The one with the lowest price in the quotation you get will always be surprisingly attractive, but blindly choosing the lowest price may lead to delayed delivery or deterioration of casting quality. In the long run, this situation will instead be a more expensive overall cost of the product.
The wise customer must weigh all the terms in the quotation, including the wax mold tooling requirements, the tolerance accuracy and finish of the product, and any special options for drawings, specifications and machining requirements. Factors outside of the quotation, such as the supplier’s casting experience and reliability, and the stability of the product delivery are particularly important in determining the actual cost and value of the casting.
Due to the different complexity and quality requirements of the products, the manufacturing cost of precision castings applied to different industries varies greatly. There are many factors that may affect the cost, ignoring some of the less significant differences, those with a large impact on the cost of the six major factors are as follows.
Cost of metal materials
For the investment casting process, the amount of material required to make a part is always greater than the volume of the finished part itself. Moreover, the cost of the same metal casting can vary greatly depending on the metal. Among steel castings, stainless steel castings have the highest cost, compared to steel castings, iron alloys are less expensive and cast iron parts are much cheaper. Most casting projects use a mixture of recycled scrap metal and alloy metal.
In investment casting, the common materials used are mainly various types of steel and cast iron.
- Cast Iron: Although both steel and cast iron contain trace amounts of carbon and look similar, there are significant differences between these two metals. Steel contains less than 2% carbon, while cast iron has between 2% and 4% carbon, along with varying amounts of silicon and manganese and trace impurities such as sulfur and phosphorus. Cast iron is the lowest-cost material in investment casting.
- Stainless steel: Although the material cost of stainless steel castings is higher than other metals. However, castings made with this material have a longer life span, which can lead to higher economic costs over time.
- Carbon Steel: Since carbon steel is produced in very large quantities, it usually costs significantly less than stainless steel.
- Alloy Steel: Since alloy steel plays a large role in the construction industry, its cost varies depending on the specific alloy content and is more influenced by supply and demand.
Another very important factor that affects the cost of casting is the time you purchase raw materials. The prices of different metal raw materials vary periodically. Metal prices are determined by the market and supply and demand, and prices may be different in the US and China at the same time. If you would like to know the cost of related materials in China, please contact our sales staff.
Confirm castings are available for production
The precision foundry needs to confirm if the blank casting process can be used to produce blank castings. Some products can be made using the wet sand process, while others may use resin sand, shell casting, and auto molding processes. The wet sand process is cheaper for producing blanks, and shell casting is the most expensive.
If there are no problems with the blank, then the relevant factors to be taken into account when making this product in large quantities through the investment casting process include the following:
- Dimensional tolerance
- Surface quality
- Structure complexity
- Product annual demand
- Weight and dimensions
Of course, if these requirements cannot be met using the investment casting method, then this product can only be processed by other options, such as forging or machining.
Output rate of castings
The output rate (yield) here is the proportion of the weight of the product to the weight of the raw metal. It is related to the structure of the product and the scheme used in the wax die set tree. It can vary from 30% to 60%, mostly between 40% and 50%. The lower the yield of the cast product, the higher the relative cost. Even if metal materials other than these castings (e.g. pouring systems) can be recycled, these materials consume a lot of energy when they are melted down during processing.
The relationship between the cost of the front end and the yield is that the cost of the front end per kilogram of casting is inversely proportional to the yield. The lower the yield, the higher the cost per unit weight of front-end precision casting. And the lower the yield, the greater the impact.
If the cost of the front section of steel casting is 8 RMB(1.23 USD) per kilogram. When the yield is 45%, the cost of the front section of the precision casting is 17.78 RMB(2.74 USD) per kilogram. When the output is 30%, the front-end cost of precision casting is 26.67 RMB(4.1 USD) per kilogram. When the output is 60%, the front-end cost of precision casting is 13.3 RMB(2.05 USD) per kg.
Deriving the cost of the pre-cast section from the yield rate can be concluded. The rate of impact of yield on the cost of the pre-cast segment per kilogram of precision casting is inversely proportional to the square of the process yield, and the impact of yield on cost is very significant.
Especially when some irregular shape of thin-walled precision castings, due to the limitations of the casting structure, its yield is difficult to have a large increase, which also leads to its cost can not be reduced.
Whether subsequent machining requirements can be met
Except for cast products with ultra-high accuracy requirements, many cast iron foundries can perform subsequent machining processes in-house. Otherwise, they will commission other specialized machining plants, such as electroplating, mirror polishing or PVD Coating, but this is sometimes not good news, as the cooperation between the foundry and other machining plants may cause more problems due to communication, such as delayed delivery time and unguaranteed product accuracy.
An accurate machining quote needs to take into account relevant machining equipment, working time, price, product quantity and other factors. Therefore, subsequent processing costs are difficult to calculate. However, what has a greater impact on this step is generally the number of workpieces; the higher the number, the lower the subsequent machining cost of the casting.
Cost of wax molds
After determining the feasibility of the product, it is time to make the wax mold for the product. Wax molds are processed in a similar way to ordinary injection molds, so their prices are calculated in a similar way. The main factors are as follows.
The size of the part has the greatest impact on the cost of the tool. Larger parts tend to require larger tools to handle them, and therefore more material is used to make the corresponding mold, and the time required to machine the cavity increases significantly. The cost of a tool and the size of the part are directly proportional to each other.
Complexity of the casting
The complexity of casting is the degree of simplicity or complexity of the part. Parts with complex geometry require tooling that adds many moving parts to the mold, and as complexity increases, so does the manufacturing of the mold. A more complex mold also means longer processing times and lower productivity during subsequent machining, corresponding to significantly higher labor costs.
Cost of other materials
In addition to metal materials, there are usually many other raw materials used in investment casting, such as water glass, silica sol, zirconium sand, etc., which are used for shell making.
Material costs for shell production
Even investment casting parts can be produced using both water-glass and silica-sol investment casting techniques. Silica sol casting will make the investment casting with better dimensional accuracy and surface finish. So the cost will be higher than water glass casting. Of course, water-glass casting is more acceptable to customers due to its lower production cost. However, if more precise tolerances and surface finish are required, silica-sol casting is preferred.
Layers of sand shells
In the investment casting process, it is likely that each casting will have a different shape and the size of the casting will have a very significant impact on the number of layers of sand shells. For complex structures, more shell layers will be required, which also means more cost. Typically, 5-6 layers of sand shells are sufficient, larger castings may require 7 or more layers. For example, castings with elongated holes or slots will require 6 or even 7 layers.
As an example, the price per kilogram of casting A is 67.8% for material, 23.9% for fuel and electricity, and 13.3% for labor wages. If the cost of shell material is calculated at $4/kg, although zirconium sand and zirconium powder are only used for the top layer, zirconium sand and zirconium powder still consume about 63% of it, accounting for 42.7% of the total cost of shell making. The cost of silica sol is about 12.2% of the shell cost.
In recent years, labor costs have continued to rise around the world. In Europe and the United States, for example, the cost of manufacturing precision castings is so high that labor costs account for a significant portion of the total cost. This is because almost every step of the investment casting process requires significant use of labor. Taking supply chain costs and labor costs into account, foundries from China are very competitive. As more and more people choose foundries from China, their technology and processing accuracy are improving.
Other cost elements
Other costs include packaging costs, surface treatment, painting, inland and sea transportation, and exchange rates. These costs will be related to the specific needs of the customer.
If you have a need, you can contact our sales staff and we will customize the most cost-effective solution for you.