JP2639571B2 - Injection molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] <Industrial application field> The present invention relates to an injection channel (hereinafter referred to as a gate) such as a sprue, a runner or a gate for introducing a molten resin into a cavity of a mold in injection molding. The present invention relates to an injection molding method for cutting before the mold opening after filling the molten resin.

<Prior Art> A gate cutting related to an injection process will be described with reference to FIG. 3 as a conventional example of gate cutting. Reference numeral 1 denotes a screw, which is rotatably mounted in a heating cylinder 2 and is capable of moving back and forth within a predetermined distance. The material supplied from the hopper 3 is guided into the heating cylinder, and is heated by a heating device provided in the heating cylinder 2. The molten resin is measured as a molten resin in a space in front of the screw while being melted. Reference numeral 4 denotes an injection cylinder for moving the screw forward and backward, and reference numeral 5 denotes a driving device for driving the screw 1 to rotate. Injection cylinder 6
Is for causing the screw 1 to move forward (leftward in the figure) by applying hydraulic pressure to the injection-side oil chamber 4 to perform injection. Reference numeral 7 denotes a movable mold attached to a movable platen (not shown), which is in contact with a fixed mold 8 to form a cavity 9. Reference numeral 10 denotes a fixed bush, which is buried in the fixed die 8, and inside the fixed bush 10, a sprue 11 serving as a flow path of the molten resin is formed. Reference numeral 12 denotes a gate, which is a molten resin inflow port into the cavity 9 through the sprue 11 in the fixed bush 10. 13
A nozzle is provided at the tip of the heating cylinder 2 and is in close contact with the fixed bush 10 during injection to inject the molten resin into the cavity via the sprue 11. Reference numeral 14 denotes a gate cutting cylinder which is operated by pressure oil acting. A gate cutting rod 15 has a gate cutting cutter 16 attached to the tip thereof. Reference numeral 17 denotes a timer, in which an injection time is set. Reference numeral 18 denotes an electromagnetic switching valve for switching the operation of the gate cutting cylinder 14. Reference numeral 19 denotes a controller, which has a function of controlling the apparatus, controls a timer 17, and operates an electromagnetic switching valve 18.

Next, the operation will be described. The molten resin measured at the tip of the screw 1 is injected from the nozzle 13, is filled into the cavity from the gate 12 through the sprue 11, and is switched to the pressure-holding step. Excites the receiving electromagnetic switching valve 18 to the A position, and the gate cutting rod of the gate cutting cylinder 14
The gate 12 is cut by a cutter 16 attached to the tip of the rod by advancing 15 (forward in the figure).

<Problem to be Solved by the Invention> As described above, after the gate disconnection is switched to the pressure-holding step, the timer 17 times out a predetermined injection operation time by the time-out signal (injection completion signal).
At this time, the fluctuation state of the molten resin in the cavity, which is a molded product, depends on the stability of the injection molding machine during the filling process, and therefore the packing state of the resin in the mold is not always constant. Therefore, variations in the quality and weight of the molded product at this time are caused by the packing state of the molten resin in the cavity at the time of switching to the pressure-holding step and the accompanying fluctuation of the packing state in the cavity during the pressure-holding step. Where you are. As described above, even if the process is switched from the filling process to the pressure holding process at a predetermined timing during the molding operation, a stable molded product having uniform quality and weight is not always obtained.

SUMMARY OF THE INVENTION An object of the present invention is to provide an injection molding method capable of always obtaining a molded product of stable quality without being affected by the variation of the packing state in the cavity, in order to eliminate the above-mentioned disadvantages.

[Configuration of the invention]

<Means for Solving the Problems> In order to achieve the above-mentioned object, the present invention provides a sprue, runner or gate for introducing a molten resin into a cavity of a mold in injection molding after filling the cavity with the molten resin. In the injection molding method of forcibly cutting the injection flow path before opening the mold, the pressure of the molten resin in the cavity or the injection side oil pressure of the cylinder for injecting the resin is set to a preset value. The injection molding method is characterized in that the injection channel is cut after a sensor detects the signal, and after the detection signal is transmitted, the state of the set pressure in the reference range is maintained by a timer for a preset time by a timer.

<Operation> With this configuration, the gate disconnection timing can be set when the resin pressure in the cavity or the injection side oil pressure of the injection cylinder is kept constant after switching the holding pressure. It is possible to obtain a molded article with little fluctuation in the state and stable in quality and weight.

<Embodiment 1> An embodiment of the present invention will be described with reference to FIG. In the description, the same members as those of the conventional apparatus are denoted by the same reference numerals, and the description thereof will be omitted. The members used in the present embodiment will be described with the new numbers. Reference numeral 22 denotes a pressure sensor for detecting the pressure in the cavity 9. 23 indicates a timer and a pressure sensor
Reference numeral 22 designates a preset time from a detection signal for detecting the resin pressure set in a setting device (not shown) to a gate disconnection instruction. 25 indicates a controller,
Pressure sensor 22 and timer 23 that have the function of controlling the device
And the electromagnetic switching valve 18 is operated. Next, the operation will be described. After filling the molten resin and entering the pressure-holding step, the resin pressure of the molten resin in the cavity 9 is set at a preset value, that is, the inflow end of the molten resin after switching the pressure-holding reaches the end of the cavity and the packing state is appropriate. Is detected by the pressure sensor 22 to indicate that the pressure has reached the predetermined pressure through the controller 25, and the timer 23 is started to operate when the pressure reaches the set pressure. When it is held, the electromagnetic switching valve 18 is excited via the controller 25 by the time-out signal, the position is set to the A position, the gate cutting rod 15 of the cylinder 14 is advanced, and the gate 12 is moved by the cutter 16 provided at the rod tip. I cut it. In this way, the timing of gate disconnection
By keeping the molten resin pressure in the cavity constant after switching the holding pressure, it is possible to obtain a molded product with little variation in the packing state in the cavity.

<Embodiment 2> Next, the case of detecting the injection side oil pressure of the injection cylinder will be described with reference to FIG. In the description, the same members as those of the conventional apparatus will be denoted by the same reference numerals and description thereof will be omitted, and members used in the present embodiment will be described with new numbers. Reference numeral 32 denotes a pressure sensor that detects the pressure on the injection side oil chamber. Reference numeral 33 denotes a timer for setting a predetermined time from the detection by the pressure sensor 32 to the gate disconnection instruction. Reference numeral 35 denotes a controller, which has a function of controlling the apparatus, controls the pressure sensor 32 and the timer 33, and operates the electromagnetic switching valve 18. Next, the operation will be described. After entering the pressure holding process after filling the molten resin,
The injection pressure of the injection-side oil chamber 6 of the injection cylinder 4 is set to a preset value, that is, the injection-side hydraulic pressure side when the tip of the molten resin after the pressure-holding switching reaches the end of the cavity 9 and is in an appropriate packing state. When the set pressure of the reference range is held for a predetermined set time of about 0 to 1 second by a timer 33 which is started to operate when the set pressure is reached via the controller 35 and reaches the set pressure via the controller 35, The electromagnetic switching valve 18 was excited by the time-out signal via the controller 35, the gate cutting rod 15 of the cylinder 14 was advanced, and the gate 12 was cut by the cutter 16 provided at the tip of the rod. Taking the gate cutting timing in a state in which the injection side oil pressure of the injection cylinder after the pressure holding switching is constant in this manner corresponds to maintaining the molten resin pressure in the cavity 9 at that time in a constant state. It is possible to obtain a molded product with little change in state.

<Effect of the Invention> As described above, it is detected that the pressure of the molten resin in the cavity or the injection-side oil pressure at the time of injection of the cylinder for injecting the resin has reached a predetermined set value, and after a predetermined time elapses, the gate is operated. According to the present invention of performing cutting, the timing of gate cutting is set in a state in which the molten resin pressure in the cavity is constant, so that the influence of variation of the molten resin in the injection process can be eliminated, and the quality and weight of the molded product can be reduced. The dispersion was reduced, and the stability and yield in molding were improved.

[Brief description of the drawings]

FIG. 1 is an illustration of one embodiment of the present invention, showing a part of an example in which a gate is cut by detecting molten resin pressure in a cavity.
FIG. 2 is an explanatory view of another embodiment of the present invention, showing an example in which a gate is cut off by detecting an injection-side oil pressure. FIG. 3 is an explanatory view of a conventional example. 1 Screw 2 Heating cylinder 3 Hopper 4 Injection cylinder 5 Driving device 6 Injection side oil chamber 7 Movable mold 8 Fixed mold 9 ... cavity, 10 ... fixed bush, 11 ... sprue, 12 ... gate, 13 ... nozzle, 14 ... cylinder, 15 ... gate cutting rod, 16 ... cutter, 17, 23, 33 ... …timer,
18… Electromagnetic switching valve, 19,35 …… Controller, 22,32 ……
pressure sensor

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-63428 (JP, A) JP-A-58-122833 (JP, A)

Claims (1)

(57) [Claims] An injection molding method for filling a molten resin into a cavity of a mold in injection molding and forcibly cutting an injection flow path such as a sprue, a runner or a gate for guiding the molten resin into the cavity before opening the mold. In the method, the pressure sensor detects that the molten resin pressure in the cavity or the injection side oil pressure of the cylinder that injects the resin has reached a preset set value, and the detection signal is transmitted, and then the timer is used. An injection molding method, wherein the injection flow path is cut after maintaining a state of a set pressure in a reference range for a preset time.