The composition of the process cost of precision castings

Update:08 Nov 2019
Summary:

The full-silica sol investment casting process can be d […]

The full-silica sol investment casting process can be divided into four stages: wax mold manufacturing, shell making, smelting pouring and post-treatment. We collect the costs of inspection, precision casting and other services for the four processes to assist the production costs. The costs incurred in the three stages of wax mold manufacturing, shell making, and smelting casting are closely related to the process yield. The cost of casting weight is more accurate than the weight of the casting directly. For example, if the wax mold manufacturing cost is calculated based on the weight of the casting, the cost relationship between the small part and the large part is obviously not realistic. Therefore, a more reasonable method is that the cost of the wax mold manufacturing, shell making, and smelting casting process (referred to herein as the front stage cost) is calculated according to the weight of the cast steel (referred to herein as the pouring weight), and the post-processing and auxiliary production costs (referred to herein) For the latter part of the cost) is calculated according to the weight of the casting.

Strictly speaking, the manufacturing costs of different castings in each process are not exactly the same, but some differences are small and can be calculated according to the average level. What we are concerned about are those factors that have a greater impact on the cost of castings. The main factors leading to the difference in the cost of the casting process are as follows: 1. Process yield rate The process yield rate is also called the yield rate, which is the actual weight of the casting as a percentage of the casting weight. For a specific casting, the process yield is equal to the same. The total weight of the casting on the tree as a percentage of the tree weight, which is related to the casting structure and the grouping scheme, may vary from 30% to 60%, generally between 40-50%. The relationship between the cost of the front section and the yield of the process is the cost of the front section of each kilogram of casting. The cost of the previous section of the casting weight per kilogram. The yield of the front section of each casting is inversely proportional to the yield of the process. The lower the yield of the process, the lower the cost of the front part of the casting. High, and the lower the process yield, the more significant the impact. The cost of pouring the front section of each kilogram of molten steel is 6 yuan. When the yield of alloy castings is 45%, the cost of the front section of each casting is 13.33 yuan; when the yield of the process is 30%, the cost of the front part of the casting is 20 yuan/kg, which is higher than the average. The high 6.7 yuan, casting parts increase the process cost by 37.6%, the impact on the total cost of 304 stainless steel castings is about 17%; when the process yield is 60%, the cost of the front part of the casting is 10 yuan / kg, 3.3 yuan lower than the average level , the process cost is reduced by 18.5%, which is equivalent to a total cost reduction of about 7% for 304 stainless steel castings; the leading cost of the casting to the process yield can be derived: the degree of influence of the process yield on the front cost per kg of casting In inverse proportion to the square of the process yield, when the process yield is 45%, the cost of the front section per kilogram of casting is increased by 0.3 yuan for every one percentage point decrease. When the process yield is 30%, the front section of each kilogram of casting is reduced by one percentage point. The cost increased by about 0.67 yuan, which shows that the impact of process yield on cost is very significant. Like the electrical power factor, reducing the process yield is equivalent to increasing the reactive power consumption. Of course, the process yield is not as high as possible, and it is not as high as it is high. Excessive process yield will reduce the shrinking capacity of the gating system, resulting in insufficient shrinkage or shrinkage defects. Some castings, especially irregularly shaped thin-walled castings, are difficult to increase due to the limitations of the casting structure and the grouping scheme. This important factor should be taken into account when determining the casting price.

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