EP0124801B1 - Method of making precision castings by using the plaster moulding process - Google Patents
Method of making precision castings by using the plaster moulding process Download PDFInfo
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- EP0124801B1 EP0124801B1 EP84104215A EP84104215A EP0124801B1 EP 0124801 B1 EP0124801 B1 EP 0124801B1 EP 84104215 A EP84104215 A EP 84104215A EP 84104215 A EP84104215 A EP 84104215A EP 0124801 B1 EP0124801 B1 EP 0124801B1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/12—Treating moulds or cores, e.g. drying, hardening
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
- B22D27/15—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using vacuum
Definitions
- the present invention relates to a process for the production of castings with a sharp reproduction of detail and high measuring accuracy according to the gypsum molding process.
- Gypsum molding processes have been known for a long time.
- the production of large-pore alpha-calcium sulfate hemihydrate casting molds is known from US Pat. No. 2,529,835, which forms the closest prior art.
- the large pores are created here by the addition of foam-forming agents.
- various types of cement, alumina, refractory materials and some setting plastics can be used as the casting material.
- the foam-forming agents are mixed into the gypsum slurry with vigorous stirring and access of air. The large air bubbles remain even after the plaster has set.
- the foam-forming agents should have no influence on the setting time of the plaster.
- precision castings cannot be produced using this process, even if the vacuum molding process is used.
- a powder mixture which contains alpha-calcium sulfate hemihydrate (binder) as essential constituents, optionally also cement and chamotte and / or quartz powder as filler. Sufficient water is added to this mixture so that sufficient gas permeability is achieved, which applies to a pore volume of at least 25%.
- the required smooth surface of the mold is achieved with a defined grain distribution.
- Auxiliaries such as setting accelerators, retarders, glass fibers, etc. can be added to the mixture.
- a key feature of the new process is that that the adhering water of the molding compound is removed by pressure drainage. In this way, considerable amounts of energy can be saved, so that the casting process can now also be used for large-area precision castings and series castings.
- the evacuation during metal casting additionally reduces the energy requirement, it being further advantageous that pressure drainage and evacuation can be carried out using the same system (drainage device).
- a drain in the form of a porous tube or a perforated glass fiber mat is applied over the original to be molded, which is coated with a release agent.
- this is expediently carried out using a close-meshed wire mesh, which is attached at a distance of approx. 10 mm above the original and is slightly flexible.
- the hose is then attached in a serpentine manner distributed over the wire mesh and led outward at one end through the mold frame or through the mold. No wire mesh is required when using perforated glass fiber mats.
- the molding compound is poured into the prepared molding box.
- an upper or lower box or multi-part molds can be produced.
- the molding compounds (negative molds) are immediately lifted from the original after solidification and connected to the compressed air line to remove the water.
- the water is advantageously squeezed out with a pressure increase of 0.1 bar per minute and until a pressure of approximately 2 bar is reached. For complete Water removal will maintain this pressure for a period of time, such as 10 to 20 minutes. In most cases, 10 to 20 minutes is enough.
- the pore space formed by the water squeezing is essential for the subsequent metal casting.
- the negative molds are left open for approx. 2 hours until fully set. A further 24 hour drying at 60 - 100 ° C may be necessary for larger molds. However, it is also necessary if a sufficient vacuum performance cannot be achieved in the subsequent metal casting.
- the vacuum lines are connected to the compressed air nozzle (s). This can be done using a direct-working vacuum pump with sufficient performance, as well as using a pre-evacuated vessel.
- the negative mold is evacuated and the melt is poured in immediately.
- the maximum amount of gas is 4 l / qdm mold surface.
- the rear wall thickness of the mold is greater than the distance between the hose and the work surface. In most cases a double to three times the wall thickness is sufficient.
- a fitting plastic original (model), size approx. 20 x 10 x 8 cm, was coated with a wafer-thin oil film as a release agent and placed in a molding box with the internal dimensions 24 x 14 x 11 cm.
- An easily deformable wire mesh with a mesh size of approx. 2-3 cm was adapted to this original surface.
- a porous fabric tube of 8 mm diameter was connected to the wire mesh with a lateral distance of about 2 cm, the tube end was connected to the pipe socket attached to the molding box and the drainage device was fixed about 1 cm above the model.
- the mold box with the negative model for the following cast aluminum was connected to a vacuum line. A negative pressure of -0.9 bar was established.
- the molten aluminum alloy (720 ° C) was filled into the evacuated mold. The casting was demolded after the alloy had completely solidified, which was the case after about 20 minutes. The negative mold could be used for three more metal castings.
- Example 1 a perforated mineral wool fiber mat with a thickness of 2 cm was used.
- the hole diameter was 1.5 cm, the distance from hole to hole was 2-3 cm.
- the molding box was filled with the casting compound about 1 cm above the original and then the mineral wool fiber mat was fixed at a distance of about 1 cm above the original surface and then the molding box was filled up. Breaking out, evacuation and metal casting were carried out as in Example 1.
- the model 7 lying in the box half 1a) is with the wire mesh fabric 6 on which the porous fabric tube 2 is arranged in a serpentine manner.
- the compressed gas is introduced through the nozzle at 4 and the vacuum is drawn off through the same nozzle.
- the molding compound is indicated with the number 3.
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Abstract
Description
Gegenstand der vorliegenden Erfindung ist eine Verfahren zur Herstellung von Gußteilen mit scharfer Detailwidergabe und hoher Meßgenauigkait nach dem Gips-Formverfahren.The present invention relates to a process for the production of castings with a sharp reproduction of detail and high measuring accuracy according to the gypsum molding process.
Gips-Formverfahren sind schon seit langem bekannt. So ist aus der den nächsten Stand der Technik bildenden US-PS 2,529,835 die Herstellung von großporigen alpha-Calciumsulfat-Halbhydrat Gußformen bekannt. Die großen Poren entstehen hier durch die Zugabe von schaumbildenden Mitteln. Gemäß dieser Patentschrift können neben Gips auch verschiedene Zementtypen, Tonerde, Feuerfestmaterialien, sowie einige abbindefähige Kunststoffe als Gußmaterial verwendet werden. Die schaumbildenden Mittel werden dem Gipsslurry unter heftigem Rühren und Luftzutritt zugemischt. Die großen Luftblasen bleiben auch nach der Abbindung des Gipses erhalten. Die schaumbildenden Mittel sollen aber auf die Abbindezeit des Gipses keinen Einfluß ausüben. Präzisionsgüsse können nach diesem Verfahren jedoch nicht hergestellt werden und zwar auch dann nicht, wenn man nach dem Vakuum-Formverfahren arbeitet.Gypsum molding processes have been known for a long time. The production of large-pore alpha-calcium sulfate hemihydrate casting molds is known from US Pat. No. 2,529,835, which forms the closest prior art. The large pores are created here by the addition of foam-forming agents. According to this patent, in addition to gypsum, various types of cement, alumina, refractory materials and some setting plastics can be used as the casting material. The foam-forming agents are mixed into the gypsum slurry with vigorous stirring and access of air. The large air bubbles remain even after the plaster has set. However, the foam-forming agents should have no influence on the setting time of the plaster. However, precision castings cannot be produced using this process, even if the vacuum molding process is used.
Die Statistik zeigt, daß ein hoher Anteil der Gußserien mit Formsanden hergestellt wird. Aus der BE-PS 564,615 ist ein Verfahren zur Herstellung von Gußformen auf Sandbasis bekannt. Hauptziel dieses Patentes war es, die Zeit bei der Gußherstellung beträchtlich zu verkürzen und die mechanische Widerstandsfähigkeit der Sandform zu erhöhen. Der Sand kann als abbindefähige Materialien z.B. Alkalisilikat, Zement oder auch organische Polymere enthalten. Die Entfernung des Wassers geschieht mit Hilfe von heißen Gasen, die durch die Form zirkulieren und auf ihrem Weg den Wasserdampf mitnehmen unterstützt durch Presssluft oder Vakuum. Das Vakuum darf einen bestimmten Wert nicht überschreiten, sonst penetriert das Metall in die Sandform mit der Folge, daß es nach dem Abkühlen eine sehr rauhe Oberfläche aufweist. Dies bedingt einen hohen Nacharbeitungsaufwand, der sehr kostenintensiv ist und heute als nicht mehr vertretbar angesehen wird.Statistics show that a high proportion of the cast series with Form sands is produced. From BE-PS 564,615 a method for producing casting molds based on sand is known. The main aim of this patent was to considerably reduce the time in the casting process and to increase the mechanical resistance of the sand mold. The sand can contain, for example, alkali silicate, cement or organic polymers as setting materials. The water is removed with the help of hot gases, which circulate through the mold and take along the water vapor on their way, supported by compressed air or vacuum. The vacuum must not exceed a certain value, otherwise the metal penetrates into the sand mold with the result that after cooling it has a very rough surface. This requires a high amount of rework, which is very cost-intensive and is no longer considered acceptable today.
Es stellte sich somit die Aufgabe, ein Formverfahren zu finden, das weder die Nachteile des Sand-Formverfahrens noch die des Gips-Formverfahrens zeigt.It was therefore the task of finding a molding process which did not show the disadvantages of either the sand molding process or the gypsum molding process.
Überraschenderweise kann die gestellte Aufgabe derart gelöst werden, daß
- a.) das abzubildende und mit einem Trennmittel beschichtete Modell mit einer Drainagevorrichtung, die mindestens je einen Zu- bzw. Ablauf außerhalb des Formkastens aufweist, versehen wird,
- b) die Formmasse in den Formkasten gegossen und erstarren gelassen wird,
- c) das Wasser der erstarrten Formmasse nach Entfernung des Modells durch Einleiten von Druckgas herausgepreßt wird und die vom Modell abgelöste Form nach Trocknung
- d) an eine Vakuumleitung angeschlossen und evakuiert wird, und daß
- e) die Metallschmelze unter Beibehaltung des Vakuums in die Form gegossen und erstarren gelassen wird.
- a.) the one to be imaged and coated with a release agent Model is provided with a drainage device, which has at least one inlet or outlet outside the molding box,
- b) the molding compound is poured into the molding box and allowed to solidify,
- c) the water of the solidified molding compound is removed after the model has been removed by introducing compressed gas and the mold detached from the model after drying
- d) connected to a vacuum line and evacuated, and that
- e) the molten metal is poured into the mold while maintaining the vacuum and allowed to solidify.
Ein Brennen der Gipsformen bei Temperaturen von 400 bis 800°C ist bei dem neuen Verfahren nicht erforderlich. Damit können erhebliche Energiemengen eingespart werden.Firing the plaster molds at temperatures of 400 to 800 ° C is not necessary with the new process. This can save considerable amounts of energy.
Zur Herstellung der Gipsformen wird eine Pulvermischung verwendet, die als wesentliche Bestandteile alpha-Calciumsulfat-Halbhydrat ( Bindemittel ), gegebenenfalls noch Zement und Schamotte und/oder Quarzmehl als Füllstoff enthält. Dieser Mischung wird soviel Wasser zugesetzt, daß eine ausreichende Gasdurchlässigkeit erzielt wird, was auf ein Porenvolumen von mindestens 25 % zutrifft. Mit einer definierten Kornverteilung wird die erforderliche glatte Oberfläche der Form erzielt. Hilfsstoffe wie Abbindebeschleuniger, Verzögerer, Glasfasern u.a., können der Mischung beigegeben werden.To produce the gypsum molds, a powder mixture is used which contains alpha-calcium sulfate hemihydrate (binder) as essential constituents, optionally also cement and chamotte and / or quartz powder as filler. Sufficient water is added to this mixture so that sufficient gas permeability is achieved, which applies to a pore volume of at least 25%. The required smooth surface of the mold is achieved with a defined grain distribution. Auxiliaries such as setting accelerators, retarders, glass fibers, etc. can be added to the mixture.
Ein wesentliches Kennzeichen des neuen Verfahrens besteht darin, daß das anhaftende Wasser der Formmasse durch Druckentwässerung entfernt wird. Auf diese Weise können beträchtliche Energiemengen eingespart werden, so daß das Gießverfahren nunmehr auch für großflächige Präzisionsgüsse und Seriengüsse einsetzbar ist. Durch die Evakuierung beim Metallguß wird der Energiebedarf zusätzlich herabgesetzt, wobei weiterhin vorteilhaft ist, daß Druckentwässerung und Evakuierung über das gleiche System ( Drainagevorrichtung ) vorgenommen werden können.A key feature of the new process is that that the adhering water of the molding compound is removed by pressure drainage. In this way, considerable amounts of energy can be saved, so that the casting process can now also be used for large-area precision castings and series castings. The evacuation during metal casting additionally reduces the energy requirement, it being further advantageous that pressure drainage and evacuation can be carried out using the same system (drainage device).
Anhand der nachstehenden Ausführungen wird nun das neue Verfahren noch näher erläutert.The new method will now be explained in more detail with reference to the explanations below.
Vor dem Formenguß wird über das abzuformende Original, das mit einem Trennmittel beschichtet wird, eine Drainage in Form eines porösen Schlauches oder einer gelochten Glasfasermatte aufgebracht. Bei der Schlauchmethode erfolgt das zweckmäßigerweise mit einem engmaschigen Drahtgewebe, das in einem Abstand von ca. 10 mm über dem Original befestigt wird und leicht biegsam ist. Anschließend wird der Schlauch schlangenförmig über das Drahtgewebe verteilt befestigt und mit einem Ende durch den Formrahmen bzw. durch die Kokulle nach außen geführt. Bei der Verwendung von gelochten Glasfasermatten wird kein Drahtgewebe benötigt.Before the mold is cast, a drain in the form of a porous tube or a perforated glass fiber mat is applied over the original to be molded, which is coated with a release agent. With the hose method, this is expediently carried out using a close-meshed wire mesh, which is attached at a distance of approx. 10 mm above the original and is slightly flexible. The hose is then attached in a serpentine manner distributed over the wire mesh and led outward at one end through the mold frame or through the mold. No wire mesh is required when using perforated glass fiber mats.
Nach Anrühren wird die Formmasse in den vorbereiteten Formkasten gegossen. Je nach Formteil können ein Ober- oder Unterkasten bzw. auch mehrteilige Formen hergestellt werden.After mixing, the molding compound is poured into the prepared molding box. Depending on the molded part, an upper or lower box or multi-part molds can be produced.
Die Formmassen( Negativformen ) werden nach dem Erstarren sofort vom Original abgehoben und zur Entfernung des Wassers an die Preßluftleitung angeschlossen. Das Auspressen des Wassers erfolgt vorteilhafterweise mit einem Druckanstieg von 0,1 bar pro Minute und zwar solange, bis ca. 2 bar erreicht sind. Zur vollständigen Wasserentfernung wird dieser Druck noch über einen Zeitraum beibehalten, etwa 10 bis 20 Minuten. In den meisten Fällen reichen 10 bis 20 Minuten aus. Der durch das Wasserauspressen gebildete Porenraum ist für den nachfolgenden Metallguß von wesentlicher Bedeutung. Nach dem Auspressen bleiben die Negativformen bis zum völligen Abbinden ca. 2 Stunden offen gelagert stehen. Eine weitere 24-stündige Trocknung bei 60 - 100°C kann bei größeren Formen erforderlich sein. Sie ist jedoch auch notwendig, wenn eine ausreichende Vakuumleistung beim nachfolgenden Metallguß nicht erbracht werden kann.The molding compounds (negative molds) are immediately lifted from the original after solidification and connected to the compressed air line to remove the water. The water is advantageously squeezed out with a pressure increase of 0.1 bar per minute and until a pressure of approximately 2 bar is reached. For complete Water removal will maintain this pressure for a period of time, such as 10 to 20 minutes. In most cases, 10 to 20 minutes is enough. The pore space formed by the water squeezing is essential for the subsequent metal casting. After pressing, the negative molds are left open for approx. 2 hours until fully set. A further 24 hour drying at 60 - 100 ° C may be necessary for larger molds. However, it is also necessary if a sufficient vacuum performance cannot be achieved in the subsequent metal casting.
Vor dem Metallguß wird (werden) an den (oder die) Druckluftstutzen die Vakuumleitungen angeschlossen. Dies kann sowohl über eine direkt arbeitende Vakuumpumpe mit ausreichender Leistung, wie auch über ein vorevakuiertes Gefäß erfolgen. Unmittelbar vor dem Metallguß wird die Negativform evakuiert und die Schmelze sofort eingegossen.Before the metal casting, the vacuum lines are connected to the compressed air nozzle (s). This can be done using a direct-working vacuum pump with sufficient performance, as well as using a pre-evacuated vessel. Immediately before the metal casting, the negative mold is evacuated and the melt is poured in immediately.
Bis zur Erstarrung der Schmelze wird die Evakuierung fortgesetzt.The evacuation continues until the melt solidifies.
Die maximale Gasmenge liegt bei 4 l/qdm Formoberfläche. Zur Reduzierung von Vakuumverlusten ist es bei dem erfindungsgemäßen Verfahren wesentlich, daß die rückwärtige Wanddicke der Form größer ist als der Abstand zwischen Schlauch und Arbeitsoberfläche beträgt. In den meisten Fällen reicht eine doppelte bis dreifache Wanddicke aus.The maximum amount of gas is 4 l / qdm mold surface. To reduce vacuum losses, it is essential in the method according to the invention that the rear wall thickness of the mold is greater than the distance between the hose and the work surface. In most cases a double to three times the wall thickness is sufficient.
Bei sorgfältiger Verarbeitung, vor allem gleichmäßiger Verteilung der Drainage, bilden sich sehr glatte Metalloberflächen aus, welche die aufgeführten technischen Vorteile bringen.With careful processing, especially even distribution of the drainage, very smooth metal surfaces are formed, which bring the listed technical advantages.
Zur Herstellung der Negativform wurde ein Armaturenkunststofforiginal (Modell), Größe ca. 20 x 10 x 8 cm, mit einem hauchdünnen Oelfilm als Trennmittel überzogen und in einen Formkasten mit den Innenmaßen 24 x 14 x 11 cm eingelegt. Auf diese Originaloberfläche wurde ein leicht verformbares Drahtgewebe mit ca. 2 - 3 cm Maschenweite angepaßt. Nach dieser Anformung wurde auf das Drahtgewebe ein poröser Gewebeschlauch von 8 mm Durchmesser mit seitlichem Abstand von etwa 2 cm angebunden, das Schlauchende mit dem am Formkasten angebrachten Rohrstutzen verbunden und die Drainage-Einrichtung ca. 1 cm über dem Modell fixiert.To produce the negative mold, a fitting plastic original (model), size approx. 20 x 10 x 8 cm, was coated with a wafer-thin oil film as a release agent and placed in a molding box with the internal dimensions 24 x 14 x 11 cm. An easily deformable wire mesh with a mesh size of approx. 2-3 cm was adapted to this original surface. After this molding, a porous fabric tube of 8 mm diameter was connected to the wire mesh with a lateral distance of about 2 cm, the tube end was connected to the pipe socket attached to the molding box and the drainage device was fixed about 1 cm above the model.
Zum Füllen des vorbereiteten Formkastens wurden 5 kg eines Pulvergemisches, bestehend aus
40,0 % alpha-Calciumsulfat-Halbhydrat
59,0 % Schamotte ( Körnung 0 - 1 mm )
0,5 % Weißkalk
0,3 % Glasfasern, 3 - 5 mm Faserlänge
0,2 % Kaliumsulfat
mit 2 l Wasser 1 Minute homogen gemischt und (zur Verdrängung von Haftblasen) im dünnen Strahl von der Mitte beginnend eingegossen.To fill the prepared mold box, 5 kg of a powder mixture consisting of
40.0% alpha calcium sulfate hemihydrate
59.0% chamotte (grain size 0 - 1 mm)
0.5% white lime
0.3% glass fibers, 3 - 5 mm fiber length
0.2% potassium sulfate
homogeneously mixed with 2 l of water for 1 minute and poured in (in order to displace adhesive bubbles) in a thin stream starting from the center.
Eine Minute nach dem Erstarrungsende der Formmasse - ermittelt durch Fingerdruck - wurde an den Rohrstutzen die Preßluftleitung angeschlossen. Der Anfangsdruck betrug 0,2 bar, die Drucksteigerung 0,01 bar pro Minute. Nach 100 Minuten betrug der Preßdruck 1,2 bar, der solange beibehalten wurde, bis kein Wasser mehr austrat.One minute after the solidification of the molding compound - determined by finger pressure - the compressed air line was connected to the pipe socket. The initial pressure was 0.2 bar, the pressure increase 0.01 bar per minute. After 100 minutes the pressure was 1.2 bar, which was maintained until no more water emerged.
Bei Anlegung des Preßdrucks trennte sich das Original von der Formmasse. Der Formkasten mit dem Negativmodell wurde gleichmäßig nach oben abgehoben und hochkant gestellt, damit das ausgepreßte Wasser frei abfließen konnte.When the pressure was applied, the original separated from the molding compound. The mold box with the negative model was lifted evenly upwards and placed upright so that the squeezed water could flow away freely.
Die Resttrocknung des Formkastens mit Negativmodell erfolgt über Nacht bei 60 - 80°C.The residual drying of the molding box with negative model takes place overnight at 60 - 80 ° C.
Nach Trocknung wurde der Formkasten mit dem Negativmodell für den folgenden Aluminiumguß an eine Vakuumleitung angeschlossen. Es stellte sich ein Unterdruck von -0,9 bar ein. Die geschmolzene Aluminiumlegierung (720°C) wurde in die evakuierte Form eingefüllt. Die Entformung des Gußteiles erfolgte nach völliger Erstarrung der Legierung, was nach ca. 20 Minuten der Fall war. Die Negativform konnte für drei weitere Metallgüsse eingesetzt werden.After drying, the mold box with the negative model for the following cast aluminum was connected to a vacuum line. A negative pressure of -0.9 bar was established. The molten aluminum alloy (720 ° C) was filled into the evacuated mold. The casting was demolded after the alloy had completely solidified, which was the case after about 20 minutes. The negative mold could be used for three more metal castings.
Anstelle des im Beispiel 1 eingelegten porösen Schlauches wurde eine gelochte Mineralwollfasermatte mit 2 cm Dicke verwendet. Der Lochdurchmesser betrug 1,5 cm, der Abstand von Lochung zu Lochung 2 - 3 cm. Um ein Hochschwimmen der Mineralwollfasermatte zu unterbinden, wurde sie kurzzeitig in Wasser getaucht. Vor dem Einbringen der Drainage wurde der Formkasten mit der Gießmasse ca. 1 cm über das Original gefüllt und anschließend die Mineralwollfasermatte mit einem Abstand von ca. 1 cm über der Originaloberfläche fixiert und danach der Formkasten aufgefüllt. Ausbrechen, Evakuieren und Metallgießen erfolgten wie im Beispiel 1.Instead of the porous tube inserted in Example 1, a perforated mineral wool fiber mat with a thickness of 2 cm was used. The hole diameter was 1.5 cm, the distance from hole to hole was 2-3 cm. In order to prevent the mineral wool fiber mat from floating up, it was briefly immersed in water. Before the drainage was introduced, the molding box was filled with the casting compound about 1 cm above the original and then the mineral wool fiber mat was fixed at a distance of about 1 cm above the original surface and then the molding box was filled up. Breaking out, evacuation and metal casting were carried out as in Example 1.
In der beiliegenden Figur, die einen Querschnitt durch die beim erfindungsgemäßen Verfahren eingesetzte Gußform zeigt, dient zur weiteren Erläuterung des Erfindungsgegenstandes.In the accompanying figure, which shows a cross section through the casting mold used in the method according to the invention, serves to further explain the subject matter of the invention.
Mit 1a) und 1b) sind in der Figur Teile des Formkastens bezeichnet. Das in der Kastenhälfte 1a) liegende Modell 7 ist mit dem Maschendrahtgewebe 6, auf dem der poröse Gewebeschlauch 2 schlangenförmig angeordnet ist, umgeben. Das Druckgas wird über die Stutzen bei 4 eingeleitet und das Vakuum über den gleichen Stutzen abgezogen. Die Formmasse ist mit der Ziffer 3 angedeutet.With 1a) and 1b) parts of the molding box are designated in the figure. The
Claims (11)
- Process for preparing precision castings using a porous casting mould from pourable moulding composition (3) containing alpha-calcium sulphate hemihydrate as binder, this composition not being calcined, wherein(a) the prototype (7) to be copied, coated with a mould release agent, is provided with a drainage device (2) which has at least one inlet and outlet (4,5) to and from the mould box (1a,b),(b) the moulding composition (3) is poured into the mould box (1a,1b) and left to harden,(c) the water from the hardened moulding composition (3) is expelled, after the removal of the prototype (7), by the introduction of pressurised gas and, after drying, the mould detached from the prototype (7) is(d) connected to a vacuum line and evacuated, and(e) the molten metal is poured into the mould while the vacuum is maintained, and allowed to harden.
- Process according to claim 1, characterised in that a porous hose is used as the drainage device (2).
- Process according to claim 2, characterised in that the porous hose is placed on a fine-mesh, deformable wire gauze (6).
- Process according to claim 1, characterised in that a perforated fibreglass mat is used as the drainage device (2).
- Process according to claims 1-4, characterised in that the drainage device (2) is arranged at a spacing from the prototype of at least 10mm.
- Process according to claims 1-5, characterised in that the water is expelled from the hardened moulding composition (3) by means of compressed air.
- Processing according to claim 6, characterised in that the water is expelled by increasing pressure.
- Process according to claim 7, characterised in that the pressure is increased by 0.01 bar per minute until it reaches about 12 bar.
- Process according to claims 1 to 8, characterised in that the mould is dried at 60-100°C.
- Process according to claims 1-9, characterised in that the molten metal is poured into the mould at an underpressure of 0.6 bar and hardened while the underpressure is maintained.
- Process according to claims 1-10, characterised in that a moulding composition (3) consisting of alpha-calcium sulphate hemihydrate, fire clay, water and adjuvants known per se is poured into the mould box (1a,b).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT84104215T ATE64114T1 (en) | 1983-05-06 | 1984-04-13 | PROCESS FOR THE MANUFACTURE OF PRECISION CASTINGS ACCORDING TO THE PLASTER MOLDING PROCESS. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3316571A DE3316571C2 (en) | 1983-05-06 | 1983-05-06 | Process for the production of precision casting molds according to the plaster of paris - molding process, casting mold and their use |
| DE3316571 | 1983-05-06 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| EP0124801A2 EP0124801A2 (en) | 1984-11-14 |
| EP0124801A3 EP0124801A3 (en) | 1988-03-23 |
| EP0124801B1 true EP0124801B1 (en) | 1991-06-05 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP84104215A Expired - Lifetime EP0124801B1 (en) | 1983-05-06 | 1984-04-13 | Method of making precision castings by using the plaster moulding process |
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| Country | Link |
|---|---|
| US (1) | US4541471A (en) |
| EP (1) | EP0124801B1 (en) |
| AT (1) | ATE64114T1 (en) |
| DE (2) | DE3316571C2 (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3320309C2 (en) * | 1983-06-04 | 1985-08-14 | Giulini Chemie Gmbh, 6700 Ludwigshafen | Process for the production of precision measuring molds, casting molds and their use |
| DE3519367A1 (en) * | 1985-05-30 | 1986-12-04 | Giulini Chemie Gmbh, 6700 Ludwigshafen | METHOD FOR THE PRODUCTION OF MOLDS, MODELS AND TOOLS ON HARD PLASTER AND / OR CEMENT BASE |
| DE3832370A1 (en) * | 1988-04-29 | 1989-11-09 | Giulini Chemie | NEW CERAMIC MIXTURES SUITABLE FOR PRODUCING WATER-WASHABLE CORES AND SHAPES |
| EP0467025A3 (en) * | 1990-07-20 | 1992-12-09 | Giulini Chemie Gmbh | Light moulds, patterns and tools on gypsum base |
| GB2408260A (en) * | 2003-11-20 | 2005-05-25 | Doncasters Ltd | Moulding composition including water-insoluble lubricant |
| BRPI0507213A (en) * | 2004-02-19 | 2007-06-19 | Jean Sam Lee | apparatus and method for the manufacture of ceramic articles |
| DE112005001528T5 (en) * | 2004-07-12 | 2007-05-24 | Dai Nippon Printing Co., Ltd. | Shielding filter for electromagnetic waves |
| CN109226704B (en) * | 2018-11-03 | 2024-06-14 | 深圳阿尔泰克轻合金技术有限公司 | Aluminum ingot production system and method |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE564615A (en) * | ||||
| US2529835A (en) * | 1947-01-18 | 1950-11-14 | United States Gypsum Co | Metal-casting molds and processes and materials for producing the same |
| US2882569A (en) * | 1957-03-29 | 1959-04-21 | Ram Inc | Method and apparatus for molding and hardening articles |
| US3153824A (en) * | 1961-12-29 | 1964-10-27 | Martin Metals Corp | Method of casting metals |
| FR1563091A (en) * | 1968-02-23 | 1969-04-11 | ||
| DE1939433B2 (en) * | 1969-08-02 | 1970-10-08 | Daimler Benz Ag | Metering catalyst into phenolic resin mould - ing material |
| DE1940924A1 (en) * | 1969-08-12 | 1971-02-25 | Michel Horst Werner | Age-hardening sand moulds of cores |
| CH524415A (en) * | 1970-04-20 | 1972-06-30 | Gruenzweig & Hartmann | Equipment for the implementation of the full mold casting process |
| US3825058A (en) * | 1972-04-15 | 1974-07-23 | Sintokogio Ltd | Mold prepared by vacuum sealed molding process |
| JPS544817A (en) * | 1977-06-15 | 1979-01-13 | Hitachi Ltd | Selffhardening casting sand |
-
1983
- 1983-05-06 DE DE3316571A patent/DE3316571C2/en not_active Expired
-
1984
- 1984-04-13 EP EP84104215A patent/EP0124801B1/en not_active Expired - Lifetime
- 1984-04-13 AT AT84104215T patent/ATE64114T1/en not_active IP Right Cessation
- 1984-04-13 DE DE8484104215T patent/DE3484663D1/en not_active Expired - Lifetime
- 1984-05-07 US US06/608,046 patent/US4541471A/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| DE3316571A1 (en) | 1984-11-08 |
| DE3316571C2 (en) | 1985-08-22 |
| EP0124801A2 (en) | 1984-11-14 |
| US4541471A (en) | 1985-09-17 |
| ATE64114T1 (en) | 1991-06-15 |
| DE3484663D1 (en) | 1991-07-11 |
| EP0124801A3 (en) | 1988-03-23 |
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