Sand casting – hand molding

Manual modeling definition – all modeling operations completed by hand or hand tools are called manual modeling.

Advantages and disadvantages: flexible manual molding operation, simple process equipment (pattern, core box, sand box, etc.), short production preparation time, strong adaptability, molding quality can generally meet the process requirements, but low productivity, high labor intensity, poor casting quality, so it is mainly used for single piece and small batch production.

Classification application scope: there are many kinds of manual molding methods. In actual production, the appropriate molding methods can be selected according to the structural characteristics, production batch and production conditions of castings.

Classification by sandbox characteristics

Two box modeling

Main features:

It is the most basic method of molding. The mold is composed of upper box and lower box, which is easy to operate.

Scope of application:

Various production batches and castings of various sizes.

Three box modeling

Main features:

The mold is made up of upper, middle and lower boxes. The height of the middle box shall be suitable for the distance between the two parting surfaces of the casting. The operation of three box molding is laborious, and it needs to be equipped with a suitable sand box.

Scope of application:

Small batch production of single piece. Castings with two parting surfaces.

Stripping molding

Main features:

The sand box shall be removed from the detachable box for molding and used for new molding again before pouring after the mold is closed. Many molds can be made repeatedly with one sand box to save sand box. It is necessary to fill the surrounding of the mold with molding sand or add a box on the mold to prevent the wrong mold during pouring.

Scope of application:

Production of small castings. Because the sand box has no box belt, the size of the sand box is less than 400 mm × 400 mm × 150 mm.

Pit modeling

Main features:

In the sand pit below the ground, no sand box or upper box is used. The large casting needs to be paved with coke under the sand bed, and the air outlet pipe is buried, so as to draw air during pouring. The cost and time of manufacturing sand box are reduced, but the molding costs labor and requires high technology.

Scope of application:

The sand box is insufficient, or the production batch is not large, and the quality requirements are not high, such as sand box iron, furnace grate, core bone, etc.

Classification by pattern features

Whole mold design

Main features:

The pattern is integral, the parting surface is flat, and the mold cavity is all in a sand box. The mould is simple and the casting will not produce wrong mould defects.

Scope of application:

A casting with a maximum section at one end and a flat surface.

Dredging molding

Main features:

The pattern is integral and the parting surface is curved. In order to lift the pattern, the molding sand that hinders the lifting of the mold is dug by hand. Molding costs labor and low productivity, requiring high technical level of workers.

Scope of application:

Small batch production of single piece. A casting whose parting surface is not flat.

Fake box molding

Main features:

In order to overcome the shortcomings of the sand digging molding, a bottom tire which is consistent with the parting surface is made in advance before the molding, and then the bottom tire is made on the bottom tire. Because the bottom tire does not participate in pouring, it is called false box. It is simpler than sand digging, and its parting surface is neat.

Scope of application:

Castings that need to be sanded in batch production.

Parting molding

Main features:

The pattern is divided into two parts along the maximum cross section. The cavity is located in the upper and lower two sand molds. The shape is simple and labor-saving.

Scope of application:

Casting with the largest section in the middle.

Movable block molding

Main features:

There are small bosses, ribs, etc. on the casting that hinder the mold lifting. During die making, these parts are made into movable (i.e. movable block). When lifting the mold, first take out the main body shape, and then take out the movable block from the side. Molding costs labor, and the technical level of workers is high.

Scope of application:

Small batch production of single piece. Castings with protrusions that are difficult to lift.

Scraper molding

Main features:

Use scraper instead of solid shape. It can reduce the cost of pattern, save wood and shorten the production cycle. However, the low productivity requires high technical level of workers.

Scope of application:

Small batch production of single piece of large and medium-sized castings with equal cross-section or revolving body, such as pulley, cast pipe, elbow, etc.

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