There are many ways to produce metal components. At FJ Industries we produce metal components by powder metal and casting processes. The casting process can be conducted in numerous ways. In this blogpost we will describe the differences between investment casting and sand casting.
Investment casting
The investment casting process consists of the following steps:
- A wax pattern, identical to the final shape, is made in a steel tool.
- The wax parts are mounted on a pattern tree.
- The pattern tree is dipped several times into a ceramic slurry and then left to dry.
- When the ceramic shell has hardened, the wax will be melted out by heating.
- We now have a ceramic mould into which the melted metal is poured.
- When the metal has cooled, the ceramic shell will be removed, revealing the cast metal components.
- Parts may be heat-treated to improve dimensional stability or properties.
- Each metal component is cut off from the tree and is now ready for the machining process and quality control.
Sand casting
The sand-casting process consists of the following steps:
- A reusable pattern, identical to the final shape, is made.
- The mold is typically produced in two pieces divided in the middle where the pattern is mounted.
- A refractory material (typically sand), which is stable at high temperature, is formed around the pattern.
- The pattern is removed. Molten metal is poured into the gates and runners in the mold.
- The mold and metal are set for cooling.
- The mold is opened, and the sand is removed from the casted component.
- The gates and runners are cut from the cast component.
- Post-processing as sandblasting and grinding is applied.
- Parts may be heat-treated to improve dimensional stability or properties.
- The component is ready for the machining and quality control.
The differences between sand casting and investment casting
Sand Casting | Investment casting | |
Base material | Mostly pig iron from iron ore. Scrap material and alloying elements as ingots can be added. | Mostly scrap steel. Alloying elements as ingots can be added. |
Part shape | Near net shape. Post machining is normally needed where narrow tolerances are required. Good surface finish but rougher. Lower density. | Near net shape. Post machining is normally needed where narrow tolerances are required. Excellent surface finish. Higher density. |
Part design | Complex design. Bigger parts. Sand mold typically produced in 2 half parts and may cause a small displacement on the casted parts (parting lines). | High complex design. Smaller parts. Thin wall thickness possible and very accurate. Produced in closed ceramic shells. |
Part size | From 1 kg to max 10 ton. | From 30g up to several kilos. |
Tolerances | ISO 8062 CT 8-11 | ISO 8062 CT 5-7 |
Materials | Mostly gray cast iron, ductile cast iron and white cast iron. But also possible for carbon steel and low alloyed steel. | Cast steels like carbon steel, low and high alloyed steel, and stainless steel. |
Waste | Recycling of pouring cup, runner and gate material. Sand material can be recycled. | Recycling of pouring cup, runner and gate material. Shell material is waste. |
Cost | Depending on size, but normally low mold cost – medium part price. | Low mold cost – higher part price. |
Volume | Typical small to medium volumes. | Typical small to medium volumes, but also suitable for higher volumes for smaller parts. |
Difference in finished component
When looking at the finished component there are some differences when comparing sand cast components and investment cast components. These differences are shown in appearance, tolerance grade and price. The appearance will differ as the components made by investment casting will be smoother on the surface. The tolerance grade for investment casting is according to ISO 8062 CT 5-7, and for sand casting it is according to ISO 8062 CT 8 -11. As for the price, investment casting will typically be higher than sand casting. The sand-casting materials and processes are cheaper which results in a cheaper final component.
We can help you to find the best processing method for your component
We have years of experience manufacturing metal parts for various industries, and our specialists are happy to share their expertise. Feel free to contact us if you want to know more.