Knowledge Hub
22/01/2024
Exploring the Art of Plastic Machining
What is Plastic Machining?
Plastic machining is a subtractive manufacturing process which involves the use of machines to remove material from a plastic object to create a component or product.
The process involves the use of lathes, mills, and other types of cutting machines to fabricate end parts.
This plastic machining process is used to create functional prototypes and low-medium volume production parts.
It is ideal during the manufacturing phase of new product development, where physical concepts need to be tested prior to full scale production.
Plastic CNC machining is a complex and highly precise process, which requires the expertise of skilled CNC programmers. These operators use computer aided design (CAD) and computer aided manufacturing (CAM) to create 3D products from raw plastic materials.
5-axis CNC machining can be employed to create high performance precision machining of engineering plastics.
After the initial run has been completed, the CNC machine can be reprogrammed using the same coordinates and numerical data. This means that CNC machining is perfect for producing highly customisable parts which are extremely accurate and very repeatable.
This allows for consistency of parts in quality, form, and dimensions.
Types of Plastic Most Commonly Used for Plastic Machining
It is important to recognise that not all types of plastic are suited to plastic machining. Different plastic types contain different properties. These varying properties determine the strength, chemical resistance, structure, and cost of a particular plastic.
When choosing a particular grade of material for plastic machining it is important to seek expert advice to ensure that the correct plastic type is selected. Care should be taken to ensure that the chosen plastic will machine correctly without incurring any unnecessary damage, warpage, overheating or shearing.
This is where the advice of a plastics expert should be sought to identify which type of plastic will be most appropriate. It is important when selecting a material that the product’s end application is carefully considered.
Some of the most commonly used plastics in CNC machining are listed below:
- ABS
- PC
- PVC
- HDPE
- UHMW
- PPS
- PEEK
- Acrylic
- PA/Nylon
- PP
- Acetal
Plastics which are tough and high in rigidity tend to be more suited to the machining process. The plastics listed above have good durability and toughness, which means that they can easily withstand the scrutiny of the cutting tool. Less tough plastics show visible signs of deformity and can easily become distorted during the process.
Other important properties to consider when choosing a suitable plastic include:
- Strength-to-weight ratio
- Performance under high temperature
- Chemical resistance
- Wear resistance
- Conductivity
- Insulation properties
- Material density
Advantages of CNC Plastic Machining
No mould is needed – parts can be created without needing to invest in tooling and the injection moulding process. This can be more cost-effective and can reduce lead times.
Ideal for low volumes – low volumes of highly repeatable, customised parts can be produced in economical production cycles.
Perfect for prototyping – CNC plastic machining of parts can be used to market test a design concept before committing to full scale tooling and injection moulding.
Large components can be accommodated – components that are too large for injection moulding can be machined from fabricated plastic.
Environmentally friendly – excess plastic in the form of swarf can be captured, compounded, and recycled.
Precision – CNC plastic machined parts offer a high level of precision compared to other methods, such as 3D printing, where 3D printer layer lines are sometime visible on the part.
Design flexibility – it’s easy to adapt the design of the part during the production process, whereas tooling modifications for injection moulded parts can be costly and time consuming.
Less Manual Labour Required – a team of toolmakers are required to make a tool. With CNC plastic machining, only one skilled operator is required to complete the process.
Quick Turnaround Times – Computer controlled CNC machines can be programmed to run during out of factory hours without the need for constant supervision. This can help to reduce cycle times and is less labour intensive.
Finishing Options – a wide range of finishing options are available, including polishing and coating.
Exploring CNC Plastic Machining as an Alternative to 3D Printing
The key difference between CNC machining and 3D printing is that CNC machining is a subtractive manufacturing process, whereas 3D printing is an additive manufacturing process.
As discussed earlier, CNC machining involves removing material from a workpiece to create a finished part. 3D printing, on the other hand, is where a component is created layer-by-layer using a source of energy such as a laser.
3D printing is one of the more commonly used forms of additive manufacturing, but a lot of people don’t often consider the many benefits that CNC plastic machining has over 3D printing. Here are just a few to consider….
- CNC plastic machined parts have better mechanical and thermal properties than 3D printed parts, which makes them stronger and more robust.
- CNC plastic machining lends itself to a greater choice of plastic types than 3D printing.
- 3D printed materials can be more expensive, which means that bigger components or larger quantities cost more.
- Plastic CNC machining provides greater dimensional accuracy than 3D printing.
- 3D printing can leave marks on the plastic, which can be detrimental to parts that require a high quality finish.
- For medium volume requirements, CNC machining is more economical, as the cost reduces significantly with increased quantity.
- CNC plastic machining is the more viable option for components that require tight tolerances.
- CNC plastic machining can achieve a greater level of detail than 3D printing.
CNC Plastic Machining Applications
CNC plastic machining lends itself to many products across a range of different industries.
Here are a few examples of those industries and some of the products that have been created:
Medical – in an industry where tight tolerances are often required, CNC machining has created many important products, including biomedical and pharmaceutical equipment, medical devices, and surgical instruments.
Electronics – CNC machining has been regularly employed to manufacture housing units, semiconductors, and plastic enclosures.
Consumer Products – CNC machining has been used to fabricate toys, kitchen appliances, and general household goods.
Automotive – interior vehicle components, including dashboard panels and fixtures, and exterior parts, such as headlight covers.
Scientific – such as laboratory and scientific apparatus, as well as chemical handling equipment.
