Application boundary of sand casting molds on structural components

Application boundary of sand casting molds on structural components
Sand casting molds have low cost and high degree of shape freedom, but their dimensional accuracy and surface quality are weaker than metal molds, making them suitable for small and medium-sized complex structural components.
Composition of Sand Mold
A sand mold consists of a pattern, a sand box, a sand core, and a casting system. The shape of the cavity is determined by the appearance, and the cost is much lower than that of metal molds.
The price of a set of wooden molds is often between 20000 and 100000 yuan, while the price of metal molds is over 150000 yuan.
Sand molds are disposable and each piece needs to be reshaped. The production efficiency is lower than that of metal molds.
Accuracy and Surface
The dimensional tolerance of sand castings is usually CT8-CT10 level, which is lower than the CT6-CT7 level of metal molds.
The surface roughness is usually Ra12.5-25 μ m, and a machining allowance of 2-3mm should be left.
Insufficient accuracy means a large amount of subsequent processing. For structural components with high size requirements, sand molds are usually not a priority option.
Suitable batch size
Sand molds are suitable for small batches ranging from single to several thousand pieces. The mold investment is low, and it is still acceptable to spread it to a single piece.
Batch production exceeds 10000 pieces, and the efficiency and precision advantages of metal molds are evident, resulting in lower overall costs.
The lifespan of sand molds is calculated based on the number of molding cycles, with wooden molds typically having 200-500 cycles and metal molds having tens of thousands of cycles.
The advantage of complex shapes
Sand molds can create complex internal cavities and inverted structures, which are difficult to achieve with metal molds.
Sand molds are commonly used for subframe and shell components, as the inner cavity is complex and the metal mold cannot be demolded.
The combination design of sand cores is crucial. The number of sand cores is large, assembly errors accumulate, and the consistency of wall thickness decreases.
Common Defects
Sand holes, sticky sand, and pores are the three major defects of sand molds. Sand holes are often caused by insufficient sand mold strength, while sand sticking is often caused by insufficient coating.
Pores are often caused by high moisture content in sand molds. After shaping, it needs to be fully dried and the moisture content should be controlled below 0.5%.
Dimensional deviations are often caused by sand mold deformation. Insufficient rigidity of the sand box may cause expansion during pouring.
cost structure
In the cost of a single piece of sand mold, the proportion of molding time is high. Automated molding lines can reduce manual labor, but require significant investment.
Small batch manual molding often results in higher unit costs than metal molds. When the batch is insufficient, the price advantage of sand molds does not hold.
Positioning of Xinfeng Mold
Xinfeng Mold mainly uses metal low-pressure and gravity molds on structural component molds, and sand mold projects are mostly provided as supporting solutions.
The choice between sand mold and metal mold depends on the batch size and precision requirements, rather than the mold unit price.
Reuse of sand molds
After regeneration treatment, old sand can be reused proportionally, with a reuse ratio of 70% -85%. The burning loss of recycled sand should be controlled below 3%.
Practical tips
After sand molding, the storage time should not exceed 4 hours. Prolonged storage can cause moisture absorption and significantly increase porosity during pouring.
The exhaust holes of the sand mold should be pierced through, and any exhaust holes that are not pierced through are equivalent to none, which can easily cause suffocation during pouring.
The rigidity of the sand box of the sand mold should be sufficient, and the expansion of the box during pouring will make the overall size of the casting larger.
Frequently Asked Questions
Question: What is the precision of the sand mold?
Answer: It is usually CT8-CT10 grade, lower than the metal type.
Q: What is the suitable batch size for sand molds?
Answer: From a single item to several thousand pieces, exceeding 10000 pieces is not economical.
Q: How many times can the wooden mold be used?
Answer: Usually 200-500 times.
Q: Can sand molds create complex cavities?
Answer: Yes, this is an advantage over the metal type.
Q: Is the cost of a single sand mold low?
Answer: Small batch handmade styling is actually higher.
Q: What are the common defects of sand molds?
Answer: There are mainly three types: sand holes, sticky sand, and air holes.
Recommended search keywords
Sand casting molds, sand casting, wood mold making, sand core design, wheel hub mold manufacturers, structural component molds, sand mold accuracy, small batch casting, sand hole defects, casting mold manufacturers