SYSTEM FOR MONITORING THE POSITION OF THE CLOSING UNIT OF AN INJECTION MOLDING MACHINE

Abstract

The invention relates to a system for monitoring the position of the closing unit of an injection-molding machine, by bypassing a light curtain that serves to secure the closing unit and the tool area of the injection-molding machine, wherein the injection-molding machine has at least one molding tool that consists of at least two parts, which tool encloses at least one mold cavity, wherein the injection-molding machine has a programmable logic controller (PLC) for controlling the movement monitoring module (MOC) for indirect position monitoring of the closing unit and of the position of the molding tool parts relative to one another, wherein distance measuring sticks are provided as sensors, the signals of which are processed in the PLC via the MOC, wherein the tool parts must maintain a spacing gap, relative to one another, after the closing pressure has been built up and the mold has been filled, during the subsequent bumping step, which gap has a specific maximal value assigned to it, with the injection-molding machine shutting off if this value is exceeded.

Claims

1. System for monitoring the position of the closing unit of an injection-molding machine (1), by bypassing a light curtain that serves to secure the closing unit and the tool area of the injection-molding machine (1), wherein the injection-molding machine (1) has at least one molding tool (4, 5, 6) that comprises at least two parts, which tool encloses at least one mold cavity, wherein the injection-molding machine (1) has a programmable logic controller (PLC) for controlling the production sequence in the machine, and the movement sequences during closing and opening of the molding tool (4, 5, 6) are detected by sensors (10, 12, 13), and the sensor signals are processed in the PLC, wherein the PLC has a movement-monitoring unit (MOC) for indirect position monitoring of the closing unit and of the position of the molding tool parts (4, 5, 6) relative to one another, wherein distance measuring sticks (10, 12, 13) are provided as sensors, the signals of which are processed in the PLC via the MOC, wherein one of the distance measuring sticks (10) is responsible for monitoring the closing movement of the tool (4, 5, 6) (distance measurement at 0 mm), and two further measurement sticks (12, 13) are responsible for determining the position of the tool parts (4, 5, 6), wherein the tool parts (4, 6) must maintain a spacing gap (16), relative to one another, after the closing pressure has been built up and the mold has been filled, during the subsequent bumping step, which gap has a specific maximal value assigned to it, with the injection-molding machine (1) shutting off if this value is exceeded.

2. System according to claim 1, wherein the movement sequence of the injection-molding machine (1) comprises the following steps: a.) the closing unit closes the mold tool (4, 5, 6) and the MOC recognizes the standstill; b.) the standstill monitoring is turned on by way of the speed monitoring in the MOC module; c.) the MOC module monitors a standstill position window of +/1-3 mm; d.) if the mold tool (4, 5, 6) remains within this +/1-3 mm window, the MOC module recognizes a standstill and the light curtain can be bypassed.

3. System according to claim 1, wherein a memory module is set at the start of monitoring, which module is reset as soon as the standstill signal drops.

4. System according to claim 1, wherein the MOC module has a separate logic editor, which communicates with the PLC by way of a fixed interface, and furthermore has two hardware inputs for the measuring sticks (10, 12, 13) that serve as position sensors.

5. System according to claim 5, wherein the hardware inputs are provided with interfaces that can be selected from the group: TTL, HTL, Incremental RS-422, SIN/COS, SSI.

6. System according to claim 1, comprising a program for monitoring the standstill position window, which is composed of two modules, wherein the first module compares the two speed signals of the hardware inputs of the MOC module and emits a reliable speed signal, which is applied to a speed monitoring module, which receives a release signal in addition to the speed signal, which release signal turns the monitoring on/off and is configured, in this regard, in such a manner that it detects the relative position change when monitoring is activated, and checks whether it remains within a window of +/1-3 mm, wherein the monitoring release presumes that the mold tool (4, 5, 6) is closed and the closing pressure has been built up, wherein these signals are monitored by way of the switch evaluation module, in terms of their signal sequence.

7. System according to claim 6, wherein the position has been reached signal is logic 1 during the entire process.

8. System according to claim 1, wherein a pressure switch monitors the closing pressure of the machine (1).

Description

[0025] These show:

[0026] FIG. 1: in a perspective representation, a vertically operating injection-molding machine;

[0027] FIG. 2: detail enlargement C from FIG. 1;

[0028] FIG. 3: placement of the distance measuring sticks on the injection-molding machine according to FIG. 1 in a side view.

[0029] A vertically operating injection-molding machine is shown in FIG. 1 and provided, in general, with the reference symbol 1. It consists of a machine bed 2 and columns 3 that rise perpendicularly from the machine bed 2, on which columns the mold tool that consists of upper plate 4, lower plate 5, and center plate 6, which plates are disposed on a lower and an upper mold clamping plate 7 and 8, can be brought into the closing or opening position. The pressure-medium cylinder 9, which builds up the closing pressure in the closing position of the mold tool 4 to 6, is moved out of the machine in the representation.

[0030] A first distance measuring stick, which monitors the closing position of the molding tool before the injection-molding process, in interaction with the magnet 11, is indicated with the reference symbol 10.

[0031] Two further distance measuring sticks 12 and 13, in interaction with the magnets 14 and 15, serve to monitor the positions of the upper/center plate 5, 6 relative to the lower plate 4, and, in this function, serve to monitor the gap width of a gap 16 between lower and center/upper plate that is required during the bumping sequence (degassing of the molded part).

[0032] The signals of the distance measuring sticks 10, 12, 13 are passed on to the machine controller, which is not shown in any detail, as has been described in detail above.