EP3271094B1 - Method and device for producing a casting mold for sand casting - Google Patents

Description

The invention relates to a method for producing a casting mold for sand casting, wherein a model is positioned in a molding box and the molding box is filled with molding sand (green or damp sand - i.e. sand, bentonite and water) and the molding sand around the model into one stable mold suitable for casting or partial mold is compacted. Furthermore, the invention relates to a corresponding device, in particular for using the method according to the invention.

The process in question is used to produce a mold for sand casting and falls under the term "molding process". Molding processes are alternative processes for the production of a casting mold for the production of workpieces from castable materials. There are different processes, which differ, for example, whether the mold is made by hand or by machine (hand molds, machine molds), whether the mold can be destroyed or reused during the casting process (lost molds, permanent molds) and whether with one-time models (lost models) , Investment casting and full mold casting), permanent models (hand molds, machine molds, mask molds, vacuum molds) or without models (continuous casting, die casting, etc.).

It is therefore about the production of a molding sand mold (casting mold), which is based on a model of the workpiece to be cast, the model being molded in the molding sand (as a molding material).

To produce such a mold, a mold box is required which, for example, like the model, can be made in two parts. Correspondingly, two mold box halves can be provided. The mold boxes are regularly open at the top and bottom. The sand used is free-flowing and has a good shape. In the classic sand foundry, the sand is covered or mixed with fine clay or bentonite. The sand-clay mixture is mixed with water. One speaks here of clay-bound or bentonite-bound sand. This moist sand is often referred to as green sand (Middle High German: green = moist).

The sand is poured around the model and compacted. After compaction, the sand adheres to the inner wall of the molding box and negatively depicts the model contour.

The more detailed the model is, the more precisely or carefully the sand has to be poured and compacted around the model.

In the prior art known from practice, the compression is carried out regardless of the model and the contour via a large head covering the molding box with compression cylinders. This causes the sand to be above the model is more compacted than the sand on the side of the model, namely due to the larger compacting section on the sides. Ultimately, no attention has been paid to how the presence of the model in the molding box affects the compression of the molding sand around the model. It was compressed unidirectionally without considering the contour of the model.

In accordance with the foregoing, large green workpieces, in particular workpieces with a complex surface structure, have been abandoned from the green sand method explained above. Instead of using green sand, it is possible to add a chemical binding agent to the molding sand, which reacts or hardens under the influence of temperature. In this way, stable molds can be produced at only low pressures under the influence of temperature, this process ("no-bake-molds") being environmentally polluting because of the chemical binders used, namely because of the mixing of sand and binder. The use of molding sand with binders is regularly justified by the fact that with large molds and correspondingly large mold boxes, homogeneous compaction of the green sand to define the shape is no longer reliably possible.

EP 295 472 A2 (BMD) shows a method and thus also a device for compacting molding sand in molding boxes with inserted models. In addition, this document also has a compaction head with several, independently working compaction stamps (also cylinders) that compress the molding sand "taking into account the contour" (the dimensions of the model) because they can either be moved differently via a control device or give in according to the pressure " can.

So too JP 2003 205347 , JP S57 142743 A , JP S60 115346 A and US 4,976,303 . Here, the compression head is just so much smaller than the molding box that the entire area of the molding box with its green sand can be compacted at once.

The invention has for its object to provide a method and an apparatus for producing a mold for sand casting, so that regardless of the size of the model or the workpiece to be cast and regardless of complex contours or surfaces, the "classic" green sand method for producing the mold can be used is, and this with a sufficiently good quality of the mold. The use of chemical binders should be avoided.

The above object is achieved as a method by the features of claim 1. The molding sand is compacted zonally (in certain areas), taking into account the contour or the dimensions of the model.

The device according to the invention achieves the above object by the features of the independent claim 12. Thereafter, the molding sand is compacted zonally (regionally) around the model, taking into account the contour or the dimensions of the model, a compression unit having a compression head comprising a plurality of compression cylinders and is movable (positionable and changeable). A projected area of the compaction unit is smaller than a base area of the molding box when it is positioned with the model in the device for compacting the molding sand.

According to the invention, it has been recognized that it is possible to use the green sand method even with large, complex models or workpieces to be cast, according to which the moist molding sand (also called "green sand") is filled and compacted around the model without chemical binders and thereby to the casting mold is solidified. This is possible by taking into account the contour or the dimensions of the model placed in the molding box when filling and compacting the molding sand.

Contrary to previous practice, the molding sand in the molding box is not compacted evenly over the entire surface. Rather, areas in which the model is located are taken into account, unlike areas that are filled with molding sand only to the bottom of the molding box, free of any other parts. In the latter areas, the molding sand can be compressed much more strongly in relation to the volume of the molding box than in the areas in which the model is located.

With the teaching according to the invention, the effect is claimed that the molding sand is subjected to different pressing forces in certain areas, as is permitted by the desired tapping or pressing density of the sand, starting from an original bulk density (claim 9).

To implement the method according to the invention, it is conceivable that the molding sand is poured gradually, quasi layer by layer, into the molding box, which initially takes place around the model, until the entire model is embedded in the molding sand to be compacted (claim 10). This is followed by layers above, taking into account the situation that layers of sand above the model make up a smaller volume than those layers of sand that are to the side of the model. The pressing forces and strokes required for compression are designed accordingly.

The molding sand is compacted using a compacting unit that includes one or more compacting cylinders. The compression cylinders can be the same (Claim 3) or have different diameters, compression cylinders with different diameters being suitable for bringing about different degrees of compression of the molding sand in some areas.

The compression takes place in several successive compression strokes, namely in that a kind of tamping of the molding sand is realized via the compression cylinders, namely to the side of the respective model, leading to a stronger compression than in the area of the contours of the model.

It is also conceivable that the molding box is filled and compacted in several, preferably alternating, work steps (claim 5) in that, after a certain compression, further molding sand is refilled into the molding box, which is then compacted again.

In an advantageous manner, molding sand is refilled in a targeted manner after individual zonal or local compression strokes, namely where, in the absence of a model lying under the molding sand, more mass of molding sand can be compacted, namely on account of the volume available (claim 6).

Taking into account the teaching according to the invention, the compression unit comprising the compression cylinders is not approximately the size of the molding box. On the contrary, the compression unit with the compression cylinders has a relatively small design, namely in accordance with the number of compression cylinders, and is positioned above the molding box via a portal, a bridge or a robot and changed in position in the area of the molding box (claim 12).

The compression unit can thus be moved in space in the region of the molding box, the compression unit as a whole being movable in the direction of the molding sand and each compression cylinder, viewed in isolation, in the direction of the molding sand in the sense of a compression stroke. Any spatial coordinate can be controlled via the portal or a robot, so that different compression strokes are possible at pre-defined locations (claim 4).

The compression unit and thus the individual compression cylinders can be controlled via a computer / processor, the control program with regard to the pressing force and the stroke (claim 8), also with regard to the number of strokes, taking into account the contour of the model, in particular also taking into account The distance from the bottom of the molding box, calculated for filling and compaction, is reduced by the dimensions of the inserted model. Optimal compaction of the molding sand around the model is possible using the method according to the invention regardless of the size and design of the model and thus also regardless of the size of the molding box, using the compression unit carried, for example, by a portal.

By means of multiple individual compression strokes, the compression comes very close to a manual pounding, as was previously the case with manual compression of the molding sand around the respective model, at that time by eye and feel.

The device according to the invention uses the method according to the invention, wherein a compression unit has a compression head comprising several compression cylinders. The projected area of the compression unit is smaller than the base area of the molding box, since the compression unit can be carried by a portal, a bridge or a robot in order to position the compression unit above the molding box at any location and also to be able to change it accordingly a predefinable compression program for actuating the compression cylinders.

The compression head can be moved in space, that is three-dimensionally, and can be positioned anywhere above the molding box in order to be able to actuate or trigger each individual compression cylinder from any position with a predetermined compression force and a predetermined stroke.

Furthermore, it is essential that each of the cylinders, irrespective of the position of the head relative to the molding box, can be moved vertically, namely in order to exert the compression stroke (claim 13).

The cylinders of the compression unit are advantageously arranged symmetrically according to a matrix and can be actuated individually and / or jointly, as required, with different strokes and different pressing forces.

It should be noted that a hydraulic system used can be assigned to (and carried by) the portal, the bridge or the robot, whereby the compression unit is carried and positioned (claim 15). A compact design is possible.

There are now various possibilities for designing and developing the teaching of the present invention in an advantageous manner. For this purpose, reference is made to the following explanation of a preferred exemplary embodiment of the invention with reference to the drawing. In connection with the explanation of the preferred embodiment of the invention, e based on the drawing are also generally refinements and developments of the teaching preferred explained.

• Fig. 1 in einer schematischen Ansicht die prinzipielle Anordnung eines Modells in einem Formkasten, wobei Formsand um das Modell herum gefüllt und verdichtet wird.
• Fig. 2 in einer schematischen Ansicht ein Ausführungsbeispiel einer erfindungsgemäßen Vorrichtung, deren Verdichtungseinheit oberhalb und entlang eines Formkastens positionierbar ist.
• Fig. 3 in einer schematischen Aufsicht die Vorrichtung aus Figur 2.
• Fig. 4 in einer schematischen Vorderansicht die Vorrichtung aus Figur 2.

Show in the drawing ...

• Fig. 1 in a schematic view, the basic arrangement of a model in a molding box, molding sand being filled and compacted around the model.
• Fig. 2 In a schematic view, an embodiment of a device according to the invention, the compression unit can be positioned above and along a molding box.
• Fig. 3 in a schematic plan view of the device Figure 2 .
• Fig. 4 in a schematic front view of the device Figure 2 .

Figure 1 shows in a highly schematic view the basic arrangement of a model 1 in a molding box 2. After positioning the model 1, the molding box 2 is successively filled with molding sand 3 (called green sand), the molding sand 3 around the model 1 to a stable, for Pouring suitable mold is compacted.

The arrows 4 indicate that the compression of the molding sand 3 takes place zonally or in regions, specifically via in Figure 1 Cylinder not shown, taking into account the contour or the dimensions of the model 1. In this respect, it is taken into account whether the molding sand 3 extends upwards continuously from the mold box base 5 or whether the molding sand 3 extends upwards from the surface of the model 1. namely by a much smaller distance than from the bottom 5 of the box.

Figure 2 shows in a schematic view the basic structure of an embodiment of an inventive device for producing a mold for sand casting, the model 1 corresponding to the representation in Figure 1 is positioned in a molding box 2. To compress the molding sand filled or to be filled in the molding box 2, a pneumatically operated compression unit 6 is provided, which comprises a compression head 7 with a plurality of compression cylinders 8.

Figure 2 reveals that the compression unit 6 is assigned to a portal 9 or is carried by it. The portal 9 can be moved horizontally along a guide device 10 linearly along the molding box 2.

The entire compression head 7 can be moved with the compression cylinders 8 on the portal 9 transversely to the guide device 10, namely along a portal guide 11.

In addition, the compression head 7 can be moved vertically on the portal 9, wherein each of the compression cylinders 8, viewed individually, can be displaced or moved in the compression direction.

According to the above, it is clear that the size or longitudinal extent of the molding box 2, including its height, hardly plays a role anymore. Thus, the compression unit 6 with the compression head 7 or the individual compression cylinders 8 can be moved over the molding box 2, whereby the compression cylinders 8 can be positioned to compact the molding sand, taking into account the contour or the dimensions of the model.

Figure 2 furthermore shows that the hydraulic system 12 is assigned to the portal 9, namely carried by the portal 9. A compact design is possible.

It is also conceivable that the guide device 10, on or in which the portal 9 is guided, can be adjusted in width in order to use different portals or to be able to use portals with adjustable widths.

The guide device 10 could also be height-adjustable, in itself, in order to be able to optimally adapt to the height of a molding box 2 to be positioned between the guide elements 13 of the guide device 10.

The drive of all of the above options can be pneumatic and / or electric. A hydraulic drive is also conceivable.

Figure 3 shows the device Figure 2 in a schematic plan view, wherein the molding box 2 can also be seen there.

The portal guide 11 is designed as a crossbar. The compression head 7 comprises a plurality of compression cylinders 8 arranged in a matrix, which serve to compress the molding sand 3 located in the molding box 2.

Figure 4 shows the device Figure 2 in a schematic front view, which also shows the molding box 2. The model 1 is positioned therein and is covered by molding sand 3 to be compacted. Also shows Figure 4 one on the actual The molding box 2 of the filling aid 14 in the sense of a head into which the compression cylinders 8 of the compression head 7 or the compression unit 6 protrude with alternating pressurization.

The arrows 15 indicate the height adjustability of the guide elements 13.

With regard to further advantageous embodiments of the device according to the invention, reference is made to the general part of the description and to the appended claims in order to avoid repetition.

Finally, it is expressly pointed out that the n e embodiment described above of the device according to the invention the claimed teaching not limited to the embodiment or the e limits.

Claims (15)

1. A method for producing a moulding sand mould as a casting mould for receiving a castable material, wherein a pattern (1) is positioned in a moulding box (2) and the moulding box is filled with moulding sand (3), and wherein the moulding sand (3) is compacted (4) around the pattern (1) to form a stable mould suitable for casting,

   - wherein the compaction (4) of the moulding sand (3) takes place zonally by a plurality of compaction cylinders (8) of a compaction head (7) of a compaction unit (6);

   - wherein the compaction (4) is carried out while respecting the contour of the model (1);

   - and the compaction unit (6) is not designed in the size of the moulding box (2) but smaller such that a projected area of the compaction unit is smaller than a base area of the moulding box (2); and the compaction cylinders (8) are positioned above the moulding box (2) with a portal (9), a bridge or a robot and their position is changed in the area of the moulding box, wherein the compaction of the moulding sand (3) in the moulding box (2) takes place in several successive compaction strokes.
2. Process according to claim 1, whereby multiple compaction takes place at different points in the moulding box (2).
3. Method according to claim 1 or 2, wherein the compression cylinders (8) each have the same diameter.
4. A method according to one of claims 1 to 3, wherein the compaction unit (6) is moved in space in the region of the moulding box and the compaction unit as a whole is moved in the direction of the moulding sand (3) and each compaction cylinder (8), viewed individually, is moved in the direction of the moulding sand (3) as a compaction stroke, wherein any desired spatial coordinate can be controlled via the portal (9) or a robot, so that different compaction strokes are possible at predeterminable points.
5. Process according to one of claims 1 to 4, wherein the filling of the moulding box and the compacting is carried out in alternating working steps.
6. Method according to one of claims 1 to 5, wherein after individual zonal compaction strokes moulding sand (3) is refilled into the moulding box (2) in such a way that where, in the absence of a model (1) lying below the moulding sand (3), more mass of moulding sand can be compacted, namely on account of the available volume, moulding sand is refilled.
7. Method according to one of the previous claims, wherein the mould suitable for casting is a partial mould, in particular a mould half.
8. Method according to one of the previous claims, wherein a control of the compression unit (6) and of the individual compression cylinders (8) is effected by means of a computer, and a control program adjusts the pressing force and the stroke of the compression cylinders (8) taking into account the contour of the model (1).
9. Method according to one of the previous claims, wherein the moulding sand (3) is subjected to different pressing forces in different areas, as is permitted by the desired tapping or pressing density of the moulding sand, starting from an original bulk density.
10. Method according to one of the previous claims, in which the moulding sand (3) is gradually filled into the moulding box, in particular layer by layer, first around the pattern, then until the entire pattern (1) is embedded in the moulding sand to be compacted, followed by layers above it, moulding sand layers above the pattern having a smaller volume than those moulding sand layers which are located to the side of the pattern (1)
11. Method according to the previous claim 10, whereby the pressing forces and strokes required for compaction (4) are designed accordingly.
12. Apparatus for producing a sand mould for casting a castable material, wherein a pattern (1) can be positioned in a moulding box (2) and the moulding box can be filled with moulding sand, and the apparatus is designed and adapted to compact the filled moulding sand (3) around the pattern (1) to form a stable mould suitable for subsequent casting;
    the apparatus
    having a compression unit (6; 7, 8) which has a compression head as a head (7) which comprises a plurality of compression cylinders (8);
    wherein
    a projected area of said compaction unit (6; 7, 8) is smaller than a base area of said flask (2) when positioned with said pattern (1) in said apparatus for compaction;
    the compaction unit (6) comprises a portal (9), a bridge or a robot in order to be positionable and position-variable over the moulding box (2),
    wherein the compaction head (7) is movable in space, i.e. three-dimensionally, and can be arbitrarily positioned over the moulding box (2);
    whereby the moulding sand is compactable zonally around the model (1),
    while respecting a contour of the model (1).
13. Apparatus according to claim 12, wherein each of the compaction cylinders (8) is vertically movable relative to the moulding box (2) irrespective of a position of the compaction head (7).
14. Apparatus according to claim 12 or 13, wherein the compression cylinders (8) are arranged symmetrically in the compression head (7) according to a matrix.
15. Apparatus according to one of the previous claims 12 to 14, wherein a hydraulic unit (12) is associated with the gantry (9), bridge or robot and is carried thereby, and the compaction unit (6) is carried by the gantry (9), bridge or robot and is positionable.

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