When it comes to creating machine parts, two of the most popular processes are CNC machining and die casting. In fact, if you want to obtain the best possible finish, then it is possible that you can combine these two processes. Nevertheless, when it comes to choosing which process is better, there are important things that should be considered. Discover when the best time is to use CNC machining and when is the best time to use die casting.

Difference Between CNC Machining and Die Casting

Die casting is a particular industrial process wherein the molten metal is injected into the steel mold or die. Once it has cooled down, it hardens and produces the shape of the part. On the other hand, Computer Numerical Control machining or CNC machining is an automated process that uses a robot in molding the part from the metal. Most often, both of these processes are used for manufacturing metal parts and fittings for particular objects that are commonly used every day. For instance, computer and car parts.

Should You Use CNC Machining or Die Casting?

Compared to die casting, CNC machining is likely more expensive. However, it all depends on the level of production and the type of parts. Oftentimes, CNC machining is used for making the die or for adding more complicated featured once a component has undergone the die cast process. When comparing these processes for forming a part, the following are some of the major factors that should be considered:

Speed

Die casting is a faster process than CNC machining. Additionally, it can be easily repeated. Regardless of if machining is needed for post-casting, it is undeniable that die casting takes less time compared to machining an intricate component from a solid metal. Since die casting is a faster production process, then it is more reliable for generating large batches. While when you are producing smaller volumes, then you can obtain a faster lead time when using CNC machining, just be sure that you are ready with your digital model. It is also more appropriate when testing prototypes since it is faster.

Volume

As mentioned above, CNC machining is more advantageous when you are producing a low volume of parts, since tooling costs are not required. Meanwhile, die casting would be an excellent choice when you are having a high-volume production. It gives you consistent quantity and quality. Die casting is the best choice for sturdy mass production, while CNC machining is appropriate for low production of particularly oddly shaped or complicated parts.

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Waste

When using die casting, there is very little scrap metal left after the process, making it more affordable. While there will be a lot of scrap metal left behind in CNC machining after carving several layers from the solid metal block. If you are more concerned about reducing waste, and would want to use CNC machining, then be sure that you have a recycling system so you will be able to reuse the scrap metal.

Accuracy

Die casting can accurately form complex geometrical shapes, however, there are times that the resulting part has some surface defects including flashes or burrs and you will need machining for cleaning it up. CNC machining can produce finished parts with high level of precision and tolerance, specifically, if they are extremely customized small parts. Nevertheless, die casting is an excellent choice for producing similar parts when it is possible to engrave the surface detail into the master mold.

What is the Perfect Tool for Producing Metal Parts?

Sometimes when choosing the right tool for the job, it all depends on the person’s point of view. The fact is, there are a lot of factors to consider when choosing the proper tool for a particular job. However, there are also times that the choice is quite obvious. When it comes to metal fabrication, some of the production tools that will be used include sand casting, die casting, and machining:

CNC Machining

CNC machining process, which involves milling and turning, can generate parts faster. Hence, they are usually used for low-volume production and swift prototyping. Die casting is just the same as plastic injection molding. Molten metal such as aluminum, zinc, or copper will be reinforced in the die and allowed to cool down. In some instances, additional machining will be needed in accomplishing the threading, specific details, or better sealing surfaces. When used for finishing process, machining permits several variations from a single casting.

Sand Casting

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Compared to die casting, traditional sand casting can be a little cruder. It can produce coarse surface finishes. Post-processing might be required due to the mismatch between the inserts and the mold halves. This mismatch can loosen the tolerance in the casting. Typical use of this process is non-cosmetic parts including engine blocks for automobiles. If you are producing complicated high-volume applications like making engine coolant channels around cylinders, then post machining will be needed to as to complete the part. Unfortunately, there is a couple of design solutions in sand casting which cannot be duplicated in die casting or CNC machining.

Generally, CNC machining is the best choice for lower volumes, which can either be in dozens to a few thousands. This process is faster and more responsive, at the same time, it does not need preparatory tooling compared to casting methods. Aside from low-volume production, this process can also be used for generating prototypes of sand-cast or die-cast parts until such time that there will be a final design and tooling can start. It is also useful when doing bridge tooling to produce parts while tooling is generated for high-volume production.

Casting is commonly used for non-cosmetic, high-volume parts like engine blocks for automobiles.

Volume Should Be Considered

When determining the right production method, it is important that the volume of the parts should be considered. Sometimes, there are situations wherein the choice of process is quite  obvious. If you are looking to produce a high volume of parts, like tens of thousands and beyond, then casting would be more economical. Creating the die will take time, however, every part can be generated quickly and at a low cost. Moreover, CNC machining can generate the first parts faster and more economically, however, after a certain point, you can find that it is not as economical compared to the other processes.

Therefore, the most important consideration when choosing a manufacturing process should be volume. If you only require dozens or hundreds or a few thousands of parts, then you should consider using machining. On the other hand, if you require 10,000 or more, then you should consider using die casting or sand casting. But aside from this, there are still a lot of factors that can influence your choice.

If you decide to move from machining to casting, then it can help in reducing machine time and the generation of metal scrap. However, it is also important to consider that has some downsides too. The flash will require some cleaning. Porosity may occur in thick cross sections that can be caused by post-machining. End-of-fill cold material and flow lines could get brittle.

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Sometimes, when 10,000 parts are required, they should be machined due to the certain requirements of the part. Most likely, this can affect the cost of the part, but sometimes, performance requirements is more important than the cost.

If you need your parts right away, then machining would be more advantageous. Machined parts can be generated within hours after the CAD model is created. While casting will take more time for creating the die and setting up the casting requirements. Hence, it is more beneficial to use machining even if production will be done by the casting method. Machining can be used for modeling a part as well as for testing. Depending on how the testing goes, you are allowed to redesign the part, in fact you can do this as much as you want. This offers fine tuning of the design before its final production. Prototypes can range from a single part to several parts for test marketing.

Ultimately, you should not only focus on the cost and make it as a factor for choosing a manufacturing process. First, you should think about the system specifications, then on your next project, you can focus more on the overall cost.

Die casting is an effective, economical manufacturing method. When you are able to use it to its full potential, then it can substitute assemblies of different parts generated by other manufacturing processes. Additionally, you can obtain significant savings in labor and cost.

Expanding Your Returns

It is only reasonable that you have to worry about your initial investment in a particular project, particularly, if there is a limited budget. If you are not totally sure which is the best method for you, then it is recommended that you should discuss this with the experts.

SEI are well-experienced when it comes to die casting. You can contact us at sales@seimw.com if you require casting parts. Tell us about your needs and we can help you find the most cost-effective solution for your die casting.