JP3677735B2 - Metal material injection molding method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an injection molding method in which a metal material melted in a heating cylinder, in particular, a non-ferrous metal having a low melting point, is injected and filled from a nozzle into a metal mold and molded into a metal product in a desired form.
[0002]
[Problems to be solved by the invention]
After melting a low melting point non-ferrous metal (eg lead, zinc, tin, aluminum, magnesium or alloys thereof) in a heating cylinder equipped with a plunger or screw and measuring the molten metal in the same way as plastic In addition, by advancing movement of a plunger or a screw, a metal mold is injected and filled directly from a nozzle at the tip of a heating cylinder or through a hot runner, and a desired metal product is formed by cooling.
[0003]
In such metal material injection molding, the molten metal is in the state of hot water, the viscosity is almost equal to that in plastic, so it is easy to leak from the nozzle port during measurement, and as a means to prevent this, Residual metal material in the nozzle port after completion of molding is cooled and solidified by nozzle touch with a mold, and the nozzle port is closed as a cold plug.
[0004]
In addition, since the nozzle port is tightly sealed by the cold plug, air suction from the nozzle port is prevented when the plunger or screw is moved backward, so that the negative pressure in the tip of the heating cylinder accompanying the backward movement is prevented. It is also possible to measure molten metal using
[0005]
This cold plug is pushed away from the nozzle port to the mold side by the pressure at the time of injection, and then melts and disappears by the molten metal that is injected and filled. The state is not uniform because it is due to cold heat on the mold side, and is different for each shot. For this reason, there is a difference in the pressure behavior from the start of injection until the cold plug is removed and thereafter, and there is a problem that the quality of the metal product to be formed tends to vary due to the pressure fluctuation for each shot.
[0006]
The object of the present invention is to control the relative position using the instability of molding due to pressure fluctuation at the time of injection caused by the cold plug as the starting point of the injection process control by using the peak value position of the injection pressure by the cold plug after the start of injection. It is an object of the present invention to provide a new metal material injection molding method which is solved by performing the above.
[0007]
[Means for Solving the Problems]
In the present invention according to the above object, the molten metal is measured into the tip of the heating cylinder by the backward movement of the plunger or screw with the nozzle port sealed with a cold plug, and the measured molten metal is moved to the nozzle by the forward movement of the plunger or screw. When the mold is injected and filled into a mold and injection molded into a metal product of the desired form, the metered molten metal is injected by moving the plunger or screw forward at a predetermined speed and pressure starting from the measurement completion position. The position where the injection pressure reached the peak value by the cold plug in the forward process is memorized and used as the injection process control starting point, and several subsequent speed / pressure switching positions are calculated from that position. The total switching position exceeds the injection stroke from the process control starting point to the most advanced position of the plunger or screw. If you stops the injection molded as metering insufficient, is that.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of an injection molding machine that employs the injection molding method of the present invention and can perform injection molding of a metal material with a plunger.
[0009]
In the figure, 1 is an injection mechanism and 2 is a mold clamping mechanism, both of which are installed on the upper surface of the machine base 3.
Reference numeral 4 denotes a pedestal provided on the upper surface of the machine base so as to be movable back and forth with respect to the mold clamping mechanism 2. A nozzle touch block 5 is fixed on the front portion, and the upper surface is directed inwardly at an angle of about 45 ° on the rear portion. A gantry 6 formed on the inclined surface is provided.
[0010]
The injection mechanism 1 is attached to the inclined surface of the gantry 6 so as to be able to advance and retreat, and the nozzle portion at the front end is positioned downward with respect to the mold clamping mechanism 2 so as to face the nozzle touch block 5. It is installed in.
[0011]
The upper part of the rear surface of the nozzle touch block 5 is formed as an inclined rear surface positioned at right angles to the axis of the injection mechanism 1, and a nozzle 7 for nozzle touching the mold 7 is attached horizontally to the front side surface. A nozzle touch device 9 fixed on the machine base 3 is connected to the rear side surface.
[0012]
The injection mechanism 1 has a cylindrical heating cylinder 11 that also serves as a metal material melting vessel provided with a band heater on the outer periphery, an injection cylinder 12 that is connected to a rear end portion thereof by a tie bar, and a heating cylinder 11. The electric motor 13 for stirring attached to the lower side of the rear end and a granular metal material supply device 14 are included.
[0013]
The inside of the tip of the heating cylinder 11 is smaller than the inner diameter of the main body, and is formed in the measuring chamber 15 by a cylinder integral with the nozzle at the front end. The stirring means 16 is a hollow shaft provided with a stirring blade inside the main body. The injection means 17 is inserted into the agitation means 16 so as to freely advance and retract.
[0014]
The injection means 17 is provided with a plunger 19 for injection and measurement at the tip of a rod 18 that is inserted into the stirring means 16 so as to be able to advance and retreat. The plunger 19 is provided with a sliding clearance (not shown), and the measurement chamber 15 is provided. The rod rear end is connected to a piston rod (not shown) of the injection cylinder 12.
[0015]
The plunger 19 has an outer diameter larger than that of the rod 18, and a seal ring 21 that blocks the sliding clearance that also serves as a suction gap with the measuring chamber 15 is provided at an interval on the outer peripheral surface of the front portion. It consists of a short columnar shape fitted twice.
[0016]
In order to perform injection molding of a metal material by the injection mechanism 1 having such a configuration, first, the plunger 19 at the most advanced position is moved backward by injection filling, and the heating cylinder 11 is completely melted (liquid phase state) or thixotropy. The molten metal 20 dissolved and accumulated in a state (a state in which some solid phase remains) is measured.
[0017]
This measurement is performed in a state where the nozzle part of the heating cylinder 11, the nozzle touch block 5, the nozzle member 8, and the mold 7 are all in an airtight nozzle touch. The nozzle member 8 is heated to a temperature higher than the solidus temperature by the heater together with the nozzle touch block 5, but the molten metal remaining in the nozzle mouth is solidified by cooling from the mold 7 and becomes a cold plug 22. The nozzle port is closed in a sealed state.
[0018]
If the plunger 19 is moved backward at a set speed (for example, 100 mm / s or less) in this state, the pressure in the measuring chamber becomes negative and the tension of the seal ring 21 is kept low so that the sliding clearance is circulated. Become. As a result, although the molten metal 20 of the heating cylinder 11 is omitted in the drawing, the molten metal 20 flows into the measuring chamber 15 that is being expanded from the sliding clearance with the backward movement until the plunger 19 stops at the measuring completion position. Thus, the measuring chamber 15 is filled, so that the set amount is measured. Incidentally, the diameter of the measurement chamber 15 is 36 mm, and the maximum injection stroke is 75 mm.
[0019]
Next, after stopping the plunger 19 to complete the measurement, the injection mechanism 1 is moved backward together with the nozzle touch block 5 to move the nozzle member 8 from the mold 7 until the mold clamping mechanism 2 completes the mold clamping. Keep away. By releasing the nozzle touch, the nozzle opening is no longer cooled by the mold 7 and the cold plug 22 is heated from the nozzle member 8, so that the cold plug 22 grows deeply in the nozzle member 8 due to the cooling. However, it is limited to a size that can be eliminated by the injection pressure. However, even if it melts by heating during measurement, most of it remains and does not leak from the nozzle opening.
[0020]
The injection filling of the above-mentioned metered molten metal (not shown) into the mold 7 is performed by performing nozzle touch again after completion of mold clamping, and setting the plunger position after completion of metering as the injection start position (S ₀ ) shown in FIG. Is called.
[0021]
First, when the plunger 19 is moved forward at a predetermined speed V ₁ and pressure P ₁ , the nozzle port of the nozzle member 8 is in a state of being tightly plugged by the cold plug 22, and as shown in FIG. The material pressure (injection pressure) is increased by being pressed by the tip surface. This acts as an injection load pressure on the plunger 19, and the seal ring 21 whose tension is kept low by the negative pressure is restored to shut off the sliding clearance, allowing backflow of the measured molten metal. Will be prevented in range.
[0022]
When the plunger 19 further moves forward, the injection pressure exceeds the resistance force by the cold plug 22, and the cold plug 22 is pushed out to the mold side and removed from the nozzle port. As a result, the metered molten metal is injected and filled from the nozzle member 8 into the mold 7 through the hot runner in the nozzle touch block 5 by the pressing force of the plunger 19.
[0023]
Further, since the material pressure rapidly decreases and drops simultaneously with the removal of the cold plug 22, the injection pressure also reaches a peak value at that time, and the injection pressure thereafter becomes low until the completion of filling, and rises again at the holding time. become. Conversely, the injection speed is high.
[0024]
The position of the peak value of the injection pressure differs depending on the formation state of the cold plug 22 even if the measured value is constant. When the cold plug 22 is formed firmly, a large material pressure that exceeds the resistance force is generated. The plunger 19 is moved forward more than necessary. In addition, since substantial injection filling is performed after the cold plug 22 is removed, the injection stroke of the plunger 19 becomes relatively shorter than the set value, and control in the injection process cannot be performed to the end. Some can even be short.
[0025]
In this invention, the position of the peak value regarded as the substantial injection filling start point of the metered molten metal is stored as the process control starting point (S ₁ ) of injection, and is preset from that position. Several subsequent speeds and pressures are subjected to process control in multiple stages to perform injection filling of the molten metal into the mold 7.
In this case, the injection stroke of the plunger 19 from the process control starting point (S ₁ ) to the most advanced position is often different from a preset injection stroke depending on the position of the process control starting point (S ₁ ). Process control set as a reference becomes difficult.
[0026]
Therefore, when the plunger 19 reaches the process control starting point (S ₁ ), several speed / pressure switching positions (S ₂ ) and (S ₃ ) after the preset necessary for the process control from that position are set. If the total of the switching positions (hereinafter referred to as the total switching position) is within the injection stroke range from the process control starting point (S ₁ ) to the most advanced position of the plunger 19 as shown in FIG. while it moves forward the plunger 19, the pressure P ₁ from the injection start position (S _0), the speed V _2, the pressure P _2, the speed V ₂ in the injection process control origin (S _1), also the switching position ( In S ₂ ), the pressure P ₃ and the speed V ₃ are respectively controlled to inject and fill the molten metal into the mold, and the pressure P ₄ and the speed V ₄ are further controlled at the holding pressure switching position (S ₃ ). And hold the pressure.
[0027]
If the total switching position from the process control starting point (S ₁ ) exceeds the injection stroke of the plunger 19 as shown in FIG. 4B, the injection process control at that injection stroke is difficult. Immediately, the forward movement of the plunger 19 is stopped, and the injection molding is stopped while the nozzle is touched due to insufficient metering. The process after the stop of molding becomes re-weighing, and the process proceeds to the next injection process.
[0028]
FIG. 5 shows a case using a normal in-line screw type injection device. The heating cylinder 31 is composed of a normal one in which band heaters are attached to the outer periphery at regular intervals, and an injection screw 32 rotates inside. It is provided so as to be movable in the axial direction. The tip of the heating cylinder 31 is closed by a tip member 34 integrated with the nozzle 33.
[0029]
The screw 23 is a normal one in which a ring valve 35 for preventing backflow is fitted to the outer periphery of the tip of the conical shape so as to be able to advance and retreat. It consists of a structure for transporting molten metal.
[0030]
The molten metal accumulates in the measuring chamber 36 generated in the tip portion of the heating cylinder 31 by forcibly retracting the screw 32 at the forward position backward by a set distance while the nozzle 33 is touching the mold 37. Is done. Further, the inside of the nozzle opening is hermetically sealed by a cold plug 38 that remains to be cooled and solidified.
[0031]
The forced retraction is performed by pulling backward while rotating the screw 32. At this time, since the nozzle tip of the metering chamber 36 is blocked, the metering chamber 36 is in a negative pressure state, and the ring valve 35 in the closed state is pulled back and opened, and at the same time, is stored around the front portion of the screw 32. The molten metal that has flowed into the measuring chamber 36 by suction and screw rotation is measured.
[0032]
First, the screw 32 is moved forward at a predetermined speed V ₁ and pressure P ₁ . The metered molten metal is pressed by the tip surface of the screw 32, and the material pressure (injection pressure) increases. This becomes the injection load pressure, the ring valve 35 is pushed back and closed, and the backflow of the metered molten metal is prevented within an allowable range.
[0033]
When the screw 32 further moves forward, the injection pressure exceeds the resistance force by the cold plug 38, and the cold plug 38 is pushed out to the mold side and removed from the nozzle port. As a result, the metered molten metal is injected and filled from the nozzle 33 into the mold 36 by the pressing force of the screw 32.
[0034]
Further, since the material pressure rapidly decreases and drops simultaneously with the removal of the cold plug 38, the injection pressure reaches the peak value at that time. Therefore, the position of the peak value regarded as the substantial injection filling start point of the metered molten metal is stored as the injection process control starting point (S ₁ ), and the position required for the process control is preset from that position. Several subsequent speed / pressure switching positions (S ₂ ) and (S ₃ ) are immediately calculated.
[0035]
As a result of the calculation, if the total switching position is within the range of the injection stroke set for the screw 32 as shown in FIG. 4A, the screw 32 is moved forward and moved from the injection start position (S ₀ ). pressure P _1, the speed V _2, the pressure P ₂ in a process control origin (S _1), and controls the speed V _2, the switching position (S ₂₎ the pressure P _3, by controlling the speed V _3, metering molten metal The mold is injected and filled, and pressure holding is performed by further controlling the pressure P ₄ and the speed V ₄ at the holding pressure switching position (S ₃ ).
[0036]
If the total switching position from the process control starting point (S ₁ ) exceeds the injection stroke of the screw 32 as shown in FIG. 4B, the process control at that injection stroke is considered difficult, and immediately The forward movement of the screw 32 is stopped, and the injection molding is stopped while the nozzle is touched due to insufficient metering. The process after the molding stop is re-weighing, and the process proceeds to the next injection process.
[0037]
As described above, the present invention memorizes the position at which the injection pressure reaches the peak value by the cold plug during the advancement of the plunger or screw, and uses it as a starting point for the process control of the injection. Since it is determined whether or not to stop the injection molding from the calculation of the switching position and the comparison between the calculation result of the switching position and the substantial injection stroke of the plunger or screw, the molding material is made of a non-ferrous metal with a low melting point. Even if the molten state is completely melted to a temperature above the liquidus or in the thixo state, injection molding can be performed without causing insufficient measurement, and injection molding is performed by relative position control. Therefore, even if it is a metal material, variation in the injection filling amount is improved, and products with excellent molding accuracy can be easily and stably molded by adopting process control. It can be.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a plunger-type injection molding machine that can carry out a metal material injection molding method according to the present invention.
FIG. 2 is an explanatory view of the injection molding method in the same as above.
FIG. 3 is an explanatory diagram of the state of pressure and speed during injection molding of molten metal.
FIG. 4 is a comparison diagram between an injection stroke from a process control starting point and a total of each switching position.
FIG. 5 is an explanatory view of an injection molding method of the present invention in an inline screw type injection molding machine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Injection mechanism 2 Clamping mechanism 5 Nozzle touch block 7 Mold 8 Nozzle member 11 Heating cylinder 15 Measuring chamber 16 Stirring means 17 Injection means 18 Rod 19 Injection plunger 20 Molten metal 21 Seal ring 22 Cold plug 31 Heating cylinder 32 Injection Screw 33 Nozzle 35 Ring valve 36 Weighing chamber 37 Mold 38 Cold plug

Claims (1)

With the nozzle port sealed with a cold plug, the molten metal is measured into the tip of the heating cylinder by the backward movement of the plunger or screw, and the measured molten metal is pushed out of the nozzle by the forward movement of the plunger or screw and injected into the mold. In filling and injection molding into the desired form of metal products,
The metered molten metal is injected by moving the plunger or screw forward at a predetermined speed and pressure, starting from the measurement completion position.
The position where the injection pressure reached the peak value by the cold plug in the advance process is memorized and used as the process control start point of injection, and several speed / pressure switching positions set in advance from that position are calculated and switched. An injection molding method for a metal material, characterized in that when the total position exceeds the injection stroke from the process control starting point to the most advanced position of the plunger or screw, the injection molding is stopped due to insufficient metering.

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