DEVICE FOR DETECTING VARIOUS ERRORS IN SET VALUES FOR INJECTION MOLDING MACHINE

Abstract: The setting value error detection device for injection moulding machine forms part of a computerised numerical control system controlling four servo motors for injection clamping, screw rotation and ejection. The setting values inputted via input means (14) are compared with established conditions and assessed by assessing means (3). If the values inputted satisfy requirements thay are stored in non-volatile memory (6); if they do not satisfy requirements an alarm is outputted.

Description: The present invention relates to an injection-molding machine controlled by means of a numerical control unit (hereinafter referred to as NC unit). An example of such a machine is provided by DE-A-3414596. In conventional hydraulic injection-molding machines, a limit switch or the like has been used to set various set values, including changing positions for the mold closing and opening speeds of a clamping unit (mold camper), injection-speed changing positions, changing positions for the rotating speed of a screw during metering, the ejection forward and reverse positions of an ejector, etc. Therefore, the set values have suffered only minor setting errors. Recently has been developed, however, an injection-molding machine which uses servomotors as various drive sources, and is controlled by means of an NC unit. In the injection-molding machine of this type, the various set values are set in the form of numerical values through a keyboard of a manual data input unit with a CRT display (hereinafter referred to as MDI/CRT). The control of the injection-molding machine by means of the NC unit is performed in accordance with the various set values indicative of, for example, the changing positions for the mold closing and opening speeds of the clamping unit, the changing positions for the injection speed of an injection unit, and the ejector forward and reverse positions of the ejector. In mold opening control of a mold, for example, the mold typically is first moved to an acceleration start position P1 at a mold release speed V1, as shown in Fig. 1. Then, the mold is moved from the acceleration start position P1 to a deceleration start position P2 at a high mold opening speed V2. From the deceleration start position P2 to a mold opening end position P3, the mold is moved at a low mold opening speed V3. Usually, an NC program for such mold opening control is composed of a macro-program for higher universality. For example, the velocities V1 to V3 and the positions P1 to P3 are set by using macro-variables #500 to #505 which can be set to various values. Thus, the following NC program is prepared. Y#503 F#500 Y#504 F#501 Y#505 F#502 Here symbols Y and F designate a clamp axis and a speed, respectively. According to the program for mold opening control, composed of the above three blocks, a command for movement is delivered in the first block such that the mold is moved to the position P1, which is set by means of the macro-variable #503, at the speed V1, which is set by means of the macro-variable #500. When the first block terminates, a command is delivered in the second block such that the mold is moved to the deceleration start position P2, which is set by means of the macro-variable #504, at the speed V2, which is set by means of the macro-variable #501. In the third block, a command is delivered such that the mold is moved to the mold opening end position P3, which is set by means of the macro-variable #505, at the speed V3, which is set by means of the macro-variable #502. The mold opening operation is controlled in this manner. The operating manual "UNILOG 2000/3000", published by the firm Battafeld Kunststoffmaschinen GmbH before our priority date, discloses the features of the preamble of attached claim 1, with the sizes of items of input data being compared with fixed numerical values. Unless there are relations: clamp stroke ≧ #505 ≧ #504 ≧ #503 ≧ 0 between the set values based on the macro-variables #503, #504 and #505, the clamping unit suffers an abnormal mold opening operation such that the mold closes again after being opened, for example, even during a mold opening cycle in which the mold should be driven only in the opening direction. In order to accomplish required operations in various control modes (items) of the injection-molding machine, as well as the aforementioned mold opening operation, there must be predetermined relations, as mentioned later in detail, between the set values related to the operations concerned. If these requirements are not fulfilled by the inputted set values, the control operations suffer troubles and are performed wrongly, as described above in connection with the mold opening operation. The object of the present invention is to provide an injection-molding machine which is controlled by means of a numerical control unit, and in which set values of inputted molding conditions are allowed to be inputted only when they fulfill requirements of the molding conditions, so that the injection-molding machine can be prevented from operating wrongly due to setting errors of the set values. In order to achieve the above object of the present invention, there is provided an error detector for an injection-molding machine controlled by means of a numerical control unit, comprising: input means for inputting set values of various items of molding conditions; memory means for storing the set values of the various items of the molding conditions; discrimination means for determining whether input data on the various items, inputted by means of the input means, fulfill requirements related to the items; memory control means adapted to cause the memory means to store the input data as set values of the items when the discrimination means concludes that the requirements are fulfilled; and alarm means adapted to deliver an alarm when the discrimination means concludes that the requirements are not fulfilled, characterised in that: said discrimination means is adapted to compare with one another the sizes of the input data on each respective item, in order to determine whether said requirements related to said each respective item are fulfilled, and to conclude that said input data fulfill their said requirements when said sizes of the input data on each respective item are in predetermined relations in size with respect to one another. According to the present invention, as described above, whether the molding requirements are fulfilled by input data related to items to be set is determined in setting the molding conditions, and the set values can be inputted for setting only when the set values are inputted properly, so that anyone can easily set various set values of the molding conditions without errors. Brief Description of the Drawings Fig. 1 is a diagram for illustrating mold opening operation; Fig. 2 is a block diagram showing an injection-molding machine according to an embodiment of the present invention; Fig. 3 is a diagram for illustrating the relations between various set values for the mold opening operation in a clamping position; Fig. 4 is a diagram for illustrating the relations between various set values for mold closing operation in the clamping position; Fig. 5 is a diagram for illustrating the relations of an ejection start position to other positions, with respect to the clamping position; Fig. 6 is a diagram for illustrating the relations of an air-ejection start position, with respect to the clamping position; Fig. 7 is a diagram for illustrating injection-speed changing positions; Fig. 8 is a diagram for illustrating metering changing positions; Fig. 9 is a diagram for illustrating ejection forward and reverse positions; Fig. 10 is an input-processing flow chart for various set values related to clamping operation; Fig. 11 is an input-processing flow chart for various set values related to ejecting operation; Fig. 12 is an input-processing flow chart for setting the injection-speed changing positions; and Fig. 13 is an input-processing flow chart for the metering changing positions. Fig. 2 shows a principal part of an NC unit for effecting an embodiment of the present invention. In Fig. 2, the NC unit 1 includes a microprocessor (hereinafter referred to as CPU) 2 for NC, and a CPU 3 for a programmable controller (hereinafter referred to as PC). The PCCPU 3 is connected with a ROM 5 which stores a sequence program for an injection-molding machine. The NCCPU 2 is connected with a ROM 7 which stores a control program for generally controlling the injection-molding machine. The NCCPU 2 is also connected, through a servo-interface 8, with servo-control circuits 9 to 12 for controlling the drive of various servomotors for injection, clamping, screw rotation, and ejector operation. Numeral 6 denotes a nonvolatile RAM which, including a backup power source, stores programs for controlling individual operations of the injection-molding machine, various set values, parameters, etc., as mentioned later. Numeral 14 denotes an MDI/CRT, which is connected to a bus-arbiter controller (hereinafter referred to as BAC) 4 through an interface 13. The BAC 4 is connected with the respective buses of the NCCPU 2, the PCCPU 3, and the nonvolatile RAM 6. The bus to be used is controlled by the BAC. The requirements to be fulfilled in setting the various set values for the molding conditions, by means of the MDI/CRT 14, will now be described. (i) Setting of mold opening operation: The predetermined requirements to be fulfilled in the setting of the mold opening operation has already been described with reference to Fig. 1. To fulfill these requirements, the following expression (1) must be established between a lockup position LCK (= 0) where a toggle link of a clamping unit (mold clamping mechanism) extends to its full length, an acceleration start position FST, a deceleration start position SLW, a mold opening end position OPN, and the maximum stroke Cmax of the clamping unit, as shown in Fig. 3. Cmax ≧ OPN ≧ SLW ≧ FST ≧ LCK = 0. If the set values of the parameters LCK to Cmax do not agree with the relationships indicated by the expression (1), wrong operations will be caused during the mold opening operation. (ii) Setting of mold closing operation: In the mold closing operation, a moving platen is moved from the mold opening end position OPN to a mold protection start position MPR at high speed, and from the mold protection start position MPR to a mold touching position TCH at low speed. Further, the moving platen is moved from the mold touching position TCH to the lockup position LCK where a toggle mechanism locks up, that is, the position where the clamping position is "0" (normally, the lockup position LCK serves as the starting point). Thus, those set values must fulfill the following expression (2), as shown in Fig. 4. Cmax ≧ OPN ≧ MPR ≧ TCH ≧ LCK = 0. (iii) Setting of ejection start position and air-ejection start position: Ejection and air ejection must be started before the clamping mechanism finishes mold opening. Accordingly, start positions EJE and AEJ for these operations must be set so that the following expressions (3) and (4) hold true, as shown in Figs. 5 and 6. Cmax ≧ OPN ≧ EJE ≧ LCK = 0, Cmax ≧ OPN ≧ AEJ ≧ LCK = 0. (iv) Setting of positions for changing injection speed and transferring from injection speed control to hold pressure control: Normally, the injection speed is changed successively in several stages. At the end of the final stage of injection speed control, the injection speed control is switched over to hold pressure control. In order to control such transferring as intended, the following inequality (5) must hold for positions for the switching, as shown in Fig. 7. If this inequality does not hold true, a screw undergoes a wrong operation, that is, it retreats. Here the origin of the coordinate for setting the switching positions is at a position Smin where the screw end is in alignment with the end of a heating cylinder. Symbol Smax designates the maximum stroke of an injection axis; SBK, a set screw-back position; IV1 to IVN-1, injection-speed changing positions between adjacent stages or first to Nth stages; and TRP, a position for transferring from injection speed control to hold pressure control. 0 = Smin ≦ TRP ≦ IVN-1 ... ≦ IV1 ≦ SBK ≦ SMAX. (v) Setting of changing positions for screw rotating speed: Also in metering, the rotating speed of the screw is changed in several stages according to the screw position. Also in this case, the changing positions for the individual stages must be set so that the following inequality (6) holds true, as shown in Fig. 8. Symbols EX1 to EXN-1 designate the changing positions for the individual metering stages. 0 = Smin ≦ EX1 ... ≦ EXN-1 ≦ SBK ≦ Smax. (v) Setting of ejection forward and reverse positions: As shown in Fig. 9, the following expression (7) must hold for the relationships between an ejection forward position EFW, ejection reverse position ERV, maximum stroke Emax of an ejector, and ejection reverse limit position Emin = 0. Emin = 0 ≦ ERV ≦ EFW ≦ Emax. Thereupon, a picture for setting required conditions is selectively displayed on a CRT screen (not shown) of the MDI/CRT 14, and various data are set by means of a keyboard (not shown) of the MDI/CRT 14. In doing this, PCCPU 3 reads out these set values x, and determines whether they satisfy the requirements of the expressions (1) to (7). Referring now to the flow charts, the operation processing will be described. (a) Setting of clamping conditions: First, a picture for setting the clamping conditions is selected on the CRT screen of the MDI/CRT 14, a cursor is moved to each of cursor positions for the input of the following various positions, and corresponding data are inputted successively by means of the keyboard. Thereupon, the PCCPU 3 determines whether the set cursor position is the mold opening end position OPN, mold protection start position MPR, mold touching position TCH, acceleration start position FST, or deceleration start position SLW (Step S1 to S5), as shown in Fig. 10. If the cursor is situated at the mold opening end position OPN, whether the input data x is larger than the value of the maximum clamping stroke Cmax of the clamping unit is determined (Step S6). If the data x is larger than the value Cmax, an alarm is delivered (Step S12) and displayed on the CRT screen, for example. If the data x is smaller than or equivalent to (hereinafter referred to simply as "smaller than") the value Cmax, whether the input data x is larger than the value of the mold protection start position MPR is then determined (Step S7). If the data x is smaller than the value MPR, an alarm is delivered (Step S12). If the data x is larger than or equivalent to (hereinafter referred to simply as "larger than"), whether the input data x is larger than the value of the deceleration start position SLW is determined (Step S8). If the data x is smaller than the value SLW, an alarm is delivered (Step S12). If the former is larger than the latter, whether the input data x is larger than the value of the ejection start position EJE is then determined (Step S9). If the data x is smaller than the value EJE, an alarm is delivered (Step S12). If the former is larger than the latter, whether the input data x is larger than the value of the air-ejection start position AEJ is determined (Step S10). If the data x is smaller than the value AEJ, an alarm is then delivered (Step S12). If the former is larger than the latter, the input data x is displayed corresponding to the mold opening end position OPN on the CRT screen, and is stored in the nonvolatile RAM 6 (Step S11). Thus, the requirements associated with the mold opening end position OPN are the following conditions (8) to (11), which have already been given by the expressions (1) to (4). Cmax ≧ OPN ≧ SLW, Cmax ≧ OPN ≧ MPR, Cmax ≧ OPN ≧ EJE, Cmax ≧ OPN ≧ AEJ. Whether the requirements of the expression (8) are fulfilled is determined in Steps S6 and S8. For the expressions (9), (10) and (11), the fulfillment of the requirements is determined in Steps S6 and S7, Steps S6 and S9, and Steps S6 and S10, respectively. If the requirements of the expressions (8) to (11) are all fulfilled, it is concluded that the input data x is set properly, and the data x is stored fixedly. If the cursor is situated at the mold protection start position MPR (Step S2), which is related only to the expression (2), the requirements are fulfilled when the input data x is smaller than the value of the mold opening end position OPN and larger than the value of the mold touching position TCH. Thereupon, the fulfillment of these requirements is determined in Steps S13 and S14. If the requirements are fulfilled, the input data is displayed on a display position of the CRT for the mold protection start position, and is stored in the nonvolatile RAM 6 (Step S15). If the requirements are not fulfilled, on the other hand, an alarm is delivered (Step S12). If the cursor is situated at the mold touching position TCH (Step S3), which is related only to the expression (2), the input data x is displayed and stored in the nonvolatile RAM 6, in the same manner as aforesaid, when it is smaller than the value of the mold protection start position MPR and larger than the value of the lockup position LOK = 0 (Steps S16 to S18). If the above requirements are not fulfilled, an alarm is delivered (Step S12). If the cursor is situated at the acceleration start position FST, the input data x is displayed and stored fixedly in the nonvolatile RAM 6 (Step S21) when it is smaller than the value of the deceleration start position SLW and larger than the value of the lockup position LCK = 0 (Steps S4, S19 and S20). If the cursor is situated at the deceleration start position SLW, on the other hand, the input data x is displayed and stored fixedly in the nonvolatile RAM 6 (Step S24) when it is smaller than the value of the mold opening end position OPN and larger than the value of the acceleration start position FST (Steps S5, S22 and S23). If the requirements are not fulfilled, an alarm is delivered for each case (Step S12). In this manner, the set conditions for clamping, related to the mold opening and closing operations, and the fulfillment of the requirements for the ejection start position and the air-ejection start position, related to the clamping operation, are checked. If the setting is proper, the individual input data are displayed on the CRT screen and stored as set values. (b) Setting of ejecting conditions: The set values EJE, AEJ, EFW, and ERV, which are related to ejection, must fulfill the following relations with respect to the expressions (3), (4) and (7). OPN ≧ EJE ≧ LCK = 0, OPN ≧ AEJ ≧ LCK = 0, Emax ≧ EFW ≧ FRV ≧ Emax = 0. Thereupon, if the cursor is situated at the ejection start position EJE (Step S25), as shown in Fig. 11, whether the expression (12) is fulfilled by the input data x is determined in Steps S26 and S27. If the expression (12) is fulfilled, the input data x is displayed and stored in the nonvolatile RAM 6 in Step S28. If the cursor is situated at the air-ejection start position AEJ (Step S29), whether the expression (13) is fulfilled is determined in Steps S30 and S31. If the expression (13) is fulfilled, the input data x is displayed and stored in the nonvolatile RAM 6 (Step S32). If the cursor is situated at the ejection forward position EFW (Step S33), whether the relation Emax ≧ EFW ≧ ERV in the expression (7) is fulfilled by the input data x is determined in Steps S34 and S35. If this relation is fulfilled, the input data x is displayed and stored in the nonvolatile RAM 6 (Step S36). If the cursor is situated at the ejection reverse position ERV (Step S37), whether the relation EFW ≧ ERV ≧ Emin = 0 in the expression (7) is fulfilled is determined in Steps S38 and S39. If this relation is fulfilled, the input data x is displayed and stored in the nonvolatile RAM 6 (Step S40). If the requirements corresponding to each of the aforementioned processes are not fulfilled, an alarm is delivered (Step S41), and the input data is not stored for setting. (c) Setting of injection-speed changing positions: As regards the setting of the injection-speed changing positions, the relation of the expression (5) must be fulfilled, as shown in Fig. 5. Thereupon, if the cursor is situated at the position TRP for transferring injection speed control to hold pressure control (Step S42), as shown in Fig. 12, whether the input data x is smaller than the value of the (N - 1)th injection-speed changing position IVN-1, between the (N - 1)th speed control stage and the final stage, and larger than the value of the end position Smin = 0 of the screw is determined. If these requirements are fulfilled, the input data x is displayed and stored in the non-volatile RAM 6, in the same manner as aforesaid (Steps S43 to 45). If the cursor is situated at an ith injection-speed changing position IVi (i = i to N - 1) (Step S46), the precedence of the changing position at which the cursor is situated is ascertained (Step S47). If the changing position concerned is the first position (IV1), whether the input data x is smaller than the value of the screw-back position SBK and larger than the value of the second changing position IV2 is determined in Steps S48 and S49. If these requirements are fulfilled, the input data x is displayed and stored in the nonvolatile RAM 6 (Step S54). If the cursor is situated at any of the second to (N - 2)th changing positions IV2 to IVN-2, whether the input data x is smaller than the value of the immediately preceding changing position IVi-1 and larger than the value of the next changing position IV + 1 is determined (Steps S50 and S51). If these requirements are fulfilled, the input data x is displayed and stored in the nonvolatile RAM 6 (Step S54). If the cursor is situated at the (N - 1)th changing position IVN-1 for switching to the final injection speed control stage, whether the input data x is smaller than the value of the preceding changing position IVN-2 and larger than the value of the transferring position TRP for hold pressure control is determined (Steps S52 and S53). If these requirements are fulfilled, the input data x is displayed and stored in the nonvolatile RAM 6 for setting, in the same manner as aforesaid (Step S54). If the cursor is situated in the screw-back position SBK (Step S55), whether the input data x is smaller than the value of the maximum screw stroke Smax of an injection mechanism, larger than the value of the first speed changing position IV1, and larger than the value of the changing position EXN-1 for the final metering stage related to the expression (6) is determined (Steps S56 to S58). If these requirements are fulfilled, the input data x is displayed and stored in the nonvolatile RAM 6 for setting. If the requirements in the aforementioned processes are not fulfilled, an alarm is delivered (Step S60), and the input data x is not stored for setting. (d) Setting of metering changing positions: For the setting of the metering changing positions, the relation of of Fig. 8 and the expression (6) must be fulfilled. In the process of this case, if the cursor is situated at a metering changing position EXi (i = 1 to N - 1) (Step S61), as shown in Fig. 13, the precedence of the changing position at which the cursor is situated is ascertained (Step S62). If the changing position concerned is the first changing position EX1, whether the input data x is smaller than the value of the next changing position EX2 and larger than the value of the screw end position Smin = 0 is determined (Steps S63 and S64). If these requirements are fulfilled, the input data x is displayed and stored in the nonvolatile RAM 6 for setting. If the cursor is situated at any of the second to (N - 2)th changing positions EX2 to EXN-2, whether the input data x is smaller than the value of the next changing position EXi +1 and larger than the value of the immediately preceding changing position EXi-1 is determined (Steps S65 and S66). If these requirements are fulfilled, the input data x is displayed and stored in the non-volatile RAM 6. If the cursor is situated at the (N - 1)th changing position EXN-1 for switching to the final metering stage, whether the input data x is smaller than the value of the screw-back position SBK and larger than the value of the immediately preceding changing position EXN-2 is determined (Step S68). If these requirements are fulfilled, the input data x is displayed and stored in the non-volatile RAM 6, in the same manner as aforesaid. If the cursor is situated at the screw-back position SBK (Step S70), whether the input data x is smaller than the value of the maximum stroke Smax of the screw, larger than the value of the changing position EXN-1 for switching to the final metering stage, and larger than the value of the first changing position IV1 for switching from the first injection speed control stage to the second injection speed control stage is determined (Steps S71 to S73). If these requirements are fulfilled, the input data x is displayed and stored in the non-volatile RAM 6 for setting. If the requirements in the aforementioned processes are not fulfilled by the input data x, an alarm is delivered, and the input data x is neither displayed nor stored in the nonvolatile RAM 6 for setting (Step S75). Thus inputted for setting, the set values for the molding conditions cannot be inputted by mistake. Thus, the injection-molding machine is prevented from suffering a wrong operation due to input errors.

Claims: An error detector for an injection-molding machine controlled by means of a numerical control unit (1), comprising input means (14) for inputting set values of various items of molding conditions; memory means (6) for storing the set values of the various items of said molding conditions; discrimination means (3) for determining whether input data on said various items, inputted by means of said input means (14), fulfill requirements related to said items; memory control means adapted to cause said memory means (6) to store said input data as set values of said items when said discrimination means (3) concludes that said requirements are fulfilled; and alarm means adapted to deliver an alarm when said discrimination means (3) concludes that said requirements are not fulfilled, characterised in that: said discrimination means (3) is adapted to compare with one another the sizes of the input data on each respective item, in order to determine whether said requirements related to said each respective item are fulfilled, and to conclude that said input data fulfill their said requirements when said sizes of the input data on each respective item are in predetermined relations in size with respect to one another. A set value error detector according to claim 1, wherein the items of said molding conditions include any of clamping conditions, ejecting conditions, injection-speed changing positions, and metering changing positions.

Inventors: NEKO NORIAKI, NEKO, NORIAKI
Applicants: FANUC LTD, FANUC LTD.
Application year: 1987
Main classification: B29C45
IPC codes: G05B19, B29C45