WO1994002271A1 - A moulding device - Google Patents
A moulding device Download PDFInfo
- Publication number
- WO1994002271A1 WO1994002271A1 PCT/GB1992/001350 GB9201350W WO9402271A1 WO 1994002271 A1 WO1994002271 A1 WO 1994002271A1 GB 9201350 W GB9201350 W GB 9201350W WO 9402271 A1 WO9402271 A1 WO 9402271A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- cavity
- moulding
- chamber
- piston
- mouth
- Prior art date
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
- B22D17/08—Cold chamber machines, i.e. with unheated press chamber into which molten metal is ladled
- B22D17/10—Cold chamber machines, i.e. with unheated press chamber into which molten metal is ladled with horizontal press motion
Definitions
- the present invention relates to moulding devices, in particular, high pressure die casting machines and is particularly, although not exclusively, concerned with the production of metal castings having low porosity.
- a high pressure die casting (hpdc) machine which is used extensively is the "cold chamber" hpdc machine which manufactures aluminium alloys.
- This machine operates by transferring molten metal from a shot sleeve into a die cavity by means of a high velocity piston or plunger.
- the molten metal is forced along a series of channels or a runner system and through a fixed, narrow gate or opening into the die cavity.
- the liquid metal is then effectively sprayed through the gate to produce a first coating over the surface of the die cavity and then the remainder of the liquid metal is introduced into the cavity to complete the cast article.
- the first coating of liquid metal commonly produces a very fine grain surface layer having a very smooth surface finish.
- the cold chamber hpdc process suffers from two major disadvantages.
- the reduction in pressure transmission will produce die castings which are notoriously porous and may, therefore, not be heat treatable for fear of blistering.
- subsequent machining operations will expose the porosity which causes a high rejection rate.
- the cold chamber hpdc process is commonly only about 33% efficient because approximately 50% of the cast metal (i.e in the runner and gate sections) needs to be removed from each casting for remelting.
- since there is an additional casting scrap rate of 5-15% the efficiency of the cold chamber hpdc process is rarely greater than 25% in material utilisation and considerably less than 20% in energy utilisation.
- Squeeze casting is the term used to denote processes in which liquid metal is solidified under the action of a high external pressure.
- squeeze casting technology Two different types of squeeze casting technology have evolved based upon different approaches to metal metering and metal movement and also upon the manner in which the pressure is applied to the metal in the mould. These two processes have been given the names “direct” and "indirect” squeeze casting.
- the die set is a split mould consisting of a lower female cavity and an upper male punch. Sufficient pressure is applied to the punch, which moves to compress the liquid/solid mixture during freezing to suppress the appearance of either gas porosity or shrinkage porosity in the casting.
- Direct squeeze casting is thus a hybrid process combining gravity die casting with closed die forging.
- liquid metal is injected into a closed die cavity by a small diameter piston, by which mechanism the pressure is also applied during freezing. Squeeze pressures are limited by the size of the piston and, for large area castings, some thin sections of the casting may freeze off locally and prevent the transmission of pressure to remoter regions thus allowing porosity to form.
- the current art of indirect squeeze casting uses vertical injection of liquid metal into the die set which has either a vertical or horizontal opening.
- squeeze casting can produce much lower levels of porosity than high pressure die casting and therefore, a combination of both types of casting would be desirable.
- hpdc usually horizontal machines
- the wad and runners are the only parts which are pressurised to a maximum extent because the gate freezes or solidifies and then the metal in the die freezes under low pressure.
- indirect squeeze casting vertical or horizontal machines
- the same is also true but to a lesser extent because the gates are wide open and are of fixed geometry.
- a moulding device comprising a moulding block defining a moulding cavity, a chamber connected to the cavity in which a piston is slidable, characterised in that a closing means is provided between the chamber and the cavity, the closing means being moveable from a first position, in which the mouth of the chamber is sealed to allow the chamber to be charged with a molten substance whilst the piston is in a retracted position, to one or more further positions which allow the molten substance to be injected directly into the cavity when the piston is activated.
- An advantage of the present invention is that because the piston acts directly on the molten substance in the mould rather than via a runner system and narrow gate, porosity levels will be reduced as there will be little or no freezing of the molten substance at the gate into the block.
- the closing means is moveable to a second position spaced at a small distance from the mouth of the chamber to define a narrow orifice such that a fine spray or jet or film of molten substance is forced through the orifice and is deposited on the inner surface of the cavity when the piston is activated. Whether the molten substance is introduced in spray, jet or film form will depend on the substance used.
- the closing means can be moved into a third retracted position which allows a less restricted entry of molten substance into the cavity.
- the closing means slides through a wall of the cavity.
- the closing means slides through a wall of the cavity opposite to the mouth of the chamber into the cavity.
- the closing means when the closing means is fully retracted it forms part of the inner surface of the cavity.
- the closing means is a pillar which is slidable in a sleeve.
- the device is for use in high-pressure die casting or indirect squeeze casting of metals.
- the present invention further provides a method of moulding an article comprising the steps of closing the mouth of a moulding block, charging a chamber connected to the mouth of the moulding block with a molten substance, opening the mouth to directly inject the molten substance by moving a piston slidable in the chamber.
- the mouth to the block can be partially opened to define a narrow orifice such that when the piston is operated, a fine spray or jet or film of the molten substance is forced through the orifice and deposited on the inner surface of cavity.
- the mouth to the block can be opened further to allow less restricted entry of the molten substance into the cavity.
- Figure 1 depicts a multi-cavity moulding block in perspective
- Figure 2 is a side view of the block in Figure
- Figure 3 is a side view of the arrangement in Figure 2 partially open;
- Figure 4 is a side view of the arrangement in Figure 2 fully open;
- Figure 5 depicts a casting produced by the moulding block in Figure 1;
- Figure 6 depicts the moulding block used to produce a typical wheel centre which can be cast using the moulding device of the present invention
- Figures 7 and 8 show a second preferred embodiment of the moulding device comprising the moulding block in Figure 6;
- Figure 9 depicts a simple square plate (single cavity) moulding block in perspective;
- Figures 10 and 11 show a third preferred embodiment of the moulding device comprising the moulding block in Figure 9.
- Figure 1 shows a moulding block 1 used for die casting of metals.
- the block 1 has a moulding cavity
- the central region 3a will form what is known as the "wad” or “biscuit” and the cavities 3b will form four “legs” or “coupons”.
- the "coupons” could be in any shape depending on end requirements.
- Figure 2 is a side view of the block 1 when connected to a piston 4 which is slidable in a chamber 5.
- a pillar 6 which is slidable in a sleeve 8 seals the central region 3a and the piston 4 is fully retracted. Chamber 5 will be charged with molten metal in this position.
- Figure 3 shows the arrangement when the pillar 6 has been partially withdrawn to produce an annular gap or gate 7 through which the molten metal can pass.
- the piston 4 will be pushed towards the central region 3a and a fine spray of molten metal will coat the inner surface of the four leg cavities 3b.
- Figure 4 shows the pillar 6 fully retracted such that it clears the region 3a forming a wall of the region 3a.
- the piston 4 is pushed to its extreme position to inject all the molten metal into the region 3a and leg cavities 3b.
- Figure 5 depicts a casting produced by the moulding block in Figure 1.
- a central "wad” 9a there is a central "wad” 9a, four “legs” 9b which are generally rectangular in shape and each of which is connected to the central wad 9a by a substantially triangular runner 9c.
- Figure 6 depicts a moulding block for a typical wheel centre which can be produced in accordance with the moulding device of the present invention
- Like reference numerals represent like features to those in Figures 1 to 5.
- Figures 7 and 8 show the configuration of a suitable moulding device used to produce such a wheel centre. In Figure 7, the piston 4 is fully retracted and the pillar is in the position which seals the moulding cavity 2 from the chamber 5.
- the pillar comprises a fixed inner cylinder 6a and a slidable outer cylinder 6b.
- outer cylinder 6b When outer cylinder 6b is withdrawn, a narrow gap or gate 7 is produced through which the molten metal can pass.
- This type of geometry is useful in moulding wheel centres, for example, so that excess metal in the centre can be avoided.
- Figure 9 depicts a simple square plate single cavity moulding block.
- Figures 10 and 11 depict the moulding device which could comprise such a moulding block before and after actuation of the pillar 6 and piston 4.
- liquid alloy in sufficient quantity to fill the moulding cavity 2 comprising a central region 3a and several leg cavities 3b is poured, pumped or syphoned into the shot sleeve 5.
- the piston 4 is retracted and the pillar 6 is in a position to close off the sleeve 5 from central region 3a.
- pillar 6 is moved to a position which creates a gap or gate 7 through which the liquid alloy is injected at high velocity into the moulding cavity 2.
- This first phase of injection coats the moulding cavity 2 with a skin of alloy which solidifies with a smooth surface finish and which possesses a fine grain size.
- the pillar 6 is then withdrawn to a further position and further liquid alloy is injected through the wider gate until the moulding cavity 2 is full of alloy. Pressure is maintained on the central wad 3a formed in the central region by piston 4 effectively squeezing the cast alloy until it has solidified.
- the central region 3a will then be hottest so as to remain liquid for the longest time to allow alloy to be fed to the extremeties of the casting as the alloy progressively solidifies. It has been found that wheel centres made in this way are of extremely high quality and have negligible porosity.
- the sleeve 5 could be positioned between a number of small die cavities.
- the pillar 6 region would then produce a wad of waste metal between the castings but the runner system would be decreased.
- the pillar 6 is machined along its length to create grooves through which gas can be evacuated from the moulding cavity 2.
- the grooves When the pillar 6 is in a closed position (e.g Figure 2) the grooves would emerge into the central region 3a and allow air or another gas to be extracted.
- the pillar 6 When the pillar 6 is partially retracted (e.g Figure 3) the grooves would be enclosed by a tool steel sleeve 8 which would prevent access of liquid metal from central region 3a into the vacuum system.
- the pillar need not be a solid cylindrical construction as depicted in Figures 7 and 8.
- the pillar will be made of tool steel or iron-nickel or an iron-nickel-cobalt alloy of low expansion coefficient.
- the front face can be coated with thin layers of, for example, Al_0 3 /TiN.
- the pillar will slide in a tool steel sleeve 8. Additionally, copper alloy bushings or rings could be provided between the pillar 6 and sleeve 8 to conduct heat away and to limit the separation between the pillar and sleeve.
- the moulding device of the present invention will overcome the problems of partial freezing of the molten metal prior to entering the moulding cavity and will benefit from the effects of squeeze casting as the piston pressure acts directly on the liquid in the cavity rather than via a long runner system.
- the moulding device of the present invention could be used both in die casting arrangements ("cold chamber” and “hot chamber”) and in injection moulding arrangements with minor design modifications to suit end requirements.
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Injection Moulding Of Plastics Or The Like (AREA)
- Molds, Cores, And Manufacturing Methods Thereof (AREA)
Abstract
Description
Claims
Priority Applications (9)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE69231004T DE69231004T2 (en) | 1992-07-23 | 1992-07-23 | A CASTING DEVICE |
CA002140784A CA2140784A1 (en) | 1992-07-23 | 1992-07-23 | A moulding device |
PCT/GB1992/001350 WO1994002271A1 (en) | 1992-07-23 | 1992-07-23 | A moulding device |
JP6503940A JPH07509407A (en) | 1992-07-23 | 1992-07-23 | Molding equipment |
EP92915726A EP0653969B1 (en) | 1992-07-23 | 1992-07-23 | A moulding device |
AU23420/92A AU665015B2 (en) | 1992-07-23 | 1992-07-23 | A moulding device |
GB9501058A GB2283445B (en) | 1992-07-23 | 1992-07-23 | A moulding device |
US08/374,547 US5611387A (en) | 1992-07-23 | 1992-07-23 | Moulding device |
AT92915726T ATE192370T1 (en) | 1992-07-23 | 1992-07-23 | A CASTING DEVICE |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CA002140784A CA2140784A1 (en) | 1992-07-23 | 1992-07-23 | A moulding device |
PCT/GB1992/001350 WO1994002271A1 (en) | 1992-07-23 | 1992-07-23 | A moulding device |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1994002271A1 true WO1994002271A1 (en) | 1994-02-03 |
Family
ID=25677746
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB1992/001350 WO1994002271A1 (en) | 1992-07-23 | 1992-07-23 | A moulding device |
Country Status (2)
Country | Link |
---|---|
CA (1) | CA2140784A1 (en) |
WO (1) | WO1994002271A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2011125015A2 (en) | 2010-04-05 | 2011-10-13 | Bar-Ilan University | Protease-activatable pore-forming polypeptides |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB310261A (en) * | 1927-09-01 | 1929-04-25 | Josef Polak | Improvements in or relating to machines for casting metals |
US2669760A (en) * | 1950-05-04 | 1954-02-23 | Hahn & Kolb | Die or press casting machine |
EP0095513A1 (en) * | 1982-05-27 | 1983-12-07 | Toyota Jidosha Kabushiki Kaisha | Vertical type pressure casting method |
GB2129343A (en) * | 1982-10-26 | 1984-05-16 | Inst Po Metalloznanie I Tekno | Pressure diecasting under the action of gaseous pressure medium |
-
1992
- 1992-07-23 CA CA002140784A patent/CA2140784A1/en not_active Abandoned
- 1992-07-23 WO PCT/GB1992/001350 patent/WO1994002271A1/en active IP Right Grant
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB310261A (en) * | 1927-09-01 | 1929-04-25 | Josef Polak | Improvements in or relating to machines for casting metals |
US2669760A (en) * | 1950-05-04 | 1954-02-23 | Hahn & Kolb | Die or press casting machine |
EP0095513A1 (en) * | 1982-05-27 | 1983-12-07 | Toyota Jidosha Kabushiki Kaisha | Vertical type pressure casting method |
GB2129343A (en) * | 1982-10-26 | 1984-05-16 | Inst Po Metalloznanie I Tekno | Pressure diecasting under the action of gaseous pressure medium |
Non-Patent Citations (1)
Title |
---|
Patent Abstracts of Japan, Vol 6, No 267, M-182,, abstract of JP, 57-159251 (TOYOTA JIDOSHA KOGYO K.K.), * |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2011125015A2 (en) | 2010-04-05 | 2011-10-13 | Bar-Ilan University | Protease-activatable pore-forming polypeptides |
Also Published As
Publication number | Publication date |
---|---|
CA2140784A1 (en) | 1994-02-03 |
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