CA2196560C - Device for producing pressed articles - Google Patents
Device for producing pressed articles Download PDFInfo
- Publication number
- CA2196560C CA2196560C CA002196560A CA2196560A CA2196560C CA 2196560 C CA2196560 C CA 2196560C CA 002196560 A CA002196560 A CA 002196560A CA 2196560 A CA2196560 A CA 2196560A CA 2196560 C CA2196560 C CA 2196560C
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- Prior art keywords
- punch
- motors
- female mold
- axial
- punches
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- 230000033001 locomotion Effects 0.000 claims abstract description 43
- 230000001105 regulatory effect Effects 0.000 claims abstract description 26
- 239000012254 powdered material Substances 0.000 claims abstract description 5
- 239000012255 powdered metal Substances 0.000 claims abstract description 3
- 238000003825 pressing Methods 0.000 claims description 16
- 230000035515 penetration Effects 0.000 claims description 5
- 230000001276 controlling effect Effects 0.000 claims description 4
- 230000000875 corresponding effect Effects 0.000 description 14
- 238000005259 measurement Methods 0.000 description 12
- 239000000843 powder Substances 0.000 description 9
- 238000000034 method Methods 0.000 description 8
- 230000008569 process Effects 0.000 description 7
- 239000002184 metal Substances 0.000 description 5
- 238000010276 construction Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000007493 shaping process Methods 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 241000283153 Cetacea Species 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 208000031513 cyst Diseases 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 235000013372 meat Nutrition 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000004663 powder metallurgy Methods 0.000 description 1
- 238000003908 quality control method Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
- B22F5/08—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of toothed articles, e.g. gear wheels; of cam discs
- B22F5/085—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of toothed articles, e.g. gear wheels; of cam discs with helical contours
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
- B22F5/08—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of toothed articles, e.g. gear wheels; of cam discs
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B30—PRESSES
- B30B—PRESSES IN GENERAL
- B30B11/00—Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses, tabletting presses
- B30B11/005—Control arrangements
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B30—PRESSES
- B30B—PRESSES IN GENERAL
- B30B11/00—Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses, tabletting presses
- B30B11/02—Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses, tabletting presses using a ram exerting pressure on the material in a moulding space
- B30B11/04—Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses, tabletting presses using a ram exerting pressure on the material in a moulding space co-operating with a fixed mould
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Apparatuses And Processes For Manufacturing Resistors (AREA)
- Powder Metallurgy (AREA)
Abstract
A device for producing pressed articles with a main cylindrically-shaped element and a secondary helically-shaped element from powdered material, especially powdered metal, with a female mold and with at least one top punch, which is supported so as to be rotatable about its longitudinal axis, and at least one bottom punch, which is supported so as to be rotatable about its longitudinal axis. The top and bottom punches, are movable axially relative to the female mold by means of motor drives and the top punch, of which there is at least one, is driven in rotation about its longitudinal axis to achieve a helical movement in addition to its axial drive the bottom punch, of which there is air least one, is also driven in rotation. Rotary motor drives of the punches are mechanically uncoupled from the drives for the axial movement of the punches and may be regulated separately by an electronic control.
Description
DEVICE FOR PRODUCING PRESSED ARTICLES
BACKGROUND OF THE INTVENTIOIV
Field of the Invention The invention is directed to a device for producing compacted or pressed articles with a main cy7_indrically-shaped element and a secondary helica:Lly-shaped element from powdered material such as powdered metal, and in particular for producing helical gearwheels in which the helical gearing or toothing is the secondary element.
Description of the Related Art A conventional device as described in European Patent Publication 0 528 761. A1 produces pre~~sed articles, e.g., helical-toothed gearwheels, from metal powder. This known metal powder press has a linearly movable upper ram in which is supported a top punch which :is rotat:able about the longitudinal axis in the pressing dire=_ction and a bottom ram which is also moveable linearly against a bottom stop and in which a bottom punch is rotatably supported. A die plate forms a mold cavity and is movable linearly in the pressing cycle.
The rotatable bottom punch and the rotatable top punch each have a toothing profile corresponding to the toothing profile or helical toothing of the mold shell or casing i.e., the mold cavity. The bottom punch which is supported so as to be freely rotatable :is constantly engaged with t:he profile of the mold cavity and therefore rotates compulsorily in a corresp-onding manner when :linear relative movements occur between the bottom punch and die plate during the press cycle. In A
BACKGROUND OF THE INTVENTIOIV
Field of the Invention The invention is directed to a device for producing compacted or pressed articles with a main cy7_indrically-shaped element and a secondary helica:Lly-shaped element from powdered material such as powdered metal, and in particular for producing helical gearwheels in which the helical gearing or toothing is the secondary element.
Description of the Related Art A conventional device as described in European Patent Publication 0 528 761. A1 produces pre~~sed articles, e.g., helical-toothed gearwheels, from metal powder. This known metal powder press has a linearly movable upper ram in which is supported a top punch which :is rotat:able about the longitudinal axis in the pressing dire=_ction and a bottom ram which is also moveable linearly against a bottom stop and in which a bottom punch is rotatably supported. A die plate forms a mold cavity and is movable linearly in the pressing cycle.
The rotatable bottom punch and the rotatable top punch each have a toothing profile corresponding to the toothing profile or helical toothing of the mold shell or casing i.e., the mold cavity. The bottom punch which is supported so as to be freely rotatable :is constantly engaged with t:he profile of the mold cavity and therefore rotates compulsorily in a corresp-onding manner when :linear relative movements occur between the bottom punch and die plate during the press cycle. In A
contrast, a rotational movement corresponding to the helical toothing is externally forced upon the top punch during the press cycle corresponding tc> its penetration depth in order to reduce the friction between the outer surfaces of the top punch and mold cavity of the female mold. The toothed-wheel mechanism provided for this purpose is driven via a mechanical linkage control corresponding to the desired helical toothing of the pressed article. The linkage control contains linkage cores rigidly connected to a guide plate and guided in a positive engagement and in a sliding manner in the coaxially arranged driving wheels of the toothed-wheel mechanism.
During the press cycle, the guide plate is temporarily rigidly coupled with the die plate and moves ,joixrtly therewith. A
withdrawal process is used to remove the produced pressed articles from the mold.
This known metal powder press gives rise to consid-erable costs with respect to mechanical construction and also retooling since for every different pressed article a set of linkage cores corresponding to this pressed article must be prepared and exchanged, aside from the special tool set including the female mold, t.op punch and bottom punch. Added to this is the cost of the guide plate and the mechanically operated locking device for rigidly coupling the guide plate to the die plate. There also remains the problem of friction between the bottom punch with respect to its rotational movement and the female mold, the bottom punch not being positively driven externally. This not only results in increased tool wear in this region, beat also leads to an uneven density distribution in the pressed article.
A press with electrically controlled movements and which is used for the :rotary press is described in the publication entitled "Quality control thr_~ough process monitoring of rotary forming press", Metal Powder Industries Federation, Volume 6, May 6 - I1, 1994 125-137. A press of this type is used for subsequent treatment of already sintered molded articles produced by powder metallurgy in order to give them a density in the .range of 95o to 98'~ of the theoretically possible density of the material in question.. T'he special construction of these presses makes it possible to generate extremely high local pressing pressures in the pressing tool with a comparatively low overall pres;~ing force of the press.
The special construction for this purpose includes an upper punch die that moves in a gyrating and rotating manner and applies locally defined extremely high pressing forces on the workpiece in order to compact the latter in a directed manner.
This reference contains no suggestion that the top punch and bottom punch, which participate direcl~ly in t;he shaping of the helically shaped secondary element of the article to be pressed, be controlled with respect to their movement in the mold cavity of the female mold by electronic means for the purpose of producing compacts with main cylindrically-shaped elements and secondary helically-shaped elements from powder material.
n SUMMARY OF THE INVENTION
The object of the invention is to improve a generic device in such a way that the friction problems mentioned above with regard to the bottom punch are solved satisfactorily, while the tool cost and expense of retooling for production of different pressed articles remains as low as possible.
According to the invention there is provided a system for producing a pressed article with a main cylindrically-shaped element and a secondary helically-shaped element from powdered material, comprising: a press frame; a female mold disposed within said press frame and defining a mold cavity; at least one top punch disposed within said press frame for operative helical rotational movement about its longitudinal axis and axial movement relative to said female mold; at least one bottom punch disposed within said press frame for operative rotational movement about its longitudinal axis and axial movement relative to said female mold; electronic rotary motors operatively connected for rotatingly driving respective said top and bottom punches; electronic axial motors operatively connected for axially driving respective said top and bottom punches, said axial motors being uncoupled from said rotary motors; and an electronic control device operatively connected to drive and independently regulate said rotary and axial motors, said electronic control device controlling the axial and rotational movements of said top and bottom punches in the mold cavity of the female mold so as to directly shape the helically shaped secondary element of the article to be pressed.
4a A substantial feature of the invention consists in that the top punch and bottom punch which directly participate in the shaping of the secondary helically shaped element of the pressed article to be produced, for example, in gearwheels with a plurality of toothings arranged axially in succession, a corresponding plurality of bottom or top punches may be required, are guided by an electronic control with respect to their movement in the mold cavity of the female mold. The rotational movement of the bottom punch and top punch, depending upon the depth to which the latter penetrate into the mold cavity, is ensured by an electronically regulated, separate, i.e., mechanically uncoupled rotary drive and is thus no longer effected by the mechanical coupling of a linear and rotary drive, i.e., no longer exclusively by the friction between the punch contour and the outer surface of the female mold as is the case with the bottom punch shaping one broad side in the press as described in European Patent Publication 0 528 761 Al, or by mechanical sensing of a linkage core as is the case with the top punch in this known press which shapes the other broad side. This means that the simultaneous move-ment corresponding to the lead or pitch of the secondary helically shaped element and the linear movement must be effected with an accuracy lying within the tool play of the toothing between the punches and the :Eernale mold. According-ly, the axial and rotational movement of the punches is effected in a position-regulated manner. Suitable sensors are provided for determining the respect.i~Je axial and rotational position e.g., linear potentiometers or incremental measurement means for linear movement and rotational angle transmitters for rotation. In this rc=gard, it will be noted that the female mold is advisably held irn a stationary manner in the utilized powder press while thc= top punch and bottom punch are moved linearly and rotationally. Of course, modifications are also possible in thf=_ sense of a kinematic reversal, e.g., in that the female mo:Ld may be held so as to be rigid with respect to rotation but accompanies the linear movement, as the press described in European Patent Publica-tion 0 528 761 Al, wherein the bottom punch is rotated in place, while the top punch is moved linearly and rotationally.
In principle, the female mold could also be moved in rotation.
This may be a meaningful addition to the rotational movability of the bottom punch and top punch or bottom punches and top punches when producing, e.g., multiple gearwheels, that is, pressed articles with a plurality of i~oothings of various width, or with different helix angles, disposed one after the other axially. In a known rruanner, core punches may also be provided in addition to the bottom punches and top punches.
These core punches may be moved by auxiliary drives and form a hub at a toothed wheel so that the toothed wheel. may be placed on a shaft.
The electronic control for the movement sequence of the top punch or top punches may be so arranged that only a purely linear movement takes place outside oi= the mold cavity of the female mold and the required rotational movement in the press cycle is initiated immediately with the=_ penetration into the mold cavity, and not until then. In thi:~ case, it is advisable to provide the top punch or top punches with a comparatively soft, resilient bearing which is defined by a stop in order to allow sufficient timE=_ for the acceleration process when starting the rotating movement. Position and torque are not regulated until the top punch has moved to the stop. This prevents damage to the tool during penetration.
Position regulation of the movements sequences is not always necessary for carrying out the present: invention. As an alternative or in addition to the position regulation, the rotational movement sequences of the top punch and bottom punch relative to the .female mold may be set in a predeter-mined manner, e.g., torque values are constant with respect to time. The rotary drives of the top punch and bottom punch are adjusted in such a way in the press phase that the tooth faces of the punches and mold shell contact one another as far as possible only on the side which would not otherwise be exposed to a direct mutual friction in the absence of_ a rotary drive when the punches move into the mold cavity of_ the female mold.
Thus, the externally applied torque acts in t:he direction of the rotating movement compelled by the mold. In a preferred embodiment, the torques of the rotary drives may be regulated, i.e., increased as the pressing force increa:~es, as a function of the pressing force actually achieved or a:~ a function of the achieved penetration depth, i.e., axial position, of the punches. It is particularly advantageous to measure the torsional moment at the punches and to set the driving torque precisely to a value at which the frir_tion losses in the bearing and drive system are compensated, i.e., the torsional moment at the punches approaches zero. The rotary drives of the punches are preferably completely shut off in the very last segment x of the press phase, i.c=., shortly before reaching the end position of the pres;~, in order to prevent cracks due to torsiona:l stresses. At a Lnelix angle ~i of the toothing, this segment x must meet the following condition:
x s s ~ cot ~3 The value s equals the transverse too_L play. Accordingly, a 30-degree toothing and a tool play of 0.03 mm, for example, produces a segment x <_ 0.05 mm.
In principle, the pressed article which is produced may be ejected from the mold by the ejection method without switching on rotary drives. However, the rotary drives are preferably used in a corresponding partially reverse manner compared with the compacting process. This ensures the gentlest possible treatment of the tool and pressed article.
Hydraulic drives should be used for the linear move-ment of the top punch and bottom punch or the moving female mold, as the case may be. The rotary drives may likewise be actuated hydraulically and in many cases, may also be operated pneumatically. Electric-motor rotary drives are preferred, especially electric stepping motors or servomotors. The invention is preferably used in connection with a CNC powder press. In another embodiment or modi:Eication, the substant-Tally mechanical parts of the device according to the invention such as the punches, female mold, rotary drives are designed as an exchangeable unit in the form of a tool adapter so as to enable especially short retooling times.
The present invention is advantageous in that it enables the manufacture, for example, of helical gearwheels with extremely low tool wear, since the friction in the region of the tooth flanks may be limited to a minimum during the pressing phase as well as when ejecting from the mold. The retooling cost may also be considerably reduced compared with known pressing tools, since only programming steps need be carried out, rather than the manufacture of linkage cores, to effect the rotary driving. Further, when the respective powder press is provided for producing a pluz:ality of differ-ent pressed articles, as is typical, this leads to substantial savings on investment costs in spite of the extra expenditure required for the rotary drives and the measuring and regulat-ing means. Finally, it should be emplzas:ized that the device according to the present invention produces pressed articles having an appreciably more uniform density distribution than was heretofore possible.
BRIEF DESCRIPTION OF THE DRAWINGS
The figure is a schematic front view of a metal powder press in accordance with the present invention.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
The hydraulic press shown in the Figure includes a press frame 16 which is outfitted with an upper ram 14 and a bottom ram 15. A female mold 1 is supported approximately in the center of the press frame 16 so as to be stationary and rigid with respect to rotation. A top punch 2 is rotatably supported in the upper ram 14 and a bottom punch 3 is rotatably supported in the bottom ram 15. The top punch 2 is supported so as to be flexible in the pressing direction by means of a pretensioned spring 9 which presses the receiving device for the top punch 2 in the pressing direction against a fixed stop. The force of the spring, whose travel is defined by a stop, is always appreciably less than the maximum pressing force for the tool, so that the top punch is at the stop before the start of the pressing process. The casing or shell of the female mold 1 and the two punches 2, 3 have a helical toothing corresponding to one another. Two path measurement systems 10, 11 are provided for a highly precise determination of the respective linear position of the two rams 14, 15 and, accordingly, also of the punches 2 and 3 connected therewith. These path measurement systems 10, 11 can be constructed, for example, as incremental measuring means or linear potentiometers. A rotary drive 5 and 7, e.g., an electric servomotor, is attached to each of the two rams 14, 15, its actual rotational angle position being determined continuously by a combined angle and torque measurement system 12 and 13, respectively. The punches 2, 3 have measurement devices 12a, 13a for detecting the actual torsional moment.
The two rotary drives 5, 7 are connected, via a spur gear unit, with one of the two punches 2 or 3 in a manner 10 consistent with drive engineering. Two servo-proportional valves 4, 6 are provided for positioning the two rams 14, 15 of the press. The press shown in the Figure includes an electronic control 8 enclosed in dashed line~~ which is designed hierarchically in itself and is formed of a CNC main processor 21, a regulating unit 19 and 20 for the linear movement of the upper .ram 14 and bottom ram 15 a.nd a regulating unit 17 and 18 far t:he rotational movement of the two punches 2 and 3. An input/output unit of. the CNC main processor for controlling and setting 'up the press via the operator is designated by 22. The data processing link between the electronic component units and sensors is shown by corresponding arrows. The two regulating units 19, 20 are subordinate to the CNC main processor 21 and the regulating units 17, 18 for the rotational movemc=nt are subordinate as slaves to one of the two regulating units 19 or 20 for the linear ram movement. In the present c=_xample, the regulating unit 19 is subordinate as master to the regulating unit 20 submaster, i.e., the movement of the upper ram 1.4 and the movement of the top punch 2, is used as a guidance variable for the movement sequence. The combined angle and torque measurement system 12 together with the rotary drive 5 and the regulating unit 17 forms <~ closed loop, whereby the regulating unit 17 receives its reference value :From the regulating unit 19 of the linear drive of the ram 14 corresponding to its current axial position as determined by the path measurement system 10. This holds true in a cons=_sponding sense for the structural component units for the drive of t;he bottom punch 3 which operate in the same way, its linear po:~ition being regulated as a function of the linear position of the top punch 2. The CNC main processor 21 takes over higher-ranked regulating and controlling functions and the processing of the preset data for the respective part to be produced. A dashed box inside the press frame 16 indicates the main functional parts of the device according to the :invention in the form of a tool adapter which may be combined :in an easily exchangeable structural component unit that is connectable with the top and bottom rams 14, 15.
The press of the present invention operates in the following manner: After a pressed arl~icle i:~ removed from the mold, the bottom punch 3 is moved down into t:he filling position in a position-regulated mannc=_r based on the actual values determined by the path measurement sy:~tem 11 and the angle measurement system 13 corresponding to the helix angle of the helical gearwheel to be produced. The bottom punch 3 ~~.
remains in the mold cavity of the female mold 1. The top punch 2 is located above the mold cavity. Ai=ter the mold cavity is filled with powdered steel, the top punch 2 is moved down in a position-regulated manner by means of the regulating unit 19 based on the data from the path measurement system 10.
At the same time, a coord:Lnated .rotating movE=meat of the top punch 2 is initiated via the regulating ~znit 17, the angle measurement system 12, and the rotary drive 5, so that the relative rotational position of the top punch 2 with respect to the toothing contour of the mold cavity oi= the female mold 1 allows the top punch 2 to penetrate into the mold cavity without making contact. This is the start of. the actual pressing phase in which the introduced powdered steel is compacted. For this purpose, the bottom punch 3 and the top punch 2 are moved into the mold cavity in opposite directions simultaneously whale the female mold :L remains stationary.
The rotary drives 7 and 5 erasure a minimum of. friction between the punches 2, 3 and the fenuale mold :1. Since the two angle measurement systems 12, 13, as combined instruments, are also set up to detect the driving torque, a regulation of torque can also be effected depending on the axial position of the punches 2, 3 in addition to, ar in l:i.eu of, t;he position regulation of the rotary drive 5, '7. After reaching the end position of the press, the drive cysts=m of the top punch 2 is reversed to remove the produced pressed article from the mold, i.e., the top punch 2 is moved out of the mo~Ld cavity linearly and rotationally in a positi..on-regulated manner corresponding to the contour of the pressed article. At the same time, the bottom punch 3 is likewise moved upwards correspondingly in a position-regulated manner until its upper end face is flush with the top of the female mold 1 and the pressed article is accordingly released in an ejection process. The pressed article can be purposely held under a desired pressing load during the ejection process.
During the press cycle, the guide plate is temporarily rigidly coupled with the die plate and moves ,joixrtly therewith. A
withdrawal process is used to remove the produced pressed articles from the mold.
This known metal powder press gives rise to consid-erable costs with respect to mechanical construction and also retooling since for every different pressed article a set of linkage cores corresponding to this pressed article must be prepared and exchanged, aside from the special tool set including the female mold, t.op punch and bottom punch. Added to this is the cost of the guide plate and the mechanically operated locking device for rigidly coupling the guide plate to the die plate. There also remains the problem of friction between the bottom punch with respect to its rotational movement and the female mold, the bottom punch not being positively driven externally. This not only results in increased tool wear in this region, beat also leads to an uneven density distribution in the pressed article.
A press with electrically controlled movements and which is used for the :rotary press is described in the publication entitled "Quality control thr_~ough process monitoring of rotary forming press", Metal Powder Industries Federation, Volume 6, May 6 - I1, 1994 125-137. A press of this type is used for subsequent treatment of already sintered molded articles produced by powder metallurgy in order to give them a density in the .range of 95o to 98'~ of the theoretically possible density of the material in question.. T'he special construction of these presses makes it possible to generate extremely high local pressing pressures in the pressing tool with a comparatively low overall pres;~ing force of the press.
The special construction for this purpose includes an upper punch die that moves in a gyrating and rotating manner and applies locally defined extremely high pressing forces on the workpiece in order to compact the latter in a directed manner.
This reference contains no suggestion that the top punch and bottom punch, which participate direcl~ly in t;he shaping of the helically shaped secondary element of the article to be pressed, be controlled with respect to their movement in the mold cavity of the female mold by electronic means for the purpose of producing compacts with main cylindrically-shaped elements and secondary helically-shaped elements from powder material.
n SUMMARY OF THE INVENTION
The object of the invention is to improve a generic device in such a way that the friction problems mentioned above with regard to the bottom punch are solved satisfactorily, while the tool cost and expense of retooling for production of different pressed articles remains as low as possible.
According to the invention there is provided a system for producing a pressed article with a main cylindrically-shaped element and a secondary helically-shaped element from powdered material, comprising: a press frame; a female mold disposed within said press frame and defining a mold cavity; at least one top punch disposed within said press frame for operative helical rotational movement about its longitudinal axis and axial movement relative to said female mold; at least one bottom punch disposed within said press frame for operative rotational movement about its longitudinal axis and axial movement relative to said female mold; electronic rotary motors operatively connected for rotatingly driving respective said top and bottom punches; electronic axial motors operatively connected for axially driving respective said top and bottom punches, said axial motors being uncoupled from said rotary motors; and an electronic control device operatively connected to drive and independently regulate said rotary and axial motors, said electronic control device controlling the axial and rotational movements of said top and bottom punches in the mold cavity of the female mold so as to directly shape the helically shaped secondary element of the article to be pressed.
4a A substantial feature of the invention consists in that the top punch and bottom punch which directly participate in the shaping of the secondary helically shaped element of the pressed article to be produced, for example, in gearwheels with a plurality of toothings arranged axially in succession, a corresponding plurality of bottom or top punches may be required, are guided by an electronic control with respect to their movement in the mold cavity of the female mold. The rotational movement of the bottom punch and top punch, depending upon the depth to which the latter penetrate into the mold cavity, is ensured by an electronically regulated, separate, i.e., mechanically uncoupled rotary drive and is thus no longer effected by the mechanical coupling of a linear and rotary drive, i.e., no longer exclusively by the friction between the punch contour and the outer surface of the female mold as is the case with the bottom punch shaping one broad side in the press as described in European Patent Publication 0 528 761 Al, or by mechanical sensing of a linkage core as is the case with the top punch in this known press which shapes the other broad side. This means that the simultaneous move-ment corresponding to the lead or pitch of the secondary helically shaped element and the linear movement must be effected with an accuracy lying within the tool play of the toothing between the punches and the :Eernale mold. According-ly, the axial and rotational movement of the punches is effected in a position-regulated manner. Suitable sensors are provided for determining the respect.i~Je axial and rotational position e.g., linear potentiometers or incremental measurement means for linear movement and rotational angle transmitters for rotation. In this rc=gard, it will be noted that the female mold is advisably held irn a stationary manner in the utilized powder press while thc= top punch and bottom punch are moved linearly and rotationally. Of course, modifications are also possible in thf=_ sense of a kinematic reversal, e.g., in that the female mo:Ld may be held so as to be rigid with respect to rotation but accompanies the linear movement, as the press described in European Patent Publica-tion 0 528 761 Al, wherein the bottom punch is rotated in place, while the top punch is moved linearly and rotationally.
In principle, the female mold could also be moved in rotation.
This may be a meaningful addition to the rotational movability of the bottom punch and top punch or bottom punches and top punches when producing, e.g., multiple gearwheels, that is, pressed articles with a plurality of i~oothings of various width, or with different helix angles, disposed one after the other axially. In a known rruanner, core punches may also be provided in addition to the bottom punches and top punches.
These core punches may be moved by auxiliary drives and form a hub at a toothed wheel so that the toothed wheel. may be placed on a shaft.
The electronic control for the movement sequence of the top punch or top punches may be so arranged that only a purely linear movement takes place outside oi= the mold cavity of the female mold and the required rotational movement in the press cycle is initiated immediately with the=_ penetration into the mold cavity, and not until then. In thi:~ case, it is advisable to provide the top punch or top punches with a comparatively soft, resilient bearing which is defined by a stop in order to allow sufficient timE=_ for the acceleration process when starting the rotating movement. Position and torque are not regulated until the top punch has moved to the stop. This prevents damage to the tool during penetration.
Position regulation of the movements sequences is not always necessary for carrying out the present: invention. As an alternative or in addition to the position regulation, the rotational movement sequences of the top punch and bottom punch relative to the .female mold may be set in a predeter-mined manner, e.g., torque values are constant with respect to time. The rotary drives of the top punch and bottom punch are adjusted in such a way in the press phase that the tooth faces of the punches and mold shell contact one another as far as possible only on the side which would not otherwise be exposed to a direct mutual friction in the absence of_ a rotary drive when the punches move into the mold cavity of_ the female mold.
Thus, the externally applied torque acts in t:he direction of the rotating movement compelled by the mold. In a preferred embodiment, the torques of the rotary drives may be regulated, i.e., increased as the pressing force increa:~es, as a function of the pressing force actually achieved or a:~ a function of the achieved penetration depth, i.e., axial position, of the punches. It is particularly advantageous to measure the torsional moment at the punches and to set the driving torque precisely to a value at which the frir_tion losses in the bearing and drive system are compensated, i.e., the torsional moment at the punches approaches zero. The rotary drives of the punches are preferably completely shut off in the very last segment x of the press phase, i.c=., shortly before reaching the end position of the pres;~, in order to prevent cracks due to torsiona:l stresses. At a Lnelix angle ~i of the toothing, this segment x must meet the following condition:
x s s ~ cot ~3 The value s equals the transverse too_L play. Accordingly, a 30-degree toothing and a tool play of 0.03 mm, for example, produces a segment x <_ 0.05 mm.
In principle, the pressed article which is produced may be ejected from the mold by the ejection method without switching on rotary drives. However, the rotary drives are preferably used in a corresponding partially reverse manner compared with the compacting process. This ensures the gentlest possible treatment of the tool and pressed article.
Hydraulic drives should be used for the linear move-ment of the top punch and bottom punch or the moving female mold, as the case may be. The rotary drives may likewise be actuated hydraulically and in many cases, may also be operated pneumatically. Electric-motor rotary drives are preferred, especially electric stepping motors or servomotors. The invention is preferably used in connection with a CNC powder press. In another embodiment or modi:Eication, the substant-Tally mechanical parts of the device according to the invention such as the punches, female mold, rotary drives are designed as an exchangeable unit in the form of a tool adapter so as to enable especially short retooling times.
The present invention is advantageous in that it enables the manufacture, for example, of helical gearwheels with extremely low tool wear, since the friction in the region of the tooth flanks may be limited to a minimum during the pressing phase as well as when ejecting from the mold. The retooling cost may also be considerably reduced compared with known pressing tools, since only programming steps need be carried out, rather than the manufacture of linkage cores, to effect the rotary driving. Further, when the respective powder press is provided for producing a pluz:ality of differ-ent pressed articles, as is typical, this leads to substantial savings on investment costs in spite of the extra expenditure required for the rotary drives and the measuring and regulat-ing means. Finally, it should be emplzas:ized that the device according to the present invention produces pressed articles having an appreciably more uniform density distribution than was heretofore possible.
BRIEF DESCRIPTION OF THE DRAWINGS
The figure is a schematic front view of a metal powder press in accordance with the present invention.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
The hydraulic press shown in the Figure includes a press frame 16 which is outfitted with an upper ram 14 and a bottom ram 15. A female mold 1 is supported approximately in the center of the press frame 16 so as to be stationary and rigid with respect to rotation. A top punch 2 is rotatably supported in the upper ram 14 and a bottom punch 3 is rotatably supported in the bottom ram 15. The top punch 2 is supported so as to be flexible in the pressing direction by means of a pretensioned spring 9 which presses the receiving device for the top punch 2 in the pressing direction against a fixed stop. The force of the spring, whose travel is defined by a stop, is always appreciably less than the maximum pressing force for the tool, so that the top punch is at the stop before the start of the pressing process. The casing or shell of the female mold 1 and the two punches 2, 3 have a helical toothing corresponding to one another. Two path measurement systems 10, 11 are provided for a highly precise determination of the respective linear position of the two rams 14, 15 and, accordingly, also of the punches 2 and 3 connected therewith. These path measurement systems 10, 11 can be constructed, for example, as incremental measuring means or linear potentiometers. A rotary drive 5 and 7, e.g., an electric servomotor, is attached to each of the two rams 14, 15, its actual rotational angle position being determined continuously by a combined angle and torque measurement system 12 and 13, respectively. The punches 2, 3 have measurement devices 12a, 13a for detecting the actual torsional moment.
The two rotary drives 5, 7 are connected, via a spur gear unit, with one of the two punches 2 or 3 in a manner 10 consistent with drive engineering. Two servo-proportional valves 4, 6 are provided for positioning the two rams 14, 15 of the press. The press shown in the Figure includes an electronic control 8 enclosed in dashed line~~ which is designed hierarchically in itself and is formed of a CNC main processor 21, a regulating unit 19 and 20 for the linear movement of the upper .ram 14 and bottom ram 15 a.nd a regulating unit 17 and 18 far t:he rotational movement of the two punches 2 and 3. An input/output unit of. the CNC main processor for controlling and setting 'up the press via the operator is designated by 22. The data processing link between the electronic component units and sensors is shown by corresponding arrows. The two regulating units 19, 20 are subordinate to the CNC main processor 21 and the regulating units 17, 18 for the rotational movemc=nt are subordinate as slaves to one of the two regulating units 19 or 20 for the linear ram movement. In the present c=_xample, the regulating unit 19 is subordinate as master to the regulating unit 20 submaster, i.e., the movement of the upper ram 1.4 and the movement of the top punch 2, is used as a guidance variable for the movement sequence. The combined angle and torque measurement system 12 together with the rotary drive 5 and the regulating unit 17 forms <~ closed loop, whereby the regulating unit 17 receives its reference value :From the regulating unit 19 of the linear drive of the ram 14 corresponding to its current axial position as determined by the path measurement system 10. This holds true in a cons=_sponding sense for the structural component units for the drive of t;he bottom punch 3 which operate in the same way, its linear po:~ition being regulated as a function of the linear position of the top punch 2. The CNC main processor 21 takes over higher-ranked regulating and controlling functions and the processing of the preset data for the respective part to be produced. A dashed box inside the press frame 16 indicates the main functional parts of the device according to the :invention in the form of a tool adapter which may be combined :in an easily exchangeable structural component unit that is connectable with the top and bottom rams 14, 15.
The press of the present invention operates in the following manner: After a pressed arl~icle i:~ removed from the mold, the bottom punch 3 is moved down into t:he filling position in a position-regulated mannc=_r based on the actual values determined by the path measurement sy:~tem 11 and the angle measurement system 13 corresponding to the helix angle of the helical gearwheel to be produced. The bottom punch 3 ~~.
remains in the mold cavity of the female mold 1. The top punch 2 is located above the mold cavity. Ai=ter the mold cavity is filled with powdered steel, the top punch 2 is moved down in a position-regulated manner by means of the regulating unit 19 based on the data from the path measurement system 10.
At the same time, a coord:Lnated .rotating movE=meat of the top punch 2 is initiated via the regulating ~znit 17, the angle measurement system 12, and the rotary drive 5, so that the relative rotational position of the top punch 2 with respect to the toothing contour of the mold cavity oi= the female mold 1 allows the top punch 2 to penetrate into the mold cavity without making contact. This is the start of. the actual pressing phase in which the introduced powdered steel is compacted. For this purpose, the bottom punch 3 and the top punch 2 are moved into the mold cavity in opposite directions simultaneously whale the female mold :L remains stationary.
The rotary drives 7 and 5 erasure a minimum of. friction between the punches 2, 3 and the fenuale mold :1. Since the two angle measurement systems 12, 13, as combined instruments, are also set up to detect the driving torque, a regulation of torque can also be effected depending on the axial position of the punches 2, 3 in addition to, ar in l:i.eu of, t;he position regulation of the rotary drive 5, '7. After reaching the end position of the press, the drive cysts=m of the top punch 2 is reversed to remove the produced pressed article from the mold, i.e., the top punch 2 is moved out of the mo~Ld cavity linearly and rotationally in a positi..on-regulated manner corresponding to the contour of the pressed article. At the same time, the bottom punch 3 is likewise moved upwards correspondingly in a position-regulated manner until its upper end face is flush with the top of the female mold 1 and the pressed article is accordingly released in an ejection process. The pressed article can be purposely held under a desired pressing load during the ejection process.
Claims (19)
1. A system for producing a pressed article with a main cylindrically-shaped element and a secondary helically-shaped element from powdered material, comprising:
a press frame;
a female mold disposed within said press frame and defining a mold cavity;
at least one top punch disposed within said press frame for operative helical rotational movement about its longitudinal axis and axial movement relative to said female mold;
at least one bottom punch disposed within said press frame for operative rotational movement about its longitudinal axis and axial movement relative to said female mold;
electronic rotary motors operatively connected for rotatingly driving respective said top and bottom punches;
electronic axial motors operatively connected for axially driving respective said top and bottom punches, said axial motors being uncoupled from said rotary motors; and an electronic control device operatively connected to drive and independently regulate said rotary and axial motors, said electronic control device controlling the axial and rotational movements of said top and bottom punches in the mold cavity of the female mold so as to directly shape the helically shaped secondary element of the article to be pressed.
a press frame;
a female mold disposed within said press frame and defining a mold cavity;
at least one top punch disposed within said press frame for operative helical rotational movement about its longitudinal axis and axial movement relative to said female mold;
at least one bottom punch disposed within said press frame for operative rotational movement about its longitudinal axis and axial movement relative to said female mold;
electronic rotary motors operatively connected for rotatingly driving respective said top and bottom punches;
electronic axial motors operatively connected for axially driving respective said top and bottom punches, said axial motors being uncoupled from said rotary motors; and an electronic control device operatively connected to drive and independently regulate said rotary and axial motors, said electronic control device controlling the axial and rotational movements of said top and bottom punches in the mold cavity of the female mold so as to directly shape the helically shaped secondary element of the article to be pressed.
2. The system of claim 1, wherein said electronic control device controls a depth of penetration of said top punch into the cavity of said female mold in a position-regulated manner with respect to the axial and rotational movement.
3. The system of claim 1, wherein said electronic control device controls said top punch so that it is axially displaced to penetrate into the mold cavity of the female mold without said top punch being rotated.
4. The system of claim 3, further comprising a spring operatively displaced in an axial direction by said top punch.
5. The system o.f claim 2, wherein said electronic control device controls the rotational movement of said top and bottom punches during compacting of the article to be pressed in a position-regulated manner.
6. The system of claim 2, wherein said electronic control device controls the rotational movement of said top and bottom punches during compacting of the article to be pressed based on predetermined torque values.
7. The system of claim 6, wherein the predetermined torque values are determines as a function of one of an actual pressing force, an actual torsional moment and an axial position of the respective punch.
8. The system of claim 7, wherein said electronic control device controls the rotational movement of said punches at a constant .rate over time.
9. The system of claim 1, wherein said rotary motors are turned off before reaching a final position based on a helix angle of toothings of the article being pressed and a tool play defined as a region between said respective top punch and bottom punch and said female mold.
10. The system of claim 5, wherein said electronic device controls the rotational movement of said punches during compacting of the article and during ejection, after the article has been pressed, in a corresponding partially reverse manner.
11. The system of any one of claims 1 to 10, wherein said axial motors are hydraulic motors.
12. The system of any one of claims 1 to 11, wherein said rotational motors are hydraulic motors.
13. The system of any one of claims 1 to 11, wherein said rotational motors are pneumatic motors.
14. The system of any one of claims 1 to 11, wherein said rotational motors are electrical stepping motors.
15. The system of any one of claims 1 to 11, wherein said rotational motors are servomotors.
16. The system of any one of claims 1 to 15, wherein said electronic control device includes a CNC main processor.
17. The system of any one of claims 1 to 16, wherein said female mold, said top punch and said bottom punch comprise a tool adapter.
18. The system of any one of claims 1 to 17, wherein said female mold is rigidly supported in said press frame.
19. The system of any one of claims 1 to 18, wherein the powdered material is powdered metal.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP4428842.5 | 1994-08-02 | ||
| DE4428842A DE4428842C1 (en) | 1994-08-02 | 1994-08-02 | Device for the production of compacts |
| PCT/DE1995/000954 WO1996004087A1 (en) | 1994-08-02 | 1995-07-13 | Device for producing compacts |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2196560A1 CA2196560A1 (en) | 1996-02-15 |
| CA2196560C true CA2196560C (en) | 2006-09-19 |
Family
ID=37056974
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002196560A Expired - Fee Related CA2196560C (en) | 1994-08-02 | 1995-07-13 | Device for producing pressed articles |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2196560C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014013290A3 (en) * | 2012-07-06 | 2014-05-08 | Yield Force S L | Stamping press |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110560684A (en) * | 2019-09-29 | 2019-12-13 | 合肥波林新材料股份有限公司 | pressing die and preparation method of powder material |
-
1995
- 1995-07-13 CA CA002196560A patent/CA2196560C/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014013290A3 (en) * | 2012-07-06 | 2014-05-08 | Yield Force S L | Stamping press |
| US9676021B2 (en) | 2012-07-06 | 2017-06-13 | Lapmaster International L.L.C. | Stamping press |
Also Published As
| Publication number | Publication date |
|---|---|
| CA2196560A1 (en) | 1996-02-15 |
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