(1) Field of the Invention
The present invention relates to an NC data management apparatus and method for use in a production system.
(2) Description of the Related Art
In the following description, a printed-circuit board mounting system will be used as an example of a production system.
A printed-circuit mounted board is composed of (a) a printed-circuit board, which is made by printing wiring patterns on a board, and (b) electronic circuit components mounted on the board. The process of mounting the electronic circuit components on the board is called a printed-circuit board mounting process.
For executing the printed-circuit board mounting process, first a “line” is necessary. The line is a series of several apparatuses including an apparatus for printing wiring patterns on the board, apparatuses (mounting equipment) for mounting the electronic circuit components onto the print-circuited board, and an apparatus for inspecting the completed printed-circuit mounted boards. For the execution of the printed-circuit board mounting process, a material management system for managing inventories of the components is also required. A mounting system is composed of the material management system and other elements such as a server for managing the entire mounting process. One system includes at least one line.
The main portion of the mounting system is the mounting equipment. Each piece of the mounting equipment includes (a) a number of cassettes which supply the parts on a one-to-one basis, and (b) a rotary head that includes a plurality of nozzles each of which sucks up one by one the parts supplied from the cassettes and mounts the sucked part on a specified position of a printed-circuit board that comes on the conveyer belt.
The series of operation of sucking the parts from the cassettes and mounting the parts on the printed-circuit board is performed based on NC data. The NC data contains an NC program showing amounting position, a parts arrangement program showing which cassettes are used to carry each part, a board program showing the size of the board to be produced, and a parts library showing conditions for mounting a large surface mounting part on a plate-like object other than a cassette.
Currently, the NC data is created by a printed-circuit board production support system (hereinafter referred to as CAM system) based on a design made by a printed-circuit board design system (hereinafter referred to as CAD system).
The created NC data is loaded onto the mounting equipment by the operator when the boards to be produced are changed based on the production plan. The loaded NC data may be tested with some boards before the actual production process, and may be modified depending on the test results, for improving the mounting quality.
The NC data may be modified by the CAM system a number of times due to design specification changes, parts changes, parts adjustments in the field or the like. As a result, many versions of NC data are generated. This requires a thorough data management since without this, spoiled or defective printed-circuit boards are produced due to erroneous NC data loaded on the mounting equipment.
High productivity is required for the printed-circuit board mounting process. To increase the productivity, the downtime of the line should be as short as possible. From the viewpoint of the productivity, a restless, continuous operation is ideal. Though a downtime for changing the NC data is unavoidable, this downtime can be reduced by using the same order of supplying the parts by cassettes for each board type. With this arrangement, the NC data change can be performed only with the setting of the equipment without loading the parts arrangement program and the parts library.
It takes a lot of time to check whether the NC data has been prepared for a production plan made by the scheduling system since the production plan changes depending on the sales of the products. This tendency is remarkable in recent days when there are demands for a variety of products with small quantities. When the NC data has not been prepared yet, even if the production plan is changed or the CAM system is urged to make the NC data, the production of the product is delayed. Accordingly, the NC data preparation status should always be checked based on the production plan.
Aside from the problem with the productivity, there is a problem that a mounting error may occur in the printed-circuit board mounting process. That is to say, in the case relating to the NC data, a mounting error may occur when a parts table obtained by each piece of mounting equipment has not been updated, while it should have been updated reflecting the changes in the parts number due to parts changes made in request of the design division or the purchasing division.
The mounting error is an error in which an erroneous part is mounted on a print-circuited board or a part is mounted on an erroneous position of a print-circuited board, which happens when a cassette is attached to the mounting equipment at an erroneous position.
The completed printed-circuit mounted boards with erroneously mounted parts are defectives and have no commercial value. When this happens, the parts, the time, the man-hours or the like used for the production are wasted, which also decreases the productivity. The mounting error may happen in both reel changes and cassette changes.
In the printed-circuit board mounting process, a generic name “NC data management process” is used for the NC data version management reflecting design changes, the parts library management reflecting the changes of parts conditions in the field, the NC preparation management reflecting the production plan changes, and the parts table management reflecting the parts name changes.
Conventionally, the NC data creation division receives the design information and the production preparation table information from the design division CAD system, the production management division scheduling system or the like, creates the NC data using the CAM system, and sends the NC data to the production division. Also, the NC data inspected through the production by the mounting equipment is sent as the feedback to the CAM system on an irregular basis by man.
The conventional methods, however, have a problem that it is difficult to recognize the latest version of NC data since various versions of NC data are created due to many design changes by the design division when the design due date comes nearer or many parts number changes are made by the purchasing division as a result of cost estimate comparisons between a plurality of parts makers. When this happens, erroneous NC data is passed to the production division, causing defective printed-circuit boards to be produced.
Also, in the conventional methods, since the NC data inspected through the production by the mounting equipment is sent as the feedback to the CAM system on an irregular basis by man, the conditions for adjusting the parts to the equipment are not reflected onto the database of the CAM system. When this happens, an erroneous parts library is loaded onto the mounting equipment, and defective printed-circuit boards are produced.
Furthermore, though, as stated earlier, high productivity is required for the-printed-circuit board mounting process, and the downtime of the line should be as short as possible to increase the productivity, and a restless, continuous operation is ideal, a downtime for changing the NC data is unavoidable. This generates a problem that it takes time to change the board types and reduces the production operation time.
Furthermore, as stated earlier, it takes a lot of time to check whether the NC data has been prepared appropriately for a production plan made by the scheduling system. This is because the production plan may change depending on the sales of the products. This tendency is remarkable in recent days when there are demands for a variety of products with small quantities. A problem arises under these circumstances that when the NC data has not been prepared yet, even if the production plan is changed or the CAM system is urged to make the NC data, the production of the product is delayed, decreasing the production operation time.