How to shoot sand tightly in core shooting machine?

June 12, 2020

In sand compaction, sand flow energy and pressure difference are the two main factors of core shooting machine sand compaction. In addition, poor exhaust can also lead to poor sand core compactness. Let’s analyze these three main influencing factors and how to solve them.

The ways to shoot sand tightly in a core shooting machine

1. Control the flow energy of sand
The factor that affects the flow energy of sand in a core shooting machine is the shot pressure. The kinetic energy is proportional to the square of the velocity V, the pressure is high, and the kinetic energy is high. Within a certain range, the greater the pressure, the greater the sand flow velocity. The general sand injection pressure is 0.45-0.65MPa. The cross-sectional area of the sand-blasting hole is too small. When the sand flow of the core shooting machine passes through, the resistance greatly affects the sand flow speed. If the cross-sectional area is too large, the sand flow rate will decrease. Therefore, according to the product to find the appropriate sand flow speed can effectively compact the sand.

2. Find the pressure difference of the product
The pressure difference P1-P2 refers to the pressure difference between the free surface P1 of the sand layer and the pressure P2 at the exhaust. The magnitude of this pressure difference is directly proportional to the thickness of the material layer formed in the core box, and it acts on the sand particles injected into the core box in accordance with the direction of the airflow and acts as a compact sand core. The main factors affecting the pressure difference:
① The depth of the core box cavity in a core shooting machine, the deeper the core box cavity, the greater the airflow resistance and the greater the pressure difference.
②Exhaust method, the lower part of the core box is exhausted, and the P1-P2 pressure difference is established, the upper part is tightly sanded, and the airflow is discharged from the upper part, and the pressure difference is lost.
③The exhaust cross-sectional area has a great relationship with the type of core sand binder. For example, the low-pressure casting machine has a large cross-sectional area for the core sand with poor fluidity.

3. Ensure the exhaust of the core shooting machine is smooth
In sand compaction, sand flow energy and pressure difference are the two main factors of sand compaction. Which factor plays a major role depends on the structure of the core box and the layout of the exhaust system. It can be known from the above principle that the exhaust structure of the core box is particularly important in core shooting. The poor exhaust will cause the sand core to be poorly compacted. The surface of the sand core is sponge-like and the strength is low. Moreover, the casting is prone to sticky sand defects or the core cavity is not full, and the sand core is scrapped.

Ways to solve poor exhaust in a core shooting machine:

Due to the thin wall of the water jacket and the shape of a circular arc, a large exhaust plug cannot be opened in the inner cavity of the core box, and the exhaust plug provided is not good for exhaust and is easily blocked. The sand core is often not full due to looseness or shot. And scrapped. If the exhaust slot is opened for exhaust, on the one hand, there will be a phenomenon of sand running, on the one hand, where a local location needs to be opened for exhaust, the exhaust hole cannot be led out of the core box. But the problem of poor exhaust has not been solved, and most waste products are produced every time.

After a period of comparison of various exhaust methods. Delin Machinery thought of a way to solve the problem of poor exhaust in a core shooting machine and prevent sand running.

The method is to combine the two exhaust methods of the exhaust groove and the exhaust plug, and the exhaust groove is opened in the place where the exhaust groove needs to be opened on the surface of the core box. However, the exhaust slot does not directly lead out of the core box, but an exhaust plug is opened in the exhaust slot. The airflow entering the exhaust groove is discharged out of the core cavity through the exhaust plug or the exhaust hole.

In this way, after the sand gas flow enters the exhaust groove, the gas is discharged under the action of the exhaust plug, and the sand particles remain, forming a compact sand core with the core cavity and the groove. Advantages of using this method:

  1. Solve the phenomenon that the exhaust groove is easy to wear and produce sandblasting during use.
  2. It can solve the problem that the sand core cannot open the exhaust plug or the exhaust groove due to the structural shape and other reasons.
  3. Because the exhaust system is set on the parting surface, it is easy to observe whether the exhaust is smooth. It can promptly detect whether there is a blockage, prevent the generation of waste products, and facilitate cleaning.

Disadvantages: A thin sheet of exhaust grooves will be formed on the sand core, increasing sand core grinding work.

In summary, by doing the above three factors that affect the sand shooting of the core shooting machine, it is possible to compact the core and produce a perfect sand core.

Delin Machinery is a professional manufacturer with years of experience in the production of the foundry machine core shooting machine, which has a professional design and production team to produce a high-quality core shooter machine and provide quotation and export of machines to various countries. You can click here: core shooting machine to view more details of our foundry machine products.

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