JPH02169225A - Sensing method for completion of purging - Google Patents

Abstract

PURPOSE:To sense the completion of purging securely and automatically by sensing the quantity of residual resin from the scale of resin pressure generated by the degree of amount of residual resin in a cylinder and completing purging when the resin pressure becomes the given value or less. CONSTITUTION:When the set given time has passed, a CPU 114 for PMC reads out the current resin pressure sensed from RAM 108 by a pressure sensor 5. Resin remains in a cylinder 2 and resin extruded by the rotation of a screw 1 are stored at the end of a nozzle, and melting pressure of said resin is applied to the screw 1 and the pressure applied from the resin is sensed by the pressure sensor 5. When the sensed resin pressure is determined to be the set value or lower, an instruction for stopping screw rotation is output to a CPU 112 for NC by putting the CPU 114 for PMC through BAC 113 and RAM 105 used in common to stop the rotation. Purging is completed by said arrangement.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an injection molding machine, and in particular, to the completion of a purge process in which resin before remaining is removed from a resin mold F'1 by removing moss, etc. Regarding detection method.

Conventional technology When changing the resin material used in an injection molding machine, or when changing the color of the same type of resin C? ), it is necessary to perform a so-called purge process to discharge all the 84 fats from the previously used heating cylinder. Conventionally, this purge process is performed by closing the lower shutter of the hopper that supplies resin into the cylinder, and then emptying the cylinder so that all the material in the cylinder is pushed out.This emptying is performed a set number of times to complete the purge process. It is considered finished. Or, empty the house,
Purging is completed by visually confirming that no resin is discharged.

Problems to be Solved by the Invention In the method of recognizing the completion of purge by rKI by visual inspection by an operator, continuous unmanned molding including resin 4; IF4 change and color change cannot be reduced to (1). With the conventional method of completing the purge by performing an empty purge, it is not certain whether all the residual resin in the cylinder has been discharged, and when performing continuous unmanned molding, it is necessary to mold a certain number of shots after changing the resin. However, even if purging is performed a predetermined number of times, residual resin may or may not be detected efficiently depending on the resin scale, temperature setting, etc., and molded products may be defective. The number of good products increases and decreases, which is not efficient.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a purge end detection method that can automatically and reliably detect the end of purge.

Means for Solving the Problems The present invention advances the screw from the retracted position to the tip of the cylinder, performs a purge process to discharge the residual resin, rotates the screw for a predetermined distance, then detects the melting pressure of the resin. The above problem was solved by repeating this operation until the detected melting pressure became a predetermined value of 1n or more and detecting that the purge was completed when the detected melting pressure became a predetermined value or less.

Move the action screw forward from the retracted position to the tip of the cylinder to discharge the residual resin and purge '2! ll'f and then
When the screw is rotated, the resin remaining between the pitches of the screw is pushed forward. After rotating the screw for a predetermined period of time, the melt pressure of the resin is detected. The detection pressure increases as more resin is present. Furthermore, if the presence of resin decreases, the melting pressure will be low and the detected pressure will be low.

Therefore, when the purge process is repeated and the detected pressure of the resin melting locus becomes smaller than a predetermined set value, it is determined that the resin has been discharged and the purge process is completed.

As a result, for any type of resin, purge ends when the detected pressure becomes equal to or less than a predetermined value, so that the end of purge can be automatically and reliably detected.

Example An embodiment of the present invention will be described below.

FIG. 2 is a diagram showing an electric injection molding machine adopted in an embodiment of the present invention and the main parts of the control system of the injection molding machine, in which reference numeral 1 is a screw, reference numeral 21. is a heating cylinder, numeral 3 is a screw rotation mechanism that is driven by a screw rotation servo motor M2 and rotates the screw 1, and numeral 4 is a screw rotation mechanism that converts the rotational force of the injection servo motor M1 into linear motion and drives the screw 1 in the axial direction. This is an injection mechanism for injecting.

In addition, Pl is for injection ~ Homo-9M1! P2 is also a pulse coder that detects the screw rotation (rotation speed). Furthermore, a pressure sensor +j5 is installed in the injection mechanism 4 to detect the reaction force from the resin acting in the axial direction of the screw 1, and the pressure sensor 5 detects the melting pressure of the resin, etc. ing.

Also, the code 1001. i Numerical system that controls the injection molding machine O
I! (hereinafter referred to as the NC device), the NC device ff1
001. Microprocessor for tNc (hereinafter referred to as CPU)
) 112 and programmable machine controller (
The CPU i14 for the PMC (hereinafter referred to as PMC) is on the right, and the CPL1114 for the PMC has an RO that stores sequence programs etc. that control the sequence operations of the injection molding machine.
M1178 and PMCIII RAMI 10 are connected. The NC CPU 112 has a ROMI 1 that stores a management program that controls the injection molding machine as a whole.
5 and for injection.

A servo circuit is connected via a servo interface 111 to drive and control one nervomotor for each axis, such as one for clamping, for rotating a screwdriver, and for a rainbow I-actuator. In addition,
In Fig. 2, a servo motor M1 for injection and screw rotation is shown. Only M2 servo circuits 103a and 103b are shown. In addition, 105 is a non-volatile shared RAM composed of bubble memory or CMOS memory, and includes a memory section that stores NC programs, etc. that control each operation of the injection molding machine, and settings that store various setting values, parameters, and macro variables. It has a memory part. 113 is a bus arbiter controller (
(hereinafter referred to as BAC), and the BAC113 includes C for NC.
CPU i i for PU112 and PMC 4. shared RA
M105. Each bus of the input circuit 106 and output circuit 107 is connected, and the bus used by the B8C113 is υ]
l2Il. In addition, 118 is a CRT display device manual data input device (hereinafter referred to as CRT/MDI) connected to the BAC 113 via the operator panel controller 116, and various setting screens and work menus are displayed on the CR7 display screen. Display and various operations 4
By operating - (soft keys, numeric keys, etc.), you can input various setting data and select setting screens. In addition, 104 is NCJTiCP (Jl 1
The RAM is connected to the bus 2 and is used for temporary storage of data.

The servo circuits 103a and 103b each have an injection servo motor M1. It is connected to the screw rotation servo motor M2, and the output of the pulse coder Pi and P2 is connected to the servo circuit 10.
3a and 103b, respectively. Further, a torque limit value for reducing the output torque of the injection servo motor 2 by 1 lilJ is output from the output circuit 107 to the servo circuit 103a.

The setting memory section of the shared RAM 105 is loaded.

Various molding conditions such as holding pressure and metering are memorized as parameters.
The NC device 100 stores the NG information stored in the shared RAM 105.
Program and various molding conditions mentioned above, ROM117
The sequence program stored in the PMC
While the CρU 114 performs sequence control, the NC CPU 112 distributes pulses to the servo circuits of each axis of the injection molding machine via the servo interface 111, and the injection molding machine moves to υII! l].

Furthermore, in this embodiment, the output of the pressure sensor 5 that detects the reaction force of the resin pressure acting on the screw 1 is
Connected to the converter 101, the A/D converted resin pressure is sequentially stored in the pressure data RAM 108 every four non-bringing cycles.
is stored in the memory.

Since the configuration and injection molding operation of the injection molding machine described above are already known, their details will be omitted.

Next, the purging process and the purge completion detection method of this embodiment will be explained with reference to the flowchart shown in FIG.

When a purge command is input when changing the resin material or adding zero, the PMC CPU 14 writes the purge command to the shared RAM 104 via the B△C 113, and
When the PIJ 112 reads this purge command via the BAC: 113, it distributes pulses to the Ri-bo circuit 103a via the servo interface 111, drives the indexing servo motor, and moves the screw to the screw tip position. and stop at that position. As a result, cylinder 2
The resin inside will be discharged from the cylinder 2 (step Sl). CPU114 for PMC is CPtJ1 for NG
12 to 8AC113, both receive a positioning completion signal of the screw 1 to the cylinder tip position via the RAM 105, start a timer T set in the RAM 109, and issue a screw rotation command to 13Ac113.
TNCnlCPtJ 112 via shared RAM 105
The NC CPU 112 distributes pulses to the servo circuit 103b of the screw rotation servo motor M2 to rotate the screw 1 (step S2).

Then, when a predetermined time of 8p has elapsed and the timer T times up, the CPU 114 reads out the actual resin pressure PA detected by the pressure sensor IJ'5 from the RAM 108 (step S4). Resin remains in the cylinder 2, and the resin pushed out by the rotation of the screw 1 accumulates at the tip of the nozzle, and the melting pressure of the resin is applied to the screw 1. Sensors 4 and 5 detect and compare the resin pressure PA with the set value PM (Step S5). If the resin pressure PA is large, it means that there is still residual resin, so the PMC CPU 114 changes to the NC CPU 112. Outputs a predetermined amount of screw retraction command and
Step 12 moves the screw 1 backward by a predetermined amount (step S6).
). First, the PMC CPtJ 114 outputs a screw rotation stop command to cause the NC CPU 112 to stop driving the screw rotation servo motor M2. Then, the process from step 81 onwards is repeated again.

Thereafter, the processes of steps 81 to S7 are repeated, and when the detected resin pressure PA becomes equal to or less than the set value PM in step S5, v
If one position is applied, the PMC CPL1114 will be BACI 1.
3. A screw rotation stop command is output to the NC CPU 112 via the shared RAM 105, and the NC CPL II 1
2 stops the screw rotation (step S8). This completes the barge process.

As described above, the pressure sensor 5 detects the pressure applied from the resin to the screw, so if there is a large amount of residual resin, the detected pressure PA will become large, and as the residual resin decreases, the detected pressure PA will also become small. Since the purge is terminated when the detected pressure PA becomes equal to or less than the predetermined setting of 1i1NPM, the purge can be reliably detected regardless of the type of resin or the set temperature, and the purge can be automatically detected. .

Effects of the Invention The present invention detects the end of the purge based on the resin pressure generated depending on the size of the residual resin in the cylinder, and determines the end of the purge when the resin pressure falls below a predetermined value. The termination can be reliably and automatically detected. Therefore, continuous unmanned molding can be performed even in cases where purge processing is required, including resin replacement.

Moreover, unlike conventional methods, which complete purge after performing a predetermined number of purges, the end of purge is detected based on the pressure of the resin actually remaining in the cylinder, so the end of purge can be detected reliably, and defective products can be removed after replacing the resin. The number of will be smaller.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow diagram of an operation process according to an embodiment of the present invention, and FIG. 2 is a block diagram of essential parts of an injection molding method implementing the same embodiment. 1...Screw, 2...Heating cylinder, Ml...
- Injection servo motor, M2... Servo motor for screw rotation, 5... Pressure sensor, 100... Numerical system (11 devices (NC>).

Claims (1)

[Claims] The screw is advanced from the retracted position to the tip of the cylinder to perform a purge process to discharge residual resin, and after rotating the screw for a predetermined period of time, the melting pressure of the resin is detected, and the operation continues until the detected melting pressure falls below a predetermined value. A purge completion detection method in which purging is completed when the detected melt pressure falls below a predetermined value by repeating the above steps.