Hey there! As a supplier of CNC milled steel parts, I often get asked about the differences between CNC milled steel parts and investment - cast steel parts. So, I thought I'd break it down for you in this blog post.
1. Manufacturing Process
Let's start with how these two types of parts are made.
CNC Milled Steel Parts
CNC (Computer Numerical Control) milling is a subtractive manufacturing process. We start with a solid block of steel, which is called the workpiece. Then, a CNC machine uses cutting tools to remove material from the workpiece based on a pre - programmed design. The machine can move the cutting tool in multiple axes, allowing for very precise shaping. It's like a super - precise sculptor, but instead of clay, it's working with steel. For example, if we're making a custom - designed gear, the CNC machine will carefully cut away the excess steel to form the teeth and the shape of the gear. You can check out some cool examples of our work on Nickel Alloy CNC Machining Part.
Investment - Cast Steel Parts
Investment casting, on the other hand, is a form of casting. First, a wax pattern is created that has the exact shape of the final part. This wax pattern is then coated with a ceramic shell to form a mold. After that, the wax is melted out, leaving a cavity in the shape of the part. Molten steel is then poured into this cavity. Once the steel cools and solidifies, the ceramic shell is broken away, and the part is finished. It's like making a mold and then filling it up with steel. This process is great for making parts with complex shapes that would be difficult to achieve with other methods.
2. Precision and Tolerance
CNC Milled Steel Parts
One of the biggest advantages of CNC milled steel parts is the high level of precision. CNC machines can achieve extremely tight tolerances, often within a few thousandths of an inch. This means that the final part will be very close to the exact dimensions specified in the design. For parts that need to fit together precisely, like in aerospace or medical devices, CNC milling is the way to go. We can also make parts with very fine details, such as small holes or thin walls. Check out our CNC Machining Optical Parts for examples of parts that require high precision.
Investment - Cast Steel Parts
While investment casting can also produce parts with good precision, the tolerances are generally not as tight as those of CNC milled parts. The process of pouring molten steel into a mold can cause some minor variations in the final part's dimensions. However, for many applications, the precision of investment - cast parts is still more than adequate. And for large - scale production of parts with complex shapes, the trade - off in precision might be worth it.
3. Surface Finish
CNC Milled Steel Parts
The surface finish of CNC milled steel parts is usually very good. The cutting tools used in CNC milling can leave a smooth surface, and additional finishing processes like polishing can be applied if needed. This smooth surface is not only aesthetically pleasing but also important for parts that need to slide or rotate against other components. For example, in automotive engines, parts with a smooth surface finish reduce friction and wear.
Investment - Cast Steel Parts
Investment - cast parts may have a rougher surface finish compared to CNC milled parts. The ceramic shell used in the casting process can leave some texture on the surface of the part. However, post - casting finishing operations can be performed to improve the surface finish. But this adds an extra step and cost to the manufacturing process.
4. Material Properties
CNC Milled Steel Parts
Since CNC milling starts with a solid block of steel, the material properties of the final part are largely determined by the properties of the original steel. The machining process doesn't significantly change the material's internal structure. This means that we can choose high - quality steel with specific properties, such as high strength or corrosion resistance, and the final part will retain those properties.
Investment - Cast Steel Parts
During the investment casting process, the molten steel cools and solidifies, which can affect the material's microstructure. The cooling rate can cause differences in grain size and orientation, which in turn can affect the part's mechanical properties. In some cases, this can lead to variations in strength and ductility from one part to another. However, proper control of the casting process can minimize these variations.
5. Design Flexibility
CNC Milled Steel Parts
CNC milling offers a high degree of design flexibility. As long as the cutting tools can reach the areas that need to be machined, almost any shape can be created. Complex geometries with internal features, such as pockets or channels, can be easily machined. We can also make changes to the design quickly by simply modifying the CNC program. For example, if a customer wants to change the shape of a part slightly, we can make the adjustment without having to start the manufacturing process from scratch. Check out our 5 Axis CNC Milling Parts to see the amazing shapes we can create with advanced CNC milling.
Investment - Cast Steel Parts
Investment casting is also good for making parts with complex shapes, especially those with intricate details and undercuts. However, there are some limitations. For example, very thin walls or sharp corners can be difficult to cast accurately. And once the wax pattern is made, making design changes can be time - consuming and expensive, as a new wax pattern and mold need to be created.
6. Cost
CNC Milled Steel Parts
The cost of CNC milled steel parts can vary depending on several factors. For small - batch production, the setup cost of the CNC machine can be relatively high. However, for parts with complex shapes that require a lot of machining, the cost per part may be reasonable. The cost also depends on the type of steel used and the amount of material that needs to be removed. In general, CNC milling is more cost - effective for small to medium - sized production runs.
Investment - Cast Steel Parts
Investment casting has a high upfront cost because of the need to create the wax pattern and the ceramic mold. But for large - scale production, the cost per part can be lower. This is because once the mold is made, the process of pouring molten steel into it is relatively quick and efficient. So, if you need a large number of the same part, investment casting might be the more economical choice.
7. Lead Time
CNC Milled Steel Parts
CNC milling can have a relatively short lead time, especially for small - batch production. Once the design is finalized and the CNC program is created, the machining process can start right away. For simple parts, we can often deliver them in a matter of days. This quick turnaround time is great for customers who need parts urgently.
Investment - Cast Steel Parts
Investment casting has a longer lead time. The process of creating the wax pattern, the ceramic shell, and then waiting for the molten steel to cool and solidify takes time. And if any post - casting finishing operations are required, this further extends the lead time. So, if you're in a hurry to get your parts, CNC milling might be a better option.
Conclusion
So, as you can see, both CNC milled steel parts and investment - cast steel parts have their own advantages and disadvantages. The choice between the two depends on various factors such as the required precision, surface finish, design complexity, production volume, and budget. If you're looking for high - precision parts with a quick turnaround time, CNC milled steel parts are a great choice. On the other hand, if you need to produce a large number of complex - shaped parts, investment casting might be more suitable.
If you're interested in our CNC milled steel parts or have any questions about the manufacturing process, feel free to reach out. We're here to help you find the best solution for your needs and get the parts you need at the right quality and price.
References
- "Manufacturing Engineering & Technology" by Serope Kalpakjian and Steven R. Schmid
- "CNC Machining Handbook" by Kurt F. Gunter
- "Investment Casting Technology" by John Campbell