Data processing: generic control systems or specific application – Specific application – apparatus or process – Robot control
Reexamination Certificate
1997-09-17
2001-02-20
Grant, William (Department: 2786)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Robot control
C700S097000, C700S103000, C700S104000, C700S165000, C700S243000, C029S017100, C059S006000, C059S007000, C059S072000, C059S073000, C059S074000, C059S075000, C059S076000, C059S077000, C072S190000, C072S420000, C072S422000
Reexamination Certificate
active
06192297
ABSTRACT:
This application is based on application No. MI96 A001912 filed in Italy, the content of which is incorporated hereinto by reference.
FIELD OF THE INVENTION BACKGROUND
The present invention relates to a method for handling metal sheets in a working area comprising a machine tool and a robot, with automatic generation of trajectories.
RELATED ART AND OTHER CONSIDERATIONS
Modern flexible manufacturing systems (FMS) are known for working metal sheets, (such as punching/shearing, bending and the like), that allow the production of unitary lots of finished metal sheets (pieces) with a proven technology consisting of “nesting”, that is, the optimised jointing of individual sheets. Using such technology, a working cycle of a numerically-controlled (NC) machine tool of a working area is has a program generated by the fusion of individual programs for numerical control inserted in casual sequence and processed so as to minimise the quantity of scrap resulting from the working process. In this way high flexibilities are obtained for pieces having arbitrary shapes and dimensions, produced at rates that range from a few seconds to some minutes.
In modern working areas, in order to feed the metal sheets to the machine tool and in order to collect and stack the finished pieces, an antropomorphous robot can be used instead of or in addition to traditional devices. The antropomorphous robot is provided with an arm having a plurality of rotational joints and one or more sliding joints. Preferably, the rotational joints are five or more than five. The robot antropomorphous allows an easy handling of the metal sheets, especially if they have shapes and dimensions that are not very suitable for conventional handling.
The trajectories required for handling metal sheets have shapes that are known and that can be expressed by just a few cases. However, the trajectories become an infinite set because, in relation to the casuality and to the flexibility of production, the initial and final points of the path vary continuously.
In order to set up the trajectories for handling the metal sheets a “self-learning” procedure is commonly used. In this “self-learning” procedure, operator, by operating a pendant control, guides the robot to execute the desired trajectory or evolution in space. The path executed in this way is memorised in a control unit of the robot for use in an autonomous manner (i.e.) without the intervention of the operator at a later time, for the handling of the metal sheets from a feeding site to the machine tool and/or from the machine tool to an unloading site.
The self-learning method greatly reduces the flexibility of the working area. In particular, if the production lots are unitary, flexibility becomes nil due to the fact that the self-learning process performed for each individual piece of a unitary lot is not used again.
Generally, the manufacturers of robots provide a programming language for the sequences of actions to be performed and a self-learning method for the initialisation of data that can be used for very generic applications. The adaptation of the sequences and of the data to a specific working cycle requires times that, in the case of punching and/or shearing or bending operations, range from thirty to three hundred minutes and up. These are very long times if compared to those required for the automatic creation of programs for numerical control by means of the “nesting” technology. In fact, “nesting” for several hours of production takes only a few minutes for the generation of the programs, starting from the ones that exist for the individual pieces. Thus, the times of the self-learning step translate into a “downtime”, (i.e., a loss of flexibility) that is very costly in the case of punching/shearing or panelling (bending) machines used, as is often the case, for the production of small lots.
The self-learning procedure also requires particular competences on the part of the operator, but this kind of specialisation is often missing in small firms or, in any case, its possible presence involves a further increase in costs.
Moreover, the self-learning procedure also involves problems of safety because it has to be performed within the field of action of the robot. In fact, in order to initialise the robot, an operator has at his disposal a portable keyboard (teach pendant or control by wire). However, in order to move the robot to the required working positions with adequate accuracy and to check that it does actually take up the pre-established final positions with respect to the machine tool, the operator is generally obliged to inspect at very close range the positions actually assumed by the robot. This takes the operator within the field of action of components in motion and, thus, in conditions of serious danger.
An object of the present invention is a method for moving metal sheets in a working area comprising a machine tool and a robot that allows the above-mentioned drawbacks to be overcome, accomplishing a handling operation of metal sheets selected by type and totally eliminating the steps of self-learning and of changing the operative sequences of the robot every time the type of metal sheets to be handled is changed.
SUMMARY
The above-mentioned object is achieved, according to the invention, with a method for moving metal sheets in a space of a working area comprising a machine tool, at least a robot, a site for feeding the metal sheets to be worked and a site for unloading the finished metal sheets, said machine tool, robot and feeding and unloading sites having each a prefixed shape and a prefixed geometric position in the space of said working area, said robot being provided with an arm and with a grasping member capable of taking said metal sheets and being operatively connected to a control unit, characterized in that (i) said robot (
101
) is antropomorphous and (ii) for handling said metal sheets (
104
)
a) preselected fixed input data are detected consisting of configuration parameters that identify the geometry in the space of said machine tool, robot and at least one of said feeding and unloading sites whithout resorting to CAD tecniques;
b) preselected variable input data are detected from said machine tool consisting of
dimensions of a preselected metal sheet to be handled,
shape of said metal sheet to be handled,
sequence of working of preselected metal sheets, whithout resorting to CAD techniques;
c) the above-mentioned fixed and variable input data are processed on a processing unit by an algorithm based on the solutions of the inverse kinematics in order to generate automatically output data that identify a preselected trajectory of said metal sheet between one of said feeding and unloading sites and said machine tool and
d) said output data are transferred to said control unit of said robot in order to drive said robot to move said metal sheet along said preselected trajectory so as to automatically handle said metal sheets selected by type.
One of the main advantages of the method according to the invention is the increase in flexibility derived from the possibility of handling the metal sheets selected by type without making recourse to the self-learning procedure and to sophisticated and costly methodologies such as CAD (Computer-Aided-Design) methodologies, artificial intelligence methodologies and expert systems.
Another important advantage is the improvement in safety, it being no longer necessary to operate within the field of action of the components in motion of the working area.
Other advantages are represented by the accuracy, efficiency and reliability of the working cycles of the antropomorphous robot generated with the method of the invention.
REFERENCES:
patent: 3881382 (1975-05-01), Rasenberger et al.
patent: 5188135 (1993-02-01), Neumann et al.
patent: 5307282 (1994-04-01), Conradson et al.
patent: 5380055 (1995-01-01), Suarez
patent: 5761951 (1998-06-01), Codatta
patent: 5822207 (1998-10-01), Hazama et al.
patent: 0 355 454 (1990-02-01), None
patent: 0 355 454 A2 (1990-02-01), None
patent: 2 211 002 (1989-06-01)
Grant William
Marc McDieunel
Nixon & Vanderhye P.C.
Salvagnini Italia S.p.A.
LandOfFree
Method for handling metal sheets in a working area... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for handling metal sheets in a working area..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for handling metal sheets in a working area... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2587517