Using data about the force flow in a press for the operation of a ram

Abstract

A method of using data on the force flow in a press for the operation of a plunger, wherein the loads of the parts involved in the force flow can differ as a result of eccentrically operating forces, in such a way that the data about the respectively acting forces that, in accordance with Hooke's law, cause an extension or compression of a movement of the parts involved in the force flow, is measured and evaluated in relation to a drive device and a position of the plunger, whereupon a skewed position of the plunger is permitted or a skewed position of the plunger is counteracted or a skewed position of the plunger is set during operation of the press.

Claims

1. A method of using data on a force flow in a press to operate a plunger, the method comprising: providing the press comprising: a substructure, at least one drive device arranged in the substructure, the at least one drive device being operatively connected to at least one drive train so as to generate a force, a plunger comprising at least one upper tool part, the plunger being configured to execute a stroke and to transmit the force, at least one bottom tool part associated with the plunger and with the at least one upper tool part, the at least one bottom tool part being arranged to the substructure, at least one traction element or pressure element configured to act on the plunger via a traction connection or pressure connection which is configured to transmit a drive for the stroke of the plunger, the at least one traction element or pressure element and the traction connection or pressure connection being configured to produce a force flow from the drive device to the at least one upper tool part, a traction point and/or pressure point, the traction connection or pressure connection and the at least one traction element or pressure element being mounted on the plunger in the traction point and/or pressure point so as to allow for a tilting of the plunger, the traction point and/or pressure point, due to elasticities of at least one traction element or pressure element, being configured to allow for a modifiable position between the plunger and the traction element or pressure element, at least one displacement/stroke measurement device configured to record data on a displacement or the stroke with regard to the position of the plunger, at least one data recording device configured to record data on at least one of a state or a function relating to, the position of the plunger, the force flow, and a targeted tilting of the plunger, at least one force flow measuring device configured to record data on the force flow, and a control and regulation device configured to process the data from the at least one displacement/stroke measurement device, the at least one data recording device, and the at least one force flow measuring device; providing a workpiece or a material; working or deforming the workpiece or the material between the at least one upper tool part and the at least one bottom tool part and the plunger with the at least one upper tool part being driven between a top and a bottom dead center in at least one single reversing stroke or in strokes passing through the bottom dead center and a top dead center so as to bear down onto the bottom tool part; and applying the data processed by the control and regulation device on the force flow acting on and leading to an expansion, a compression, or a movement in an area of the traction point and/or pressure point or of at least one traction element or pressure element in relation to the at least one drive device and a position of the plunger so as to allow, counteract or initiate a tilting of the plunger during an operation of the plunger.

2. The method as recited in claim 1, wherein at least one traction element or pressure element is provided as a tie rod, a feed rod, a connecting rod, a spindle, or a piston/cylinder unit.

3. The method as recited in claim 1, wherein the press further comprises a convex spherical segment bearing and a concave spherical segment bearing which are configured to correspond with each other in a manner of a calotte, wherein the traction connection or pressure connection in the traction point and/or pressure point is arranged with the convex spherical segment bearing and the concave spherical segment bearing so as to allow for an articulately changeable bearing of the at least one traction element or pressure element.

4. The method as recited in claim 1, wherein the processing of the data by the control and regulation device is performed based on a relation according to Hooke's function F=D.

5. The method as recited in claim 1, wherein the press further comprises at least one force-recording or displacement-recording element.

6. The method as recited in claim 1, further comprising: using at least the at least one displacement/stroke measurement device, or the at least one data recording device, or the at least one force flow measuring device for a controlled or regulated process sequence; and establishing a relation between data on occurring deformation forces processed by the at least one data recording device or by the at least one force flow measuring device, and data on the position of the plunger detected by the at least one displacement/stroke measurement device or the at least one data recording device.

7. The method as recited in claim 1, further comprising: controlling/regulating data detected by the at least one data recording device or by the at least one force flow measuring device, and data on the position of the plunger detected by the at least one displacement/stroke measurement device as reference values so as to implement a desired force flow/force compensation in a process operation.

8. The method as recited in claim 7, wherein, in the process operation, the process further comprises: providing the data detected on the position of the plunger as reference values; and adjusting a desired force flow/force compensation based on the reference values.

9. The method as recited in claim 7, further comprising: changing the reference values based on the data detected on the force flow or on the deformation forces, and the reference values based on the data detected on the position of the plunger during the process operation.

10. The method as recited in claim 9, further comprising: processing the data resulting from the force flow or from the position of the plunger, which respectively change during the process operation, via at least one of the at least one displacement/stroke measurement device, the at least one data recording device, and the at least one force flow measuring device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is described in greater detail below on the basis of embodiments and of the drawings in which:

(2) FIG. 1 shows a simplified representation of the press 1 with a bottom drive and a tie rod connection 2.4.1 and the schematic operation principle by means of a control and regulation device 4 as well as the means 4.1, 4.2, 4.3; and

(3) FIG. 2 shows details of the tie rod connection 2.4.1 with the convex spherical segment bearings 2.4.2 and concave spherical segment bearings 2.4.3 in which each tie rod 2.1.2 is borne on the plunger 1.1 in a pressure point 2.4.

DETAILED DESCRIPTION

(4) In the present invention addresses these aspects based on the action of Hooke's law in the structural system of a press. According thereto, a tilting of the plunger caused by eccentric forces generates different loads acting on the parts located in the force flow which expand or compress or move according to Hooke's law as a function of the acting force.

(5) Until now, such forces acting on components of the press were already being recorded and analyzed, but only for an immediate monitoring of the forming process of the workpiece between the upper tool part and the bottom tool part and in order to control excessive loads/loads with regard to the loads acting on the press and the tools.

(6) The present invention discloses two embodiments, while taking into account that a looming tilting of the plunger due to eccentric forces causes different loads on the parts located in the force flow, which, according to Hooke's law, expand, compress, or move differently as a function of the acting force.

(7) A first embodiment of the present invention additionally uses the data about these different expansions, compressions, or movements of the components and of the press in the force flow of the press for operating a plunger, wherein the press comprises at least one drive device connected via at least one drive train and generating a force, at least the plunger executing a stroke and transmitting the force and carrying at least one upper tool part, and at least one bottom tool part associated with the plunger and the corresponding upper tool part, said parts of the press producing the force flow from the drive device to the upper tool part, wherein a workpiece or material is worked or deformed between the upper tool part and the bottom tool part, and the plunger with the upper tool part is driven between a top and a bottom dead center in at least one single reversing stroke or in strokes passing through the bottom dead center and the top dead center so that it bears down onto the bottom tool part,

(8) so that the data about different loads caused by eccentric forces acting on the entire force flow or an all the parts involved in the force flow, said forces causing an expansion or compression or movement of the involved parts according to Hooke's law, is recorded and analyzed in relation to the drive device (2) and to the position of the plunger (1.1), whereupon, a tilting of the plunger (1.1) is allowed, or a tilting of the plunger (1.1) is counteracted, or a tilting of the plunger (1.1) is initiated,

(9) for operation.

(10) As opposed in particular to DE 196 42 587 A1, the present invention achieved that generic presses can be operated by way of two drive units. It is thus possible to influence the synchronous operation of the plunger by means of a control and regulation of the drives. Data about both drives can here be recorded in order to derive decision criteria for the control and regulation process, wherein all the components or drives involved in the force flow are taken into account.

(11) A second embodiment of the present invention uses the data about the force flow of a press for the operation of a plunger, wherein the press comprises at least one drive device disposed in a sub-structure and connected via at least one drive train and generating a force, at least the plunger executing a stroke and transmitting the force and carrying at least one upper tool part, and at least one traction element or pressure element acting on the plunger by means of a traction connection or pressure connection for transmitting the drive for the stroke of the plunger, and at least one bottom tool part associated with the plunger and the corresponding upper tool part, said parts of the press producing the force flow from the drive device to the upper tool part, wherein a workpiece or material is worked or deformed between the upper tool part and the bottom tool part, and the plunger with the upper tool part is driven between a top and a bottom dead center in at least one single reversing stroke or in strokes passing through the bottom dead center and the top dead center so that it bears down onto the bottom tool part,

(12) so that the traction connection with the traction element or the pressure connection with the pressure element is mounted on the plunger in a traction/pressure point allowing for a tilting of the plunger, data about the force flow acting there and leading to an expansion or a compression or a movement in the area of the traction/pressure point or of the traction element or the pressure element is recorded and analyzed in relation to the drive device and the position of the plunger, whereupon, a tilting of the plunger (1.1) is allowed, or a tilting of the plunger (1.1) is counteracted, or a tilting of the plunger (1.1) is initiated,

(13) for operation.

(14) In an embodiment of the present invention, the traction element can, for example, be configured as a tie rod or feed rod. In an embodiment of the present invention, the pressure element can, for example, be configured as a connecting rod or a shaft or a piston/cylinder unit.

(15) In an embodiment of the present invention, an arrangement of the traction connection or of the pressure connection can, for example, advantageously be used for the second embodiment in the traction/pressure point, each having a convex spherical segment bearing and a concave spherical segment bearing corresponding to each other in the manner of a calotte and allowing for an articulately changeable bearing of the traction element or pressure element, wherein compensatory forces/movements are absorbed by the spherical segment bearings.

(16) In an embodiment of the present invention, a detachable or permanent or fixed arrangement of the traction connection or of the pressure connection can, for example, be alternately used in the traction/pressure point, which allows a modifiable position due to acceptable resiliencies of the traction element or pressure element, wherein compensatory forces/movements are then elastically absorbed by the traction element or the pressure element.

(17) In an embodiment of the present invention, the data can, for example, be analysed in a relation according to Hooke's function F=D, wherein F refers to the force, D to a spring constant, and is the distance of expansion or compression.

(18) In an embodiment of the present invention, at least one first means can, for example, be used for recording data about a displacement or the stroke with regard to the position of the plunger.

(19) In an embodiment of the present invention, at least one second means can, for example, be provided for analyzing data about at least one of the states or one of the functions such as: the position of the plunger, the force flow of the involved parts, for a targeted tilting of the plunger.

(20) In an embodiment of the present invention, at least one third means can, for example, be responsible only for recording data about the force flow of the involved parts.

(21) In an embodiment of the present invention, in order to record the data about parts subjected to an expansion or a compression or a movement, at least one element recording a force or movement can, for example, be provided in at least one part of the press, wherein said element can, for example, be fastened in the force- or movement-sensitive areas of the expansion or compression or articulately modifiable bearing of the traction element or pressure element and is configured as a piezo-element, a strain gauge or a similarly acting element.

(22) In an embodiment of the present invention, a control and regulation device can, for example, process the data of the first, second and third means for at least one of the control signals such as: allowing a tilting of the plunger, counteracting a tilting of the plunger, or initiating a tilting of the plunger,

(23) for operating the plunger.

(24) In an embodiment of the present invention, an integration of at least the first means or the second means or the third means can, for example, take place for a controlled or regulated process sequence, wherein a relation is established between the data about occurring deformation forces processed by the second means or third means and the data about the position of the plunger detected by the first means or the second means.

(25) In an embodiment of the present invention, the data detected by the second means or the third means and the data about the position of the plunger detected by first means can, for example, be controlled/regulated as reference values in the process operation in such a manner that the desired force flow/force compensation is implemented.

(26) In an embodiment of the present invention, the detected data about the position of the plunger can, for example, also be provided as reference values, according to which the desired force flow/force compensation is adjusted.

(27) In an embodiment of the present invention, the reference values based on the detected data about the force flow of the involved parts or the deformation forces and the reference values based on the detected data about the position of the plunger can, for example, be changed during the process operation.

(28) In an embodiment of the present invention, the data resulting from the forces or positions of the plunger, which respectively change during the process, can, for example, be processed by at least one of the first, second and third means.

(29) As a whole, the present invention establishes a relation between the respective drive devices and the monitored position of the plunger based on this data, analyses this relation, and can influence a tilting of the plunger in a targeted manner in spite of different forces and thus different compressions of the components, so that a tilting of the plunger is deliberately allowed or counteracted or initiated in the operation.

(30) The present invention therefore provides a solution that is respectively useful for a targeted tilting of the plunger or for a tilting of the plunger that is to be accepted as well as for one that results from a malfunction.

(31) The present invention is thus applicable in presses with a top drive as well as for presses with a bottom drive, wherein quasi-sensory means for recording data about the parts involved in the force flow can be parts, that can, for example, be located in areas that are relevant to the force flow and sensitive to the components, such as e.g., a pressure or traction connection (respectively in a top or bottom drive) with the plunger.

(32) In a press with a bottom drive, it can, for example, be advantageous to provide an arrangement of the traction connection in the traction/pressure point having a convex spherical segment bearing and a concave spherical segment bearing corresponding to each other in the manner of a calotte.

(33) This arrangement of the traction connection in the traction/pressure point having a convex spherical segment bearing and a concave spherical segment bearing corresponding to each other in the manner of a calotte can, however, also be used as a pressure connection in a press with a top drive.

(34) This structure according to the invention can be implemented e.g., in a generic press with a bottom drive as described in PCT/DE2011/075197, which already uses data for a force-optimized process operation.

(35) However, to date, this data merely relates to: a course or a position in the stroke of the plunger, an actual value of a force or a force-equivalent value in at least one of the drive elements of the drive device, values of a power consumption, a torque, an electric current, a rotational speed or a rotation angle of at least one drive element such as a motor or servomotor, an actual value of an output or output increase in the system of the press,

(36) which are functionally processed in a control and regulation device, e.g., for modifying values that are to be adjusted or set for operating the press, for overload protection, emergency operation or shutdown of the press and/or for a synchronous or asynchronous run of drive elements of the drive device

(37) for operating the press.

(38) The present invention can be integrated into this prepared system with a marginal effort so that it is technologically easily implementable.

(39) If the present invention is used, the area of the tie rod connection with the plunger, i.e., the traction/pressure point used as a quasi-sensory means, can, for example, be equipped with strain gauges or piezo-elements for recording the data.

(40) In this regard, the development according to the present invention, namely the control and regulation device protecting the mechanical structure of the press and providing the compensation of asymmetrical press forces as well as processing data from the first, second and third means, is also insertable into an existing system configured as proposed above.

(41) A controlled or regulated process sequence can thus be defined, for example, during forming by taking into account at least the first means or the second means or the third means. In doing so, a relation is established between the data about occurring forming forces processed by the second means or third means and the data about the position of the plunger detected by the first means or the second means.

(42) In view of the issue presented above, the teaching according to the present invention also allows initiating asymmetrical press forces and drawing cushion forces in a targeted manner, for example, in a press with a bottom drive, by way of tie rods not rigidly connected with the plunger in four pressure points, the possible movable bearing in respectively one calotte and the definable tilting of the plunger also serving to this end.

(43) In general, in generic presses, regardless of whether it has a top drive or a bottom drive, once the upper tool part has borne down on e.g., a workpiece holder of e.g., a drawing cushion, or after the plunger as borne down on the bottom tool part, the different forces resulting from the tilting will be easier to adjust in the press of the machine by means of the present invention, according to the rotational angle of the eccentric and the spring constant, i.e., according to Hooke's law.

(44) In particular in a press with a bottom drive implemented as described, for example, in PCT/DE2011/075197, pressure points as well as, according to a kinematic reversal, traction points act on the tie rod connections used therein, which is why this area of the tie rod connections is referred to as traction/pressure points herein. Indeed, according to the present invention, the force application occurring there has different causes, namely, an oblique or inclined position of the plunger caused by a malfunction of the press or controlled in a targeted manner. For both causes, the present invention provides a uniformly effective advantage regarding elements such as the guide, the adjusting mechanism of the plunger and the overload protection. Since the application of a force on the pressure point can come e.g., from a connecting rod disposed above it (as in a press with a top drive) and the press force is transmitted via e.g., a transverse bolt to a threaded spindle, which is part of a pressure point, the length of said threaded spindle would be decisive for a potential adjustment of the plunger. A necessary consequence of this arrangement determined by the geometry of the press would be that the length of the spindles and thus the height of the plunger adjusting mechanism would be disadvantageous to the height of the press. In contrast, by using a traction point in combination with a pressure point, this disadvantage of having to factor the spindle length into the height of the entire machine can be eliminated a priori by the use according to the present invention and the tilt or tilting of the plunger, e.g., initiated in a targeted manner, can be additionally controlled to an almost unlimited extent.

(45) In this regard, the present invention provides an additional effect which has an impact not only on the interaction of the deformation forces as well as the drawing cushion forces but also advantageously on the structural complexity of generic presses and more specifically on an optimized design of the hydraulic components when using a drawing cushion.

(46) The principle of the present invention can therefore also be integrated or retrofitted with little effort into available control and regulation systems of the involved drives.

(47) The present invention is hereafter described based on an exemplary embodiment, for example, in a press with a bottom drive, by means of the drawings.

(48) FIG. 1 shows a press 1 with a bottom drive, whose drive device 2 disposed in a sub-structure 3 comprises eccentric drive elements 2.1, motors or servomotors 2.2, tie rods 2.3 and connecting rods 2.5. A plunger 1.1 executing a stroke h between a top dead center (not labeled) and a bottom dead center (not labeled) has an upper tool part 1.2. Two pairs of tie rods 2.3 and connecting rods 2.5 as part of a drive train 2.6 act on the plunger 1.1, respectively, in the area of a traction/pressure point 2.4 for transmitting the drive for the stroke h of the plunger 1.1. The plunger 1.1 with the upper tool part 1.2 corresponds to a bottom tool part 3.2 disposed on the substructure 3, wherein the upper tool part 1.2 acts onto a workpiece 5 located on the bottom tool part 3.2 for forming. The bottom tool part 3.2 is disposed on a table 3.1 belonging to the substructure 3.

(49) A control and regulation device 4, whose operation can be designed according to the system described in PCT/DE2011/075197, is provided for operating the press 1. By way of the tie rods 2.3 and the connecting rod 2.5, forces acting in a differentiated manner are applied to the workpiece 5 to be formed between the upper tool part 1.2 and the bottom tool part 3.2 so that the press 1 can be permanently operated according to a system of forces required exclusively by the workpiece 5, but still without the use of a traction connection 2.4.1 disclosed according to the invention.

(50) The press 1 operating according to that system takes sequences into consideration, in terms of control, which are usable for the new inventive process according to the features disclosed in the claims on the one hand and which transcend them in terms of their effects.

(51) This proposed control solution and the complex operational and constructional design required for it can be assisted on the one hand by generating the force actually acting in each respective position of the respective drive train 2.6 or of e.g., an eccentric drive element 2.1 of the drive device 2 and on the other hand by using the data in consideration of Hooke's law in accordance with the invention.

(52) Based on a press 1 designed in such a manner, the present invention goes beyond that and solves the issue presented in the introduction and the problem of tilted or inclined positions of the plunger, i.e., when the position of the plunger 1.1 deviates from a normal parallel operation, in accordance with the following new example.

(53) A force compensation caused by opposing, returning forces (Hooke's law) countering the deformations initiated in the constructional system of the press 1 by the asymmetrically acting forces is initiated by an interaction between the involved deformation forces, a rotation angle and a spring constant or at least respectively one of these dimensions of at least one machine element of the press 1 in relation with its constructional stiffness or of an eccentric element of the drive device 2.

(54) To this end, the traction connection 2.4.1 non-rigidly borne in a traction/pressure point 2.4 allowing a modifiable position between the plunger 1.1 and the tie rod 2.3 is used, which means that this area is used as a quasi-sensory means and is re-constructed in a surprisingly functional new manner.

(55) It is alternately possible to choose an arrangement of the traction connection 2.4.1 that is rigid due to acceptable elasticities.

(56) Whether the tilted or inclined position of the plunger 1.1 is caused by a malfunction of the press 1 or is initiated in a targeted manner, the force compensation is respectively supported, optimized or implemented by means of data to be recorded or to be input in the area of the traction/pressure point 2.4. To this end, the non-rigid traction connection 2.4.1 is borne in the traction/pressure point 2.4 in an arrangement having, respectively, one convex spherical segment bearing 2.4.2 and one concave spherical segment bearing 2.4.3 corresponding to each other in the manner of a calotte.

(57) If the tilted or inclined position of the plunger 1.1 is caused by a malfunction of the press 1, a first means 4.1 records the data about this position of the plunger 1.1, which is input in order to support the force compensation and to preserve the operation of the construction system of the press 1.

(58) If the tilted or inclined position of the plunger 1.1 is to be controlled in a targeted manner, a second means 4.2 provides the data for this desired position of the plunger 1.1, whereby, a resulting unequal movement of the two drive trains 2.6 is continued, e.g., after the upper tool part 1.2 has borne down onto the bottom tool part 3.2. The upper tool part 1.2 and the bottom tool part 3.2 are now closable in a parallel relation, wherein asymmetrical and unequally acting forces are generated in a targeted manner by the unequally continuing movement and the spring stiffness of the press 1.

(59) In this example, third means 4.3 provide for a recording of data about the force flow by way of a force/displacement recording mean 2.4.4.

(60) The control and regulation device 4 provided for operating the press 1 processes the data from the first, second and third means 4.1, 4.2, 4.3 for protecting the mechanical structure of the press and for a compensation of the asymmetrical press forces and provides control signals such as: allowing a tilting of the plunger, or counteracting a tilting of the plunger, or initiating a tilting of the plunger.

(61) During forming, the third means 4.3 thus establishes and adjusts a relation between the occurring forces (deformation forces) in the force flow and the position of the plunger 1.1 based on the data about the traction/pressure point 2.4, respectively, from the first means 4.1 in case of a malfunction of the press 1 or from the second means 4.2 in case of a tilted or inclined position of the plunger 1.1 initiated in a targeted manner.

(62) The data obtained from the respective deformation force is then used as a reference value and the position of the plunger 1.1 is guided so that a desired force flow is implemented. The force compensation preserving the constructional system of the press 1 is thus optimized or carried out.

(63) Data gathered from the position of the plunger 1.1 can also play a decisive role as reference values.

(64) The force compensation controlled in such a manner during the forming process based on the data detected in the traction/pressure point 2.4 by means of the quasi-sensory means also considers the fact that the respective forces or positions of the plunger 1.2 change and that the respective reference values derived from the force or the position of the plunger 1.1 can vary.

(65) Known force/displacement recording means 2.4.4 such as strain gauges or piezo-elements or similarly acting means, which can be chosen by the person skilled in the art in the usual manner, can be used for recording the data in the area of the traction/pressure point 2.4.

(66) The design of the first, second and third means 4.1, 4.2, 4.3 is also chosen by the person skilled in the art in a customary manner and does not have to be described in more detail herein.

(67) The principle according to the invention is also applicable in a press with a top drive, not explained here, in which the force flow occurs from a drive device disposed at the top via a plunger with an upper tool part to a bottom tool part by way of a pressure connection. The plunger with the upper tool part can here too be moved between a top and a bottom dead center in at least one single reversing stroke or in strokes passing through the bottom dead center and the top dead center, so that it bears down on the bottom tool part.

(68) The use of data about the force flow in that press for operating a plunger occurs so that in case of a tilting of the plunger caused by eccentric forces and of different resulting loads on the parts involved in the force flow, which are also subject to an expansion or a compression as a function of the respectively acting force according to Hooke's law, the data is recorded and analysed in relation to the drive device and the position of the plunger, whereupon: a tilting of the plunger is allowed, or a tilting of the plunger is counteracted, or a tilting of the plunger is initiated.

(69) In an application according to the present invention, the parts involved in the force flow can be connecting rods or spindles, which act on the plunger in a pressure point and which are connected in that point with the plunger. In the area of said pressure point, similar force/displacement recording means 2.4.4, such as strain gauges or piezo-elements or similarly acting means, are used for recording the data about the force flow.

(70) The use of data in a press according to the invention can be implemented on the one hand in existing basic systems without a substantial construction effort on the one hand and ensure on the other hand: an allowable tilting, or a counteraction of the tilting, or a targeted initiation of a tilting,

(71) of the plunger and supports the efficiency of acting forces for an energy-saving operation of any generic press.

(72) The present invention is not limited to embodiments described herein; reference should be had to the appended claims.

LIST OF REFERENCE NUMBERS

(73) 1 press 1.1 plunger 1.2 upper tool part 2 drive device 2.1 eccentric drive element 2.2 motor or servomotor 2.3 traction element, tie rod, feed rod (bottom drive), pressure element, spindle, piston/cylinder unit (top drive) 2.4 traction/pressure point 2.4.1 traction connection (bottom drive), pressure connection (top drive) 2.4.2 convex spherical segment bearing 2.4.3 concave spherical segment bearing 2.4.4 force/displacement recording means 2.5 connecting rod 2.6 drive train 3 substructure 3.1 table 3.2 bottom tool part 4 control and regulation device 4.1 first means for recording data about the position of the plunger (1.1) 4.2 second means for recording data 4.3 third means for recording data about the force flow 5 workpiece h stroke