JPS61229521A - Monitoring of injection process - Google Patents

Abstract

PURPOSE:To decide whether a molded product is acceptable by a method wherein a molten resin temperature in a molding cycle is detected continuously by the position of a screw or a plunger during filling process and a pressure keeping time during pressure keeping process, in order to compare a difference between a corresponding value on a reference temperature curve. CONSTITUTION:In an injection molding machine 11, an operation and comparison unit 8 compares a temperature (a), detected one of temperature sensors attached to a cylinder head 12, a nozzle 13 and the cavity 14 of a mold, with the preset temperature curve (c) in the case of molding a good product to monitor whether the temperature is within a preset allowable value DELTAT or not by the position (s) of the screw 17 during filling process and the pressure keeping time (t) during the pressure keeping process. The result of comparison can be fed back to the heating control unit 19 of the molding machine or outputted as the signals 20, 21 or the like which indicates the quality 24 of the product, operating or stopping 20 of the molding machine or the alarm 21. The result may also be outputted to a CRT 22 or a printer 23.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] ``The present invention relates to a method for monitoring the quality of a molded product produced by an injection molding machine. The present invention relates to an injection process monitoring method for determining the quality of products.

[Prior art and its drawbacks]

Traditionally, the quality of molded products has been determined by checking the amount of adhesive, adhesive, filling time, etc. in injection molding machines.
There is a way to check the weighing time, etc. However, these methods can only detect data from one point in one point.

There is also a method of continuously monitoring the cavity internal pressure and injection pressure during one shot, but the pressure inside the mold and the pressure in the injection cylinder are also determined by the viscosity of the plasticized resin and the surface temperature of the mold in which it is filled. When a fluctuation is detected, it is unclear whether the cause is due to the viscosity mentioned above or the surface temperature of the mold. Therefore, it was not possible to decide which one to correct.

Furthermore, there is a method of continuously monitoring the resin pressure and resin temperature based on the time from the start to the completion of the injection process, but if time is used, the set time will elapse regardless of the state of the molten resin. The molten state of the resin is unknown.

[Purpose of the invention]

The present invention provides the following advantages when determining the quality of conventional molded products:
It is an object of the present invention to provide an injection process monitoring method that eliminates the above-mentioned drawbacks and makes it possible to judge the quality of a molded product by monitoring the injection process.

[Key points of the invention]

In order to achieve the above-mentioned purpose, the injection process is divided into a filling process in which the molten resin is filled into the mold, and a contraction caused by cooling and assimilation of the molten resin filled in the mold throughout the entire injection process during one shot. During the filling process, the resin temperature is continuously varied depending on the position of the screw or plunger, and during the pressure holding process, depending on the time from the start of holding pressure to the completion of holding pressure. The temperature of the molten resin in the subsequent molding cycle is continuously detected by the position of the screw or plunger during the filling process, and by the holding time during the pressure holding process, and the temperature is measured on the reference temperature curve. An injection process monitoring method in an injection molding machine, characterized in that the deviation from a corresponding value is compared, and it is determined whether the deviation exceeds a predetermined tolerance value, and the quality of the molded product is determined. Temperature detection of the molten resin is carried out to the nozzle or cylinder of the injection molding machine, or inside the mold cavity, and the reference curve is also measured during the filling process depending on the position of the screw or plunger, and during the pressure holding process depending on the pressure holding time. This is an injection process monitoring method that can also be used as an average temperature curve of resin temperatures detected twice.

〔Example〕

Next, one embodiment of the present invention will be described with reference to FIGS. 1 and 2. Reference numeral 11 is an injection molding machine, and resin temperature detection sensors are attached to the cylinder, the door 12, the nozzle 13, and the mold cavity 14. It is being Reference numeral 15 denotes a changeover switch for switching the sensors 12 to 14. 16 is a position detection device that detects the position of the screw 17.

Reference numeral 18 denotes an arithmetic comparator which is connected to the sensor 1 as shown in FIG.
The temperature a detected by one of the units 2 to 14 is compared with a preset temperature curve C during molding of a good product, and during the filling process, the position S of the screw 17 is determined, and during the pressure holding process, the holding pressure time 1 is set. The system monitors whether or not JT is within a preset tolerance value, and feeds the results to the heating control section 19 of the molding machine, and determines whether the molded product is good or not.
It is possible to stop the operation of the molding machine and issue signals 20, 21 such as alarms. The results can also be output to the CRT 2.2 or printer 23 as shown in FIG.

[Effect]

With the configuration described above, changes in resin temperature during the injection process can be observed, so changes can be made at the screw or plunger position during filling, and at what time during the pressure holding process. Prove. For example, if a sink mark appears on a molded product, the resin temperature will change during pressure holding, and if there is gas entrainment during the measurement process before the filling process, the filling process will begin and the resin temperature will change during the pressure holding process. An increase in finger temperature is observed.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the present invention. FIG. 2 is a diagram showing an example of displaying continuous resin temperature in the injection process according to the present invention.

Claims (5)

[Claims] (1) The injection process in an injection molding machine is divided into a filling process in which the mold is filled with molten resin, and a pressure holding process to compensate for the shrinkage caused by the cooling and solidification of the molten resin filled in the mold during the filling process. During the pressure holding process, the resin temperature during molding of a good product is continuously sampled at multiple points depending on the position of the screw or plunger and the time from the start of pressure holding to the completion of pressure holding is used as a reference temperature curve. The temperature is continuously detected by the screw or plunger position during the filling process and by the pressure holding time during the pressure holding process, and the deviation from the corresponding value on the reference temperature curve is compared, and the deviation is determined to be within the predetermined tolerance. A method for monitoring an injection process in an injection molding machine, characterized by determining whether a value exceeds a value and determining whether a molded product is good or bad. (2) The injection process monitoring method according to claim 1, wherein the temperature of the molten resin is detected by a temperature sensor attached to a nozzle of an injection molding machine. (3) The injection process monitoring method according to claim 1, wherein the temperature of the molten resin is detected by a temperature sensor attached to a cylinder head of an injection molding machine. (4) The injection process monitoring method according to claim 1, wherein the temperature of the molten resin is detected within a mold cavity. (5) The reference temperature curve is an average temperature curve of resin temperatures detected multiple times depending on the position of the screw or plunger during the filling process and based on the pressure holding time during pressure holding. The injection process monitoring method according to items 1 to 4.