i.e. it is here assumed for the sake of modelling that the wheel moves around the workpiece), and thus illustrates a geometrical and kinematical framework for a functional determination of the relative workpiece velocity, v w .
  • the workpiece may for example be a crankpin 2 as shown in Figures 1 a and 1 b and for sake of clarity the workpiece will in the following be exemplified by such a crankpin 2 of a crankshaft.
  • the workpiece has a radius, r w , from a central axis 3b of the cylindrical bearing surface 3 to the peripheral surface thereof 3a, and the grinding wheel 6 has a radius, r s , from its rotational centre 6b to the peripheral surface 6a thereof.
  • the crankshaft 1 is a radius, r w , from a central axis 3b of the cylindrical bearing surface 3 to the peripheral surface thereof 3a, and the grinding wheel 6 has a radius, r s , from its rotational centre 6b to the peripheral surface 6a thereof.
  • crankpin 2 has a rotational axis A.
  • d ws ( ⁇ p ws ) between the rotational axis A of the crankshaft and the rotational axis 6b of the grinding wheel, wherein the angle cpws constitutes the independent variable used.
  • the eccentricity of the crankpin relative to the rotational axis A is denominated ecc w -
  • the kinematics of the grinding wheel relatively to the fixed crankshaft is a combination of the grinding wheel rotation and the wheel translation.
  • the vector d ws ((p ws )o)((p ws ) has a direction perpendicular to the line between rotational axis A and rotational axis 6b, and the magnitude is known due to the known rotational speed of crankshaft in real application.
  • the vector v fa ( ⁇ p ws ) has a direction parallel to the line between the rotational axis A and rotational axis 6b.
  • the relative workpiece velocity v w as given above takes into account a possibility of the angular speed of the workpiece changing during the grinding cycle. However, in case the angular speed of the workpiece is not variable, or where it is purposively selected to be constant, only the average workpiece velocity needs to be taken into account.
  • the average relative workpiece velocity may be calculated in accordance with Eq. 2. vw — r bs M (Eq. 2) where the general workpiece radius, r w , is substituted with the radius, r bs , of the cylindrical bearing surface 3 of the crankpin.
  • Figures 3a and 3b illustrate the basic geometry of crankpin grinding.
  • the grinding wheel 6 has an axial extension b s , i.e. a width, a radius r s from the rotational axis to the radial peripheral surface 6a, and comprises a curved transition portion 6c between the peripheral radial and the peripheral axial surface of the grinding wheel.
  • the curved transition portion 6c of the grinding wheel has a radius r 0 , which suitably may correspond to the intended radius of the curved transition portion 5 of the workpiece.
  • the cylindrical bearing surface 3 has a radius, r bs , when the intended total stock to be removed in radial direction 5 X:to t has been removed.
  • the total stock to be removed at the sidewall 4, i.e. axial direction, of the workpiece is illustrated by 5 z ,tot-
  • the sidewall 4 extends radially outward from the cylindrical bearing surface such that the radial peripheral surface of the sidewall has a radius r sw , i.e. the sidewall is formed of a cylindrical portion having the radius r sw . Grinding may be performed by different feeds in z-direction (axial direction) and x-direction (radial direction) of the workpiece as previously discussed.
  • the grinding wheel may be moved an axial distance a z into the workpiece, and a radial distance a x ,i (radial depth) into the workpiece, with / ' being the iteration number of workpiece revolutions, i.e. the number of the grinding increment.
  • a z the radial distance into the workpiece
  • a x ,i radial depth
  • the contact between the grinding wheel and the workpiece is in reality a three-dimensional surface.
  • a surface can be geometrically described using two parameters.
  • the parameter "s” is used and represents an arc length on the wheel profile with the origin at the beginning of the radius and is in a cross sectional plane.
  • the parameter "s” is in the model used as an independent variable in the grinding model, as will be further described below.
  • the second parameter for describing the surface of contact between the grinding wheel and the workpiece may for example be the angle in
  • each point s on the grinding wheel profile i.e. peripheral surface of the grinding wheel
  • the workpiece axis may be analysed with respect to the grinding wheel profile arc length starting from the cylindrical bearing surface (negative values), moving up the radius r 0 (positive values, from the perspective of the wheel) and then up the sidewall of the grinding wheel, i.e. the axial peripheral surface of the grinding wheel.
  • the contact portion of the grinding wheel profile can be determined by a lower limit, s 0 , and an upper limit, Si , depending on the wheel position, given by distances d z ,, and d x ,i, and feeds a z and a x .
  • a robust model for the grinding process of a crankpin (or grinding of any other workpiece comprising a cylindrical bearing surface, sidewalls and curved transition portions as disclosed above) may be developed by substituting the actual, inherently complex, three- dimensional geometrical scenario along the wheel profile with an equivalent plane-surface- grinding scenario at every point of the profile, s, in terms of fundamental grinding parameters. Said model may then be used for process planning, i.e. design of a grinding cycle in terms of feeds for the grinding increments, and for simultaneous process optimisation, i.e. minimising the grinding cycle time.
  • modelling of the grinding geometry is performed by determination of simplified relations between axial and radial feeds (a z , a x ), corresponding depth of cut, a e , and contact length, l c , at the cylindrical bearing surface (Eq. 3 and Eq. 4), the curved transition portion (Eq. 5 and Eq. 6) and the sidewall of the workpiece (Eq. 7 and Eq. 8). More specifically:
  • r eq is the equivalent radius and is defined by Eq. 9.
  • the fundamental grinding parameters specific material removal rate Q w ' , aggressiveness number aggr, grinding power P g and maximum surface temperature Q m can be calculated as given below by Eq. 10 to Eq. 13 in every point s of the grinding wheel profile.
  • v s is the grinding wheel speed.
  • k is the thermal conductivity
  • p the density
  • c p the specific heat of the workpiece material.
  • a core part of thermal modelling is the determination of the specific energy into the workpiece characteristic (versus aggressiveness number), e w (aggr), which is based on the total specific energy characteristic, e tot aggr), and the thermal model.
  • the total specific energy characteristic, e tot (aggr), may be obtained from grinding
  • the experiments may suitably be conducted in two separate stages, i) sidewall grinding where only axial feed is used and ii) cylindrical bearing surface grinding where only radial feed is used.
  • the total specific energy characteristic is given below with reference from Eq. 14 to Eq.18.
  • aggr 0z is the optimal aggressiveness for sidewall grinding.
  • aggr 0x is the optimal aggressiveness for bearing-surface grinding.
  • the specific energy into the workpiece characteristic, e w (aggr), is then determined by calculating energy partition ratios, ⁇ ⁇ and ⁇ ⁇ , for each grinding type separately. Calculations are based on the use of the thermal model combined with the measured Barkhausen noise signals, which are correlated with certain maximum surface temperature values. In this way, the specific energy into the workpiece characteristic is obtained based on the total specific energy characteristic as given below with reference from Eq. 19 to Eq.21 .
  • grinding of a workpiece comprising a cylindrical bearing surface, a radial sidewall and a curved transition portion connecting the cylindrical bearing surface with the sidewall can be optimised as disclosed below.
  • the grinding method is optimised by determining axial and radial feeds (a z and a x ) within each increment, necessary to grind the workpiece at a set maximum surface temperature, thereby also obtaining the number of increments needed (which inherently also is the lowest possible for the grinding cycle). The lowest number of grinding increments gives the minimum grinding cycle time.
  • the present invention provides a method of determining processing parameters of a grinding method for grinding a workpiece by means of an essentially rotational symmetrical grinding wheel, the workpiece comprising a cylindrical bearing surface 3, a radially extending sidewall 4 extending outward from the cylindrical bearing surface, and a curved transition portion 5 connecting the cylindrical bearing surface with the sidewall, wherein the grinding wheel has an axial extension less than the axial extension of the cylindrical bearing surface, the method comprising, based on a pre-set maximum surface temperature, determining a number of increments and the respective axial feed and radial feed of said increments.
  • the method comprises the following steps: a) based on a position of the grinding wheel at the end of the grinding cycle, determining the distance into the workpiece in radial respectively axial direction and hence determine the corresponding contact portion set by a lower limit and an upper limit (of the grinding wheel profile;
  • step b) based on the axial feed and the radial feed determined in step b) determining the resulting grinding wheel position after completion of one increment with said axial feed and radial feed,
  • step d) based on the grinding wheel position obtained in step c) determining a corresponding contact portion with a corresponding lower limit and upper limit of the grinding wheel profile;
  • step d) in case the lower limit of the contact portion is less than the upper limit of the contact portion obtained in step d) repeating steps b) to d) until the lower contact limit of the contact portion is not less than the upper limit;
  • Figure 4 illustrates a first exemplifying embodiment of such a method for determining grinding parameters.
  • Both total grinding allowances, 5 z , to t and ⁇ , ⁇ may include a certain offset needed to compensate for a possible run-out in the incoming workpiece dimensions.
  • the corresponding contact portion set by a lower limit Soj and an upper limit s ⁇ j of the grinding wheel is determined, 401 .
  • the central part of the method is a constant-temperature process, where the axial feed, a z j, and radial feed, a x j, needed to keep the pre-set maximum surface temperature at a point of the contact portion of the grinding wheel resulting in a highest surface temperature of the workpiece, while achieving maximum material removal rate, Q w j, during such an increment, is determined, 402.
  • the limit depth of cut, a* is calculated as a function of wheel profile position, s, in order to match the pre-set maximum surface temperature, ⁇ *.
  • the thermal model is written in the following form (Eq. 22): which includes grinding parameters as functions of both wheel profile position and limit depth of cut.
  • the limit depth of cut a* is calculated in every point s of the wheel profile, regardless of a grinding increment / and contact portion limits Soj and Sij.
  • a e * (s, 6 *) is only one function for all increments and can be calculated in advance for given pre-set temperature ⁇ * .
  • function a* (s, 0 * ) represents the pre-set temperature (which has the same value for all points s) translated into the limit depth of cut (which is, because of changing geometry, a different value in every point s).
  • the algorithm determines the axial feed, a z j, and radial feed, a x j, in a way that: ⁇ the pre-set maximum surface temperature is not exceeded in the wheel-profile
  • the pre-set maximum surface temperature would be achieved at every point s.
  • the feeds a ZJ and a X j are used in order to adjust in a current increment. This means that the pre-set temperature can only be achieved in two points s of the contact portion in the current increment. Therefore, two critical points of the limit depth of cut function should be selected in the current contact interval.
  • the values of a ZJ and a x are to be determined in such a way as to match the pre-set maximum surface temperature ⁇ * only in two points of the contact interval (Scri, y and Scr2, j ).
  • the algorithm then choses two critical points of the calculated limit-depth-of-cut function in the current grinding increment. Candidates for those two points are the ones in the current contact interval that simultaneously fulfil the conditions given by Eq. 23 and Eq. 24.
  • the two critical points are further used to determine the corresponding axial and radial feeds as:
  • the new wheel position is determined by reducing for the calculated feeds, and hence the new wheel-profile contact limits are determined, 403.
  • FIG. 5 illustrates a second exemplifying embodiment of a method for determining grinding parameters.
  • the second exemplifying embodiment corresponds to the exemplifying embodiment as shown in Figure 4 except that it provides the possibility to set two input surface temperatures, ⁇ and ⁇ 2 * , 500.
  • the first set temperature, ⁇ can be higher than Q 2 * in order to have an additional possibility to even further reduce the grinding cycle time, because it is used to control the first grinding portion, which is related to the defined amount of axial grinding allowance, ⁇ ⁇ 1 .
  • the process planer has the possibility to set a higher ⁇ to induce slight thermal damage into the workpiece (e.g. slight tensile residual stresses) in a controlled way if grinding cycle time is crucial. Then, in the second grinding portion, which is the final one, the remaining allowance, i.e. 5 z tot - ⁇ ⁇ 1 , is ground with a lower set temperature ⁇ 2 to improve quality (surface integrity) of the ground workpiece surface without any thermal damage.
  • the process planner needs to be careful that the depth of eventual thermal damage into the workpiece is lower than the remaining allowance 5 z tot - 5 z l .
  • the grinding method is not limited to the specific embodiments described above but may be varied within the scope of the appended claims.
  • grinding may be performed with a constant or non-constant rotational speed of the workpiece during each increment.
  • the rotational speed of the workpiece in one increment may be different from a rotational speed of the workpiece in a subsequent increment if desired.
  • the grinding method may for example be an angle-plunge grinding method, or a combined radial and axial plunge grinding method wherein for the majority of the process the grinding wheel is plunged radially into the workpiece.
  • Other types of grinding processes are also feasible.
  • FIG. 6 is a diagram of an exemplified device 600.
  • An electronic control unit of a grinding machine may for example comprise the exemplified device 600 or the device may be a separate unit from the grinding machine.
  • the device 600 comprises a non-volatile memory 620, a data processing unit 610 and a read/write memory 650.
  • the non-volatile memory 620 has a first memory element 630 in which a computer programme, e.g. an operating system, is stored for controlling the function of the device 600.
  • the device 600 may further comprise a bus controller, a serial communication port, I/O means, an A D converter, a time and date input and transfer unit, an event counter and an interruption controller (not depicted).
  • the non-volatile memory 620 has also a second memory element 640.
  • a computer programme P which comprises routines for determining processing parameters, more specifically number of increments and feed in each of the increments, of a grinding method for grinding a workpiece by means of an essentially rotational symmetrical grinding wheel, wherein the processing parameters are determined by:
  • step b) based on the axial feed and the radial feed determined in step b) determining the resulting grinding wheel position after completion of one increment with said axial feed and radial feed,
  • step d) based on the grinding wheel position obtained in step c) determining a corresponding contact portion with a corresponding lower limit and upper limit of the grinding wheel profile;
  • step d) in case the lower limit of the contact portion is less than the upper limit of the contact portion obtained in step d) repeating steps b) to d) until the lower contact limit of the contact portion is not less than the upper limit;
  • the computer programme may further be arranged to provide the determined processing parameters to an electronic control unit or another computer connected to or adapted to communicate with the electronic control unit.
  • the computer programme may be stored in an executable form in a compressed form in a memory 660 and/or in a read/write memory 650.
  • the data processing unit 610 is described as performing a certain function, it means that the data processing unit 610 effects a certain part of the programme stored in the memory 660, or a certain part of the programme stored in the read/write memory 650.
  • the data processing device 610 can communicate with a data port 699 via a data bus 615.
  • the non-volatile memory 620 is intended for communication with the data processing unit 610 via a data bus 612.
  • the separate memory 660 is intended to communicate with the data processing unit 610 via a data bus 61 1 .
  • the read/write memory 650 is adapted to communicate with the data processing unit 610 via a data bus 614.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Grinding Of Cylindrical And Plane Surfaces (AREA)
  • Constituent Portions Of Griding Lathes, Driving, Sensing And Control (AREA)

Abstract

L'invention concerne un procédé de meulage d'une pièce à travailler à l'aide d'une roue de meulage. La pièce à travailler comprend une surface de portée cylindrique (3), une paroi latérale s'étendant radialement (4) s'étendant vers l'extérieur à partir de la surface de portée cylindrique, et une partie de transition incurvée (5) reliant la surface de portée cylindrique à la paroi latérale. Pendant le meulage, l'avance par un incrément est sélectionnée de façon à obtenir une température de surface maximale pré-établie de la pièce à travailler en un point de la roue de meulage ayant comme conséquence la température de surface la plus élevée de la pièce à travailler. L'invention concerne également un procédé pour déterminer des paramètres de traitement pour un tel procédé de meulage.
PCT/EP2016/065153 2015-07-08 2016-06-29 Procédé de meulage d'une pièce à travailler ayant une surface de portée cylindrique et procédé pour déterminer des paramètres de traitement Ceased WO2017005577A1 (fr)

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JP2018500580A JP2018525235A (ja) 2015-07-08 2016-06-29 円筒形状の軸受表面を有するワークピースを研削する方法および処理パラメーターを決定するための方法
CN201680039935.8A CN107735218B (zh) 2015-07-08 2016-06-29 研磨具有柱形支承面的工件的方法和用于确定工艺参数的方法

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EP15175782.0A EP3115149B1 (fr) 2015-07-08 2015-07-08 Procédé de meulage d'une pièce ayant une surface de palier cylindrique et procédé de détermination de paramètres de traitement
EP15175782.0 2015-07-08

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CN120630887A (zh) * 2025-05-23 2025-09-12 中南大学 螺旋锥齿轮磨齿机床主轴转速和进给速度的优化方法

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CN110807263B (zh) * 2019-11-07 2023-04-28 河北工业大学 一种杯形砂轮曲面磨削加工的磨削力预测方法及预测系统
CN114091272B (zh) * 2021-11-23 2024-07-12 东华大学 基于双绝热边界假设的磨削温度计算方法、系统、介质
CN115647491B (zh) * 2022-10-14 2024-09-27 重庆大学 一种行星滚柱丝杠副的滚柱锥度磨削方法

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CN120630887A (zh) * 2025-05-23 2025-09-12 中南大学 螺旋锥齿轮磨齿机床主轴转速和进给速度的优化方法
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CN107735218A (zh) 2018-02-23
EP3115149B1 (fr) 2018-03-14
EP3115149A1 (fr) 2017-01-11
CN107735218B (zh) 2019-11-12

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