The structural forms of the lower core clamp of sand casting cylinder block are various in production practice, but according to the different balance structures, it can be summarized into two types: single-layer structure and multi-layer structure; And according to the different clamping power, it can be divided into: the lower core clamp of manual clamping mechanism and the lower core clamp of pneumatic clamping mechanism.
In production practice, the characteristics of the lower core fixture of sand casting cylinder block, as well as the difficulty and cost of its design, manufacture and use, are mainly reflected in the single-layer structure or multi-layer structure of the lower core fixture of sand casting cylinder block. Therefore, this section mainly takes this as the research object and makes the following comments:
1. Multi layer structure lower core clamp
The so-called multi-layer structure lower core clamp of sand casting cylinder block refers to the falling process of balancing the lower core clamp when preparing the whole set of cylinder block sand core to clamp the sand core on the core assembly platform (also known as core assembly clamp or core assembly mould), and the falling process of the lower core clamp before lowering the whole set of cylinder block sand core into the mold cavity, Whether the lower core clamp (and the whole set of sand core) falls stably (evenly), the clamp structure adopted is the lower core clamp with more than two layers of structure, as shown in Figure 1. The research on the structure and production practice shown in Figure 1 and Figure 2 show that its two-layer and even three-layer structure seems to have the advantages of luxury and good balance; But it also shows the following important deficiencies.
First, the structure is complex and the production cost is high. In order to reduce its weight, the frame of sand casting cylinder block multi-layer structure lower core clamp is often made of aluminum alloy. For two-layer structure, the lower frame and the upper and lower frames of three-layer structure are often made of aluminum alloy light alloy; Even so, the multi-layer structure lower core clamp of sand casting cylinder block shown in Figure 1 is heavier than the single-layer lower core clamp shown in Figure 2. Therefore, it is not difficult to see that its complex structure not only makes the design workload large, but also its manufacturing cost is doubled higher than the single-layer structure shown in Figure 2.
Second, it is inconvenient to use and increases kinetic energy consumption. The multi-layer lower core clamp of sand casting cylinder block shown in Figure 1 is inconvenient to operate because of its bulkiness, and also increases the kinetic energy consumption. To a certain extent, it not only increases the physical consumption of operators, but also increases the production cost of the factory.
2. Single layer structure lower core clamp
The production practice shows that the sand casting cylinder block single-layer structure lower core clamp shown in Figure 2 can well overcome the above shortcomings of the sand casting cylinder block multi-layer structure lower core clamp shown in Figure 1. In production practice, the structure shown in Figure 2 is also the most commonly used structure in cylinder block sand mold foundry.
For the sand casting cylinder block shown in Figure 2, the key element of the balance (stability) and reliability of the single-layer lower core fixture is to use 3 ~ 4 balance bars in Figure 2; Only in this way, the stability of the single-layer structure shown in Figure 2 can reach the same degree as the lower core clamp of the multi-layer structure of sand casting cylinder block shown in Figure 1. This point is just a process element that has not been recognized by sand mold foundry using multi-layer structure lower core fixture.