EP2347856A2 - Method for construction of a profile grinding process - Google Patents

Abstract

The method involves determining power demand referred on the tool (10) or on the workpiece (30) from the erosion of an air passage of the workpiece or geometry of the tool or relative feed speed between the workpiece and the tool. The determined value is compared with a technological limit value in such a manner that the infeed rate and the relative feed speed between the tool and the workpiece in dependence of the workpiece or of the tool geometry is selected in such a way that their mathematical product, is multiplied by correcting function, smaller or equal to the technological limit value.

Description

The invention relates to a method for designing a profile grinding process.

The design of a grinding process, the selection of a feed rate and a delivery, is generally carried out as a function of the Zeitspanvolumens, the product of the feed rate and the delivery or related to the grinding wheel width Zeitspanvolumens. For example, given a given maximum radial delivery then the choice of feed rate for the entire processing is done so that the technological limit of the Zeitspanvolumens or the related Zeitspanvolumens is not exceeded. Mostly work is done with high feed rates and low delivery amounts.

The present invention is based on the problem to develop a method for profile grinding with low peak time.

This problem is solved with the features of the main claim. For this purpose, the removal of the oversize of the workpiece and / or the geometry of the tool and / or the relative feed rate between the workpiece and the tool determines a required, related to the tool and / or the workpiece power requirements and / or the value thus determined compared with a technological limit and / or the feed amount and the relative feed rate between the tool and the workpiece in Depending on the workpiece and / or the tool geometry selected so that their mathematical product multiplied by a correction function, is less than or equal to the technological limit.

Figur 1:

Profilschleifen;

Figur 2:

Bewegungsrichtungen des Werkstücks und des Werkzeugs;

Figur 3:

Zahnlücke mit Werkzeug;

Figur 4:

Werkzeug mit großem Durchmesser im Eingriff;

Figur 5:

Werkzeug mit kleinem Durchmesser im Eingriff;

Figur 6:

Schleifscheibenkontur;

Figur 7:

Bezogenes Normalzeitspanvolumen und bezogenes Zeitspanvolumen über der Abwicklung der Schleifscheibenkontur bei Zahnfuß- und Zahnflankenbearbeitung;

Figur 8:

Bezogenes Normalzeitspanvolumen und bezogenes Zeitspanvolumen über der Abwicklung der Schleifscheibenkontur bei Zahnflankenbearbeitung;

Figur 9:

Grenzwerte des bezogenen Zeitspanvolumens und des bezogenen Normalzeitspanvolumens über der Zeit;

Figur 10:

Auswahl des Produkts aus dem Normalenabstand bzw. der radialen Zustellung und der Vorschubgeschwindigkeit.

Further details of the invention will become apparent from the dependent claims and the following description of schematically illustrated embodiments.

FIG. 1:

Profile grinding;

FIG. 2:

Movement directions of the workpiece and the tool;

FIG. 3:

Tooth space with tool;

FIG. 4:

Large diameter tool engaged;

FIG. 5:

Small diameter tool engaged;

FIG. 6:

Grinding wheel contour;

FIG. 7:

Referenced normal time chip volume and related time span volume on the execution of the grinding wheel contour in Zahnfuß- and tooth flank processing;

FIG. 8:

Referenced normal time chip volume and related time span volume over the execution of the grinding wheel contour in tooth flank processing;

FIG. 9:

Limit values of the related time span volume and the reference normal time span volume over time;

FIG. 10:

Selection of the product from the normal distance or the radial infeed and the feed rate.

The FIG. 1 schematically shows the profile grinding. In the illustrated method is as a tool (10) a profile grinding wheel (10) in engagement with a workpiece (30), for example a gear (30). Instead of the illustrated spur gear with a straight involute toothing, the workpiece (30) may also have a helical gearing, a worm gearing, etc. It is also conceivable to process trapezoidal profile gaps with the method, for example in the case of a toothed rack. When profile grinding, the flanks limiting the profile gaps can be offset from each other either individually and in time or can be processed simultaneously and simultaneously.

Both the workpiece (30) and the tool (10) are rotationally driven in the illustrated embodiment. The axes of rotation (11, 31) are not parallel to each other and do not intersect.

In the exemplary embodiment, the tool (10) is further movable relative to the workpiece (30) parallel to the workpiece axis (31), cf. FIG. 2 , The relative movement is at least approximately parallel to the workpiece axis (31). This means that the axial feed movement with the workpiece axis (31) can include an angle of eg up to 10 degrees. For example, in the in this FIG. 2 shown in the same direction processing the toothing (32) the axial feed direction (21) of the tool (10) directed from top to bottom. It is also conceivable to move the workpiece (30) relative to the tool (10) in a feed direction.

For example, when machining a gearing, the workpiece (30) stops, while the rotating tool (10) moves along a tooth gap (37) oriented parallel to the workpiece axis (31) during grinding. The feed rate along the tooth gap (37) corresponds to the speed of the axial tool feed.

When machining an uncorrected helical toothing, the feed rate of the tool relative to the workpiece results, for example, from a superimposition of the axial tool feed with the angular speed of the workpiece rotation during the axial tool stroke.

To bring the tool (10) into engagement with the workpiece (30), the tool (10), for example, in the FIG. 2 shown initial position in the direction of the workpiece (30) delivered. The feed direction (22) of the tool axis (11) is directed radially on the workpiece axis (31). Also, the workpiece (30) can be delivered in the direction of the tool axis (11).

That in the FIG. 1 shown gear (30) is pre-toothed, for example by means of a Wälzfräsverfahrens and was then cured. It has at least on the tooth flanks (33, 34) an allowance (35) on the finished measure (44), cf. FIG. 3 , The finished measure (44) of the workpiece (30) describes the geometric dimensions of the finished and ready-to-use workpiece (30).

The illustrated gear (30) has 17 teeth (36). Each tooth (36) is bounded by two tooth flanks (33, 34). Two tooth flanks (33, 34) define a tooth gap (37). The single tooth (36) has a head (38), the two tooth flanks (33, 34) connecting the tooth base (43).

The profile grinding wheel (10) is repeatedly dressed during its use on the grinding machine. Their outer diameter is reduced, for example, from 500 millimeters to 250 millimeters, cf. the FIGS. 4 and 5 , The disc (10) shown has a cylindrical central portion (12), for example, adjoining edge regions (13, 14) on both flanks, the generatrices of which, for example, correspond to the nominal profile lines of the toothing (32) in the case of straight toothing.

Before the rotating tool (10) is delivered, the workpiece (30) is rotated about its workpiece axis (31) so that a tooth gap (37) faces the grinding wheel (10). The single tooth gap (37) has the contour (45) before grinding, cf. FIG. 3 , During delivery, the profile grinding wheel (10) contacts both tooth flanks (33, 34) adjoining the tooth space (37) simultaneously in the example of the two-flute cut. Upon further delivery, the tool (10) penetrates into the workpiece (30) and cuts a portion of the allowance (35) of both tooth flanks (33, 34) with a geometrically indeterminate cutting edge, cf. FIG. 3 , During this processing, the tool (10) is moved along the tooth gap (37) at a set feed rate. Optionally, the foot (41) and / or the head regions (42) can be mitgeschliffen. The active surface (15) of the grinding wheel (10) is the sum of the surface of the cylindrical portion (12) and the lateral surfaces (16) of the edge regions (13, 14), which upon rotation of the tool (10) about its axis (11 ) Have contact with the gear (30). The processing takes place, for example, with simultaneous cooling by means of a coolant.

During grinding, the grinding wheel (10) contacts the gear (30) along a line. In the case of two-flank grinding, this contact line generally connects the tooth head (38) to the tooth root (39, 46) on each of the two tooth flanks (33, 34). For example, this contact line may be a profile line of the toothing (32). The toothing (32) may have a head or foot return, a height crowning, etc. Grinding wheel side, the contact line is e.g. in each case a surface line of the edge regions (13, 14) in the case of gear teeth. These can be connected on the face side by a contact line oriented parallel to the grinding wheel axis (11). The last-mentioned section of the contact line contacts the tooth base (43) when it is ground.

In dieser Gleichung ist

Q'w_n(s):

bezogenes Normalzeitspanvolumen [mm²/s],

Z_n(s):

Abtrag Z_n(s) in Normalenrichtung [mm],

v:

Vorschubgeschwindigkeit [mm/s]

In order to determine the amount of delivery and the feed rate, a power requirement is first determined from the geometric data of the actual and the desired toothing and the geometric data of the active surface (15) of the grinding wheel (10). From the comparison of the actual and the desired profile of the individual tooth flank (33, 34), the tooth head (38) and the tooth base (43) results for each point of the active surface (15) of the grinding wheel (10) in a normal direction (7 ) oriented removal. The removal per stroke is a partial amount of a notional normal distance (8), cf. FIG. 3 , He is usually less than or equal to this value. The fictitious normal distance (8) - it corresponds to the measured normal to the tooth flank (33, 34) allowance (35) - is generally not constant over the profile height of the toothing (32). In the exemplary embodiment, this normal spacing (8) at the transition of the tooth flank (33, 34) into the tooth base (43) is, for example, 64% of the fictitious normal value at the transition of the tooth flank (33, 34) to the tooth head (38). In the presentation of the FIG. 3 the fictitious normal distance (8) at the tooth base (43) is twice the notional normal distance (8) at the transition of the tooth flank (33, 34) to the tooth head (38). From these quantities, taking into account the feed rate, a related normal-time chip volume Q'w _n results. For example, this is calculated to $${\mathrm{Q\text{'}w}}_{\mathrm{n}}\left(\mathrm{s}\right)\mathrm{=}{\mathrm{Z}}_{\mathrm{n}}\left(\mathrm{s}\right)\mathrm{*}\mathrm{v}$$

In this equation is

Q'w _n (s):

referenced standard time chip volume [mm ² / s],

Z _n (s):

Removal Z _n (s) in normal direction [mm],

v:

Feed rate [mm / s]

It is the product of the removal Z _n (s) of the grinding wheel in the respective normal direction (7) in millimeters at the profile point s and the feed rate v along the tooth gap (37) in millimeters per second. Q'w _n takes into account the feed rate v, the profile shape of the tool (10) and the different oversizes (35) of the tooth flanks (33, 34) measured normal to the flank line.

This value is determined for each profile point s of the active surfaces (15) of the grinding wheel (10). The thus-ascertained related normal-time chip volume is a performance variable of the grinding process. It has the dimension square millimeters per second. For example, it specifies the power required to remove the oversize (35).

The FIG. 6 shows the over the grinding wheel width b and the grinding wheel diameter d plotted course of the grinding wheel profile. The digits along the profile give the unwound distance of the corresponding point from the origin the processing, here in Schleifscheibenmitte to. The gearing profile on which this development is based has 27 teeth and a module of 10 millimeters.

In the FIG. 7 is the required chip volume Q'w (5) and the related normal time chip volume Q'w _n (6) as the power requirement over the development of the profile of FIG. 6 applied. In this figure, the values of a toothing are shown, in which the tooth root is mitgeschliffen. The value of the related Zeitspanvolumens Q'w is constant along the settlement, in the exemplary embodiment, it is 16 square millimeters per second. The related normal-time chip volume Q'w _n is constant, for example, along the end peripheral surface (17) of the grinding wheel. In this area, its value corresponds to the value of the normal time chip volume purchased. During the transition into the lateral surfaces (16), the relative normal-time chip volume Q'w _n decreases to a minimum. For example, it rises steadily along the lateral surface (16). The referenced normal-time chip volume Q'w _n is lower along the entire lateral surface (16) than the related time-sliced volume Q'w.

The limit value Q'w _{n, Gr} (4) determined for the design according to the normal-time chip volume _, for example from tests _, is constant for the end peripheral surface (17). Along the lateral surfaces (16), for example, it decreases linearly. In the example shown, the selection of the radial feed of the tool (10) relative to the workpiece (30) and the feed rate of the tool (10) relative to the workpiece (30) to the limit in the region of the end peripheral surface (17).

The FIG. 8 shows analogous to FIG. 7 the curve for a toothing, in which the tooth root is not mitgeschliffen. The maximum power requirement of the normal-time chip volume (6) Q'w _n is in the area of the grinding wheel (10), the the transition of the tooth flank (33; 34) processed to the tooth head (38). The power value chosen for this range must be less than or equal to the limit Q'w _{n, Gr} . The limiting value curve dependent on the geometry of the grinding wheel (10) is shown in FIG FIG. 8 identical to that in the FIG. 7 illustrated limit value course. How the comparison of FIGS. 7 and 8 shows, if the Zahnfußbereich is not mitgeschliffen, in a design after the normal-time chip volume Q'w _n a higher grinding performance can be used as in a design according to the Zeitspanvolumen Q'w. In the embodiment of FIG. 8 For example, this increase is 55% compared to the example of FIG. 7 , The grinding wheel can thus remove more without damaging the workpiece (30), z. B. caused by grinding burn.

Decisive for the design is the maximum value of the related normal-time chip volume Q'w _n (s). This results in the setting parameters of the grinding process with the technological limit value Q'w _{n, Gr} (4) of the related normal-time chip volume determined as a function of the tool geometry. Due to the large Schleifabtrag results in a lower peak processing time. In this case, different profile shapes and different curvatures of the teeth are taken into account.

After the grinding of the tooth gap (37) limiting tooth flanks (33, 34), the tool (10) against the feed direction (22) is moved out of the tooth gap (37). The workpiece (30) is rotated about its axis of rotation (31) by one pitch, so that now shows the next tooth gap (37) to the grinding wheel (10). The processing of this tooth gap (37) takes place, as described above. By means of this discontinuous profile grinding method, the toothing (32) can be processed quickly and accurately.

During grinding, the grains of the grinding wheel (10) wear out and the grinding wheel (10) settles with grinding dust. For example, after predetermined intervals, due to the increase of the motor current, etc., the grinding wheel (10) is dressed. Here, the end peripheral surface (17) and the lateral surfaces (16) of the grinding wheel (10) are processed. The diameter of the grinding wheel (10) is thereby reduced.

A dressing of the grinding wheel (10) is all the more necessary the smaller the grinding wheel (10). At the same time, the non-productive time required for dressing is reduced. These two opposing effects do not cancel, so that the bottom-to-bottom time of the workpiece is increased with increasing tool life (10).

After dressing, based on the new grinding wheel geometry, a new course of the related normal-time chip volumes is determined. Thereafter, starting from the maximum value of the referenced normal-time chip volume, the new feed rate and the new delivery are determined in comparison with a tool geometry and / or workpiece-dependent technological limit value of the normal-time chip removal volume. In this case, for example, either the feed rate or the new delivery amount is specified and the other value is designed so that from the set sizes and the geometric data of the grinding wheel (10) results in a value less than or equal to the permissible related Normalzeitspanvolumens. An adjustment of the feed rate and the delivery amount is conceivable.

In the FIG. 9 A qualitative course of the tool geometry-dependent technological limit is shown. In the abscissa represents the time, the ordinate the applied time span volume and the related normal time span volume. The time axis describes the main time of the grinding process. At predetermined intervals, the grinding wheel (10) is dressed and thereby reduced its diameter. The grinding wheel diameters (18), which are constant between the dressing processes (51), are shown as horizontal lines.

The limit value of the related time-wasting volume Q'w _Gr determined according to the prior art remains constant throughout the grinding process. The limit value of the related normal-time chip volume Q'w _{n, Gr} determined, for example, in tests decreases with increasing process time and / or with decreasing grinding wheel diameter. As the diagram further shows, it is possible, for example, to work with a used normal-time chip volume until the time of the second dressing, which is significantly higher than the limit of the relative chip removal volume. The usable loop energy is thus higher than in a design according to the related Zeitspanvolumen.

The FIG. 10 represents as a product of the selected delivery and the selected feed rate, the selected time chip volume or the selected normal time chip volume. Due to the higher limit of the referenced normal time chip volume, a higher removal rate can be selected as in a design according to the related Zeitspanvolumen. For example, in the FIG. 10 at the same feed rate a larger delivery amount selected.

In the in the FIGS. 6 to 10 For the sake of simplicity, the constants and correction factors are not taken into account. The setting of the parameters of the radial infeed and the relative feedrate For example, one of these parameters can be automated after specification.

Instead of the active wheel width, the volume to be removed or abraded may be related to the active wheel surface (15). The thus determined related power requirement H'w has the dimension millimeters per second. This value is also determined for each point of the settlement.

The related power requirement H'w is different for profile points which lie on different profile lines, since both the distance of the respectively contacting grinding wheel point from the axis of rotation (11) of the grinding wheel (10) to the tooth head (38) becomes smaller as well as the fictitious Normal distance (8) towards the tooth head (38) towards increases.

wobei die Variablen bedeuten:

H'w:

bezogener Leistungsbedarf [mm/s]

k(s):

Korrekturfunktion, dimensionslos

s:

Bogenlänge der Abwicklung [mm]

v:

Vorschubgeschwindigkeit in Lückenrichtung [mm/s]

Z (s) :

Abtrag, z.B. pro Hub [mm]

N(D_sls(s)):

Funktionswert in Abhängigkeit der Bogenlänge der Abwicklung s [mm].

The related power requirement H'w is given by $$\mathrm{H\text{'}W}\mathrm{=}\mathrm{k}\left(\mathrm{s}\right)\mathrm{*}\mathrm{v}\mathrm{*}{\mathrm{Z}}_{\mathrm{n}}\left(\mathrm{s}\right)\mathrm{/}\left(\mathrm{\pi }\mathrm{*}\mathrm{N}\left({\mathrm{D}}_{\mathrm{sls}}\left(\mathrm{s}\right)\right)\right)$$

where the variables mean:

H'W:

related power requirement [mm / s]

k (s):

Correction function, dimensionless

s:

Arc length of the processing [mm]

v:

Feed rate in gap direction [mm / s]

Z (s):

Removal, eg per stroke [mm]

N (D _sls (s)):

Function value depending on the arc length of the settlement s [mm].

The correction function k (s) takes into account, inter alia, the influences of the contact line course, the contour to be ground, the contact line length, the coolant quantity, the coolant removal, the heat dissipation, the number of grains and the pore volume.

The functional value as a function of the diameter of the grinding wheel (10) takes into account, for example, the profile shape of the grinding wheel (10). So the value takes e.g. at a decreasing pressure angle on the pitch circle too.

The determined power requirement is compared with a limit value. This e.g. The limit value determined in tests is independent of the geometry of the tool (10) and of the workpiece (30). For example, it is dependent on the material combination of the tool (10) and the workpiece (30), the grain of the tool, etc.

To select the adjustment parameters of the grinding process, the selected power requirement is determined to be less than or equal to the limit value. From this, the delivery and the relative feed rate are selected.

mit

v:

Vorschubgeschwindigkeit in Lückenrichtung [mm/s]

Z_n(s):

Abtrag des Werkzeugs am Werkstück in Normalenrichtung [mm]

H'w_Gr:

Grenzwert des bezogenen Leistungsbedarfs [mm/s)

N(D_sls(s)):

Funktionswert in Abhängigkeit der Bogenlänge der Abwicklung s [mm].

k(s):

Korrekturfunktion, dimensionslos

The product of the removal and the relative feed rate results in too $$\mathrm{v}\mathrm{*}{\mathrm{Z}}_{\mathrm{n}}\left(\mathrm{s}\right)\mathrm{\le }{\mathrm{H\text{'}W}}_{\mathrm{Gr}}\mathrm{*}\mathrm{\pi }\mathrm{*}\mathrm{N}\left({\mathrm{D}}_{\mathrm{SLS}}\left(\mathrm{s}\right)\right)\mathrm{*}\mathrm{/}\mathrm{k}\left(\mathrm{s}\right)$$

With

v:

Feed rate in gap direction [mm / s]

Z _n (s):

Removal of the tool on the workpiece in normal direction [mm]

H'w _Gr :

Limit value of the required power requirement [mm / s]

N (D _sls (s)):

Function value depending on the arc length of the settlement s [mm].

k (s):

Correction function, dimensionless

This product is a function of the constant limit H'w _Gr , the correction factor and the dressing wheel diameter changing through the dressing. The value of the product is thus dependent on the total active surface of the grinding wheel (15). The interpretation takes place, for example, analogous to that in connection with the FIGS. 6 to 10 described interpretation after the normal time chip volume.

If, after each dressing, the mathematical product is chosen to be smaller than or equal to the function value, a large grinding wheel (10) allows a large removal, while a small grinding wheel (10) avoids a critical setting or a grinding burn. Thus, a lower main time of processing can be achieved.

For example, after specifying the relative velocity between the tool (10) and the workpiece (30), the radial feed amount, e.g. automatically determined. It is also conceivable to automatically set the relative speed for a given delivery amount. An optimization according to both parameters is also conceivable.

The prior art is that the grinding wheel is profiled for all strokes so that the end profile can be ground. As FIG. 3 As an example, Z _n (s) and thus the power requirement along the grinding wheel contour vary.

However, for example, the grinding wheel (10) can be profiled and / or positioned for some or each stroke in such a way that the related maximum power requirement is reduced or constant over the development of the grinding wheel contour. The selected related efficiency should be less than the limit.

LIST OF REFERENCE NUMBERS

4

technological limit value Q ' _{WnGr of} the purchased time span _volume ;

5

related time-wast volume Q'w

6

referenced normal-time chip volume Q'w _n

7

normal direction

8th

normal distance

10

Tool, profile grinding wheel, double cone pulley

11

Rotation axis, tool axis

12

central section

13

border area

14

border area

15

active area

16

lateral surfaces

17

End peripheral surface

18

Grinding wheel diameter d

21

axial feed direction

22

infeed

30

Workpiece, gear

31

Rotation axis, workpiece axis

32

gearing

33

Tooth flank, right flank

34

Tooth flank, left flank

35

oversize

36

teeth

37

gap

38

head

39

tooth roots

41

footer

42

head area

43

tooth root

44

finished size

45

Contour before grinding

46

tooth roots

51

dressing operations

b

Grinding wheel width

d

Grinding wheel diameter

Q'w

related time span volume

Q'w, gew

chosen Q'w

Q'w _n

referenced standard time chip volume

Q'w _{n, gew}

chosen Q'w _n

Q'w _nGr

technological limit value of the related standard time chip volume

s

Bow length, handling

V _gew

selected feed rate

Z _gew

chosen delivery

Claims (11)

Method for designing a profile grinding process, characterized - that from the removal of the oversize (35) of the workpiece (30) and / or the geometry of the tool (10) and / or the relative feed rate between the workpiece (30) and the tool (10) a required, on the tool ( 10) and / or on the workpiece (30) related power demand is determined, and / or - That the value thus determined is compared with a technological limit value and / or - That the delivery amount and the relative feed rate between the tool (10) and the workpiece (30) depending on the workpiece and / or the tool geometry are chosen so that their mathematical product multiplied by a correction function, less than or equal to the technological limit is. A method according to claim 1, characterized in that the removal is less than or equal to the maximum normal distance (8). A method according to claim 1, characterized in that the design is carried out per stroke and / or stroke position. A method according to claim 1, characterized in that the technological limit value is independent of the workpiece geometry and of the tool geometry. Method according to claim 1, characterized in that the correction function is dependent on the contact line between the tool (10) and the workpiece (30). A method according to claim 1, characterized in that the correction function is dependent on the pivot angle between the tool (10) and the workpiece (30). A method according to claim 1 and 3, characterized in that the tool is profiled and / or positioned so that the related maximum power requirement on the execution of the grinding wheel contour is reduced. A method according to claim 1, characterized in that the delivery amount and / or the feed rate is set automatically. A method according to claim 8, characterized in that after setting the delivery amount, the feed rate is set automatically. A method according to claim 8, characterized in that after setting the feed speed of the delivery amount is set automatically. A method according to claim 8, characterized in that after setting the ratio between feed speed and delivery amount, these two are set automatically.

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