GROUP CONTROL SYSTEM OF INJECTION MOLDING MACHINES

Abstract: This invention relates to a group control system of injection molding machines which can determine rapidly a molding condition for each of a plurality of injection molding machines without using an expensive apparatus. When data representing the kinds of molding defects that occur in molded articles produced tentatively by 1st to 11th injection molding machines (12a ∼ 32c) forming 1st to 3rd injection molding machine groups (12,22,32) in accordance with temporary molding conditions are inputted through 1st to 11th input devices (13a ∼ 33c), 1st to 3rd workstations connected to the first to third injection molding machine groups (12,22,32) determine at least one molding condition and a change quantity of this molding condition to be changed for each of 1st to 11th molding machines by use of an incorporated multi-user operating system, a program for molding condition determination and a database, and transmit the result of determination to corresponding injection molding machines. Each injection molding machine tries once again injection molding in accordance with the molding condition after the change. Such a molding condition change processing is repeated to determine the optimum molding condition that does not introduce molding defect. The processing is completed when this optimum molding condition is determined for all the injection molding machines.

Description: Technical Field The present invention relates to a group management system for injection molding machines, which is capable of rapidly and accurately determining optimum molding conditions for a plurality of injection molding machines. Background Art When manufacturing molded articles by injection molding machines, a large number of molding conditions such as mold clamping force, injection speed, hold pressure, hold time, resin temperature, mold temperature, back pressure, screw rotating speed, suck-back amount, cooling time, etc. must be determined. Therefore, in general, injection molding is first carried out by way of trial under the molding conditions which are tentatively determined on the basis of expert knowledge and experience in accordance with the type of article to be molded. Whereupon, one or more molding conditions are modified in accordance with the expert knowledge and experience, depending on the type of molding defect appearing in the resultant molded article, such as flash, sink mark, warp, weld mark, flaw mark, etc., and then injection molding is tried again. This molding condition determination process is repeatedly executed to find optimum molding conditions that do not cause any molding defect. Accordingly, the determination of optimum molding conditions involves considerable labor. In particular, when producing various molded articles of different types by using a plurality of injection molding machines having different structures from one another, the process for determining the molding conditions must be performed for each of the injection-molding machines, requiring much labor to determine the optimum molding conditions. Some problems of controlling several machines with one computer are discussed in the article "BDE-Systeme der Spritzgiessmachinen-Hersteller" (Manufacturers' systems for the acquisition of operating data in injection-molding machines) by Menges et al. in Plastverarbeiter, Vol 39, no. 5, pages 150-160 (May 1988). A system shown in Fig. 1 of that article has a host computer connected to a group of CNC machines. In order that several machines can be controlled simultaneously it is necessary to make this connection via a multiplexer. Data not automatically measured by the machine can be entered via the panel of the NC unit itself. This system allows collection of data concerning each machine once it is in operation, such as length of cycle or kinds of malfunction. However, it does not assist the operator to set the correct operating parameters. An object of the present invention is to provide a group management system for injection-molding machines, which is capable of rapidly and accurately determining optimum molding conditions for a plurality of injection-molding machines. To achieve the above-mentioned object, a group management system for injection-molding machines of the present invention comprises a plurality of injection-molding machines, a general-purpose high-performance computer connected to the injection-molding machines, the computer having a multi-user operating system and adapted to use a molding-condition-determining program and a molding-condition-determining database, and input means for manually entering data indicative of the type of any molding defect appearing in a molded article produced by each of the injection-molding machines. The computer can automatically modify the molding conditions of the individual injection-molding machines in accordance with the data indicating the type of molding defect and with the molding-condition-determining program and database. As described above, with a system following the present invention, all that is necessary is to input data indicative of a type of molding defect occurring in the molded articles being produced by the injection-molding machines to the single general-purpose high-performance computer. The molding conditions of each injection-molding machine are then automatically modified online by the computer using the molding-condition-determining program and database. This makes it possible to determine the optimum molding conditions rapidly and accurately for each injection-molding machine. Further, since the single general-purpose high-performance computer uses a multi-user operating system, the individual processes of determining the molding conditions for the plurality of injection-molding machines can be executed by the single computer in an independent and substantially simultaneous manner. Moreover, the group management system can be constructed at a relatively low cost, because it is not necessary to provide individual computers, each having the mold-condition-determining program and database, for the injection-molding machines; the single computer is adapted to use the molding-condition-determining program and database for all the machines it controls. Further, since the molding-condition-determining program and database are used in common, it is easy to manage the program and database. Furthermore, renewal of the database in accordance with the results of the molding-condition-determining processes of the individual injection-molding machines is permitted, whereby accumulation of know-how for the determination of the molding conditions can be facilitated, a sophisticated database can be constructed, and further the efficiency of the molding-condition-determining process can be improved. JP 63-94810 (Mitsubishi Heavy Industries) shows a crude system for sharing data concerning machine and mold type, apparently by physically moving a memory containing the data, and for converting data using prestored formulae. This shortens the time required for setting up a new run but is cumbersome to use and not usable for the control of several machines. In order to shed further light on the invention an example of it will now be described with reference to the accompanying drawing, which is a schematic diagram of a group management system for injection-molding machines representing one embodiment of the present invention. Referring to the appended drawing, a group management system for injection molding machines according to one embodiment of the present invention comprises first, second and third general-purpose high-performance computers (hereinafter referred to as work stations) 10, 20 and 30 individually connected to a host computer 1 through a network 2 for exchange of signals therewith, and constitutes, as a whole, a local area network. In this embodiment, the first to third work stations are identical in structure, and are respectively connected, through first to third sub-networks 11, 21 and 31, to first to third groups 12, 22 and 32 of injection molding machines for exchange of signals therewith. The first to third injection molding machine groups 12, 22 and 32 are made up of first to third injection molding machines 12a to 12c, fourth to eighth injection molding machines 22a to 22e, and ninth to eleventh injection molding machines 32a to 32c, respectively. The first through eleventh injection molding machines 12a - 32c each have a structure known in the art and comprise a numerical control unit (not shown) with a built-in computer, etc. First through eleventh manual data input devices with CRT display (hereinafter referred to as CRT/MDI) 13a to 13c, 23a to 23e, and 33a to 33c are respectively connected to the injection molding machines. In this embodiment, at least one or more of the first through eleventh injection molding machines 12a - 32c are different in structure (type) from the other machines. The first to third work stations 10, 20 and 30 are each installed with a multi-user operating system, as well as with a program containing a molding condition determining algorithm, and a database including various data which is referred to during an execution of the program. The program and the database for the molding condition determination are created based on expert knowledge and experience, and constitute a so-called artificially intelligent expert system. In this embodiment, the first to third work stations are installed with the same multi-user operating system, the same molding condition determining program and the same database. The operation of the group management system for injection molding machines as constructed above will be now described. When producing molded articles, an operator inputs initial values of various molding conditions for the first to eleventh injection molding machines 12 - 32c, such as mold clamping force, injection speed, hold pressure, hold time, resin temperature, mold temperature, back pressure, screw rotating speed, suck-back amount, cooling time, etc., which values are determined tentatively based on the expert knowledge and experience, in accordance with the types of the first to eleventh injection molding machines 12a - 32c and the types of articles to be molded by the respective injection molding machines, to the injection molding machines 12a - 32c through the first to eleventh CRT/MDIs 13a - 33c, respectively. In this case, the types of articles to be molded by the first to eleventh injection molding machines 12a - 32a may not necessarily be identical with one another. On receiving the initial molding conditions, the first to eleventh injection molding machines 12a - 32c carry out tentative injection molding under the respective initial molding conditions. The operator then examines whether or not the molded articles produced tentatively by the first to eleventh injection molding machines 12a - 32c have a molding defect such as flash, sink mark, warp, weld mark, flaw mark, etc. When one or more molded articles have some molding defect, the operator inputs data indicative of the type of the molding defect, through one or more CRT/MDIs connected to the injection molding machines that produced the defective articles. Here, let it be assumed that all of the molded articles produced by the first to eleventh injection molding machines 12a - 32c, respectively, had one or more molding defects, and that one or more items of data each indicative of a type of molding defect were input to each of the first to eleventh injection molding machines 12a - 32c. In this case, the first to third work stations 10, 20 and 30 read corresponding ones of the thus input data indicative of types of molding defects. The first work station 10, which received the data indicative of the types of molding defects associated with the first to third injection molding machines 12a to 12c, carries out on-line molding condition modifying processes with respect to the first to third injection molding machines 12a to 12c, for example, in a time-sharing manner, i.e., apparently simultaneously and in parallel, using the multi-user operating system, and the program and the database for the molding condition determination. More specifically, one or more routines in the molding condition determining program corresponding to one or more items of data indicative of the type of molding defect associated with the first injection molding machine 12a are executed with reference to the molding condition determining database, and one or more molding conditions to be modified and an amount of each modification are respectively determined. Then, data specifying the one or more molding conditions to be modified and each modification amount is transmitted to the first injection molding machine 12a. A similar process is carried out with respect to the second and third injection molding machines 12b and 12c. The second and third work stations 20 and 30 carry out a molding condition modifying process similar to the above, with respect to the fourth to eighth injection molding machines 22a - 22e and the ninth to eleventh injection molding machines 32a - 32c, respectively. After the molding condition modifying process is executed once for the individual injection molding machines in the aforesaid manner, the injection molding machines carry out injection molding again under the modified molding conditions. The operator then examines whether or not the resulting molded articles have a molding defect, and if a molding defect exists, inputs data indicative of the type of the molding defect, through the corresponding CRT/MDI. The corresponding injection molding machine then carries out an injection molding again under the molding conditions that have been modified by the work station associated therewith. Thereafter, when a defect-free molded article is produced, the operator inputs a command to terminate the molding condition determining process, to the corresponding injection molding machine through the associated CRT/MDI, whereby optimum molding conditions which entail no molding defect are set into the injection molding machine. When optimum molding conditions are set into all of the first through eleventh injection molding machines 12a - 32c in this manner, the whole of the molding condition determining process is ended. The present invention is not limited to the above embodiment, and various modifications can be made. For example, although in the above embodiment, some of the first through eleventh injection molding machines are different in type from others, all of the injection molding machines may be of the same type, or may be all different in type. Further, when the molding condition determining process is completed, the molding condition determining databases which were respectively updated in the first to third work stations may be integrated under the control of the host computer so that the databases used in the respective work stations are matched. Moreover, the same type of molded articles may be produced by all of the injection molding machines, or different types of articles may be produced by different injection molding machines. The present invention is useful also in the case of producing molded articles of the same type by using injection molding machines having the same structure, because even in such case, the optimum molding conditions may differ from machine to machine, depending on the environmental conditions (e.g., ambient temperature). Furthermore, in the above embodiment, the molding condition determining database is installed in individual work stations, but it may be installed in the host computer.

Claims: A group management system for injection-molding machines, comprising: a plurality of injection-molding machines (12a, 12b, 12c) and a computer (10) for controlling these machines; and input means (13a, 13b, 13c) for the manual entry of data concerning the operation of each of the injection-molding machines; characterised in that the computer (10) is a general-purpose high-performance computer, is installed with a multi-user operating system and further with a program and a database for determining the molding conditions; the input means (13a, 13b, 13c) is adapted for the input of data indicative of a type of a molding defect appearing in a molded article produced by each of the injection-molding machines; and the general-purpose high-performance computer (10) is operable under the said program to modify the molding conditions of the individual injection-molding machines automatically in accordance with the said data and the molding-condition-determining database. A group management system according to claim 1, wherein the injection-molding machines are not all of the same type, the input means (13) is adapted also for the input of data indicative of the types of the injection-molding machines, and the general-purpose high-performance computer (10) is operable to modify the molding conditions of the individual injection-molding machines automatically in accordance with the said data indicative of the types of the injection-molding machines. A group management system according to claim 1 or 2, wherein the injection-molding machines are arranged to produce molded articles of differing types, the input means (13) is adapted also for the input of data indicative of the types of molded articles to be produced by the respective injection-molding machines, and the general-purpose high-performance computer (10) is operable to modify the molding conditions of the individual injection-molding machines automatically in accordance with the said data indicative of the types of molded articles. A group management system according to any preceding claim, wherein the said program and database are installed in the general-purpose high-performance computer (10). A group management system according to any preceding claim, in which the input means (13) includes individual input devices (13a, 13b...), one for each molding machine (12a, 12b...). A group management system according to claim 5, in which a display means is associated with each input device. A group management system according to any preceding claim and also including further such general-purpose high-performance computers (20, 30) each connected similarly to corresponding further sets of injection-molding machines (22, 32), the whole being under the control of a host computer (1).

Inventors: KAMIGUCHI MASAO ROOM - FANUC M, KUBOTA KAZUO, KAMIGUCHI, MASAO ROOM 6-207 FANUC MANSHONHARIMOMI, KUBOTA, KAZUO
Applicants: FANUC LTD, FANUC LTD.
Application year: 1989
Main classification: B29C45
IPC codes: B29C45