Advantages of Plastic Machining
- Cost effective since molds are not necessary
- Plastic components can be manufactured with short lead times
- Low volume of plastic components can machined at low cost
- A trial design or sample can be made before committing to tooling
- Thicker wall sections can be easily accommodated
- Components that are too large to be molded can be machined from fabricated plastic
- Forced required in Plastic Machining are low
- Plastics normally machine dry
- Swarf can be recycled back into the compounding process
Important considerations in Plastic Machining
The soft nature of plastic
Due to the softer nature of plastic, the holding jigs and fixtures have to be designed with jaws in order to protect plastic while machining. The jigs should be robust in order to properly support plastic that is being cut. Cutting tools that are used on machining all types of materials typically rely on the rigidity of the material being cut. For example, cutting metal is relatively easier than plastic because of its rigidity. Metal resists any distortion when the cutting tool is applied.
In the case of plastics, machining tends to be better with more rigid materials such as fiber reinforced thermosetting plastic materials like glass reinforced nylons and acrylic with good relative stiffness. During Plastic Machining of soft and flexible plastic, deformation is difficult to avoid and the material tends to bend away from the cutter when attempts are made to cut the component. The achievement of fine dimensional tolerances can be significantly difficult.
Plastic Machining of thermoplastic materials
Thermoplastic materials when machined can be cooled with an air blast that will provide the resultant swarf with a continuous and not a chipping form. Liquid coolants can also be used to cool thermoplastic materials but care should to be taken with plastics that are prone to swelling in water to ensure that the machined dimensions do not change. Heat that is generated in the process may cause thermal expansion which should be factored in since the dimensions may be altered when cooling.
CNC Plastic Machining
When cutting complex shapes from the component, the profile can be programmed into a computer. CNC machining can be used to manufacture duplicate number of components. Multiple interchangeable cutters are typically used on CNC machines so that varied complex components can be machined. Different shapes can also be punched using metal type punching presses that are also computer controlled and are multi-tool equipped. However, this process is only limited to thinner thermoplastics and thermosheets.