JP4102953B2 - Injection molding machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an injection molding machine according to a molding technique.
[0002]
[Prior art]
In the past, as a countermeasure against air / gas related defects, the mold cavity was filled with high vacuum by evacuation with a vacuum pump, but the parting surface was sealed to prevent burr leakage. In addition, since vacuuming by the vacuum pump stops immediately after filling, the degree of vacuum in the cavity decreases due to air gas generated from the dough and compression of the unfilled part due to filling, and filling Air / gas related defects may occur at the end.
[0003]
Also, as countermeasures, (1) movement of defective parts to non-functional parts due to change of mold structure, (2) addition of roughness and air vent to parting surface near defective parts, (3) deburring molding However, these have disadvantages such as (1) increase in mold cost, (2) need for maintenance such as clogging of the air vent, and (3) addition of finishing process.
[0004]
[Problems to be solved by the invention]
In view of the above, the present invention is directed to the air gas generated at the product filling end by filling the mold cavity with the molding material while forcibly discharging the air gas in the cavity from the parting surface of the mold. An object of the present invention is to provide an injection molding machine capable of preventing a related defect and eliminating the disadvantages found in the above-described conventional technology.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, in the injection molding machine according to claim 1 of the present invention, the size of the gap between the parting surfaces is changed from large to small as the clamping pressure is switched from low pressure to high pressure. A mold having a surface roughness on the parting surface so that the mold can be switched, an injection unit for filling the mold cavity with a molding material, and a mold clamping pressure and a mold clamping pressure. A mold clamping unit that switches the size from low pressure to high pressure, a circuit that evacuates the cavity, and a circuit that communicates directly with the cavity and a circuit that communicates with the cavity via a parting surface. and a vacuum mechanism to perform respectively from the circuit, according to the surface roughness parting surface to set the clamping pressure before the start clamping after material filled to a low pressure Forming a Kina gap performs vacuum in this state, to start the filling, but the air gas gap parting plane switching the clamping pressure to a high pressure while continuing the evacuation immediately before filling is completed passes It is characterized by being made small so as not to cause burrs leakage .
[0006]
According to a second aspect of the present invention, there is provided an injection molding machine having a function of switching a mold clamping pressure from a low pressure to a high pressure immediately before completion of filling of a molding material into a mold cavity, and a parting surface of the mold. And providing a surface roughness on the parting surface to change the size of the gap from large to small according to the switching of the clamping pressure, and before and after the switching, Air gas is forcibly discharged from the gap by vacuuming, and after clamping and before filling the material, the clamping pressure is set to a low pressure to form a large gap due to the surface roughness on the parting surface. performs pull starts filling, but the air gas gap parting plane switching the clamping pressure to a high pressure while continuing the evacuation immediately before filling is completed passes no burr leakage occurs It is characterized in that small.
[0007]
In the injection molding machine according to the first or second aspect of the present invention having the above-described configuration, the size of the mold clamping pressure is set to a relatively low pressure before starting the material filling, so that the parting surface of the mold is relatively A large gap is formed. Therefore, in this state, evacuation is performed from outside the cavity through the cavity and a parting surface having a relatively large gap (the former vacuum evacuation is from the circuit directly communicating with the cavity, Vacuuming from the outside of the cavity through the latter parting surface with a relatively large gap from the circuit communicating with the cavity via the parting surface) , which causes the vacuum piping inside and outside the cavity to be in a high vacuum state It becomes. After that, when filling is started, the evacuation from the inside of the cavity is stopped, but the evacuation from outside the cavity through the parting surface having a relatively large gap is continued. The degree is kept at a certain high level. Next, immediately before the completion of material filling, the size of the mold clamping pressure is switched to a relatively high pressure, whereby the gap between the parting surfaces is switched to a relatively small one. Therefore, in this state, the air gas is discharged by the subsequent evacuation, but the burr leakage is prevented because the gap is small.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, an injection molding machine 1 according to the embodiment includes a mold 2, an injection unit 9, a mold clamping unit 12, and a vacuuming mechanism 15. In addition, a vacuum pump 18, a hydraulic unit 19 and a PLC 20 are provided to operate them.
[0009]
First of all, the mold 2 is composed of a combination of an upper mold 3 and a lower mold 4 that can be brought into contact with and separated from each other, and includes a sprue 5, a gate (not shown), a cavity 7, a parting surface 8, and a vacuum. It has a chamber 6 and the like, and the size of a gap (not shown) formed in the parting surface 8 in response to switching of the clamping pressure (also referred to as clamping force) from low pressure to high pressure. Surface roughness (also referred to as roughness, not shown) is formed on the parting surface 8 so that the thickness can be switched from large to small. This surface roughness is formed on the entire circumference or a part of the parting surface 8. Examples of the forming method include a satin finish process by electric discharge machining and an iris pattern process by grinding stone polishing. The standard value of the surface roughness to be formed is determined by the required degree of vacuum in the cavity 7, the amount of fabric generated air / gas, filling conditions, and the like.
[0010]
The injection unit 9 includes an injection hydraulic cylinder 10, an injection screw 11, and the like, and controls the injection pressure and the injection speed with the hydraulic pressure adjusted by the hydraulic unit 19.
[0011]
The mold clamping unit 12 includes a mold clamping cylinder 13 and a hot platen 14 and controls the mold clamping pressure and the mold clamping speed with the hydraulic pressure adjusted by the hydraulic unit 19.
[0012]
The evacuation mechanism 15 is a vacuum circuit provided in the mold 2 or the like for evacuating the cavity 7 and includes a circuit 16 from the cavity 7 that is closed immediately after filling of the molding material, and a party until filling is completed. It is configured by a combination with a circuit 17 outside the cavity 7 that can be evacuated via the ring surface 8, and the inside of the cavity 7 is evacuated by the operation of the vacuum pump 18. The vacuum pump 18 is a vacuum pump for evacuating the cavity 7, and performs evacuation by a control signal from the PLC 20 from the start of filling of the molding material to the end of filling.
[0013]
The hydraulic unit 19 includes a hydraulic pump, a motor (none of which are shown), and the like, and adjusts the hydraulic pressure to a set value by a control signal from the PLC 20.
[0014]
The PLC 20 is a control device that controls the operation of the hydraulic unit 19 and the vacuum pump 18.
[0015]
The injection molding machine 1 according to this embodiment has the above-described configuration. In other words, the injection unit 9 can control the injection pressure by controlling the hydraulic pressure, and the mold clamping pressure can be controlled by controlling the hydraulic pressure. The mold clamping unit 12, the hydraulic unit 19 that performs hydraulic control, the injection molding machine 1 having the vacuum pump 18 and the vacuum circuits 16, 17, and the mechanism that can evacuate the cavity 7 from inside the cavity 7 and from outside the cavity 7. And a mold 2 having a parting surface 8 formed with a certain surface roughness, and a PLC 20 capable of controlling the operation of an injection molding machine, from the start of filling of the molding material to the completion of filling. In the meantime, the mold cavity 7 is always kept at a high vacuum, and specifically operates as follows.
[0016]
That is, as shown in FIG. 2, the injection pressure transmitted from the hydraulic unit 19 to the injection unit 9 is P1h at the start of material filling, and is switched to the holding pressure P1l to prevent mold opening at the filling rate f2. On the other hand, the mold clamping pressure transmitted from the hydraulic unit 19 to the mold clamping unit 12 is initially P21, and is switched to P2h in order to prevent burrs leakage at the filling rate f1. The gap generated on the parting surface 8 when the mold 2 having the parting surface 8 having a certain roughness is clamped is h1 at P2l and h2 at P2h. By vacuuming from inside the cavity 7 and outside the cavity 7 through the parting surface 8 having the gap h1 before starting the material filling, the vacuum piping inside the cavity 7 and outside the cavity 7 is in a high vacuum state. Thereafter, filling is started and evacuation from inside the cavity 7 is stopped, but the degree of vacuum inside the cavity 7 is fixed by evacuation from outside the cavity 7 through the parting surface 8 having the gap h1. Kept at a high level. At the filling rate f1 immediately before the material reaches the parting surface 8, the mold clamping pressure is switched to P2h to prevent burr leakage, and accordingly, the gap generated on the parting surface 8 is h2, and the air gap from the gap of h2 Gas passes, but no burrs leak.
[0017]
Therefore, by the above operation, it is possible to fill the material in a state where the cavity 7 is kept in a high vacuum until just before filling, and it is possible to prevent the occurrence of air / gas related defects, and also the occurrence of burr leakage. This can be prevented.
[0018]
Further, by filling the forming material into the cavity 7 while forcibly removing the air gas in the cavity 7 from the parting surface 8 of the mold 2, the required clamping pressure before filling and the level of the degree of vacuum in the cavity are lowered. As a result, the cycle time can be shortened. That is, in general, a thermoplastic plastic does not cause burrs even if there is a gap of several μm to several tens of μm on the mold parting surface. Therefore, sufficient air / gas measures can be taken with an air vent or the like, and there is no need to consider the degree of vacuum in the cavity before filling. However, in thermosetting plastics, especially rubber, etc., burrs leak even from minute gaps on the order of microns, so the parting surface is often sealed and formed on the order of microns, so air and gas countermeasures must be taken before filling. It is carried out by evacuating the cavity, and a considerable high vacuum (several Torr or comma Torr) is often required. Therefore, in the past, the mold was clamped at a high pressure before filling and the parting surface was sealed, and the inside of the cavity was evacuated by a vacuum pump. long. On the other hand, according to the injection molding machine 1, since it is not necessary to make the inside of the cavity 7 particularly high vacuum, the cycle time can be shortened.
[0019]
That is, as shown in FIG. 3, injection molding with rubber vulcanization is generally performed by cycles of “clamping”, “SK (evacuation)”, “injection (filling)”, “vulcanization”, “mold opening”, and “mold release”. However, since it is not necessary to make the inside of the cavity 7 high vacuum as described above, it is possible to shorten the mold clamping time and the vacuuming time. In some cases, the vacuuming time can be eliminated by performing the mold clamping operation and the vacuuming operation in parallel.
[0020]
【The invention's effect】
The present invention has the following effects.
[0021]
That is, in common for each claim,
(1) First, as a relatively low clamping pressure until just before completion of filling, a sufficient parting surface clearance for air and gas venting is secured, and the inside of the cavity is vented by a vacuum pump through the parting surface. By performing filling while maintaining a high vacuum, it is possible to prevent air / gas-related defects occurring at the product filling end.
[0022]
(2) Further, by filling with degassing with a vacuum pump, mold contamination due to gas generated from the material can be reduced, the mold cleaning frequency can be reduced, and the mold life can be extended.
[0023]
(3) By using a lower clamping force than before until just before filling, mold deterioration (parting surface sag, etc.) due to clamping pressure can be reduced and the mold life can be extended. it can.
[0024]
(4) Furthermore, the mold clamping time and the evacuation time can be shortened, and the cycle time can be shortened.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a configuration of an injection molding machine according to an embodiment of the present invention. FIG. 2 is an operation explanatory diagram of the injection molding machine. FIG. 3 is an operation explanatory diagram of the injection molding machine.
1 Injection molding machine 2 Mold 3 Upper mold 4 Lower mold 5 Sprue
6 Vacuum Chamber 7 Cavity 8 Parting Surface 9 Injection Unit 10 Injection Hydraulic Cylinder 11 Injection Screw 12 Mold Clamping Unit 13 Clamping Cylinder 14 Hot Plate 15 Vacuum Pulling Mechanism 16, 17 Circuit 18 Vacuum Pump 19 Hydraulic Unit 20 PLC

Claims (2)

The surface roughness of the parting surface (8) is changed so that the size of the gap of the parting surface (8) is switched from large to small as the size of the clamping pressure is switched from low pressure to high pressure. A mold (2) in which a mold is formed, an injection unit (9) for filling a cavity (7) of the mold (2) with a molding material, and a mold clamping pressure is applied to the mold (2). A clamping unit (12) for switching the pressure level from a low pressure to a high pressure, and a circuit for evacuating the cavity (7) are connected to the circuit (16) and the cavity (7) directly communicating with the cavity (7). A evacuation mechanism (15) that is configured by a circuit (17) that communicates with each other via a nip surface (8) and that performs evacuation from both the circuits (16) and (17),
After mold clamping and before material filling starts , the mold clamping pressure is set to a low pressure to form a large gap due to the surface roughness on the parting surface (8). In this state, vacuuming is performed, filling is started, and filling is completed. An injection molding machine characterized in that the clamping pressure is switched to a high pressure while vacuuming is continued immediately before, and the gap between the parting surfaces (8) is reduced so that air gas passes but no burr leakage occurs . A function of switching the pressure of the clamping pressure from a low pressure to a high pressure just before the filling of the molding material into the cavity (7) of the mold (2), and a surface on the parting surface (8) of the mold (2) A function of switching the size of the gap set in the parting surface (8) from large to small according to switching of the mold clamping pressure by providing roughness; 7) The air and gas inside are forcibly discharged from the gap by evacuation,
After mold clamping and before material filling starts , the mold clamping pressure is set to a low pressure to form a large gap due to the surface roughness on the parting surface (8). In this state, vacuuming is performed, filling is started, and filling is completed. An injection molding machine characterized in that the clamping pressure is switched to a high pressure while vacuuming is continued immediately before, and the gap between the parting surfaces (8) is reduced so that air gas passes but no burr leakage occurs .

Images