EP0281752B1 - Lost foam process and installation - Google Patents

Lost foam process and installation Download PDF

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Publication number
EP0281752B1
EP0281752B1 EP88101270A EP88101270A EP0281752B1 EP 0281752 B1 EP0281752 B1 EP 0281752B1 EP 88101270 A EP88101270 A EP 88101270A EP 88101270 A EP88101270 A EP 88101270A EP 0281752 B1 EP0281752 B1 EP 0281752B1
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EP
European Patent Office
Prior art keywords
sand
pattern
reduced pressure
mould method
full mould
Prior art date
Legal status (The legal status 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 status listed.)
Expired - Lifetime
Application number
EP88101270A
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German (de)
French (fr)
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EP0281752A3 (en
EP0281752A2 (en
Inventor
Joachim Dipl.-Ing. Bolle
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rieter Ingolstadt Spinnereimaschinenbau AG
Original Assignee
Schubert und Salzer Maschinenfabrik AG
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Publication of EP0281752A2 publication Critical patent/EP0281752A2/en
Publication of EP0281752A3 publication Critical patent/EP0281752A3/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/02—Sand moulds or like moulds for shaped castings
    • B22C9/03—Sand moulds or like moulds for shaped castings formed by vacuum-sealed moulding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/02—Sand moulds or like moulds for shaped castings
    • B22C9/04—Use of lost patterns
    • B22C9/046—Use of patterns which are eliminated by the liquid metal in the mould

Definitions

  • the invention relates to a full molding process in which a completely positive model made of a thermally decomposable material is inserted into a molding box with sand, the sand is solidified by shaking, the casting metal is poured onto the thermally decomposable model and the model is decomposed by the casting heat, and a device to perform the procedure.
  • Molds which consist of two halves are usually used to produce castings. However, this division of the molds can only be carried out within certain dimensional tolerances, which means that errors can occur on the casting within the division level due to offset burrs, sand leaching, penetration of metal into the sand mold, burnt-on sand, etc. All of these errors occur on the casting Appearance and must be remedied by sanding, severing, chopping, sawing, etc.
  • an undivided model is inserted into a molding box with loose dry sand in the so-called full molding process.
  • it is made of a thermally decomposable material, so that the model is decomposed by the casting heat.
  • a burr-free casting is created.
  • not all types of models can be molded in this way, in particular shaped pieces with dome-like cavities such as pump housings and the like cannot be embedded satisfactorily in the sand, since the sand does not rise into these cavities.
  • a disadvantage of this known full molding process is therefore that such shaped pieces cannot be molded and cast by this process, but must be produced with loose cores or according to the conventional multi-part molding process. All fittings in which the sand would have to rise into such cavities as in communicating tubes are thus excluded from the known advantageous full molding process.
  • the object of the present invention is to improve the full molding process in such a way that moldings with critical cavities are securely molded and filled by the molding sand.
  • Another task here is to compact the molding sand in a controlled manner.
  • the object is achieved in that during the sand filling the sand for enclosing the model is exposed to a pressure difference in the sand filling direction.
  • the filling and solidification of the sand in the critical cavities is particularly favored by the fact that, while the sand is subjected to a vacuum, it is simultaneously shaken.
  • the negative pressure is only switched off after the shaking has ended.
  • the sand is securely solidified on all sides around the shaped piece, without the risk of the sand loosening again.
  • the negative pressure is introduced into the mold box below the casting model, preferably through the bottom of the molding box, it is achieved that all cavities of the casting model are properly filled with sand and this is compacted on the model.
  • the level of the vacuum is determined depending on the nature of the sand. Because the vacuum is reduced with increasing filling height of the molding sand, the force counteracting the vibrating force is gradually reduced and thus enables a uniform compression at all filling levels. In any case, however, when the level of the model is reached, the negative pressure is brought to the height specified for enclosing the model.
  • the rising of the sand in the model hollow Space is favored in that the fill level of the molding sand in the vicinity of the cavity of the model to be filled is kept approximately constant until the cavity is completely filled.
  • the model is enclosed with unbound sand.
  • the device for carrying out the method is characterized in that the interior of the molding box is connected to a vacuum device via a feed line. A rapid and uniform application of negative pressure to the sand is brought about in that the molding box is surrounded by a ring line which is connected to its interior and the supply line via air outlet openings. Because the air outlet opening is arranged below the casting model, the model cavities are filled particularly reliably. The air outlet opening is preferably arranged on the bottom of the molding box.
  • a control device is assigned to the vacuum device.
  • a molding box 1 In a molding box 1, one or more complete positive models are inserted as grapes, of which only one model 2 with a cavity 20 is shown in FIG. 1.
  • the model 2 - like the pouring tube 21 and the grape runs 22 - made of a - thermally decomposable material, for example polystyrene, and represents a section through part of a radial pump housing.
  • the molding box 1 is filled with dry sand, preferably with unbound sand.
  • a somewhat coarser quartz sand, as is usually used for molding, has proven to be suitable.
  • a vibrating device 4 is assigned to the molding box 1, which is mounted so that it can vibrate, by means of which the sand is shaken and thereby compacted.
  • a pressure difference in the filling direction is built up in molding box 1 during filling, this pressure difference being able to be generated by applying overpressure to the top of the molding box or preferably being generated by a vacuum device 50.
  • This vacuum device 50 is connected to the interior of the molding box 1 via a feed line 5.
  • the air outlet opening 51 of the molding box 1 is expediently provided below the model 2 in a side wall of the molding box 1, or, what is preferred, in the bottom of the molding box 1. This is indicated by the supply line 5 ⁇ .
  • the side walls of the molding box 1 are provided with a multiplicity of air outlet openings 51 and enclosed by a ring line 52, so that the vacuum is effective quickly and uniformly in the molding box 1.
  • Ring lines 52 can be installed at different heights, which are acted upon one after the other according to the filling level.
  • a ring line 52 can also be provided, the height of which can be adjusted.
  • the molding sand is filled from a sand feed device 6 into the molding box 1 via a shut-off device 61.
  • the application of negative pressure to the sand during the filling of the molding box surprisingly causes the sand to rise into the critical cavities 20 of the model 2 or other fittings previously excluded from the full molding process.
  • the critical cavities are filled with sand and solidified particularly reliably when a negative pressure of 0.5 bar is applied and the negative pressure below the model 2 is introduced into the molding box, in particular also through the bottom of the molding box 1 through.
  • the negative pressure counteracts the vibrating force
  • the negative pressure is brought to the required and fixed height during the filling (FIG. 2 c).
  • the air and thus also the sand entrained by it flows into the cavity 20 It is also essential for a reliable and complete filling of the cavity (s) 20 that the air and thus also the sand entrained by it flows into the cavity 20. This is ensured by the fact that the filling height of the molding sand in the vicinity of the cavity 20 to be filled is kept approximately constant during the time of filling.
  • a flow lane is indicated by the flow arrows, through which the sand is entrained and transported into the cavity 20.
  • the sand feed into the molding box 1 is interrupted, for example, when the model level is reached, or is moved to a location at which this flow lane is not filled up and thus the filling of the model is not hindered.
  • Filling the cavity 20 is supported and favored by shaking the sand while it is subjected to negative pressure. This can be preceded by shaking without negative pressure.
  • the actuation of the vacuum device and the sand feed device 6 in the manner described in the method can be carried out manually or also by a control device, as is shown schematically for example in FIG. 1.
  • a measuring sensor 7 is assigned to the molding box 1, which in each case emits a signal to a microprocessor 71 when a predetermined lowering depth of the box corresponding to the filling height in the molding box 1 is reached.
  • the microprocessor 71 is connected to the vacuum device 50 and a measuring element 53 assigned to it and regulates the vacuum in relation to the fill level in the molding box 1 and when the model level is reached.
  • the microprocessor 71 controls the sand feed into the molding box 1 via the shut-off element 61.
  • the microprocessor 71 can also be connected to the vibrating device 4 for control purposes. Corresponding information, for example about the level of the negative pressure then to be applied, can also be input to the microprocessor 71 when using a molding sand of a different nature and thus with other compression properties.

Description

Die Erfindung betrifft ein Vollformverfahren, bei dem ein komplettes positives Modell aus einem thermisch zersetzbaren Material in einen Formkasten mit Sand eingesetzt, der Sand durch Rütteln verfestigt, das Gießmetall auf das thermisch zersetzbare Modell ge­gossen und das Modell durch die Gießhitze zersetzt wird, sowie eine Vorrichtung zum Durchführen des Ver­fahrens.The invention relates to a full molding process in which a completely positive model made of a thermally decomposable material is inserted into a molding box with sand, the sand is solidified by shaking, the casting metal is poured onto the thermally decomposable model and the model is decomposed by the casting heat, and a device to perform the procedure.

Zur Herstellung von Gußstücken werden üblicherweise Formen verwendet, die aus zwei Hälften bestehen. Diese Teilung der Formen läßt sich allerdings nur in bestimm­ten Maßtoleranzen durchführen, was zur Folge hat, daß am Gußstück innerhalb der Teilungsebene Fehler ent­stehen können durch Versatzgrate, Sandauswaschungen, Eindringen von Metall in die Sandform, angebrannte Sandpartien usw. Alle diese Fehler treten am Gußstück in Erscheinung und müssen durch Abschleifen, Abtren­nen, Abschlagen, Sägen usw. behoben werden.Molds which consist of two halves are usually used to produce castings. However, this division of the molds can only be carried out within certain dimensional tolerances, which means that errors can occur on the casting within the division level due to offset burrs, sand leaching, penetration of metal into the sand mold, burnt-on sand, etc. All of these errors occur on the casting Appearance and must be remedied by sanding, severing, chopping, sawing, etc.

Zur Vermeidung dieser umfangreichen Handarbeiten wird bei dem sogenannten Vollformverfahren ein ungeteiltes Modell in einen Formkasten mit losem trockenem Sand eingesetzt. Um das Modell entfernen zu können, ist dieses aus einem thermisch zersetzbaren Werkstoff her­gestellt, so daß das Modell durch die Gießhitze zer­setzt wird. Bei Verwendung eines ungeteilten Modelles entsteht ein gratfreies Gußstück. Es hat sich aller­dings gezeigt, daß nicht alle Arten von Modellen auf diese Weise eingeformt werden können, insbesondere Formstücke mit kuppelartigen Hohlräumen wie Pumpen­gehäuse und ähnliches lassen sich nicht zufriedenstel­lend im Sand einbetten, da der Sand nicht in diese Hohlräume aufsteigt. Ein Nachteil dieses bekannten Vollformverfahren ist somit, daß derartige Formstücke nicht nach diesem Verfahren eingeformt und gegossen werden können, sondern mit Loskernen oder nach dem herkömmlichen mehrteiligen Formverfahren hergestellt werden müssen. Alle Formstücke, bei denen der Sand in derartige Hohlräume wie in kommunizierenden Röhren auf­steigen müßte, sind somit von dem bekannten vorteil­haften Vollformverfahren ausgeschlossen.To avoid this extensive manual work, an undivided model is inserted into a molding box with loose dry sand in the so-called full molding process. In order to be able to remove the model, it is made of a thermally decomposable material, so that the model is decomposed by the casting heat. When using an undivided model, a burr-free casting is created. However, it has been shown that not all types of models can be molded in this way, in particular shaped pieces with dome-like cavities such as pump housings and the like cannot be embedded satisfactorily in the sand, since the sand does not rise into these cavities. A disadvantage of this known full molding process is therefore that such shaped pieces cannot be molded and cast by this process, but must be produced with loose cores or according to the conventional multi-part molding process. All fittings in which the sand would have to rise into such cavities as in communicating tubes are thus excluded from the known advantageous full molding process.

Aufgabe der vorliegenden Erfindung ist es, das Voll­formverfahren dahingehend zu verbessern, daß auch Form­stücke mit kritischen Hohlräumen sicher durch den Form­sand eingeformt und aufgefüllt werden. Eine weitere Aufgabe besteht hierbei darin, den Formsand kontrol­liert zu verdichten.The object of the present invention is to improve the full molding process in such a way that moldings with critical cavities are securely molded and filled by the molding sand. Another task here is to compact the molding sand in a controlled manner.

Die Aufgabe wird erfindungsgemäß dadurch gelöst, daß während des Sandeinfüllens der Sand zum Einschließen des Modells einer Druckdifferenz in Einfüllrichtung des Sandes ausgesetzt wird.The object is achieved in that during the sand filling the sand for enclosing the model is exposed to a pressure difference in the sand filling direction.

Dies wird in vorteilhafter Weise dadurch erzielt, daß während des Sandeinfüllens der Sand einem Unterdruck ausgesetzt wird.This is advantageously achieved in that the sand is subjected to a negative pressure during the sand filling.

Die Auffüllung und Verfestigung des Sandes in den kritischen Hohlräumen wird dadurch besonders begün­stigt, daß während der Beaufschlagung des Sandes mit Unterdruck gleichzeitig gerüttelt wird.The filling and solidification of the sand in the critical cavities is particularly favored by the fact that, while the sand is subjected to a vacuum, it is simultaneously shaken.

In vorteilhafter Weiterbildung des Verfahrens wird vor­gesehen, daß der Unterdruck erst nach Beenden des Rüttelns abgeschaltet wird. Dadurch wird eine sichere Verfestigung des Sandes allseits um das Formstück herum erreicht, ohne daß die Gefahr einer erneuten Auflockerung des Sandes besteht.In an advantageous development of the method, it is provided that the negative pressure is only switched off after the shaking has ended. As a result, the sand is securely solidified on all sides around the shaped piece, without the risk of the sand loosening again.

Dadurch, daß die Einführung des Unterdruckes in den Formkasten unterhalb des Gießmodells, vorzugsweise durch den Boden des Formkastens erfolgt, wird er­reicht, daß alle Hohlräume des Gießmodells einwandfrei mit Sand gefüllt und dieser an dem Modell verdichtet wird. Um eine gewünschte Gasdurchlässigkeit des Sandes zu erreichen, wird die Höhe des Unterdruckes in Abhän­gigkeit von der Beschaffenheit des Sandes festgelegt. Dadurch, daß der Unterdruck mit zunehmender Füllhöhe des Formsandes reduziert wird, wird die der Rüttel­kraft entgegenwirkende Kraft allmählich verringert und damit eine gleichmäßige Verdichtung bei allen Füllungs­graden ermöglicht. In jedem Fall wird aber bei Er­reichen des Niveaus des Modells der Unterdruck auf die zum Einschließen des Modells festgelegte Höhe ge­bracht. Das Aufsteigen des Sandes in den Modellhohl­ raum wird dadurch begünstigt, daß die Füllhöhe des Formsandes in Nähe des auszufüllenden Hohlraumes des Modells in etwa konstant gehalten wird, bis der Hohl­raum vollständig gefüllt ist. Vorzugsweise wird das Modell mit ungebundenem Sand eingeschlossen.Characterized in that the negative pressure is introduced into the mold box below the casting model, preferably through the bottom of the molding box, it is achieved that all cavities of the casting model are properly filled with sand and this is compacted on the model. In order to achieve a desired gas permeability of the sand, the level of the vacuum is determined depending on the nature of the sand. Because the vacuum is reduced with increasing filling height of the molding sand, the force counteracting the vibrating force is gradually reduced and thus enables a uniform compression at all filling levels. In any case, however, when the level of the model is reached, the negative pressure is brought to the height specified for enclosing the model. The rising of the sand in the model hollow Space is favored in that the fill level of the molding sand in the vicinity of the cavity of the model to be filled is kept approximately constant until the cavity is completely filled. Preferably, the model is enclosed with unbound sand.

Die Vorrichtung zum Durchführen des Verfahrens ist dadurch gekennzeichnet, daß der Innenraum des Form­kastens über eine Zuleitung an eine Unterdruckvorrich­tung angeschlossen ist. Eine rasche und gleichmäßige Beaufschlagung des Sandes mit Unterdruck wird dadurch bewirkt, daß der Formkasten von einer Ringleitung um­geben ist, die über Luftaustrittsöffnungen mit seinem Innenraum und der Zuleitung verbunden ist. Dadurch, daß die Luftaustrittsöffnung unterhalb des Gießmodells angeordnet ist, werden die Modellhohlräume besonders zuverlässig ausgefüllt. Vorzugsweise ist dabei die Luftaustrittsöffnung am Boden des Formkastens angeord­net. In einer weiteren vorteilhaften Ausbildung ist der Unterdruckvorrichtung eine Steuervorrichtung zuge­ordnet.The device for carrying out the method is characterized in that the interior of the molding box is connected to a vacuum device via a feed line. A rapid and uniform application of negative pressure to the sand is brought about in that the molding box is surrounded by a ring line which is connected to its interior and the supply line via air outlet openings. Because the air outlet opening is arranged below the casting model, the model cavities are filled particularly reliably. The air outlet opening is preferably arranged on the bottom of the molding box. In a further advantageous embodiment, a control device is assigned to the vacuum device.

Ausführungsbeispiele der Erfindung werden anhand der Zeichnungen beschrieben. Es zeigt

  • Figur 1 die wesentlichen Teile einer Vollformanlage in schematischer Darstellung im Schnitt;
  • Figur 2 Zusammenhänge zwischen Unterdruck- und Füll­höhe in graphischer Darstellung.
Embodiments of the invention are described with reference to the drawings. It shows
  • Figure 1 shows the essential parts of a full molding system in a schematic representation in section;
  • Figure 2 Relationship between vacuum and level in graphical representation.

In einen Formkasten 1 sind ein oder mehrere komplette positive Modelle als Traube eingesetzt, von denen in Fig. 1 lediglich ein Modell 2 mit einem Hohlraum 20 ge­zeigt ist. Das Modell 2 besteht - ebenso wie das Eingußrohr 21 und die Traubenläufe 22 - aus einem - thermisch zersetzbaren Material, beispielsweise Poly­styrol, und stellt einen Schnitt durch einen Teil eines Radialpumpengehäuses dar. Der Formkasten 1 wird mit trockenem Sand gefüllt, vorzugsweise mit ungebun­denem Sand. Ein etwas gröberer Quarzsand, wie er üb­licherweise zum Formen verwendet wird, hat sich als geeignet erwiesen. Dem mittels Federn 3 schwingfähig gelagerten Formkasten 1 ist eine Rüttelvorrichtung 4 zugeordnet, durch die der Sand gerüttelt und dadurch verdichtet wird.In a molding box 1, one or more complete positive models are inserted as grapes, of which only one model 2 with a cavity 20 is shown in FIG. 1. The model 2 - like the pouring tube 21 and the grape runs 22 - made of a - thermally decomposable material, for example polystyrene, and represents a section through part of a radial pump housing. The molding box 1 is filled with dry sand, preferably with unbound sand. A somewhat coarser quartz sand, as is usually used for molding, has proven to be suitable. A vibrating device 4 is assigned to the molding box 1, which is mounted so that it can vibrate, by means of which the sand is shaken and thereby compacted.

Erfindungsgemäß wird in Formkasten 1 während des Ein­füllens eine Druckdifferenz in Einfüllrichtung aufge­baut, wobei diese Druckdifferenz durch Anlegen von Überdruck an der Oberseite des Formkastens erzeugt werden kann oder vorzugsweise durch eine Unterdruckvor­richtung 50 erzeugt wird. Diese Unterdruckvorrichtung 50 ist über eine Zuleitung 5 an den Innenraum des Formkastens 1 angeschlossen. Die Luftaustrittsöffnung 51 des Formkastens 1 wird zweckmäßig unterhalb des Modells 2 in einer Seitenwand des Formkastens 1 vorge­sehen, oder, was bevorzugt wird, im Boden des Form­kastens 1. Dies ist durch die Zuleitung 5ʹ angedeutet. Im Ausführungsbeispiels sind die Seitenwände des Form­kastens 1 mit einer Vielzahl von Luftaustrittsöffnun­gen 51 versehen und von einer Ringleitung 52 umschlos­sen, so daß der Unterdruck rasch und gleichmäßig im Formkasten 1 wirksam wird. Es können auch mehrere Ringleitungen 52 in verschiedener Höhe installiert sein, die entsprechend der Füllhöhe nacheinander beauf­schlagt werden. In einer anderen Ausführung kann auch eine Ringleitung 52 vorgesehen werden, die in ihrer Höhe verstellbar ist. Der Formsand wird aus einer Sandzuführvorrichtung 6 über ein Absperrorgan 61 in den Formkasten 1 gefüllt.According to the invention, a pressure difference in the filling direction is built up in molding box 1 during filling, this pressure difference being able to be generated by applying overpressure to the top of the molding box or preferably being generated by a vacuum device 50. This vacuum device 50 is connected to the interior of the molding box 1 via a feed line 5. The air outlet opening 51 of the molding box 1 is expediently provided below the model 2 in a side wall of the molding box 1, or, what is preferred, in the bottom of the molding box 1. This is indicated by the supply line 5ʹ. In the exemplary embodiment, the side walls of the molding box 1 are provided with a multiplicity of air outlet openings 51 and enclosed by a ring line 52, so that the vacuum is effective quickly and uniformly in the molding box 1. You can also have several Ring lines 52 can be installed at different heights, which are acted upon one after the other according to the filling level. In another embodiment, a ring line 52 can also be provided, the height of which can be adjusted. The molding sand is filled from a sand feed device 6 into the molding box 1 via a shut-off device 61.

Die Beaufschlagung des Sandes mit Unterdruck während des Füllens des Formkastens bewirkt überraschender­weise ein Aufsteigen des Sandes auch in die kritischen Hohlräume 20 des Modells 2 oder anderer bisher vom Vollformverfahren ausgeschlossener Formstücke. Wie sich inzwischen gezeigt hat, erfolgt das Auffüllen der kritischen Hohlräume mit Sand und dessen Verfestigung besonders zuverlässig dann, wenn ein Unterdruck von 0,5 bar aufgebracht und der Unterdruck unterhalb des Modells 2 in den Formkasten eingeleitet wird, insbe­sondere auch durch den Boden des Formkastens 1 hin­durch.The application of negative pressure to the sand during the filling of the molding box surprisingly causes the sand to rise into the critical cavities 20 of the model 2 or other fittings previously excluded from the full molding process. As has now been shown, the critical cavities are filled with sand and solidified particularly reliably when a negative pressure of 0.5 bar is applied and the negative pressure below the model 2 is introduced into the molding box, in particular also through the bottom of the molding box 1 through.

Es ist jedoch nicht unbedingt erforderlich, während des gesamten Befüllens des Formkastens 1 den Unter­druck auf der für das Ausfüllen der Hohlräume 20 festgelegten Höhe zu halten. Der Unterdruck kann viel­mehr lediglich während des Ausfüllens des Hohlraumes 20 des Modells 2 oder - gemäß Fig. 2 - mehrerer Modelle 2 aufgebracht werden. Dies ist in Fig. 2 b graphisch dargestellt.However, it is not absolutely necessary to maintain the negative pressure at the level specified for filling the cavities 20 during the entire filling of the molding box 1. The negative pressure can rather only be applied during the filling of the cavity 20 of the model 2 or - according to FIG. 2 - several models 2. This is shown graphically in Fig. 2 b.

Im Hinblick darauf, daß der Unterdruck der Rüttelkraft entgegenwirkt, kann ferner vorgesehen werden, den Sand zwar während des gesamtem Befüllvorganges mit Unter­ druck zu beaufschlagen, jedoch den Unterdruck mit zu­nehmender Füllhöhe zu reduzieren (Fig. 2 a). Dabei wird von einem Maximalwert bei geringer Füllhöhe ausge­gangen, der geeignet ist, ein Fluidisieren des Sandes zu unterdrücken und damit ein Verdichten zu erreichen. Um auch bei dieser Verfahrensweise das sichere Ausfül­len der Hohlräume 20 des Modells 2 bzw. der Modelle 2 sicherzustellen, wird während des Ausfüllens der Unter­druck auf die dafür erforderlich und festgesetzte Höhe gebracht (Fig. 2 c).In view of the fact that the negative pressure counteracts the vibrating force, provision can also be made for the sand to be admitted during the entire filling process to apply pressure, but to reduce the vacuum with increasing fill level (Fig. 2 a). It is assumed that the maximum value at a low fill level is suitable for suppressing fluidization of the sand and thus achieving compaction. In order to ensure the safe filling of the cavities 20 of the model 2 or the models 2 even with this procedure, the negative pressure is brought to the required and fixed height during the filling (FIG. 2 c).

Wesentlich für ein zuverlässiges und vollständiges Aus­füllen des oder der Hohlräume 20 ist ferner, daß die Luft und damit auch der von ihr mitgerissene Sand in den Hohlraum 20 einströmt. Dies wird dadurch sicherge­stellt, daß die Füllhöhe des Formsandes in Nähe des auszufüllenden Hohlraumes 20 während der Zeit des Aus­füllens in etwa konstant gehalten wird. Wie aus Fig. 1 ersichtlich, bildet sich in Nähe der Öffnung 20ʹ zum Hohlraum 20 eine durch die Strömungspfeile angedeutete Strömungsgasse, durch die der Sand mitgerissen und in den Hohlraum 20 transportiert wird. Die Sandzufuhr in den Formkasten 1 wird hierzu bei Erreichen des Modell-­Niveaus beispielsweise unterbrochen oder an eine Stel­le verlegt, an der diese Strömungsgasse nicht zuge­schüttet und so das Ausfüllen des Modells nicht be­hindert wird.It is also essential for a reliable and complete filling of the cavity (s) 20 that the air and thus also the sand entrained by it flows into the cavity 20. This is ensured by the fact that the filling height of the molding sand in the vicinity of the cavity 20 to be filled is kept approximately constant during the time of filling. As can be seen from FIG. 1, in the vicinity of the opening 20ʹ to the cavity 20, a flow lane is indicated by the flow arrows, through which the sand is entrained and transported into the cavity 20. For this purpose, the sand feed into the molding box 1 is interrupted, for example, when the model level is reached, or is moved to a location at which this flow lane is not filled up and thus the filling of the model is not hindered.

Durch Rütteln des Sandes während seiner Beaufschlagung mit Unterdruck wird das Ausfüllen des Hohlraumes 20 unterstützt und begünstigt. Dabei kann dem Rütteln mit Unterdruck ein Rütteln ohne Unterdruck vorausgehen.Filling the cavity 20 is supported and favored by shaking the sand while it is subjected to negative pressure. This can be preceded by shaking without negative pressure.

Dies sollte allerdings nach dem Rütteln mit Unterdruck vermieden werden, da die Gefahr besteht, daß der ver­festigte Sand sich durch das Rütteln allein wieder lockert. Der Unterdruck wird aus diesem Grund zumin­dest so lange aufrechterhalten, bis das Rütteln be­endet ist.However, this should be avoided after shaking with negative pressure, since there is a risk that the solidified sand will loosen again by shaking alone. For this reason, the negative pressure is maintained at least until the shaking has ended.

Die Betätigung der Unterdruckvorrichtung und der Sand­zuführvorrichtung 6 in der verfahrensmäßig beschrie­benen Weise kann manuell oder auch durch eine Steuer­vorrichtung erfolgen, wie sie beispielsweise in Fig. 1 schematisch dargestellt ist.The actuation of the vacuum device and the sand feed device 6 in the manner described in the method can be carried out manually or also by a control device, as is shown schematically for example in FIG. 1.

Dem Formkasten 1 ist ein Meßwertaufnehmer 7 zugeord­net, der jeweils bei Erreichen einer vorbestimmten, der Füllhöhe im Formkasten 1 entsprechenden Absenk­tiefe des Kastens ein Signal an einen Mikroprozessor 71 abgibt. Der Mikroprozessor 71 ist mit der Unter­druckvorrichtung 50 und einem diesem zugeordneten Meß­glied 53 verbunden und regelt den Unterdruck im Verhäl­tnis zur Füllhöhe im Formkasten 1 und bei Erreichen des Modell-Niveaus. Außerdem wird durch den Mikropro­zessor 71 die Sandzufuhr in den Formkasten 1 über das Absperrorgan 61 gesteuert.A measuring sensor 7 is assigned to the molding box 1, which in each case emits a signal to a microprocessor 71 when a predetermined lowering depth of the box corresponding to the filling height in the molding box 1 is reached. The microprocessor 71 is connected to the vacuum device 50 and a measuring element 53 assigned to it and regulates the vacuum in relation to the fill level in the molding box 1 and when the model level is reached. In addition, the microprocessor 71 controls the sand feed into the molding box 1 via the shut-off element 61.

Der Mikroprozessor 71 kann ferner zu Steuerzwecken mit der Rüttelvorrichtung 4 verbunden sein. Ebenso können dem Mikroprozessor 71 bei Verwendung eines Formsandes von anderer Beschaffenheit und damit anderen Verdich­tungseigenschaften entsprechende Informationen, zum Beispiel über die Höhe des dann anzulegenden Unter­druckes, eingegeben werden.The microprocessor 71 can also be connected to the vibrating device 4 for control purposes. Corresponding information, for example about the level of the negative pressure then to be applied, can also be input to the microprocessor 71 when using a molding sand of a different nature and thus with other compression properties.

Claims (15)

1. Full mould method, in which a complete, positive pattern consisting of a material, which can be decomposed under the action of heat, is inserted in a moulding box with sand, the sand is consolidated by vibrating, the casting metal is poured onto the pattern, which can be decomposed under the action of heat and the pattern is decomposed by the casting heat, characterised in that during filling with sand, the sand is exposed to a pressure difference in the filling direction of the sand, for enclosing the pattern.
2. Full mould method according to Claim 1, characterised in that during the filling of the sand, the sand is exposed to a reduced pressure for enclosing the pattern.
3. Full mould method according to Claim 2, characterised in that whilst reduced pressure is applied to the sand, the sand is simultaneously vibrated.
4. Full mould method according to Claim 2 or 3, charac­terised in that the reduced pressure is only switched off after the vibration is terminated.
5. Full mould method according to one or more of Claims 2 to 4, characterised in that the introduction of the reduced pressure into the moulding box takes place below the moulding pattern, preferably through the bottom of the moulding box.
6. Full mould method according to one or more of Claims 2 to 5, characterised in that the level of the reduced pressure is established depending on the type of sand.
7. Full mould method, in particular according to one of Claims 2 to 6, characterised in that the reduced pressure is reduced as the filling level of the moulding sand increases.
8. Full mould method according to one of Claims 2 to 7, characterised in that on reaching the level of the pattern, the reduced pressure is brought to the level fixed for enclosing the pattern.
9. Full mould method according to one of Claims 1 to 8, characterised in that the filling level of the moulding sand in the vicinity of the cavity of the pattern to be filled is kept approximately constant, until the cavity is filled.
10. Full mould method according to one of Claims 1 to 9, characterised in that the pattern is enclosed with non-bonded sand.
11. Apparatus for carrying out the method according to one of Claims 1 to 10, with a moulding box and a vibrat­ing device associated with the moulding box, characterised in that the interior of the moulding box (1) is connected by way of a supply line (5) to a reduced pressure apparatus (50).
12. Apparatus according to Claim 11, characterised in that the moulding box (1) is surrounded by a ring conduit (52), which is connected by way of air outlet openings (51) to its interior and the supply line (5).
13. Apparatus according to Claim 11 or 12, characterised in that the air outlet opening (51) is located below the casting pattern (2).
14. Apparatus according to one of Claims 11 to 13, characterised in that the air outlet opening (51) is located on the bottom of the moulding box (1).
15. Apparatus according to one of Claims 11 to 14, charac­terised in that associated with the reduced pressure apparatus (50) is a control device (7, 71).
EP88101270A 1987-03-09 1988-01-29 Lost foam process and installation Expired - Lifetime EP0281752B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3707467A DE3707467C1 (en) 1987-03-09 1987-03-09 Full molding process and device
DE3707467 1987-03-09

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EP0281752A2 EP0281752A2 (en) 1988-09-14
EP0281752A3 EP0281752A3 (en) 1989-03-15
EP0281752B1 true EP0281752B1 (en) 1991-03-06

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US6453976B1 (en) 1999-10-29 2002-09-24 Hitchiner Manufacturing Co., Inc. Lost foam countergravity casting
US6715536B1 (en) 2002-07-25 2004-04-06 Torque-Traction Technologies, Inc. Full mold casting process and device for a differential case
DE102004027638B3 (en) * 2004-06-05 2006-02-09 Albert Handtmann Metallgusswerk Gmbh & Co. Kg Transport and compression of particles for producing lost foam process molds using vibrating table, on which mold container is mounted, comprises tipping container using e.g. hydraulic cylinders so that it is at angle to force of gravity
CN102974762A (en) * 2012-12-24 2013-03-20 昌图县吉派机械铸造有限责任公司 Vacuum evanescent die casting process
CN103920850B (en) * 2014-04-28 2016-07-06 文水县易鑫铸造有限公司 A kind of V method casting technique
CN104325075A (en) * 2014-10-08 2015-02-04 柳州金茂机械有限公司 V method casting process
JP6235524B2 (en) * 2015-04-17 2017-11-22 ファナック株式会社 Sand mold manufacturing system and sand mold manufacturing method for manufacturing sand mold
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Also Published As

Publication number Publication date
EP0281752A3 (en) 1989-03-15
EP0281752A2 (en) 1988-09-14
US4958674A (en) 1990-09-25
ES2021764B3 (en) 1991-11-16
DE3707467C1 (en) 1988-08-04
DE3861876D1 (en) 1991-04-11

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