JPH0224181B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a casting method for a die-casting machine in which casting is carried out by reducing the pressure in the cavity of a mold by suction.

[Conventional technology]

Casting using a die-casting machine has traditionally been widely used as a method for manufacturing precision products in large quantities.In this type of casting, molten metal is filled into the cavity of a mold at high speed and high pressure. Since the gas may not escape sufficiently and may mix with molten metal and remain in the product as voids, it may not be suitable for products where integrity without voids is important.

In order to solve this inconvenience, the present applicant has proposed Utility Application No. 56-107265 (Utility Model Application No. 57-13873).
We developed and proposed a degassing device for molds that removes gas from the mold cavity during casting, eliminates gas entrainment, and produces healthy die-cast products.

This device is equipped with a gas vent valve in the gas exhaust path leading from the mold cavity to the outside of the mold, and when the valve is open, molten metal is injected into the cavity, and the gas with a small mass in the cavity is exhausted. When the molten metal has finished being discharged through the gas passage, the inertial force of the large mass of the molten metal that has entered the gas exhaust passage from inside the cavity acts on the valve to close it, thereby blocking the outflow of the molten metal. Therefore, gas inside the mold can be reliably and easily vented.

The applicant has also developed a reduced-pressure or vacuum-type die-casting method and an apparatus therefor, in which the gas in the mold cavity is actively exhausted by connecting the gas exhaust path to a vacuum generator. This reduced pressure die casting method reduces the pressure by suctioning an amount of gas from the outside that is greater than the amount of gas that flows into the cavity from outside the mold through the gap, thereby eliminating gas from inside the mold. It can be made more reliable.

[Problem that the invention seeks to solve]

However, in such conventional casting methods, gas flows from the outside to the inside in the gap between the injection sleeve and the plunger tip due to the difference between the amount of gas discharged from the cavity and the amount of gas flowing into the cavity. As a result of this flow, as the vacuum is drawn, some of the molten metal in the injection sleeve is randomly sucked up into the cavity in a state close to foaming before injection, and a thin solidified layer is formed along the inner surface of the cavity. arise. Therefore, after reaching this state, a proper injection product cannot be obtained even if injection is performed. Furthermore, even if injection is attempted, moisture, mold release agent, lubricant, etc. outside the cavity may be sucked into the cavity, or molten metal inside the injection sleeve may be sucked into the cavity before the degree of vacuum has increased. Impurities such as lubricants may get mixed into the product, reducing the quality of the product, or moisture may come into contact with the injected molten metal and gasify, creating cavities that may prevent sufficient vacuum effectiveness from being achieved. Otherwise, the molten metal may be sucked in before the specified degree of vacuum is reached, which may entrain gas, or may not mix well with the molten metal injected in the subsequent high-speed injection region, which may affect the appearance of the product. There was a problem with the damage. Furthermore, even if an attempt is made to block the intrusion of air by a solidified layer of molten metal that is formed in close contact with the end surface of the plunger tip,
As shown in the cross-sectional view near the plunger tip, when the cavity is suctioned to reduce the pressure, the molten metal is lifted because the degree of vacuum between the plunger tip and the casting sleeve is lower than the degree of vacuum in the cavity. Due to the force, the molten metal floats up from the end of the plunger tip, and the air that flows into the bottom of the molten metal and the end of the plunger tips insulates the bottom of the molten metal, and the solidified layer that has formed on the bottom of the molten metal softens due to the heat of the molten metal. The center part ruptures due to the difference in air pressure between the cavity and the end of the plunger tip.
External air freely entered the mold cavity through the gap between the plunger tip 2 and the injection sleeve 3 and through the holes in the torn solidified layer 1, making it difficult to shut off.

[Means for solving problems]

In order to solve these problems, the present invention provides an annular groove on the outer circumferential surface of the plunger tip that communicates with the mold cavity through the gap, and also provides a gas venting device in the mold cavity so that the plunger tip can be removed before the plunger tip starts moving forward. During the forward movement, the air in the annular groove began to be sucked to the outside, and after a short delay, the air in the mold cavity was sucked to the outside via the gas venting device.

[Effect]

By doing this, when air is sucked to the outside from the annular groove on the outer circumferential surface of the plunger tip before or during its forward movement, the solidified layer adheres to the end surface of the plunger tip, and after a short delay, the air inside the mold cavity is drawn. Even if air is sucked in from the gas venting device side, the outside air is blocked by the coagulation layer and does not mix with the molten metal in the mold cavity.

〔Example〕

1 to 7 are diagrams shown to explain the casting method of the die casting machine according to the present invention, in which FIG. 1 is a schematic configuration diagram of a casting device and a pneumatic piping diagram, and FIG. An enlarged sectional view of the injection sleeve and plunger, Fig. 3 is a sectional view AA of Fig. 2, Fig. 4 is a sectional view BB of Fig. 2, Fig. 5 is a sectional view CC of Fig. 2, and Fig. 6 is a sectional view of CC of Fig. 2. Vertical sectional view of mold degassing device, No. 7
The figure is a sectional view of DD in FIG. 6. In the figure, a fixed mold 11 and a movable mold 12 are joined and clamped at a dividing surface 13, and inside thereof, a cavity 14, a constriction 15, and a vertical hole 16 are provided on both sides of the dividing surface 13. A fixing sleeve 17 is fitted into the vertical hole 16. The die casting machine of this embodiment is of a horizontal mold clamping and vertical casting type, and the mold clamping and mold opening are performed by moving the movable mold 12 in the horizontal direction. is located directly below.
The injection cylinder 18 is equipped with a piston rod 19 that moves forward and backward under hydraulic pressure, and a plunger 20, which is shown in detail in FIGS. 2 to 5, is concentrically connected to the working end of the piston rod 19 by a coupling 21. Reference numeral 22 denotes an injection sleeve formed to have the same diameter as the fixed sleeve 17 and moved up and down by a cylinder (not shown) toward and away from the fixed sleeve 17;
is slidably fitted into the casting sleeve 22.
Remove the plunger tip 2 from the fixing sleeve 17.
3 is inserted, and the injection cylinder 18 is rotated by a tilting cylinder (not shown) to remove the casting sleeve 2.
It is configured to inject molten metal into the molten metal. After pouring, the injection cylinder 18 is erected, the casting sleeve 22 is inserted into the fixed sleeve 17, and the piston rod 19 is advanced by hydraulic pressure.
Plunger tip 23 injects molten metal into cavity 14.

Therefore, details of the plunger tip 23 will be explained. A plunger rod 24 connected to the piston rod 19 with a coupling 21 includes, from above, a screw hole 24a, a pressure reducing pipe support hole 24b, an air passage hole 24
c and a bottom hole 24d, and the lower threaded portion 25a of the threaded pipe 25 is screwed into the uppermost threaded hole 24a as far as it will go until it stops at the stepped portion. ing. A pair of upper and lower adapters 26 and 27 are attached to the central threadless portion 25b of the threaded pipe 25.
is loosely installed, and the upper threaded part 25 of the threaded pipe 25
The plunger tip 23 and the plunger rod 24, which are screwed into the plunger tip 23 and the plunger rod 24, are clamped and fixed. 28 is a holding cylinder 28a and a pipe 2 welded thereto.
The tube 28b is inserted from the bottom hole 24d side and the holding cylinder 28a is fitted to the upper end of the bottom hole 24d.
4c, and its upper portion is fitted into the pressure reducing tube support hole 24b. Further, 29 is a water-cooled tube consisting of a holding shaft 29a and a tube 29b welded to the holding shaft 29a,
The holding shaft 29a is fitted into the bottom hole 24d to hold down the holding cylinder 28a from below, and the pipe 29b passes through the holding cylinder 28a, the pipe 28b, and the threaded pipe 25, and its tip is inserted into the space 23a of the plunger tip 23. I'm making you come. Reference numeral 30 indicates six O-rings as sealing materials provided at various locations. 30a is an oil supply port for sliding lubrication of the plunger tip 23.

An annular groove 23b provided on the outer periphery of the plunger tip 23 and an annular groove 26a provided on the adapter 26 communicate with each other through an air passage 23c, and an annular groove 27a provided on the adapter 27 is provided with a filter 31 made of wire mesh. It is composed of an air passage 27b.
Air passage hole 24c of plunger rod 24 and pipe 2
An air passage 33 communicates between the air passage 32 formed between the annular groove 27a and the annular groove 27a.
A suction hole 34 opened at the lower end of the air passage 32 is connected to a pipe 35 of a pneumatic circuit (described later) shown in FIG.
is connected. On the other hand, the water cooling pipe 29b
The lower end opening is connected to the cold water passage 29d and the annular groove 29c.
The upper end opening is connected to the cold water inlet 35b through the space 23a, and a cold water passage 36 and water channel 37 extending downward around the pipe 29b.
It communicates with a cold water outlet 39 via an annular groove 38 . The cold water inlet 35b is connected to a pump or the like through a flexible hose or the like, and the cold water supplied to the cold water inlet 35b by the operation of the pump rises in the pipe 29b and fills the space 23a, and the plunger tip 23 After cooling, the water flows down the cold water passage 36 and is drained from the cold water outlet 39.

Next, the mold degassing device will be explained. On the outer periphery of the cavity 14 of both the molds 11 and 12,
A degassing path 40 and a degassing groove 41 communicating with this are formed on both sides of the dividing surface 13, and a mold degassing device, designated as a whole by reference numeral 42, is located directly above the degassing groove 41, for example. It is fixed to the movable mold 12 side. That is, the cylinder 4 is attached to the upper end of the bracket 43 fixed to the movable mold 12.
A cylindrical spool 46 connects the lower end of the piston rod 46, which is the active end of the piston rod 45 that moves back and forth with the fluid pressure, to the lower end of the piston rod 45.
1 and 12 so that they can be inserted and removed freely. And when mold clamping and mold opening,
The spool 46 is inserted into and removed from the molds 11 and 12 via the piston rod 45 by the operation of the cylinder 44. Mold 11,
Below the spool 46 inserted into the spool 12, there is a valve chamber 47, a degassing groove 41 which detours laterally.
A bypass 48 is provided to communicate between the spool 46 and a valve seat 49 facing the valve chamber 47 is formed on the lower end surface of the spool 46. A pair of elongated holes 50 provided in the outer peripheral wall of the spool 46 have a return rod 51.
Both rod portions 51a of the piston rod 45 are slidably engaged with each other, and between the return rod 51 and the flange portion of the piston rod 45, there is a tension spring 52, a cylinder, a solenoid device, and a gravity spring that urges the return rod 51 upward. Components such as equipment are strung up. Below the return rod 51, a valve guide 53 integrally formed with a cylindrical portion 53a and a pair of screw hole portions 53b is fixed to the spool 46 with the screw hole portion 53b attached inside the elongated hole 50, A valve rod 56 whose upper end threaded portion is screwed into a screw hole of the return rod 51 is slidably supported on the cylindrical portion 53a. At the lower end of the valve stem 56 is a valve body 56 that seats on the valve seat 49 as it rises.
a is provided, and the valve body 56a, which had been opened by the gas pressure in the cavity 14, is seated due to the inertia of the molten metal advancing at high speed from the cavity 14, and the valve body 56a is seated in the inner chamber of the spool 46 and the gas vent groove. 41 and bypass 48. Reference numeral 57 denotes a ball that engages with the groove 56b of the valve stem 56 under the bias of a compression coil spring 58, 54 a bolt, and 55 a nut, which form a locking mechanism. The valve body 56a, once closed by the pressure of the molten metal, is configured so that it will not open again due to the action of members such as the tension spring 52 unless an external force is applied. Note that the valve body 56a is opened by pushing down the rod portion 51a of the return rod 51. 59
is a stopper fixed to the bracket 43 that restricts the upper limit of the rise of the rod portion 51a of the return rod 51 which rises together with the spool 46 due to the operation of the cylinder 44. An exhaust hole 60 is opened at the lower end of the spool 46, and this exhaust hole 60 is connected to the first
It is connected to piping 61 of the pneumatic circuit shown in the figure (described later).

Next, the plunger 20 and the gas venting device 42
The pneumatic circuit will be explained based on FIG. The pipe 63 connected to the vacuum pump 62 is branched into a pipe 64 and a pipe 65 in the middle, and the pipe 63,
64, a vacuum tank 66 and an auxiliary vacuum tank 6 are installed.
7 are provided respectively, and the piping 6
3 and 64 are connected to the pipes 61 and 35 via filters 68 and 69, respectively. Solenoid valves 70 and 71 are disposed on the pipes 64 and 65, respectively. When the solenoid of the solenoid valve 70 is excited from the state shown in the figure, the air in the plunger 20 is sucked, and the solenoid of the solenoid valve 71 is When energized, air inside the cavity 14 is sucked through the gas venting device 42. In this case, the suction on the degassing device 42 side is faster than the suction on the plunger 20 side by about 0.2 seconds to 1 second, preferably by 0.3 seconds, according to a command from a timing regulating device (not shown).
It is set to be delayed by ~0.5 seconds. Also, the degree of vacuum is, for example, 200~ on the plunger 20 side.
300 Torr, 150 to 250 Torr on the gas venting device 42 side
This is achieved by providing an auxiliary vacuum tank 67. Auxiliary vacuum tank 6
7 is provided as close to the plunger 20 as possible in consideration of resistance generated in relatively thin piping sections and passages during vacuum suction. Further, the pipe 35 having the flexible hose 35a is made as short as possible and has a relatively large pipe diameter, for example, 1 inch.

Further, the other ports of the solenoid valves 70 and 71 are connected to piping 74 and 75 equipped with solenoid valves 72 and 73, respectively.
are joined to a pipe 77 equipped with a variable throttle valve 76 and connected to, for example, an air compressor 78 in a factory. Then, close the solenoid valves 70 and 71 and close the solenoid valve 7.
By opening 2 and 73, high pressure air is sent to the plunger 20 and the degassing device 42 and is used for spraying for internal cleaning.

A casting method using the die casting machine configured as above will be explained. The movable mold 12 is moved to the illustrated position and the mold is clamped, and the gas venting device 4
The second cylinder 44 is operated to engage the spool 46 into the spool holes of the molds 11 and 12 as shown. At this time, the piston rod 19 of the injection cylinder 18 and the injection sleeve 22 are lowered, so the injection cylinder 18 is tilted, the plunger 20 injects the molten metal into the lowered injection sleeve 22, and then raised again. Injection sleeve 22
is raised to engage the fixation sleeve 17 as shown. After evacuation, oil is supplied to the injection cylinder 18 and the piston rod 19 is raised, causing the plunger 20 to rise and injection of molten metal, indicated by reference numeral 80 in FIG. 2, to begin. At this time, cold water is supplied to the plunger 20 from the cold water inlet 35b, and this cold water rises in the pipe 29b and then overflows into the space 23a and flows into the cold water passage 36.
Since the water is flowing down inside, the plunger tip 23 and the plunger rod 24 are cooled.
Furthermore, the injection sleeve 22 is also cooled from the outside by a cooling device (not shown). Therefore, the upper end surface of the plunger tip 23 and the inner wall surface of the injection sleeve 22 that follows the upper end surface of the plunger tip 23 are
A solidified layer indicated by reference numeral 1 in the figure is generated by the solidification of the molten metal. Then, inside the vacuum tank 60 and the auxiliary tank 6
7 has been previously depressurized by suction with the vacuum pump 62, so when the solenoid valve 70 is first opened before or during injection, negative pressure acts on the suction hole 34 of the plunger rod 24.
The air in the annular groove 23b of the plunger tip 23 flows through the air passage 23c, the annular groove 26a, and the filter 3.
1. Air passage 27b, annular groove 27a, air passage 3
3 and the outgoing path of the air passage 32. Also, after a delay of, for example, 0.3 to 0.5 seconds, the solenoid valve 71
Since the valve body 56a of the gas venting device 42 is open at this time, the gas in the cavity 14 is sucked from the exhaust hole 60 via the gas venting path 40, the gas venting groove 41, and the bypass 48, and the gas in the cavity 14 The gas inside is discharged. In this way, by suctioning from both the plunger 20 side and the gas venting device 42 side, the cavity 14
Inside, injection sleeve 22, plunger tip 23
Although the vacuum level is the same in the gaps between the two, by sucking the plunger 20 side slightly faster and making the vacuum level on the plunger 20 side larger than the vacuum level on the gas venting device 42 side, the vacuum level shown in Fig. 1 is obtained. As shown, the solidified layer 1 is strengthened by adhering to the end face of the plunger tip 23 and the annular recess around it, and as the plunger tip 23 is cooled, the solidified layer 1 is strengthened by 300 degrees
The solidified layer 1 becomes thicker by cooling to ~400°C. This prevents outside air from entering through the gap between the injection sleeve 22 and the plunger tip 23. Moreover, the molten metal does not get inserted into the cavity 14 before the molten metal is injected.

After creating a vacuum inside the cavity 14 in this way, the injection operation begins, and when the plunger 23 is advanced while degassing, the molten metal 80 in the injection sleeve 22 spreads between the fixed sleeve 17 and the constricted portion 15. is injected into the cavity 14,
When the cavity 14 is filled with the molten metal 80, the molten metal 80 rises in the gas vent groove 41 and comes into contact with the lower surface of the valve body 56a together with the gas. At this time, the impact applied to the valve body 56a is larger than the impact applied to the gas valve body 56a, because the mass of the molten metal 80 is extremely large compared to the mass of the gas and has a large inertia.
The valve body 56a moves upward while compressing the compression coil spring 58 with the ball 57, and the valve body 56a closes the valve seat 49. Therefore, even if the molten metal 80 is blocked from flowing out from the valve seat 49 and mixes with the gas in the gas venting path 40 and the gas venting groove 41 and hits the valve body 56a discontinuously in the form of droplets, the molten metal 80 is prevented from flowing out from the valve seat 49. Since the valve body 56a pushed up by the molten metal 80 is pulled upward by the tension spring 52, the upper position is maintained and the valve body 5
The exhaust passage is reliably closed by 6a.

After being pressurized and cooled for a predetermined time with the valve body 56 a closed, the movable mold 12 is opened, and the spool 46 is raised by the cylinder 44 of the degassing device 42 to release the engagement with the movable mold 12 . Remove the product from the

Note that when the spool 46 is raised, the valve body 56
Due to the separation resistance between a and the solidified metal, only the spool 46 rises and the valve stem 56 rises with a delay.As a result, the ball 57 that had come off from the groove 56b of the valve stem 56 engages with the groove 56b again, and the next time Preparation for casting will be completed. Furthermore, at the upper limit of the spool 46, the return rod 51 contacts the stopper 59 and pushes down the valve rod 56, so that the valve body 56a is reliably opened and ready for the next casting.

Note that this embodiment shows an example in which the present invention is applied to a vertical casting type die-casting machine, but in this case, the timing of evacuation can be performed immediately after the molten metal inlet of the injection sleeve is closed after the start of injection. For example, the same method can be applied to a horizontal casting type die-casting machine.

〔Effect of the invention〕

As is clear from the above description, in the casting method for a die casting machine according to the present invention, an annular groove communicating with the mold cavity through a gap is provided on the outer peripheral surface of the plunger tip, and a gas venting device is provided in the mold cavity. After the plunger tip starts to move forward or in the middle of its forward movement, the air in the annular groove starts to be sucked to the outside, and after a short delay, the air in the mold cavity is sucked to the outside via the gas venting device. As a result, the solidified layer of molten metal formed on the end face of the plunger tip adheres to this end face, and as it cools, it becomes thicker and stronger, preventing outside air from entering through the gap between the plunger tip and the injection sleeve. This solidified layer prevents intrusion and prevents molten metal from penetrating into the mold cavity, and eliminates the mixing of impurities into the molten metal, ensuring good injection and quality of cast products. is significantly improved.

[Brief explanation of drawings]

1 to 7 are diagrams shown to explain the casting method of the die casting machine according to the present invention, in which FIG. 1 is a schematic configuration diagram and pneumatic piping diagram of the casting device, and FIG. 2 is an injection An enlarged sectional view of the sleeve and plunger, Fig. 3 is a sectional view AA in Fig. 2, Fig. 4 is a sectional view BB in Fig. 2, Fig. 5 is a sectional view CC in Fig. 2, and Fig. 6 is a sectional view in Fig. 2. Longitudinal cross-sectional view of the mold degassing device, No. 7
The figure is a DD sectional view of FIG. 6, and FIG. 8 is an explanatory diagram of the state of the solidified layer in the conventional casting method. 11...Fixed mold, 12...Movable mold, 14...
...Cavity, 20...Plunger, 22...Injection sleeve, 23...Plunger tip, 23b
...Annular groove, 23c...Air passage, 24...Plunger rod, 24c...Air passage hole, 26...
Adapter, 26a... Annular groove, 27... Adapter, 27a... Annular groove, 27b... Air passage, 2
8...Reducing pipe, 31...Filter, 32, 33...
...Air passage, 42...Mold gas venting device.

Claims (1)

[Claims] 1 Before the plunger tip moves forward inside the injection sleeve for casting, or during its forward movement, the air in the annular groove provided on the outer circumferential surface of the plunger tip begins to be sucked to the outside, and after a slight delay, the metal A casting method for a die-casting machine, which is characterized in that air in the mold cavity is started to be sucked to the outside through a gas venting device, and casting is performed while continuing suction from these annular grooves and the mold cavity.