Patent Application
20090177306
The invention concerns a press line of the type used for pressings, stamping, drawing or punching of principally metal parts from blanks. In particular, the invention discloses a press line comprising an improved mechanical press that may be synchronized with other devices in the press line in a dynamic or adaptive way. The invention is of particular advantage for use in producing stamped or pressed parts for the automobile industry and for white goods.
Mechanical presses are commonly used to produce stamped automobile parts from metal forms such as steel blanks or workpieces. One or more such mechanical presses are usually arranged in a press line to carry out a series of operations on a blank or workpiece.
Press lines were automated in the late 1970's by using mechanical arms to load-unload the parts from the presses. During the late 1980's robots where introduced into press shops to do the same function. The control system (normally a Programmable Logic Controller or PLC) typically managed all the information coming from the robots and the presses and gave digital authorisations to the press and other devices in the press line to load, stamp and unload. Press line systems operated in an asynchronous way, so that if a robot arrived early to unload it had to wait until the press was open enough. Similarly it could happen that a robot arrived late to load, which meant that the press waited. Such and other actions result in move-stop-move cycles for the robots, and for a press, which caused extra wear the gearboxes and may also have caused wear in the motor brakes. Also the speed rate of the line could not go beyond certain limits. An important improvement in press lines comprising robot loaders/unloaders was achieved with industrial robots from ABB which incorporated a function called Sync to Sensor. By means of a sensor or an encoder, the robot with sync to sensor can read the position of the press and the robot controller then dynamically adapt the robots speed so that the robot arrives at the unloading point “on time”. A corresponding improvement was achieved for the loading operation. The loading robot reads the position of the unloader through a bus connection and the robot controller adapts the robots speed to be “on time” to load as well. Thus far then a press line has been developed in which a robot loader/unloader can be synchronised to certain movements of a press.
However mechanical presses have a fixed cycle. Traditionally the press drive and power transmission system, or kinematics, of a mechanical press is driven via a flywheel. The function of the flywheel is to store the necessary energy to make a cycle. The flywheel is connected and disconnected to the kinematics by means of a clutch and brake system (which may be pneumatic or hydraulic). Maintenance is required for any clutch or brake in the drive chain.
Once setup to run with a given die, the working cycles of traditional flywheel driven mechanical presses, link presses, crank presses and similar are fixed. For example once the speed of the flywheel is set and the clutch engaged, the press will move following a fixed pattern, such as that of
The press is normally brought to a standstill by mechanical braking.
The aim of the present invention is to provide an improved method for operating a press line and a system comprising such an improved press line. This and other aims are obtained by a method, and a system characterised by the attached independent claims. Advantageous embodiments are described in sub-claims to the above independent claims.
According to an embodiment of the invention a method for operating a press line is provided said press line comprising at least one mechanical press with at least one electric drive motor, a ram, a mechanical means for operating said press, said press line comprising at least one other associated device, wherein said press is arranged so that the speed of the at least one said electric drive motor may be varied during at least one pressing or non-pressing part of a press cycle and by controlling the speed of said motor a movement of said press may be synchronized to a movement or position of at least one said other device in said press line.
According to another embodiment of the invention a method for operating a press line is provided comprising controlling said other device during the at least one pressing or non-pressing a part of a press cycle and synchronizing the movement of the said other device to a movement of said press, another device or another press in said press line.
According to another embodiment of the invention a method for operating a press line is provided comprising controlling the said other device in order to synchronize to a movement or position of a device downstream of said other device in said press line during a first part of a press cycle and by controlling the movement of the said other device in order to synchronize it to a movement or position of a device upstream of said other device in said press line during a second part of the press cycle.
According to an embodiment of the invention a method for operating a press line is provided comprising controlling the said other device in order to operate as fast as possible during a first part of a press cycle and by controlling the movement of said press in order to operate the press as fast as possible in a second part of the press cycle, wherein the said other device may be any from the group of: a loader, an unloader, a robot, another press.
According to an embodiment of the invention a method for operating a press line is provided comprising controlling a loader or unloader device or robot arranged to load, respective unload said press and also control the device to operate as an unloader, respective loader of another press.
According to another embodiment of the invention a method for operating a press line is provided wherein a robot control unit calculates a path for a robot, and calculates motion or position setpoint values for a press and speed and/or position control values to a control unit or drive unit of a press.
According to an embodiment of the invention a method for operating a press line is provided comprising controlling the speed of at least one electric drive motor and optimising the said press line dependent on parameters from any of the group of: a state of a downstream process; a state of an upstream process; overall power or energy consumption; smoothing of power consumption peaks.
According to another embodiment of the invention a method for operating a press line is provided comprising controlling the speed of a said at least one electric drive motor during the at least one pressing or non-pressing part of a press cycle of said press so as to vary and be greater than the speed of said drive motor during a pressing part of the press cycle.
According to another embodiment of the invention a method for operating a press line is provided comprising controlling said at least one drive motor such that said press cycle carried out in said first rotation direction comprises a step of reversing said drive motor at the end of each complete press cycle and operating in a second rotational direction.
According to another embodiment of the invention a method for operating a press line is provided comprising controlling said at least one drive motor such that said press cycle carried out in said first rotation direction comprises a step of reversing said drive motor at the end of each complete press cycle before beginning a new press cycle in the first rotational direction.
According to another embodiment of the invention a method for operating a press line is provided comprising controlling said motor such that said motor is decelerated to a reduced speed or a zero speed by means in part of regenerative braking.
According to another embodiment of the invention a method for operating a press line is provided wherein said press line includes at least one press comprising a second drive motor or actuator arranged connected to said ram such that by controlling the speed of said second drive motor a movement of said press may be varied during at least one part of a press cycle.
According to an aspect of the invention a press line is described that comprises at least one improved mechanical press comprising at least one electric drive motor, and a motor control means such as a frequency converter and mechanical couplings for operating said press, said press line comprising at least one other device, wherein said press is arranged so that the speed of the at least one said electric drive motor may be varied during at least one pressing or non-pressing part of a press cycle and wherein by controlling the speed of said motor a movement of said press may be synchronized to a movement of at least one said other device in said press line.
The variable speed direct drive between motor and crank (or ram) enables the speed of the press along the slide stroke to be dynamically controlled during different parts of a press cycle. Parts of a press cycle such as: before the moving die contacts the workpiece or blank to be pressed; after die closing and during a part-cycle in which the workpiece is being pressed; and after die opening again and during the part-cycle between end of pressing and start of pressing the next workpiece.
The control system of the improved press line preferably comprises a closed loop arrangement composed of device-to-press synchronisation, device to device synchronisation, and press to device synchronisation. Thus in some embodiments this may comprise at least in part a triangle arrangement of robot-to-press synchronisation, robot-to-robot synchronisation and press-to-robot synchronisation. The ability to synchronize the press to an external device is enabled by means of a mechanical press arranged for operation with a variable speed drive motor providing the means for a press to operate at variable speeds. The control system of the improved press line allows press lines to achieve higher production rates by optimizing the coordination of movements of robots and presses.
The improved motor drive and control method allows the motor speed during parts of a total production cycle to be varied, something which is not possible for flywheel presses of the prior art. The motor speed may even be varied in a continuous or dynamic or adaptive manner so that motor speed and/or ram speed are not limited to one or more predetermined speeds. In contrast to prior art presses, an improved mechanical press, such as that described in a patent application U.S. No. 60/765183 and hereby incorporated in full in this specification by means of this reference, is arranged with a motor speed control means which is variable between zero and a maximum speed providing a rotational speed W1 of the eccentric or crankshaft which may be greater than the pressing speed Wp of the eccentric. In some embodiments the speed may vary between a negative speed, ie speed in a reverse direction, through zero and up to a maximum of say W1 in a forward direction, as detailed below in the description of the preferred embodiments. In the prior art, mechanical presses with a flywheel are limited to a fixed crankshaft speed because the flywheel speed is normally more-or-less constant.
A press line of the Prior Art comprising one traditional mechanical press is shown schematically in
In the improved press line the motion of the improved mechanical press may be adapted to the operation of other machines involved in a production sequence. Press motion may be optimised in relation to other machines in a production sequence. For example the press motion may be optimised to actions by external devices steps, for example, when workpieces are loaded in the press and/or stamped parts unloaded from the press by transfer devices or other automated devices. Such other machines in the production sequence may comprise one or more industrial robots or manipulator arms. Controlling the press in synchronisation with control of the feeding by automatic feeders, other feeders, robot loaders/unloaders, etc provides improved control and opportunities of synchronization of feeder/loader/unloader motion and press motion, providing in turn, for example, reduced overall production cycle times without compromising pressing quality. In control terms, the improved press comprised in the improved press line may be run such that a press is a slave to an unloader device in a part of the press cycle. The press construction and control system also permit the press to be run as a slave to the loader device in another part of the same press cycle. This variability in control configuration is simply not possible using a traditional mechanical press powered by a flywheel where the press motion in a press cycle is fixed from the moment that the clutch is engaged.
Typically the preferred advantage of the improved press line compared to a press line that uses one or more traditional mechanical presses is a shortened production cycle time. When compared to press lines comprised of traditional mechanical presses advantages of the invention may include:
In another aspect of the invention, the improved press line comprises at least one mechanical press with two or more electric drive motors as described in international application WO/SE2006/050055 and hereby incorporated in full in this specification by means of this reference. In this improved press, a second motor is added to a mechanical press. The most important function of the second motor is to drive the press during that/those part(s) of the cycle where the press is not actually pressing. For the actual pressing stage, the flywheel may still be used as today. The clutch and brake, while still needed, may be much simpler and cheaper than in the traditional mechanical press. This solution achieves the performance of a servo drive press type without the need for very large electrical power installations. The solution is especially suited as an add-on, retrofit or refurbishment option for existing presses. In addition, an option to use both motors at the same time, preferably during the working (pressing) part of the press cycle for example, is provided.
In contrast to prior art presses, the motor of the improved mechanical press, whether it is a servo press first described in U.S. No. 60/765183, or the hybrid servo press of WO/SE2006/050055 is operated so that the speed during a press cycle is variable between zero and a maximum speed providing a rotational speed W1 of the eccentric which may be greater than the pressing speed Wp of the eccentric. In some embodiments the speed may vary between a negative speed and zero, meaning a speed in a reverse direction, as well as speed in a forward direction between zero and W1, as detailed below in the description of the preferred embodiments.
In another embodiment of the invention the required dimensions of the motor of the improved press are reduced by arranging the press and the press control to allow the motor a greater part of the press cycle in which to accelerate up to the required speed(s). In one or more advantageous embodiments the improved press control methods are so arranged that a complete press cycle is provided which is in excess of the traditional 360 degree crank rotation angle, or in terms of TDC position twice past TDC, and may yet still have a shorter total production cycle time for the complete production cycle when compared to flywheel-based mechanical presses of similar tonnage. The press cycle comprising a crank angle rotation of more than 360 degrees may be achieved in either of at least two ways, as described in detail in U.S. No. 60/765183 servo or the WO/SE2006/050055 hybrid press. Summarily the methods of these embodiments comprise reversing a press at the end of a cycle and either starting the next cycle from a position before the stop position of the previous cycle; or, by reversing a press at the end of the cycle and running the following complete cycle in the reverse direction to the direction of rotation of the first press cycle.
In a synchronisation between robot-to-press, robot-to-robot and/or press-to-robot synchronisation according to an embodiment of the invention the loader robot may be controlled in, for example, four stages such as:
Of course there may be some variations at beginning and end of the line. The press has typically two stages: synchronized to loader or unloader, and free.
The primary advantage of the improved press line is that it provides greater opportunity for optimization of a press line by coordinating the motion of one press, any presses or all presses in the press line and feeder or transfer mechanisms loaders/unloaders such as loading/unloading robots, in the process or press line. Coordination between presses and/or presses and loaders/unloaders may be carried out by, for example, controlling such a line using a single controller. Coordination may be optimised dependent on parameters such as: a state of a downstream process; or a state of an upstream process or another consideration such as overall power or energy consumption; smoothing power consumption peaks in the press line.
In a preferred embodiment of the method of the invention the method may be carried out or controlled by one or more computing devices comprising one or more microprocessor units or computers. The control unit(s) comprise memory means for storing one or more computer programs for carrying out the improved methods for controlling the operation of one or more mechanical presses. Preferably such computer programs contain instructions for the processor to perform the method as mentioned above and described in more detail below. In another embodiment the computer program is provided recorded on a computer readable data carrier such as a DVD, an optical or a magnetic data device, or supplied via a data network from a server, data server or similar.
Embodiments of the invention will now be described, by way of example only, with particular reference to the accompanying drawings in which:
a (Prior Art) shows a standard 360 degree press cycle according to a known press cycle;
b-7d shows in schematic diagrams press cycles in relation to start/stop position and rotation direction according to embodiments of the invention;
A separate controller, press safety controller 120 is arranged connected to all the press safety switches, and emergency stop switches arranged on and around the press. The press safety controller 120 includes a press safety controller PLC 121 which is also connected to the motor drive 101 and arranged to stop press motion if an unsafe situation is detected by an open switch or by an alarm or emergency button being pressed. The press safety controller PLC 121 is also connected to the clutch and brake operating valves or switches 126, and also arranged to stop press motion if an unsafe situation arises. The press safety controller PLC may receive input from safety devices such as emergency stop buttons 122, door switches 123, light curtains 124, safety blocks 125, and/or from clutch and brake valves 126.
An important aspect of the layout or control topology of
Synchronisation state for an unloader device or robot on the middle level is shown then
Synchronisation state for a loader device or robot on the lowest level is shown then to be
In these synchronisation modes, the press or a device such as load/unloader may have only a status of slave or free.
Another important aspect according to the invention is the use of an improved mechanical press capable of a variable press cycle, such as the servo press disclosed in U.S. No. 60/765183 and/or the hybrid press disclosed in WO/SE2006/050055. Such presses may be driven at speeds which may be variably controlled and therefore be controlled so as to synchronise press movement with movement of other devices. Traditional mechanical presses with a flywheel and a clutch have a fixed movement cycle once the clutch is engaged and the movement for a press cycle begins. An improved press line with more degrees of freedom available for optimization to quality requirements and/or production and/or energy use constraints is thus achieved by combining the improved press control topology described above in relation to
Typically synchronization between two robots is achieved by continuously adapting the motion of the “slave” robot to the motion of the “master” robot. Thus, if at any instant the motion of the master robot is for some reason delayed, this delay is immediately mirrored in the motion of the slave robot. In the same way, if the master at any instant is accelerated, this deviation is also mimicked by the slave. This type of synchronization works properly in case the motion of the master is relatively smooth, i.e. the slave receives a motion reference without much noise or variations around a desired average. Another condition for this to work is that the slave should have sufficient power available in relation to its mass or inertia so that it is capable of following the motion of the master. This is usually the case when master and slave are similar machines with similar motion capabilities.
The case of synchronization of the press to the loader robot is more challenging in that the press drive has only limited power available compared to the press inertia. It may be that during the part of the press cycle where the press is required to synchronize to the loader, it may be operating at full motor torque—first to slow down the press to a standstill, then possibly to reverse the press to a desired starting position of the next press cycle, and finally to accelerate the press from standstill up to a high speed. Between these parts of the motion at either full positive or negative motion torque, there may be short periods of press standstill or constant speed (zero torque), but in many cases the operation is using full torque to obtain the shortest possible press time (see for example T2 in
In a motion profile where the press drive is using full torque, synchronization in the traditional way is not possible or desirable, for the following reason. The motion profile of the press is normally optimized for giving the shortest possible cycle time. For this, the press—in the part of the motion where it is not dependent on the loader robot—has to move at highest possible or allowable speed. Thus, at the point where the loader leaves the press, i.e. the point where synchronization of the press-to-robot stops, the press must already be at a very high speed. To reach this speed, the drive typically has to accelerate at full torque from a start position. Any attempt to slow down the press (for synchronization) in this part of the motion would negatively affect the duration of the press motion in the unsynchronized part of the cycle. Any attempt to accelerate the press even more, for synchronization, is likely to fail since the drive is already giving full torque.
The inventors have determined that the motion of the loader robot, and especially the last part of this motion, is very predictable. Regardless of the exact motion of the robot, it will be sufficiently well known more than e.g. one second in advance at what instant the loader robot will leave the press. This knowledge can be used to plan the motion of the press in advance, in such a way that not only the press reaches the desired point of synchronization at the same instant when the robot leaves the press, but also that the press reaches this point with a very high speed such that the shortest possible cycle time is obtained. Depending on how much time is left before reaching such a point of synchronization, the motion of the press can be adapted to reach the synchronization point in the optimal way by using any or a combination of any of the following methods:
Thus in an embodiment, the control hierarchy may be arranged as follows:
An improved electrical drive controller configuration 210 is shown. The three drive motors Ma-c of presses 100a-c are shown each supplied by a drive device, such as drive 101c. In this example this electrical drive device is a converter which may supply power to the motor in a controlled way. With this improvement, all three converters are supplied by one rectifier 201, a single power device such as an inverter, which supplies power to one or more motors each driving one of a plurality of presses. A multi-drive may optionally include one or more inverters. Such a multi-drive 201 may optionally also supply power to other press line devices such as hydraulic pumps, cooling equipment, transfer equipment, turntables and so on. The power supply arrangement comprises a connection PWR to a power grid, and a power management device, arrangement or function. For example, a power limiter arrangement to limit the total power or peak power of the flywheel motor plus the auxiliary second motor. Associated with the control function of the power supply arrangement is a unit or function D for processing die information and a unit or function SC for synchronizing robot movements. Unit or function D is also connected to the automation control PLC 200, for example via control fieldbus 117. The die information processing functions D may also be comprised in the automation controller PLC 200, or may be distributed in some other way, similar to the way that the SC functions may be distributed.
The function of synchronisation calculations (SC) for the devices, robots and press movements may be comprised in an independent unit as indicated SC in the diagram. The synchronisation calculations and algorithms for synchronisation function may optionally be included in one or more of the robot control units for controlling robots 118, 119 etc, (see embodiment of
An improved press line such as the press line of
The drive motor may have an AC supply as shown or a DC supply. The motor speed control means may be a frequency converter, an inverter/rectifier as shown or other motor speed control means. The embodiment shown has a relatively large drive motor. Alternatively a smaller motor is used and arranged in a configuration that comprises extra inertia. The extra inertia may be in the form of a small constantly connected flywheel, or a motor which has high inertia, or a high inertia gearbox 33 or other mechanical means. The extra inertia may also be variable or detachable in some way.
It may be seen from the cycle diagram in
Thus in
The improved press cycle provided by the improved control method allows the total time for a production cycle to be shorter than the production cycle time of a traditional mechanical press of the prior art by shortening the time taken to carry out non-pressing parts of the press cycle between DP and UC. In particular, the time period from the latest loading point DP to the earliest unloading point UC, denoted as T2, may be shortened by means of running the drive motor at increased speeds such as W1 to drive the eccentric at speeds greater than the pressing speed Wp and then reducing to eccentric speed Wp or, at the cycle end, reducing to zero. This is indicated schematically on the diagram by the difference in time for T2, ΔT2 in the speed profile of
Thus when a hybrid type press is present in the press line, a press comprising a second drive motor as well as a first (flywheel) drive motor, synchronisation may be carried out in which the first motor (20) is not always mechanically coupled to said press and where the second motor (22) is always mechanically coupled to said press.
This method may be applied to the improved servo-type press as well as a hybrid type. It should be noted that if the pressing speed is to be reduced during pressing, or the press held at a standstill under pressure during the pressing stage P then the clutch must be dis-engaged to de-couple the flywheel from the eccentric in the case of the hybrid press.
One of more drive motors may be controlled to run at high speeds during a part of a press cycle by means of a control method known as field weakening.
This method comprises steps to control the improved press so as to achieve a total production cycle which takes as little time as possible. Other constraints may be included or conditionally included in the above method for controlling a press line, for example to coordinate or synchronise with loading/unloading requirements for the press and/or to optimise peak power and/or energy consumption for this press. This peak power and/or energy consumption may for example be optimised with regard to acceleration and regenerative braking during speed reduction periods.
41 maintain drive motor at W1.
The time when the loader will be out of the press is predictable. The control unit calculates a maximum acceleration for the drive motor in the period of time up to loader out, at or just before DP. The drive motor is thus accelerating but will not close the press before the predicted time.
Electrical energy consumption of the drive motor of a press may be improved or smoothed by use of regenerative braking. The motor may be decelerated to a reduced speed or to a zero speed by means in part of regenerative braking. For example a motor speed reduction during the first pre-pressing stage from W1 to Wp, and a motor speed reduction after pressing from W1 to zero. A system comprising an improved press according an embodiment of the invention may comprise energy recovery means for recovering energy from the motor, for example during deceleration or braking. Energy recovery may also be arranged to take place during any other reduction in kinetic energy of the system, or part of, such as during variation in inertia of a press system. The energy recovery means may be any recovery means such as for example electrical, mechanical or chemical. For example in
The stored energy is principally reused during one or more of the following periods of the press cycle: initial acceleration at start of the press cycle; pressing; reacceleration after pressing. Recovered energy may also or instead be fed back to the supply grid.
In for example the automobile industry typical production volumes mean that the energy optimisation features of the improved press line may be very beneficial in, for example, reducing energy consumption. However the improved press line may also be used in other stamping, cutting, blanking, notching, pressing or deep drawing applications where mechanical presses are to be found, and even some application where hydraulic presses are used, such applications as in production of household appliances or white goods, of industrial shelving, metal cladding panels, metal cabinets and metal furniture, and for blanking coins or minting coins.
As well as offering an improved press line for presses used for forming, bending, stamping, punching, deep-drawing etc metal parts, a press line comprising the features of one or more embodiments of the invention may also be used to form parts from plastic materials. An improved press line comprising one or more improved mechanical presses as previously described may also be arranged suitable for moulding plastic materials, both thermoplastic and thermosetting plastics and/or polymer blends and composites. Thermoplastics allow the use of injection moulding, thermoforming, blow-moulding, extrusion, and other processing techniques. For example at least the press function parts, die holder and die clamping functions, of an injection moulding machine may be carried out by the mechanical press according to an embodiment of the invention. Thermoplastic forming presses may comprise a high-speed servo-controlled motors giving the press the ability to carry out a a rapid close at up to 1,000 ipm when moulding processing speeds are typically up to 100 ipm. The presses may be of moderate size of a few hundred tons up to 1500 tons pressure, or more.
Thermosetting plastics form chemical bonds between polymer molecules, also called crosslinking, or sometimes when applied to rubber materials, vulcanizing. Some thermosets can be further polymerized by adding heat. Materials such as phenolics and epoxies can be injected or transferred into or compressed within a hot mold. RIM-molded polyurethanes (Reaction Injection Moulding) require a controlled chemical reaction within the mould. Not only is a part made but the plastic material is also created as the mould is also a polymerization reaction vessel as components mix and react as they enter the mould. Polyurethane RIM processing can produce parts varying from a very flexible foam-core part to a rigid solid part. Part density can vary widely, too, with specific gravities ranging from 0.2 to 1.6. The process is widely used in the automobile industry for both interior parts such as instrument boards and also external parts such as hoods, fenders, bumpers. Hydraulic presses are often used for compression moulding. The present invention is very suitable because of the ease with which parameters of a press cycle may be changed to suit products which may vary according to the process requirements of the plastic material and the wall thicknesses of the part, and so on. For example to adjust dwell times, times of standstill with the die still under pressure is easily configured with the improved press. The presses may be arranged for heating or curing cycles ranging for several seconds up to more than an hour. Moulding dimensional tolerances are improved by the increased opportunity for precise speed/position control during the pressing process due to the servo control of the electric press motors. Press sizes for compression moulding may also be moderate in size, being from a few hundred tons up to 2000 tons, or more.
Such a plastic moulding press line may synchronise unloaders or other devices to the press. The press may also be synchronised to an unloader, trimmer, stacker or other device in a press line. Loading plastic materials into a die for moulding by means of robots will not be necessary for most plastic materials, but a robot or manipulator arm may be used to place inserts etc into a die before for plastic to be moulded around the insert. Removing moulded products and transferring them to a clipping, cleaning, sprue removing tool or similar process may be carried out by an unloader or robot unloader. Stacking moulded parts, or transferring to another process may also be carried out by a robot or other device.
According to another embodiment of the invention, the drive motor of the press is controlled to operate the press in an improved press cycle which extends over greater than 360 degrees crank angle or equivalent when expressed in terms of a press opening distance. A conventional mechanical press has a press cycle of up to 360 deg and typically begins and ends at Top Dead Centre (TDC).
a shows a standard press cycle of the Prior Art. It shows a 360 degree cycle in one rotational direction. The cycle starts and stops at 0/360 degrees. Relative positions for DP and UC are schematically indicated.
b shows a general embodiment. The position of T1, the period T1 between UC and DP, is indicated on
d shows an alternative embodiment in which the press rotates in a first rotational direction through a press cycle greater than 360 degrees. At the end of the production cycle the press then reverses to the start position. This is the type of method which is flowcharted in
According to another embodiment of the present invention an improvement is provided to methods for operating a mechanical press comprising an electric drive motor wherein the press is moved backwards between successive press production cycles operations instead of changing rotation direction of press operation for every alternate cycle. This embodiment is particularly advantageous for presses which, due to design or other reasons, cannot be driven in reverse for a complete press cycle.
According to another and preferred embodiment of the present invention an improvement is provided to methods for operating a mechanical press comprising an electric drive motor wherein the press is controlled in part by a robot control unit.
In this embodiment the calculations for synchronisation and for certain necessary speed references for the press are carried out in a robot control unit 218, 219. At least one robot control unit 218, 219, is arranged capable of controlling an axis that is external to the robot. Thus a robot controller during at least one part of a press cycle controls the press as though it were an additional axis of the robot. For example in the schema of
It should also be noted that in the first stage (i) the press and the loader robot may be driven as slave to the unloader during a time when unloading takes place, then during a time when loading takes place, the press becomes slave to the loader.
One or more microprocessors (or processors or computers) comprise a central processing unit CPU performing the steps of the methods according to one or more aspects of the invention, as described for example with reference to
The computer program comprises computer program code elements or software code portions that make the computer or processor perform the methods using equations, algorithms, data, stored values, calculations and the like for the methods previously described, for example in relation to
It should be noted that while the above describes exemplifying embodiments of the invention, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention as defined in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 06011673.8 | Jun 2006 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/SE07/50058 | 2/2/2007 | WO | 00 | 8/5/2008 |
| Number | Date | Country | |
|---|---|---|---|
| 60765182 | Feb 2006 | US | |
| 60765183 | Feb 2006 | US |
