WO2008086181A1 - Machine à couler sous pression avec pression d'injection statique réduite - Google Patents

Machine à couler sous pression avec pression d'injection statique réduite Download PDF

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Publication number
WO2008086181A1
WO2008086181A1 PCT/US2008/050236 US2008050236W WO2008086181A1 WO 2008086181 A1 WO2008086181 A1 WO 2008086181A1 US 2008050236 W US2008050236 W US 2008050236W WO 2008086181 A1 WO2008086181 A1 WO 2008086181A1
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WO
WIPO (PCT)
Prior art keywords
valve
injection
plunger rod
shot cylinder
coupled
Prior art date
Application number
PCT/US2008/050236
Other languages
English (en)
Inventor
James A. Yurko
Thomas L. Scholten
Robert J. Ii Mcinerney
Rodger W. Brower
Mark E. Los
Original Assignee
Buhlerprince, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Buhlerprince, Inc. filed Critical Buhlerprince, Inc.
Publication of WO2008086181A1 publication Critical patent/WO2008086181A1/fr

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D17/00Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
    • B22D17/20Accessories: Details
    • B22D17/32Controlling equipment
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D17/00Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
    • B22D17/08Cold chamber machines, i.e. with unheated press chamber into which molten metal is ladled
    • B22D17/10Cold chamber machines, i.e. with unheated press chamber into which molten metal is ladled with horizontal press motion
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17Component parts, details or accessories; Auxiliary operations
    • B29C45/46Means for plasticising or homogenising the moulding material or forcing it into the mould
    • B29C45/53Means for plasticising or homogenising the moulding material or forcing it into the mould using injection ram or piston

Definitions

  • the present invention relates to die casting machines and methods for controlling the injection pressure, particularly during the final stages of the injection process.
  • Die casting machines inject metals, polymers, or other material in a controlled fashion into a mold (a.k.a. tool or die) that is clamped in a closed position by the machine.
  • the metal is typically injected into a die using a hydraulic cylinder.
  • the metal is injected into the die with a controlled or predetermined velocity and/or pressure.
  • Backpressure from pushing the metal through a thin die entrance i.e., gate
  • the hydraulic force of the injection cylinder applies hydrostatic pressure to the metal in the die.
  • the metal undergoes a volumetric change that typically contracts the metal, causing porosity in the part known as shrinkage. Shrinkage is minimized through the injection of more molten metal via the high pressure applied to the injection cylinder. Frequently, especially in the casting of aluminum alloys, a higher pressure source is actuated on the head side of the injection cylinder, to further increase the force of the cylinder by a factor of up to five times the injection force used for the initial die filling.
  • the projected area of the casting that is the surface area of the casting that is perpendicular to the closing axis of the die casting machine, is limited by the hydrostatic metal pressure of the solidifying metal.
  • the product of the projected area and hydrostatic metal pressure cannot exceed the clamping force of the die casting machine. For example, a part with 100 sq. in. of projected area and 10,000 psi of applied metal pressure from the injection cylinder would have 1,000,000 pounds of separating force, or 500 tons.
  • the 500 tons of force requires a die casting machine with 500 tons of clamping force to maintain the die closed during the casting process.
  • This product of hydrostatic metal pressure and casting projected area constrains the size of parts that can be produced for a given size of die casting machine.
  • Fig. 1 shows a typical molten metal injection system including a hydraulic shot cylinder 10 having a piston 12 coupled to a plunger 14.
  • the diagram represents part of an overall die cast machine which can be of a conventional commercially available design.
  • Shot cylinder 10 is activated by a pressurized source of hydraulic fluid applied at an inlet 16.
  • An outlet 18 releases hydraulic fluid from the shot cylinder to a reservoir 19 through valve 17.
  • Plunger 14 extends into a cylindrical cold chamber 20, which has a molten metal inlet 22.
  • Plunger 14 has a plunger tip 24, which typically has a smaller diameter than the diameter of the shot cylinder piston 12. Plunger tip 24 forces molten metal out of an exit end 26 of cold chamber 20.
  • the exit end 26 of cold chamber 20 communicates with one or more runners 32 formed in die halves 30, 31.
  • the width of runner(s) 32 is typically less than 1 inch.
  • the runner(s) 32 each communicate with a gate 34 leading to the mold cavity 36 in die halves 30, 31.
  • the mold cavity 36 typically will also communicate with one or more overflow cavities 38.
  • FIG. 2 An example of a typical injection profile for the operation of the machine of Fig. 1 is shown in Fig. 2.
  • the available force of the shot cylinder 10 is plotted versus the position of the plunger rod 14.
  • the hydraulic cylinder pushes the molten metal in the cold chamber 20 towards the cavity 36.
  • the cold chamber is not completely filled after pouring, so in this flow regime, an injection cylinder advances the metal to completely fill the cold chamber 20.
  • the cold chamber is typically a cylinder with large diameter (greater than 1").
  • the separating force is now equal to the metal pressure in the cold chamber multiplied by the cross-sectional area of the cold chamber.
  • the runner 32 begins to fill with metal.
  • the runner is substantially smaller in cross section than the cold chamber, typically less than 1" in diameter.
  • the smaller cross section begins to create back pressure in the metal within the runner and cold chamber, and thus the hydraulic fluid in shot cylinder 10.
  • the separating force increases by an amount equal to the metal pressure multiplied by the projected area of the runners plus the increased pressure applied to the cross-sectional area of the cold chamber.
  • the metal begins to flow into the part through the gate 34.
  • the gate is relatively thin, with a thickness which can vary from .020" to .500", but is typically less than .100" for most die castings.
  • Overflows are designed to create back pressure within the casting, and also capture metal ridden with gas, lubricants, defects, etc.
  • the pressure rises yet again within the metal and the hydraulic cylinder, and the die separating force correspondingly increases because of the increased back pressure on the metal in the casting portion of the cavity.
  • a die casting machine injection system of the present invention decreases the hydraulic force during the final stages of injection of a molten alloy into a die, culminating with a final hydrostatic pressure on the alloy in the filled cavity that is less than the dynamic injection pressure. This is in contrast to current state of the art die casting machines which use either the same hydraulic force for injection and intensification, or a higher intensification force and do not decrease force during the final stages of injection and intensification.
  • a method of die casting parts according to the present invention includes initially injecting a molten alloy having the characteristics of minimal volumetric contraction during solidification into a die cavity during a filling stage, monitoring at least one of: 1) the pressure of the shot cylinder for injecting a molten alloy into the die cavity or 2) the position of the plunger rod for injecting the molten alloy into a die cavity, and reducing the injection pressure during the final stage of filling of the die mold for reducing the die separating force at the end of a molding cycle.
  • a die casting machine embodying the present invention includes a shot cylinder having one of a pressure detector located for detecting the hydraulic pressure applied to the cylinder or a position sensor for a plunger rod.
  • the plunger rod includes a tip extending into a cold chamber, which receives a molten alloy having a minimal shrinkage characteristic.
  • the machine also includes a source of hydraulic pressure, a control valve coupling said hydraulic pressure source to said shot cylinder, and a control circuit coupled to said valve and to one of said detector or sensor for reducing the injection pressure near the end of an injection cycle.
  • the resultant machine and operation greatly reduces the die separating forces at the end of a casting cycle where low shrinkage alloys are employed and allows the casting of larger parts with lower tonnage die casting machines. Larger projected areas of parts can be made on the same size of die casting machine that was previously limited by the higher final force. This increases the size and/or number of castings that may be made on a given die casting machine. The cost of the die casting machine can also decrease, because less clamping force is necessary to perform the process for a given sized part.
  • Fig. 1 is a schematic diagram of the injection system of a typical molten metal die casting machine
  • Fig. 2 is a diagram showing an injection profile (force verses stroke) of such a typical die casting machine
  • Fig. 3 is a schematic diagram of the injection system of a die casting machine incorporating the present invention
  • Fig. 4 is a diagram showing an injection profile (force verses stroke) of the method of operation of the machine shown in Fig. 3
  • Fig. 5 is an electrical diagram in schematic and block form of the control system for the machine shown in Fig. 3.
  • the injection system shown in Fig. 3 and its method of control can be employed. It should be understood that the injection system of Fig. 3 is part of an overall die casting machine, which can be of the type disclosed in U.S. Published Patent Application 2003/0217829, the disclosure of which is incorporated herein by reference. The injection method and equipment of Fig. 3, however, can be incorporated in any conventional die casting machine to achieve the desired result of reducing the final injection pressure during the casting process.
  • an injection system 60 which includes a shot cylinder 70 supplied on its intake side through an inlet 72 coupled to a control servo valve 74 and, in turn, coupled to a source of hydraulic fluid pressure 76.
  • the net forward force provided by shot cylinder 70 can be reduced by decreasing the head-side pressure in the shot cylinder.
  • a servo valve 74 (Figs. 3 and 5), under the control of circuit 50, can be used to reduce the pressure during the final stages of filling from a high pressure source of hydraulic fluid 76, reducing the head pressure and, thus, the net forward force.
  • Shot cylinder 70 includes a piston 80 and plunger rod 82 extending therefrom having a plunger tip 84 which extends into a cold chamber 86 coupled to die halves 90 and 91.
  • Cold chamber 86 has an inlet 88 through which molten alloy, such as a glass metal alloy is poured for filling the cold chamber 86 prior to the injection molding of the alloy into a die cavity 96 through gate 94 and outlet 89 of cold chamber 86.
  • Die cavity 96 also communicates with an overflow 98. Cavity 96 forms, with die halves 90 and 91, the shape of a part to be molded.
  • Restricting the hydraulic flow out of the rod-side outlet 71 of the shot cylinder 70 is a technique for controlling velocity of the shot cylinder plunger rod 82.
  • a servo-hydraulic, flow-control valve 73 (Figs. 3 and 5), such as the Parker TDL valve, controls the amount of hydraulic fluid exiting the rod-side of the shot cylinder into a reservoir 75. Restricting this exiting flow raises the pressure in the rod-side hydraulic fluid, also decreasing the net forward force of the shot cylinder.
  • the servo-hydraulic valve 73 can completely restrict the flow from the rod-side of the shot cylinder, thus stopping the shot cylinder and decreasing its net forward force to zero.
  • the servo-hydraulic valve can be controlled by different techniques; two examples include shifting the valve at a predetermined position of the shot cylinder based upon an input signal from a position sensor 54 (Fig. 5) associated with rod 82 or shifting the valve when the pressure (detected by pressure detector 52 shown in Fig. 5) rises above a selected level that is associated with the end of the part-cavity filling, regime 3 of Fig. 4.
  • the Fig. 4 example of an injection profile using the invention shows the large injection forces in regime 3 necessary to inject the molten alloy through the thin orifice (gate) into the casting, which itself is quite thin. The available force is shown by the dotted line. However, when the casting is nearly filled, the force is reduced (dash-dot line). The force cannot be decreased too early in the process, otherwise the casting will not completely fill with molten alloy.
  • One major benefit of the process is the reduced die separating force in regime 5, especially when compared with that of Fig. 2, regime 5.
  • a bypass conduit 100 couples outlet 71 to inlet 72 by means of a control valve 102 for further controlling the force applied by the plunger rod 82 to plunger tip 84.
  • the control circuit 50 has outputs which provide signals to control servo valve 74, bypass valve 102, and discharge valve 73.
  • Circuit 50 receives pressure information from detector 52 and rod 82 position information from sensor 54.
  • Circuit 50 is programmed to control the pressure on piston 80 of shot cylinder 70 for controlling the movement of plunger rod 82 and, therefore, the pressure applied to the metallic alloy in cold chamber 86 by plunger tip 84 according to the desired characteristics as shown in the pressure profile of Fig. 4.
  • mold cavity 96 may require a specific pressure profile also the use of different glass metal alloys may result in different operating pressure profiles.
  • One typical profile is illustrated in Fig. 4. Because the flow is restricted out of the rod-side outlet 71 of the shot cylinder 70, the net force of the cylinder is near zero, as shown at regime 5 in Fig. 4.
  • the ratio of the pressure on the head and rod side of the shot cylinder is inversely proportional to the area of the head and the annular area on the rod-side of the cylinder.
  • a shot cylinder with a 4" diameter head and a 2" diameter rod would have a head area of 12.6 sq. in. and an annular area of 9.4 sq. in. Therefore, if the head pressure was 3000 psi, the rod-side pressure would be 4000 psi.
  • a 1 : 1 head to annular area shot cylinder can be utilized.
  • the 1 :1 ratio cylinder could be utilized to decrease net forward force to zero by not only completely restricting the flow-out of the rod-side, but also by allowing hydraulic fluid to flow between the head and rod side of the cylinder by opening bypass valve 102 in the coupling (bypass) circuit 100.
  • the pressure on the head and rod side are, therefore, equal, known as a regenerative mode.
  • this regenerative mode if the head- side of the cylinder has a larger area than the rod annular area, there is a net forward force (a reduced force compared to the capability of the cylinder), and with a 1 : 1 head to annular area cylinder, the net forward force is zero.
  • a shot cylinder will also have a net-forward force of zero if the cylinder has fully extended.
  • the stroke of the shot cylinder piston 80 of the die casting machine can be controlled to reach its limit (detected by a limit sensor) during the overflow filling regime of cavity fill thus stopping the shot cylinder.
  • the important criteria is to decrease the force within a short period time, on the order of 10 ms or less, or to stop the injection after the part is filled, but the overflows and therefore the complete cavity have not yet filled.
  • the overflows can be designed to be filled over a longer time frame.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Injection Moulding Of Plastics Or The Like (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)

Abstract

L'invention concerne un procédé de coulage sous pression qui injecte initialement un alliage ayant une contraction volumétrique minimale pendant la solidification dans une cavité de moule, surveille au moins l'une de la pression du vérin d'injection et de la position du plongeur, et réduit la pression d'injection au stade final de remplissage du moule. Une machine à couler sous pression comprend un vérin d'injection ayant l'un d'un détecteur de pression situé pour détecter la pression hydraulique appliquée au vérin ou d'un capteur de position pour une tige de plongeur. La tige de plongeur comprend un embout s'étendant dans une chambre froide, qui reçoit un alliage de métal ayant une caractéristique de retrait minimal. Une source de pression hydraulique est couplée au vérin d'injection par une soupape de commande et un circuit de commande est couplé à ladite soupape et à l'un dudit détecteur ou dudit capteur pour réduire la pression d'injection à proximité de l'extrémité d'un cycle d'injection.
PCT/US2008/050236 2007-01-05 2008-01-04 Machine à couler sous pression avec pression d'injection statique réduite WO2008086181A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US87900007P 2007-01-05 2007-01-05
US60/879,000 2007-01-05

Publications (1)

Publication Number Publication Date
WO2008086181A1 true WO2008086181A1 (fr) 2008-07-17

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WO (1) WO2008086181A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102008055536A1 (de) * 2008-12-17 2010-07-01 Bühler Druckguss AG Verfahren zum Betreiben eines Antriebskolbens einer Druckgiessmaschine und Vorrichtung zur Durchführung des Verfahrens

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009067512A1 (fr) * 2007-11-20 2009-05-28 Buhlerprince, Inc. Machine et traitement de coulée sous vide
CN103624236B (zh) * 2013-09-16 2017-02-08 华南理工大学 一种挤压铸造定量浇注装置及方法
CN103722150B (zh) * 2013-12-30 2015-06-24 宁夏惠冶科技有限公司 镁合金压铸集成控制管理方法
CN104368783B (zh) * 2014-10-17 2016-09-28 烟台三和新能源科技股份有限公司 压力铸造系统及方法
DE102015202273A1 (de) 2015-02-09 2016-08-11 Oskar Frech Gmbh + Co. Kg Druckübersetzervorrichtung und Druckgießmaschinen-Gießaggregat
JP7434017B2 (ja) 2020-03-26 2024-02-20 株式会社日本製鋼所 射出装置
CN116511455B (zh) * 2023-05-09 2024-05-07 佳威科技(海安)有限公司 一种投影仪壳体压铸冷室省料装置

Citations (4)

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Publication number Priority date Publication date Assignee Title
US5365999A (en) * 1992-06-05 1994-11-22 Maschinenfabrik Mueller-Weingarten Ag Method for the process control of a pressure diecasting machine and an apparatus for carrying out the method
US20010013403A1 (en) * 1998-11-02 2001-08-16 Shinobu Kodama Injection control method and device of die-casting machine
US20040016230A1 (en) * 2002-07-23 2004-01-29 Caterpillar Inc. Noise attenuation in a hydraulic circuit
US6699305B2 (en) * 2000-03-21 2004-03-02 James J. Myrick Production of metals and their alloys

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US5618359A (en) * 1995-02-08 1997-04-08 California Institute Of Technology Metallic glass alloys of Zr, Ti, Cu and Ni
KR101190440B1 (ko) * 2002-02-01 2012-10-11 크루서블 인텔렉츄얼 프라퍼티 엘엘씨. 비결정질 합금의 열가소성 주조

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5365999A (en) * 1992-06-05 1994-11-22 Maschinenfabrik Mueller-Weingarten Ag Method for the process control of a pressure diecasting machine and an apparatus for carrying out the method
US20010013403A1 (en) * 1998-11-02 2001-08-16 Shinobu Kodama Injection control method and device of die-casting machine
US6699305B2 (en) * 2000-03-21 2004-03-02 James J. Myrick Production of metals and their alloys
US20040016230A1 (en) * 2002-07-23 2004-01-29 Caterpillar Inc. Noise attenuation in a hydraulic circuit

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102008055536A1 (de) * 2008-12-17 2010-07-01 Bühler Druckguss AG Verfahren zum Betreiben eines Antriebskolbens einer Druckgiessmaschine und Vorrichtung zur Durchführung des Verfahrens

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