There are four main categories of the manufacturing process:
- Forming or die-cutting
Of these categories, forming is a type of additive manufacturing and machining is a subtractive type. In this article, we will explore the differences between subtractive and additive manufacturing and consider the best methods for each approach.
What is Additive Manufacturing?
Additive manufacturing is the process of making a product by joining – or adding – materials together. The material is normally added in layers of powder, wire, sheets or liquid and is fused together by a method commonly known as 3D printing.
Advantages and Disadvantages of Additive Manufacturing:
- As the item is created from scratch to a precise model, there is no waste.
- Quick process from design to production.
- Excellent for producing items with more complicated designs.
- Not suitable for high-volume production.
- Limited selection of suitable materials.
- Comparatively expensive to use with metal.
What is Subtractive Manufacturing?
Subtractive manufacturing is a style of engineering that starts with a block of material. It might be metal, plastic, wood, stone or any solid mass. The process of creating the item involves removing – or subtracting – parts of the whole block to leave only what is required.
The methods used to remove the excess material can be mechanical or manual.
Manual Subtractive Manufacturing:
The manual subtraction of material to create a product can involve a range of tools, such as chisels, saws, routers and other specialist equipment. This equipment is used by hand to shape the desired item. For example, think about the work of a sculptor who chips away at a block of marble to reveal the artwork, or a luthier who carves the body of a guitar from a solid piece of wood.
Mechanical Subtractive Manufacturing:
Many materials require machines to form them into products. Equipment like saws, lathes and rotating wheels are used for shaping items; and innovative devices, such as lasers, can cut through metal with a high-energy light beam.
An advanced system of fully-mechanised manufacturing is computer numerical control (CNC) machining. This technique involves programming a computer which then automatically moves the tools that cut the material. The entire product can be produced in 3D from one set of instructions, so the process is highly efficient with a reduction in waste, time and human error.
CNC machines utilise various different cutting methods, including:
CNC mill - A mill uses a spinning tool to break material into smaller pieces using grinding, crushing or cutting. Traditional mills use movable tables on which the mass of raw material is mounted, while the cutting tool remains stationary. However, modern milling machines can include both parts as movable. A mill is one of the biggest CNC machines, but also one of the most versatile with its range of functions.
CNC router - Similar to a traditional router, the CNC version is used to cut wood, steel, plastic or foam. This machine can work in three dimensions and is ideal for smaller projects or complicated designs.
CNC lathe - A lathe is another stationary cutting tool used to shape a piece of material rotated around it in a process commonly known as 'turning'. CNC lathes are very precise in their operation and are generally smaller than other types.
CNC electrical discharge - As its name suggests, electric discharge machining (EDM) employs electrical charges or sparks to remove material to create specific shapes. This type of machine is typically used for very hard metals that might otherwise be difficult to work with.
CNC laser - Used mainly on metal, plastic or wood, CNC lasers utilise light to cut. The intensity of the beam can be adjusted for the type and relative strength of the material.
CNC plasma cutter - Similar to the laser, the plasma cutter also works in two dimensions to melt away material. This machine uses a torch to blow gas from a nozzle at high speed. An electric arc is added to the gas, creating plasma at temperatures of about 6,000-25,000 degrees Celsius. This extreme temperature makes this type of machine ideal for cutting heavy metals, such as steel.
Advantages and Disadvantages of Subtractive Manufacturing:
- Ideal for creating products with excellent strength and heat-conducting properties compared to formed items.
- Fine dimensional accuracy with possible tolerances as small as 0.025 mm.
- Suitable for manufacturing from a wide selection of raw materials.
- Quicker and cheaper for large production runs, as the price decreases inversely proportional to the number of items made.
- Requires more time and greater effort to set up the system, so less suitable for smaller production runs.
- Some material waste in the form of the material removed from the block during the creation process.
Choosing the Right Type of Manufacturing:
Use our handy guide to determine whether you should be using subtractive manufacturing.
Kerry Beeby, Director, Pro Moulds - https://www.pro-moulds.co.uk
Kerry had been a long-standing director at Pro Moulds after helping to start the company back in 1994. She’s been a driving force within the company, making sure that they push for innovation across their departments