Mohou.com Concise Digital Manufacturing Handbook (2): Comparison between Additive Manufacturing and Subtractive Manufacturing

Mohou.com Concise Digital Manufacturing Manual (1): Why Use Digital Manufacturing?

In this chapter, Mohou.com will learn with you:

1.A first introduction to additive and subtractive processes

2.Understand the advantages and disadvantages of each

Although digital manufacturing uses different technologies to quickly produce various components, machining and 3D Printing technology can be very clearly divided into additive and subtractive manufacturing methods. This chapter explains the differences between addition and subtraction, examines the advantages and disadvantages of each method, and examines how the two methods complement each other.

Understand the fundamental difference

Both additive manufacturing and subtractive manufacturing have suitable uses in digital manufacturing, but there are fundamental differences between the two. It is important that you understand these differences so that you can better understand how to use these methods.

Additive manufacturing

Additive manufacturing is a method of building parts by adding thin, stacked layers of material, with each layer serving as the basis for the next layer.

3DPrinting is a common name for additive manufacturing. In general, the two terms are interchangeable in certain particular scenarios, or more strictly speaking.3DPrinting generally refers to the process of manufacturing parts using melted plastic or similar materials, while additive manufacturing processes include more processes, particularly some industrial grade, which can offer more material options and better printing quality, closer to production tools than to the mass. consumer products. For example, there is a process called metal powder sintering (GDT) – a process that creates metal parts by fusing layers of powder – might prefer to call it “additive manufacturing” rather than “additive manufacturing.”3DPrint”.

Subtractive manufacturing

Subtractive manufacturing is a method of machining parts that starts with a large piece of material and continues to remove unwanted materials until the finished part is complete. We can use different types of tools to remove excess material, such as turning and milling which are the most common subtractive manufacturing processes.

To better visualize subtractive manufacturing, consider how a sculptor begins with a large block of stone. The sculptor used a hammer and chisel to remove the stone to create the statue. The statue is smaller than the original stone blocks because the sculptor had subtracted blocks that did not fit the final design.

Today, subtractive manufacturing often incorporates computer numerically controlled machines.(CNC),For exampleCNCTowers andCNCMilling machines to produce precision parts. CNCThe equipment is often faster and more precise than human-operated machines. CNC The device also offers good repeatability, which isCNCBefore its advent, this was a problem for most human operators.

Injection molding is technically defined as an equal-material process, but because subtractive processes are used to make injection molds, they are often classified as such.

Advantages and disadvantages

No manufacturing method (or material) is suitable for all purposes. The replicators featured in the science fiction television series Star Trek are still the stuff of legend. It is therefore important to understand the advantages and disadvantages inherent in additive and subtractive manufacturing methods.

Advantages of additive manufacturing

Because additive manufacturing is made up of thousands of extremely thin layers stacked to form a part, very complex geometries can be created that might not be possible with other methods. For example, parts may contain channels and internal holes that cannot be made with any modern milling machine. This also means that a very complex assembly can be manufactured in a single part, rather than requiring multiple mated parts.

Additive manufacturing also offers unique opportunities to create custom parts at very low volumes. For example, additive manufacturing offers the possibility of customization in the fields of dentistry and jewelry. Obviously, custom-made prostheses cannot be mass-produced; Instead, it is ideally suited to the use of additive manufacturing.

Although additive and subtractive manufacturing methods have the ability to use a variety of materials, the properties of these materials can vary as the processing method changes. If you have an experienced and knowledgeable digital manufacturing partner (like Mohou.com), seek advice on how the process impacts material properties.

Disadvantages of additive manufacturing

Although additive manufacturing is versatile, it does not meet all situations for several reasons:

Additive manufacturing is best suited for small batch production. As production reaches tens of thousands of parts, additive manufacturing becomes too expensive to use sustainably. Generally speaking, if more than a few hundred parts are produced, additive manufacturing generally no longer presents a cost advantage. With technological advancements in the future, the cost of additive manufacturing will be reduced and production efficiency will be improved. The price premium for this type of large-scale production could be reduced, and additive manufacturing could also be commonly used for large-scale products. large-scale production. But for now, if you need to produce parts in large quantities, you may want to carefully consider costs.

Another weakness of additive manufacturing lies in the part manufacturing process. Unlike cast or machined parts, parts made using additive manufacturing tend to have a rougher appearance. It is often possible to polish or post-treat the surface of parts made by additive manufacturing, but this additional processing step increases production time and cost.

Advantages of material reduction

Milling and turning are well-known processes in traditional subtractive manufacturing. Machined parts can be made from most materials in solid form. For example, most metals, wood, and plastics can be processed using subtractive manufacturing methods.

Subtractive manufacturing makes it easy to produce perfect-looking, often ready-to-use parts without additional processing. Additionally, because processing begins from a solid block of material, you generally do not experience the porosity issues that sometimes occur with additive processes. Additionally, due to the cost of materials, subtractive manufacturing can be cheaper than additive manufacturing, especially in volume production.

Disadvantages of material reduction

Just as additive manufacturing has certain weaknesses, the subtractive manufacturing industry also has certain weaknesses. For example, to machine channels or internal holes in a part, the tool or mold must be able to reach these characteristic areas. This requirement means that individual parts may not be as complex as additive manufacturing processes. In some cases, this means that multiple parts must be designed so that they can be machined correctly and then joined together in the final assembly process.

Subtractive manufacturing is also limited by the capabilities of the molds used to make the parts. Depending on the mold manufacturer, there may be size restrictions (minimum or maximum size limits) on the materials that different molds can process.

Combined use of additive and subtractive materials

Of course, you don’t need to limit yourself to using a single process and material to make your entire product. In fact, you may find that different processes are suitable for different parts or stages of the product.

As we did in chapter 1 As mentioned in Chapter 1, you may also find that you need to use a different approach to rapid prototyping. For example, your initial3DPrinted prototypes may be given a rough surface finish, but customers may report the rough feel that additive processes can produce. Possible solutions at this stage include secondary finishing, switching to machined parts, or even using injection molding during prototyping. Your digital manufacturing partner can advise you on the manufacturing methods best suited to producing the parts you need.

Regardless of which digital manufacturing method is best for creating your product, you need to start with a good3DThe digital model begins. Your digital manufacturing partner should be able to use this model to provide design recommendations and help you select an appropriate manufacturing process.