JP3240513B2 - How to set screw speed of injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an injection molding machine,
In particular, the present invention relates to an improvement in a method of setting the number of rotations of a screw in a heating cylinder in a measuring process.

[0002]

2. Description of the Related Art In recent years, instead of hydraulic actuators,
A so-called electric injection molding machine using a servomotor has begun to be widely used. Hereinafter, the operation of the injection device driven by the servo motor will be briefly described.

[0003] (1) By rotating the screw by a servomotor for screw rotation, a certain amount of resin is dropped from the hopper to the rear of the screw and fed to the tip of the heating cylinder while being melted (plasticizing / metering step). At this time, the screw moves backward while receiving the pressure (back pressure) of the molten resin accumulated at the tip of the heating cylinder.

[0004] An injection shaft is directly connected to the rear end of the screw, and the injection shaft is rotatably supported by a pressure plate via a bearing. This injection shaft is driven by an injection servomotor supported on the same pressure plate. The pressure plate moves forward and backward along the guide bar by a servomotor for injection via a ball screw. The back pressure of the molten resin is detected by a load cell and controlled in a closed loop as described later.

(2) Next, the pressure plate is advanced by driving the injection servomotor, and the molten resin is fed into the mold using the screw tip as a piston (filling step).

(3) At the end of the filling process, the molten resin fills the cavity of the mold, at which time the forward movement of the screw switches from speed control to pressure control.

(4) After the VP switching, the resin in the cavity of the mold cools under the set pressure (pressure keeping step). The resin pressure is controlled in a closed loop, as in the back pressure control described above.

In the injection apparatus, after the step (4),
Returning to the step (1), the next cycle is started. On the other hand, in the mold clamping device, in parallel with (1), after the mold is opened and the product cooled and solidified by the ejector mechanism is taken out, the mold is closed and the process of (2) is started.

Next, with reference to FIG. 2, an injection molding machine for converting the rotational motion of a servo motor into a linear motion by a ball screw and a nut and filling the molten resin will be described. In FIG. 2, the rotation of the injection servomotor 10 is transmitted to a ball screw 12. A nut 13 that moves forward and backward by the rotation of the ball screw 12 is fixed to a pressure plate 14, and the pressure plate 14 is movably mounted on guide bars 15, 16 fixed to a frame (not shown). The forward and backward movement of the pressure plate 14 is transmitted to the screw 20 via the bearing 17, the load cell 18, and the injection shaft 26. The screw 20 is rotated by the rotation of the injection shaft 26 by a screw rotation servomotor (not shown).

As the screw 20 advances while rotating in the heating cylinder 21, the molten resin stored in the plasticizing / metering process is filled in a mold, and molding is performed by applying pressure. At this time, the force pressing the resin is detected as a reaction force by the load cell 18, amplified by the load cell amplifier 12, and input to the controller 25.
A position detector 19 for detecting the amount of movement of the screw 20 is attached to the pressure plate 14.
This detection signal is amplified by the amplifier 23 and input to the controller 25. The controller 25 outputs a command corresponding to each process to the servo amplifier 24 according to the setting of the operator, and the servo amplifier 24
And the servo motor 10 is controlled by controlling the drive current of the servo motor 10.

The configuration shown in FIG. 2 is merely for convenience of explanation, and the specific configuration of the injection device is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-174626.

Next, the screw 20 will be described in detail with reference to FIG. In FIG. 3A, the screw 2
0 indicates the supply unit 20-1, the compression unit 20-2, and the measurement unit 20-
3, the head unit 20-4. Supply unit 20-1
Is a portion for feeding the resin supplied from the hopper as solid or melting only part of the resin and sending it forward. During this time, the resin is heated to near the melting point. For this reason, in the supply unit 20-1, the diameter of the bar-shaped body forming the spiral body shown in FIG. 3B is generally constant.

In the compression section 20-2, there is a gap between the resin particles supplied from the supply section 20-1, and the volume of the compression section 20-2 is reduced to about half by melting the resin.
To compensate for this volume reduction, the space through which the resin can pass is reduced. This is realized by providing a taper to the rod-shaped body forming the spiral body in the compression unit 20-2 to make the groove of the spiral body shallow. This serves to compress the molten resin, enhance the heat generation effect by friction, increase the resin pressure, and push the moisture / volatile gas contained in the air / resin back to the hopper side. As is apparent from this, the resin pressure in the heating cylinder is reduced by
-2 is the highest.

The metering section 20-3 is the shallow portion of the groove of the spiral body, during which the resin is subjected to a large shearing force and is heated to a uniform temperature with self-heating. Then, it acts to send out a certain amount of resin to the nozzle side.

The feeding of the molten resin from the measuring section 20-3 to the nozzle side is performed through a backflow prevention ring 20-5 in the head section 20-4. Backflow prevention ring 2
In the measuring step, 0-5 is located on the left side in the drawing, and in this state, the molten resin can be sent from the measuring section 20-3 to the nozzle side. When the weighing process is completed, the backflow prevention ring 20-5 moves to the right side position in the figure due to the pressure difference. As a result, the measuring unit 20-
The return of the resin to the third side is prevented.

Next, the setting of the number of rotations of the screw in the measuring step will be described with reference to FIG. FIG. 4 shows an example of setting the screw back pressure and the screw rotation speed in four stages. Of the four stages, the former three stages are generally used to equalize the resin temperature, and the resin in the first half of the heating cylinder, which has a longer residence time for the resin and a higher temperature, has a relatively faster screw rotation speed and lower height. The resin is weighed by a combination of pressures, and as the weighing progresses, the residence time of the resin is prolonged, and the rotational speed is gradually decreased to increase the shear heat generation of the resin, and conversely, the back pressure is increased. 4
In the last stage of the stage, settings for improving the accuracy of the weighing value serving as the starting point of the filling process are performed. That is, measurement completion 2-3
An ultra-low speed rotation to prevent overrun of the screw rotation and an ultra-low back pressure to prevent resin backflow are set before mm.

[0017]

As is apparent from the above description, the screw speed setting up to now in the metering process can be performed in a large number in accordance with the screw stroke, that is, the screw position, in consideration of the residence time of the resin. The setting operation of the numerical value of is required. Moreover, this setting must be changed even when the diameter of the screw is changed, which is troublesome.

It is an object of the present invention to provide a screw rotation speed setting method which can easily perform a screw rotation speed setting operation in a measuring step.

[0019]

According to the present invention, there is provided an injection device including a driving source for screw rotation and a driving source for injection driving an injection shaft, and the injection device detects the position of the screw. An injection molding machine provided with a controller for controlling the driving source for screw rotation in accordance with the detected value, the number of rotations of the screw in the measuring process, Ns at the start of the measuring process At the end, the controller sets Ne as Ne, and the controller weighs the set rotation speeds Ns and Ne.
Screw position Ss at the start of the process and screw position at the end
From the start to the end of the weighing process.
A method of setting a screw rotation speed of an injection molding machine, wherein the rotation speed of the screw is complemented by the detection value .

The above-mentioned complementation is performed, for example, at the current screw position.
Therefore, linear interpolation is performed .

The screw position Ss at the start of the measuring step is a position at which the screw rotation speed reaches the set rotation speed Ns.

Further, the controller sets the rotational speed of the screw to Ns up to a position corresponding to a predetermined ratio between the screw position Ss at the start of the weighing process and the screw position Se at the end of the measuring process. for between a position corresponding to the determined ratios and the screw position Se, using said the rotational speed Ns and Ne and the intermediate position and the screw position Se, complement the rotational speed of the screw by the detection value Kan You may do it.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. Here, a case will be described in which the screw rotation speed setting according to the present embodiment is applied to the electric injection device described with reference to FIG. Therefore, the following description is also made with reference to FIG.

The rotation speed setting operation in the present embodiment only requires the operator to set the screw rotation speed Ns at the start of the weighing process and the screw rotation speed Ne at the end of the weighing process in the controller 25.

The controller 25, a screw rotation speed from the beginning to the end of the metering process is controlled by complement by the detection value from the position detector 19 and the rotational speed Ns and Ne is set. Specifically, the controller 25 uses the set rotation speeds Ns and Ne, the screw position Ss at the start of the weighing process, and the screw position Se at the end, as shown by the solid line in FIG. detected value the number of revolutions of the screw to the end, that is, linear complement by the current screw position. The screw position S at the start of the weighing process
s is a position where the screw rotation speed has reached the set rotation speed Ns.

In the case of Figure 1, when the current screw position with X, screw rotation speed Y is complement it is calculated by the following equation.

Y = Ne + {(Ns−Ne) / (Se−Ss)} · (Se−X) As shown by a broken line in FIG.
The rotational speed of the screw is set to Ns up to a position (Ss + Se) / 2 (an intermediate position of 1/2 in the embodiment) between the screw position Ss at the start of the weighing process and the screw position Se at the end, and thereafter, interpolation The rotation speed control may be performed. In this case, the controller 25 sets the rotation speeds Ns and Ne, the intermediate position (Ss + Se) / 2, and the screw position S between the intermediate position and the screw position Se, as described above.
by using the e, a linear complements rotational speed of the screw by the current screw position. Note that the range of the rotation speed Ns is not limited to the halfway intermediate position, but may be a position corresponding to a predetermined ratio.

As described above, in the present embodiment, the setting of the number of revolutions of the screw in the measuring step may be set for two values at the start and end of the measurement, and the setting operation and the setting change operation are very simple. .

In the above embodiment, the case of an electric injection molding machine has been described. However, it goes without saying that the present invention can be applied to a hydraulic injection molding machine.

[0030]

According to the present invention, the setting of the number of revolutions of the screw in the weighing process can be performed simply by inputting two values, thereby greatly simplifying the setting operation by the operator. The work at the time of the change can be easily performed.

[Brief description of the drawings]

FIG. 1 is a view for explaining an embodiment in a case where a screw rotation speed setting during a measuring step according to the present invention is applied to an electric injection molding machine.

FIG. 2 is a diagram schematically showing a configuration of an injection device in an electric injection molding machine to which the present invention is applied.

FIG. 3 is a view for explaining a structure of a screw in the electric injection molding machine.

FIG. 4 is a view for explaining an example of a screw rotation speed setting in a measuring step in a conventional electric injection molding machine.

[Explanation of symbols]

 Reference Signs List 10 Servo motor for injection 12 Ball screw 13 Nut 14 Pressure plate 15, 16 Guide bar 17 Bearing 18 Load cell 19 Position detector 20 Screw 21 Heating cylinder

Claims (4)

(57) [Claims] 1. An injection device comprising a driving source for screw rotation and a driving source for injection for driving an injection shaft, wherein the injection device is provided with a position detector for detecting a position of the screw. In an injection molding machine provided with a controller that controls a drive source for screw rotation according to a detected value, the number of rotations of the screw in a measuring process is set to Ns at the start of the measuring process and Ne at the end of the measuring process. The controller controls the set rotation speeds Ns and Ne.
And screw position Ss at the start of measuring process and screw at the end
From the start position Se to the end of the weighing process until the end.
A screw rotation speed setting method for an injection molding machine, wherein the screw rotation speed is complemented by the detected value . 2. The screw rotation speed setting method according to claim 1, wherein the screw position Ss at the start of the measuring step is:
When the screw rotation speed reaches the set rotation speed Ns
Screw rotation speed setting process of the injection molding machine, which is a location. 3. The screw rotation speed setting method according to claim 1 , wherein the complement is a straight line depending on a current screw position.
A screw rotation speed setting method for an injection molding machine, characterized by complementing . 4. The screw rotation speed setting method according to claim 1, wherein the controller adjusts the screw position to a position corresponding to a predetermined ratio between the screw position Ss at the start of the weighing process and the screw position Se at the end. The rotation speed of the screw is Ns, and between the position corresponding to the predetermined ratio and the screw position Se, using the rotation speeds Ns and Ne, the intermediate position, and the screw position Se, screw rotation speed setting process of the injection molding machine, characterized in that supplements the rotational speed of the screw by the detection value.