JPH0729230B2 - Control method of compression molding machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for controlling a compression molding machine for compression molding a resin processed product with a hydraulic press.

(Prior Art) A compression molding machine for compressing a resin processed product by moving a slide with a hydraulic cylinder is well known. There are various types of this compression molding machine depending on the material and shape of the workpiece.

SMC (Sheet Molding Compound), which is a thermosetting sheet material for automobile front panels, body panels, etc.
For example, the compression molding machine described in JP-A-60-15119 was used.

This conventional compression molding machine includes a base, an upright installed upright on the base, a crank installed above the upright, a hydraulic cylinder installed on the crank, and a rod lower end of the hydraulic cylinder. And a slide that moves up and down guided by the upright, a lower mold is fixed to the upper surface of the base, an upper mold is fixed to the lower surface of the slide, and a resin is compression-molded in a cavity between the upper and lower molds. It was something to do.

In the conventional compression molding machine, in order to compression-mold the SMC material, the hydraulic cylinder was controlled as shown in FIG. That is, the speed control that controls the speed of the hydraulic cylinder in multiple stages is adopted until the slide descends from the top dead center and is clamped (t ₁ , t ₂ , t ₃ ). After filling the inside, until the compression molding is completed (t ₄ , t ₅ ).
Is employed a pressure control for the pressure of the hydraulic cylinder constant during mold opening from the forming completion (t _6, t ₇₎ has been switched to speed control again.

The switching from the speed control to the pressure control is performed by setting up a timer.

(Problems to be Solved by the Invention) The conventional control switching by the timer has the following problems.

That is, in order to perform pressure control within the range of t ₅ shown in FIG. 7 and to achieve results, it is necessary to completely fill the mold with resin (SMC). Despite the fact that the mold is filled with resin, the external control (timer) was the only control, and the pressure control was used. Therefore, sufficient results could not be obtained.

For example, when the setting of t ₃ and t ₄ shown in FIG. 7 is short, the material is pressure-controlled before it is filled in the mold.
No pressure was applied to the resin in the mold, and when it was remarkable, problems such as short shots or chipping occurred.

On the other hand, if t ₃ and t ₄ are set too long, the resin will begin to heat and solidify after filling the mold, and some of the solidification has started, so pressure will not act on the resin. In some cases, the molded product could not have sufficient strength.

Therefore, the present invention provides a control method for a compression molding machine, which enables switching from speed control to pressure control at a time suitable for the filling condition of a workpiece in the compression molding machine. And

(Means for Solving the Problems) In order to solve the above problems, a control method for a compression molding machine according to the present invention is such that at least one of a pair of molds is moved by a hydraulic cylinder, and a resin is provided in a cavity between the molds. In compression-molding a work piece, the moving speed of the hydraulic cylinder is controlled until the pressurization of the work piece is started, and the pressing force of the hydraulic cylinder is controlled after the pressurization is started. Switching to the pressure control is performed when the hydraulic cylinder reaches a predetermined stroke value Z _0, and the cavity internal pressure P at the time of the switching is detected, and the detected value P and the preset internal pressure P ₀ are set. By comparison, the stroke correction amount Z for setting the cavity internal pressure P to the predetermined internal pressure P ₀ is obtained by Z = α (P ₀ −P) α; coefficient, and the speed control at the time of the next molding is switched to the pressure control. Hydraulic cylinder strobe The click value, corrected to Z ₀ + Z, and wherein the point repeating this correction operation for each molding.

(Operation) According to the present invention, a fixed amount of resin processed material is filled in the cavity of the opened mold, and the mold is closed by a hydraulic cylinder to close the mold, and then the pressurization is performed. The product is compression molded. The speed of the movement of the hydraulic cylinder up to the mold clamping is controlled, and the pressure is controlled during pressurization.

The timing of switching from this speed control to pressure control is
This is performed by detecting the stroke position of the hydraulic cylinder.

That is, first, the stroke position Z ₀ of the hydraulic cylinder when the mold cavity is filled with the predetermined amount of resin and the cavity internal pressure P ₀ at that time are set. The values of Z ₀ and P ₀ can be preliminarily obtained by preforming, experimentation or calculation.

Next, in actual operation, in the first molding, when the stroke of the hydraulic cylinder reaches the set value Z ₀ , the speed control is switched to the pressure control. At the same time, the cavity pressure P
To detect. This detected value P is compared with the preset internal pressure P ₀ .

If the detected value P is equal to the set value P ₀ , it is considered that the resin is completely filled in the cavity as expected.
Also in the next molding, the control is switched when the hydraulic cylinder reaches the set stroke position Z ₀ .

If the detection value P is smaller than the set value P ₀ , it is considered that the resin does not fill the cavity.

Therefore, at the time of the next molding, the control switching point is corrected. This correction amount Z is Z = α (P ₀ −
P). The coefficient α is determined by a preliminary experiment or the like.

Therefore, at the next molding, when the stroke position of the hydraulic cylinder becomes Z ₀ + Z, the speed control is switched to the pressure control.

Further, when the detected value P is larger than the set value P ₀ , it is considered that the resin is in an overfilled state. Therefore, in this case as well as in the case of the unfilled state, the control switching stroke is set in the next molding. Correct the position to Z ₀ + Z.

Even in the second molding, the cavity internal pressure P
Is detected, the detected value P is compared with the set value P _0, and the stroke value correction similar to the above is performed.

By repeating the correction operation, it is possible to find an appropriate stroke position for control switching as the number of molding times increases.

(Example) Hereinafter, the Example of this invention is described based on drawing.

2 shows a compression molding machine for SMC, a bed 1 fixed to the floor, uprights 2 standing upright at the four corners of the bed 1, and upper ends of these four uprights 2. And a crown 3 for connecting and fixing. A single-acting main cylinder 4 is attached to the center of the crown 3, and the piston rod 5 of the main cylinder 4 is attached to the crown 3
And a slide 6 is connected to the lower end of the piston rod 5. The slide 6 is guided by the four uprights 2 and is vertically movable. Also,
Double-acting sub-cylinders 7 are provided on both left and right sides of the crown 3, and a piston rod 8 of the sub-cylinder 7 is connected to a slide 6.

Leveling cylinders 9 are provided at four corners of the bed 1, and an upper end surface of a piston rod 10 of the cylinder 9 comes into contact with a lower surface of the slide 6 so as to be freely contactable and separable.

An upper die 11 is detachably attached to the lower surface of the slide 6, and a lower die 12 is detachably attached to the upper surface of the bed 1.

The upper and lower molds 11 and 12 are configured so that when the molds are clamped, a cavity 13 is formed at the mating portion of the two, and the lower mold 12 has a mold pressure sensor 14 for detecting the pressure in the cavity 13. Is built in.

A rotary encoder 15 is attached to a side surface of the bed 1, and a chain 18 is provided between a sprocket 16 attached to an input shaft of the encoder 15 and a sprocket 17 rotatably attached to a side surface of the crown 3. Wrapped around,
Both ends of the chain 18 are locked to brackets 19 attached to the slide 6. Then, the encoder
Reference numeral 15 detects the position and moving speed of the slide 6.

An oil tank 20 is placed on the crown 3, and the oil tank 20 and the main cylinder 4 are connected via a full oil valve 21. Further, the main cylinder 4 and the sub-cylinder 7 are connected to a pressurizing cylinder hydraulic unit 25 via hydraulic pipes 22, 23, 24. Further, the leveling cylinder 9 is connected to a leveling hydraulic unit 27 via a hydraulic pipe 26.
It is connected to the.

The pressure cylinder hydraulic unit 25, the leveling hydraulic unit 27, the mold pressure sensor 14, and the rotary encoder 15
Are electrically connected to each other to the control means 28.

In addition, 29 is a die loading / unloading stand.

What is shown in FIG. 3 is the hydraulic unit for the pressurizing cylinder.
It is a hydraulic circuit diagram in 25.

In the figure, 30 is an oil tank, and M ₁ and M ₂ are first and second motors for driving a hydraulic pump. First motor M ₁
Drives two speed control first and second servo pumps P ₁ , P ₂ , and a second motor M ₂ drives third and fourth hydraulic pumps P ₃ , P 2.
₄ and the servo hydraulic pump P ₅ are being driven.

Discharge port of the first to fourth pumps (P ₁ to P ₄₎ are respectively connected to the first to fourth hydraulic line 31, 32, 33 and 34. The first to fourth hydraulic lines 31, 32, 33, 34 are gathered in the fifth hydraulic line 35,
The fifth hydraulic line 35 branches into sixth and seventh hydraulic lines 36, 37. The sixth hydraulic line 36 branches into the hydraulic pipe 22 connected to the main cylinder 4 and the hydraulic pipe 23 connected to the head side of the sub cylinder 7. The seventh hydraulic line 37 is connected to the hydraulic pipe 24 connected to the rod side of the sub-cylinder 7. Pilot hydraulic line 38 connected to the outlet of the servo hydraulic pump P ₅
Is indicated by a dotted line in the figure.

Remotely operated relief valves 39, 40, 41, 42 are interposed in the first to fourth hydraulic lines 31, 32, 33, 34, respectively, and the respective relief valves 39, 40
40, 41, 42 are connected to the drain line 43. A cooler 44 is interposed in the drain line 43.

The sixth hydraulic line 36 includes first to third on / off valves 45, 46,
47 are intervening. The first on / off valve 45 opens and closes the sixth hydraulic line 36. The second on / off valve 46 is the sixth
Open the hydraulic line 36 to the oil tank 30. 3rd on
The off valve 47 opens and closes the main cylinder pipe 22. Each of these on / off valves 45, 46, 47 is a pilot hydraulic pipe.
Operated by 38 hydraulic pressure. This operation is the control means
It is done by the command from 28.

A pressure control valve 48 is interposed in the sixth hydraulic line 36 between the first on / off valve 45 and the third on / off valve 47. The pressure control valve 48 can change its set pressure steplessly or stepwise by a command from the control means 28.

Also in the seventh hydraulic line 37, there are fourth to sixth on / off valves 49, 50, 51.
Is intervening. Each of these on / off valves 49, 50, 51 is also opened / closed by a command from the control means 28.

A check valve 52 is built in the oil filling valve 21, and the check valve 52 is turned on / off by the hydraulic pressure of the pilot hydraulic pipe 38. This operation is also performed by the command of the control means 28.

FIG. 4 is a hydraulic circuit diagram of the leveling hydraulic unit 27. The hydraulic oil in the oil tank 53 is connected to the hydraulic pipe 26 connected to the leveling cylinder 9 through the hydraulic pump P ₆ and the eighth hydraulic line 54. Has been done. This 8th hydraulic line
A servo valve 55 is interposed in 54, and the servo valve 55 is operated by a command from the control means 28. This servo valve 55
Are provided corresponding to each leveling cylinder 9.

What is shown in FIG. 5 is an operation flow chart of the compression molding machine having the above configuration, and what is shown in FIG. 6 is an operation diagram thereof.

In these drawings, STEP1 shows the start time when the slide 6 is at the top dead center position. In this state, the cavity 13 of the lower mold 12 is filled with the SMC material 56.

Next, STEP 2 shows a state in which the slide 6 descends at a high speed. At this time, in the hydraulic circuit diagram of FIG.
The hydraulic oil from the four pumps P ₁ , P ₂ , P ₃ , P ₄ passes through the first to fourth hydraulic lines 31, 32, 33, 34 and the fifth hydraulic line 35, and
It is supplied to the main cylinder 4 and the sub cylinder 7 from the sixth hydraulic line 36 through the hydraulic pipes 22 and 23 of the main cylinder 4 and the sub cylinder 7. At this time, the first, third, fifth,
6, each on / off valve 45, 47, 50, 51 is open, and the second and fourth on / off valves 46, 49 are closed. At this time, the oil on the rod side of the sub-cylinder 7 passes through the fifth on-off valve 50 and goes to the tank 30.
Returned to.

Step 3 indicates a middle speed lowering state of the slide 6, and the discharging speed of the speed control servo pumps P ₁ and P ₂ is controlled by the control means 28 to make the lowering speed of the slide 6 medium speed. To switch from STEP2 to STEP3, use the rotary encoder 15
Is performed based on the position detection of the slide 6 by.

In STEP 4, speed control and leveling control are performed simultaneously. That is, based on the position detection of the slide 6 by the rotary encoder 15, the step is switched from STEP3 to STEP4. At this time, the lower surface of the slide 6 softly touches the upper end surface of the rod 10 of the leveling cylinder 9. Then, the slide 6 moves down while pressing the rod 10 of the leveling cylinder 9. In each of the four leveling cylinders 9, each servo valve 55 is controlled so that all four cylinders have the same level, and the levelness of the slide 6 is maintained with high accuracy.

In this STEP 4, the speed control servo pumps P ₁ and P ₂ are controlled, and the descending speed of the slide 6 is controlled in multiple stages. At the end of STEP4, the upper die 11 and the lower die 12 are clamped, and the cavity 13 is filled with the SMC material 56.

When the cavity 13 is filled with SMC material 56, the control of the pressure cylinders 4, 7 is switched from speed control to pressure control. The switching timing is performed when the position of the slide 6 is detected by the encoder 15 and the detected value reaches a predetermined value. This control switching is shown in STEP5.

STEP 6 shows a state in which pressure control and leveling control are performed simultaneously.

That is, the discharge amount from the hydraulic pump is kept constant and the pressure control 48
Controls the pressure in the hydraulic circuit.

In this pressure control, a state change of the SMC material 56 in the cavity 13 is detected by the die pressure sensor 14, and the applied pressure is controlled in multiple stages (including stepless) in response to the state change. This control command is given by the control means 28.

The multi-stage pressure control, when the state change of the SMC material 56 in the cavity 13 over time is known in advance,
It can also be achieved by controlling the preset pressure at predetermined intervals in multiple stages.

In the pressure control, the leveling cylinder 9 is controlled according to the pressure change of the main cylinder 4 and the sub cylinder 7, and keeps the slide 6 horizontal.

Then, when the pressure control is completed, the slide 6 is slightly moved up through the pressure release process, and the in-mold coating is performed. This process is shown in STEP 7. This STEP7
The speed is controlled by the servo valve 55. The second, third and fifth on / off valves 46, 47 and 50 are required when the slide is raised.
Is closed and the first, fourth, sixth on / off valves 45, 49, 51 are opened. Then, the hydraulic oil is supplied from the fifth hydraulic line 35 through the sixth and seventh hydraulic lines 36, 37 to the cylinder side and the rod side of the sub-cylinder 7, and the sub-cylinder 7 becomes free. The oil in the main cylinder 4 can flow into the oil tank 20 via the full oil valve 21 by operating the check valve 52 with pilot pressure.

Then, the slide 6 is raised by raising the leveling cylinder 9 via the servo valve 55 of the leveling cylinder 9.

Even when the slide 6 is raised, the leveling cylinder 9 is controlled and the slide 6 is raised while maintaining the horizontal state.

The rising speed and position of the slide 6 are detected by the rotary encoder 15 and fed back to the speed control.

When the in-mold coating is completed, the slide 6 descends again, and when it reaches a predetermined position, the speed control is switched to the pressure control. This switching is performed based on the pressure detection of the die pressure sensor 14 or the slide position detection of the encoder 15. This step is shown in STEP8.

In STEP8, the multistage pressure control is performed as in STEP6, and the compression molding including the in-mold coating is completed. Then, after depressurizing, the slide 6 is raised to the original top dead center. This ascending process is shown after STEP9, and the speed control is performed after STEP9. When ascending the slide after this STEP 9,
The 3,5 on / off valves 45,47,50 are closed and the second, 4,6 on / off valves 46,49,51 are opened. The hydraulic oil is the fifth
It is supplied to the rod side of the sub-cylinder 7 from the hydraulic line 35 through the seventh hydraulic line 37. The oil on the cylinder head side of the sub-cylinder 7 is returned to the tank 30 through the second on / off valve 46 of the sixth hydraulic line 36, and the oil of the main cylinder 4 is operated by operating the check valve 52 with pilot pressure. It is returned to the oil tank 20 via the full oil valve 21.

Then, all the steps of compression molding are completed.

The control switching of the compression molding STEP 5 is performed by detecting the position of the slide 6, in other words, the stroke position of the pressure cylinders 4 and 7, but it was extremely difficult to determine an appropriate switching position. Therefore, in this embodiment, as shown in FIG. 1, an appropriate stroke position is determined.

First, the stroke position Z _{0 at the} time of control switching and the cavity internal pressure P ₀ at that time are set in advance. This setting
Z ₀ , P ₀ is the material when a certain amount of SMC material 56 is filled.
It is the slide position when 56 fills the cavity 13 and the pressure in the cavity 13, which is obtained in advance, in experiments, and the like.

And in the first compression molding, the set position
The control is switched when the slide 6 reaches Z ₀ . This timing is performed by the encoder 15. At the same time, the mold pressure sensor 14 detects the internal pressure P of the cavity 13. Then, the detected value P is compared with the set internal pressure P ₀ .

Then, in the case of P = P ₀ , the control switching position Z _{0 of the} slide 6
Since the internal pressure of the cavity in Fig. 2 shows an appropriate value, the control switching position in the next compression molding is kept at Z ₀ which was initially set.

If P ≠ P _0, the internal pressure of the cavity at the control switching position Z ₀ of the slide 6 is larger or smaller than an appropriate value, so the control switching position in the next compression molding is corrected. The correction amount Z is obtained by Z = α (P ₀ −P). The coefficient α is set in a preliminary experiment or the like. Then, in the second compression molding, the stroke position Z _{0 at the} time of control switching is Z ₀
→ Change to Z ₀ + Z.

The same correction operation as described above is repeated in the second compression molding and thereafter. By repeating this operation, it is possible to find the optimum slide position when switching the control. The control device 28 has a learning function of finding out the optimum position.

If the first control switching stroke position is the set position Z ₀ itself, the correction amount Z is represented by + and −, and Z → 0.
The number of times to converge to increases. Therefore, by setting the first control switching stroke position slightly before the set position Z ₀ , the correction amount Z can be converged from + side to 0, and the number of corrections can be small.

Further, in the comparison between the internal pressure detection value P and the set value P ₀ , P> P ₀
In the case of P <P ₀ , the product is not adversely affected as much as in the case of P <P _0. Therefore, there is no practical problem even if the stroke position correction is performed only when P <P ₀ .

The present invention is not limited to the above embodiment.

(Effect of the Invention) According to the present invention, the machine itself corrects the timing for switching the control of the hydraulic cylinder according to the state quantity, and finds the optimum molding condition. The work that had been done can be greatly reduced, the production efficiency is improved, and the switching from speed control to pressure control becomes appropriate, and in the subsequent pressure control, the pressing force sufficiently acts on the work piece, Strength, dimensional accuracy, cracks, etc. can be improved.

[Brief description of drawings]

FIG. 1 is a flow chart showing an embodiment of the present invention, and FIG.
FIG. 3 is a partial sectional front view of a compression molding machine used in an embodiment of the present invention, FIG. 3 is a hydraulic circuit diagram of a main cylinder, FIG. 4 is a hydraulic circuit diagram of a leveling cylinder, and FIG. 5 is an embodiment of the present invention. FIG. 6 is an operation flow chart of the example compression molding machine, FIG. 6 is a press operation diagram thereof, and FIG. 7 is a graph showing control of the conventional compression molding machine. 4 ... Main cylinder, 6 ... Slide, 7 ... Sub-cylinder, 11 ... Upper mold, 12 ... Lower mold, 13 ... Cavity, 14 ... Mold pressure sensor, 15 ... Encoder, 28 ... … Control means.

Claims (1)

[Claims] 1. When at least one of a pair of molds is moved by a hydraulic cylinder and a resin processed product is compression-molded in a cavity between the molds, the moving speed of the hydraulic cylinder is controlled until the pressurization of the processed product is started. In the control method of the compression molding machine which controls and controls the pressure of the hydraulic cylinder after the start of pressurization, switching from the speed control to the pressure control is performed when the hydraulic cylinder reaches a predetermined stroke value Z ₀ , and The cavity internal pressure P at the time of the switching is detected, and the detected value P is compared with a predetermined preset internal pressure P ₀ to determine the cavity internal pressure P.
Stroke correction amount Z for making the specified internal pressure P ₀ Z = α (P ₀ -P) α; coefficient, and stroke value of the hydraulic cylinder at the time of switching from speed control to pressure control at the next molding Is corrected to Z ₀ + Z, and the correction operation is repeated for each molding.