JP3105282B2 - Method of setting origin of mold clamping device of injection molding machine and method of controlling mold clamping device of injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for controlling a mold clamping device of an injection molding machine and a method for setting the origin of a position scale therefor.

[0002]

2. Description of the Related Art Mold clamping in an injection molding machine is generally performed by a mold clamping ram mechanism which is a hydraulic piston mechanism. Such a ram mechanism often has a structure having a main ram and a boost ram for improving the moving speed thereof. Such a hydraulic type has a feature that a high-pressure (high horsepower) and high-speed mold clamping operation is possible, but also has a disadvantage that fine position control characteristics cannot be obtained. In particular, the accuracy of the speed switching position is not sufficient,
There is a problem that a large impact is likely to occur at the moment when the mating surface of the mold is closed, and in extreme cases, the mold may be damaged.
For this reason, a highly accurate AC
It is considered to be performed by a servomotor.

[0003]

However, when clamping a large injection molding machine by driving only an AC servomotor, the servomotor has a mold opening / closing speed of 40-50 m / min. Various characteristics such as sufficient mold clamping force and rapid start-up of the mold opening / closing operation are required. In order to satisfy these required characteristics, a servo motor having a very high rating and excellent performance is required. Further, since such a servomotor is expensive, there is a problem that the price of the injection molding machine is increased. In particular, there is no appropriate means in the case where it is necessary to temporarily stop during high-speed operation.
In accurate mold clamping control, it is necessary to accurately recognize the position of a member that moves for mold clamping and to set an accurate origin, but many dies are used for the same injection molding machine. Even though the thickness is different, the thickness of the mold is usually different, and there is a problem that setting the origin of the scale is not always easy.

Accordingly, an object of the present invention is to provide a method of setting the origin of a mold clamping device of an injection molding machine, which can easily and accurately set the origin of a scale position for mold clamping control.

Another object of the present invention is to provide a method for controlling a mold clamping device of an injection molding machine, which has high accuracy and low cost while having necessary mold clamping characteristics.

According to the present invention, a hydraulic drive unit that presses and drives a movable base, and a servo that is fixed to the movable base and moves to close a mold used for injection molding via a moving mechanism and a movable plate by rotation of the hydraulic drive unit. Injection molding comprising a motor and a position scale for detecting the position of the movable base, wherein high-speed movement is performed by the hydraulic drive unit, and low-speed movement immediately before mold clamping and pressure increase during mold clamping are performed by the servomotor. In a method of setting an origin relative to a relative position of the movable base and the movable plate in a mold clamping device of a machine, the movable base is moved at a high speed by the hydraulic drive unit while the movable plate and the movable base are in close contact with each other. A step of moving forward until the value of the seat position scale does not change due to the low-speed movement by the servomotor; A step of fixing the hydraulic drive unit, driving the servomotor to advance the movable platen to increase the pressure, and a step of obtaining an encoder value (Sx) of the servomotor when the mold clamping pressure reaches a set value. The difference (Sc− | Sx |) between the final value (Sc) of the position scale and the absolute value of the encoder value (Sx) of the servomotor when the mold clamping pressure reaches a set value is calculated as the origin of the position scale. The method of setting the origin of the mold clamping device of the injection molding machine, comprising the steps of:

Further, according to the present invention, a hydraulic drive unit for pressing and driving a movable base and a hydraulic drive unit fixed to the movable base and moved to close a mold used for injection molding via a moving mechanism and a movable plate by the rotation thereof. A servomotor to be moved, and a position scale for detecting the position of the movable base, wherein the hydraulic drive unit performs high-speed movement, and the servomotor performs low-speed movement immediately before mold clamping and a pressure increase during mold clamping. A method for controlling a mold clamping device of an injection molding machine, comprising:
The position scale of the movable base with respect to the entire stroke with reference to the origin obtained by the above is detected by the position scale, and the detection of the relative position (Sx) between the movable base and the movable plate with reference to the origin is determined. This is performed by an encoder attached to the servomotor, the movable platen is separated from the movable base by a predetermined distance in advance, and the movable platen is set by the set command value (Sc). The deviation (Su-S) from the position (Su)
A method for controlling a mold clamping device of an injection molding machine, wherein the position (Sx) of the movable platen is controlled to be moved by the servomotor using c) as a control amount.

[0008]

According to the method for setting the origin of the mold clamping device of the injection molding machine according to the present invention, the mold clamping ram and the AC servomotor which are the hydraulic drive units are both provided, and the movable platen and the movable base are closed. By setting the origin of the position scale to the difference between the position scale value when it is brought into close contact with the encoder and the encoder value of the servo motor when the movable plate is driven and the pressure value rises to the set value, the position scale can be easily adjusted. It is possible to set the origin of the scale.

According to the method of controlling a mold clamping device of an injection molding machine according to the present invention, high-speed movement is performed by a mold clamping ram, which is a hydraulic drive unit, and low-speed speed control is performed by an AC servomotor using the above-mentioned origin. Pressure control is performed. Position detection for the entire stroke is performed by a position scale attached to the movable base, and the relative position between the movable base and the movable board is detected by an encoder signal of an AC servomotor. The movable platen is separated from the movable base by a predetermined distance in advance, and the position of the movable platen is controlled using the encoder signal of the AC servomotor so that the deviation between the current value of the movable base and the command value becomes zero. This enables high-precision position control over an arbitrary short distance.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a partial sectional view showing a mold clamping mechanism of an injection molding machine to which the present invention is applied. This mold clamping mechanism is a tie bar 11
It has a sliding shaft called. The movable platen base 12 and the main movable platen 13 are engaged with the sliding shaft by through holes 12a and 13a provided in the movable platen base 12 and the main movable platen 13, and are slidable with respect to the tie bar 11. The movable platen base 12 is connected to the mold clamping ram 14 by a connecting member 15. The speed control of the mold clamping ram is performed by a control device (not shown).

At the center of the movable platen base 12, a bearing 16 and a substantially cylindrical rotating member 17 having a flange portion which engages with the bearing are provided, and these are attached to the movable platen base 12 by bolts 20. The rotating member 17 is held so as to be freely rotatable by a fixed lid 19 and a bearing retainer 18 provided in contact with the inner surface thereof. A concave portion is formed on a surface of the lid body 19 that is in contact with the bearing retainer 18, and a pressure sensor 21 such as a load cell is attached to the concave portion. Has been given. A screw is cut inside a through hole provided at the center of the rotating member 17, and a first gear 22 is provided with a bolt 2 on the end surface of the rotating member 17 on the side of the mold clamping ram.
3 is fixed.

On the other hand, an AC servo motor 26 is fixed to the lower surface of the movable platen base.
A pinion 25 is attached to the rotation shaft 6, and a second gear 24 that engages with the pinion 25 is provided between the pinion 25 and the first gear 22. These gears 22, 2
4, 25 are such that their central axes are on the same straight line,
It is rotatably mounted on an arm (not shown). Note that the AC servomotor used here is 1/6 to 1 / compared to the case where all are driven by the AC servomotor.
A rating of 2 is sufficient. The AC servomotor has a built-in encoder for detecting rotation, and its output is given to a control device (not shown), whereby speed control and torque control are performed. A shaft 27 whose surface is threaded is fixed to the center of the main movable platen 13, and this screw forms a ball screw together with the screw provided in the through hole of the rotating member 17 described above. The movable base 12 is provided with a scale 30 for detecting its position.

By adopting such a structure, A
When the C servo motor 26 is driven, the pinion 25, the second
Gear 24 and the first gear 22 in this order, and the rotating member 1
7 rotates around the shaft 27. As a result,
The main movable platen 13 is moved relatively to the movable platen base 12. The main movable platen 13 is connected to a part of a mold (not shown).
When the mold is opened and closed and a force is applied to the main movable platen 13, pressure is applied to the mold.

In order to control the mold clamping device having the above structure, the position of the movable platen base 12 is detected by the scale 30, and the relative position of the main movable platen 13 with respect to the movable platen base 12 is determined by the encoder signal of the AC servomotor 26. Is detected by The scale 30 has a scale value 0 at the origin before driving the mold clamping ram, and takes a scale value Sc to the left as a position detection value for all strokes in FIG. Also, the coordinates of the main movable platen 13 are set to the origin 0 when the movable platen base 12 and the main movable platen 13 are brought into close contact as described later, and the encoder output is set to the origin 0. Takes a negative scale value Sx in the opening direction. That is, the scale value Sx represents the relative position between the main movable platen 13 and the movable platen base 12.

The control operation in such a configuration will be described with reference to FIG. At the start of mold clamping, the movable platen base 12 and the main movable platen 13 are opened about 5 mm in advance (step S101). Therefore, Sx = −5 mm. In this state, the mold clamping ram and the servomotor are driven so that the movable platen base 12 matches the set command value Su (step S102). At this time, if the value Sc obtained by the scale 30 with respect to the set command value has a deviation of δ (step S103), the AC servomotor 26 is driven to reduce this deviation (step S103). Step S104). That is, the position (Sx) of the main movable platen 13 is controlled by the AC servomotor using (Su-Sc) as a control amount. Therefore, the movement amount of the servomotor is originally the sum of 5 mm where the main movable platen is separated from the movable platen base and a dimensional error of a mold or the like. By doing so, the position control is performed by highly accurate local position control by the AC servomotor. Such position control is particularly effective when stopping during high-speed operation.

Next, the control relationship between the mold clamping ram and the AC servomotor in the mold clamping device will be described. First, at the time of mold clamping, the movable platen base 1 is controlled by controlling the speed of the mold clamping ram 14 and the boost by hydraulic pressure as shown in FIG.
2 and the main movable platen 13 are moved to the position of LS2A. This position is slightly before the limit of forward movement during mold clamping.

In this position, the movable platen base 12 is fixed,
The AC servomotor 26 is immediately driven to rotate. Thereby, the gear mechanisms 22, 24, 25 and the ball screw mechanism 1
The main movable platen 13 is moved by the speed control 7 and 22 to the position of the forward limit LS2 while being speed-controlled. The main movable platen 13
After passing the position of LS2A, the position change detected by the encoder of the AC servomotor is smaller than a predetermined value, that is, the vehicle does not move forward, and the pressure detection value by the load cell 21 is reduced as shown in FIG. When the pressure rises and reaches a predetermined switching pressure value, after confirming that the main movable platen 13 has reached the forward limit position LS2, a switching signal for switching to pressure control is generated to perform a boosting operation. This pressure control is performed by feeding back the detection output of the load cell 21.

On the other hand, when the mold is opened, the pressure is reduced by feedback-controlling the AC servomotor 26 using the detection output of the load cell 21 so that the pressure curve in FIG. After a sufficient decrease in the speed is confirmed, the flow shifts to speed control by the AC servomotor 26. As a result, after the main movable platen 13 reaches the high-speed mold release start position LS3A, which is a position sufficiently distant from the forward limit, the mold clamping ram 14 and the boost are released at a high speed by controlling the speed by hydraulic pressure. By performing such control, high-speed and high-pressure movement by hydraulic pressure and high-precision mold clamping by an AC servomotor are possible.

In the above control, the movable platen base 12
When the main movable platen 13 is brought into close contact with the main movable platen 13, the origin is set to 0, and this position is also the forward limit position of the mold. Therefore, this origin setting is extremely important. Even though many dies are used for the same injection molding machine, the thickness of the dies is usually different, and setting the origin of the scale is not always easy.

For this reason, the following origin setting is performed. This origin setting is performed according to the flow shown in FIG. 6 stored in the memory in the control device. According to FIG. 6, when the preset switch is first pressed in the mold mounting mode (step S201), the main movable platen and the movable platen base are brought into close contact with each other by driving the AC servomotor which is the main mold clamping device. And close (Step S20)
2), confirm that the closing limit has been reached. Next, the movable platen base is advanced with respect to the mold at low speed and low pressure by the mold clamping ram as the main mold clamping device (step S203). The position scale value Sc at this time is read (step S20).
4) It is checked whether or not there is a change in the read value (step S205). If there is a change, the state is not yet in contact with the mold. When the change has ceased, the main mold clamping device is locked assuming that the complete closing limit has been reached (step S206). Next, the AC servomotor is driven to move the main movable platen forward to perform a step-up operation (step S207). The increased pressure is obtained by reading the pressure sensor (step S208), and the pressure increase at this time is represented by ΔP. It is compared whether the read pressure value is equal to the set value (step S209). If the read pressure value has not reached the set value, the process returns to step S207 to further increase the pressure. Read the position Sx (step S
210). By setting (Sc− | Sx |) as the origin of the scale from Sc and Sx obtained in this way (step S211), the origin preset is completed. Through such a procedure, the local origin can be easily set, and the relative position with respect to the movable platen base can always be recognized.

In the above embodiment, the movement of the main movable platen and the application of pressure are performed by the gear mechanism and the ball screw. However, the present invention is not limited to this. Any mode may be used as long as pressure and pressure are applied.

Further, the switching from the speed control to the pressure control by the servo motor at the time of mold clamping is performed by satisfying both the position and pressure conditions in the embodiment.
The switching may be performed under only one of the conditions.

[0023]

As described above, according to the method for setting the origin of the mold clamping device of the injection molding machine according to the present invention, the origin of the position scale can be reliably set by a simple procedure, so that the positioning characteristics are improved. Further, according to the control method of the mold clamping device of the injection molding machine according to the present invention, the relative position between the movable base and the movable platen is detected on the position scale with respect to the entire stroke using the origin set in this manner. Since the position is determined by each encoder attached to the AC servomotor, the positioning characteristics are improved, and it is possible to obtain high-speed movement by hydraulic pressure and good mold clamping characteristics with high accuracy by the servomotor.

Further, according to the present invention, since the origin of the position scale can be reliably set by a simple procedure, the positioning characteristics are further improved.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing a configuration of a mold clamping device of an injection molding machine used in the present invention.

FIG. 2 is a flowchart showing a control method according to the present invention.

FIG. 3 is a graph showing a state of control near a switching point between speed control and pressure control to which the method according to the present invention is applied.

FIG. 4 is a graph showing a state of speed control when the mold is opened, to which the method according to the present invention is applied.

FIG. 5 is a graph showing a state of switching to pressure control when a detected pressure value reaches a predetermined pressure value.

FIG. 6 is a flowchart showing a method for setting the origin of a position scale according to the present invention.

[Explanation of symbols]

 Reference Signs List 11 tie bar 12 movable plate base 13 main movable plate 14 mold clamping ram 16 bearing 17 rotating member 21 pressure sensor 22 first gear 24 second gear 25 pinion 26 AC servomotor 27 shaft 30 scale

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 45/00-45/84 B29C 33/20-33/28 B22D 17/26

Claims (2)

(57) [Claims] A hydraulic drive unit for pressing and driving a movable base, a servomotor fixed to the movable base, and moved by a rotation thereof to close a mold used for injection molding via a moving mechanism and a movable plate; A position scale for detecting the position of the movable base, wherein a high-speed movement is performed by the hydraulic drive unit, and a low-speed movement immediately before the mold clamping and a pressure rise during the mold clamping are performed by the servomotor. In the method for setting the origin of the position scale in an apparatus, a step of moving the movable base forward with the movable plate and the movable base in close contact with each other until the value of the position scale does not change due to low-speed movement by the hydraulic drive unit. And fixing the hydraulic drive unit in a state where the value of the position scale does not change, and driving the servo motor to advance the movable platen. Pressure, a step of determining an encoder value (Sx) of the servomotor when the mold clamping pressure reaches a set value, and a final value (Sc) of the position scale and the mold clamping pressure have reached a set value. Servo motor encoder value (S
setting the difference (Sc− | Sx |) from the absolute value of x) as the origin of the position scale. 2. A hydraulic drive unit for pressing and driving a movable base, a servomotor fixed to the movable base, and moved to close a mold used for injection molding via a moving mechanism and a movable plate by the rotation thereof; A position scale for detecting the position of the movable base, wherein a high-speed movement is performed by the hydraulic drive unit, and a low-speed movement immediately before the mold clamping and a pressure rise during the mold clamping are performed by the servomotor. A method for controlling an apparatus, comprising: detecting a position (Sc) of the movable base with respect to an entire stroke with reference to an origin obtained according to claim 1 on the position scale; Sx) is respectively detected by an encoder attached to the servomotor, the movable platen is separated from the movable base by a predetermined distance in advance, and the movable base is The position (Sx) of the movable platen is moved and controlled by the servomotor using a deviation (Su-Sc) from the position (Sc) of the movable base when moved by the set command value (Su) as a control amount. A method for controlling a mold clamping device of an injection molding machine.