CNC（Computer Numerical Control）plastics machining is a technique that involves cutting, drilling and milling plastic materials using CNC machines. What follows is a CNC plastics machining guide designed to help understand the entire process from material selection to machining completion.
Why Choose CNC Plastics?
High Precision:
- CNC machining achieves very high precision, which is crucial for parts requiring tight tolerances. With precise programming and control, each part can be made consistently accurate.
High Efficiency:
- Compared to traditional manual methods, CNC machining is faster and more efficient. Once programmed, machines can run continuously, producing large quantities of parts.
Good Repeatability:
- CNC machining can repeatedly produce identical parts, ensuring consistent quality and specifications across all pieces. This is useful for applications requiring large volumes of standardized parts.
High Material Utilization:
- By optimizing the cutting path, material waste can be reduced, improving material utilization and lowering production costs.
High Flexibility:
- CNC machining can easily adapt to design changes by simply modifying the program. This allows for quick switching between different types of parts on the production line.
Good Surface Finish:
- Using appropriate cutting tools and parameters can achieve good surface finish, reducing the need for post-processing.
High Level of Automation:
- The high degree of automation in CNC machining reduces the need for human intervention and minimizes the risk of human error.
Pros and Cons of Common CNC Plastics
1. ABS (Acrylonitrile Butadiene Styrene)
- Pros:
- Good impact resistance.
- Easy to process and suitable for secondary operations like bonding and painting.
- Moderate strength and toughness, ideal for models and prototypes.
- Cons:
- Not resistant to solvents, susceptible to some chemicals.
- Decreased strength at high temperatures.
2. PC (Polycarbonate)
- Pros:
- High transparency similar to glass.
- Good impact resistance.
- Higher heat resistance.
- Cons:
- Tends to develop stress cracks during machining.
- Sensitive to UV light, can become brittle over time.
3. PVC (Polyvinyl Chloride)
- Pros:
- Economical and suitable for mass production.
- Corrosion-resistant, ideal for outdoor use.
- Can be modified with plasticizers to change hardness.
- Cons:
- Narrow processing temperature range, requires careful control.
- Not environmentally friendly; burning releases harmful gases.
4. PE (Polyethylene)
- Pros:
- Lightweight and easy to handle.
- Good chemical stability and impact resistance.
- Wear-resistant, suitable for containers and pipes.
- Cons:
- Low hardness, not suitable for precision parts.
- Low melting point, not heat-resistant.
5. PP (Polypropylene)
- Pros:
- Good chemical stability, resistant to acids and bases.
- Excellent fatigue resistance, suitable for parts that need repeated use.
- Non-toxic, can be used for food packaging.
- Cons:
- Brittle at low temperatures.
- Low surface hardness, prone to scratching.
6. POM (Polyoxymethylene)
- Pros:
- Excellent mechanical strength and stiffness.
- Good dimensional stability.
- Suitable for making gears and other parts requiring high precision.
- Cons:
- Tends to degrade at high temperatures.
- Sensitive to UV light, requires protection.
7. PMMA (Polymethyl Methacrylate, Acrylic Glass)
- Pros:
- High transparency similar to glass.
- Good weather and aging resistance.
- Easy to dye and polish.
- Cons:
- Brittle, prone to cracking.
- Poor impact resistance.
8. Nylon
- Pros:
- Good wear resistance and self-lubricating properties.
- Excellent toughness, suitable for making gears and bearings.
- Lightweight, low water absorption.
- Cons:
- Strong hygroscopicity, can affect dimensional stability.
- Decreased strength at high temperatures.
Design and Preparation
CAD Design:
- Use CAD software to design the three-dimensional model of the part, ensuring it meets the machining requirements.
CAM Programming:
- Convert the 3D model into CNC-readable instructions (G-code), optimize the cutting path to minimize material waste.
Material Preparation:
- Prepare the appropriate plastic sheets or rods based on the design requirements.
Pre-Machining Preparation
Machine Calibration:
- Ensure the CNC machine is calibrated for accuracy and stability.
Tool Selection:
- Choose the appropriate cutting tools, such as end mills or drills, based on the machining requirements.
Clamping Device:
- Properly secure the workpiece to prevent movement during machining.
Machining Steps
Positioning:
- Secure the plastic material on the worktable.
Start the Program:
- Input the programmed G-code and start the CNC machine.
Monitor the Process:
- Monitor the machining progress to ensure no abnormal situations occur.
Mid-Process Inspection:
- Perform mid-process inspections to verify the quality of the machining.
Post-Processing
Deburring:
- Use sandpaper or a file to remove burrs left from the machining process.
Surface Finishing:
- Perform polishing, painting, plating, or other treatments as needed.
Assembly Check:
- Ensure the parts meet the design requirements and conduct necessary assembly tests.
Considerations
Safety First:
- During machining, observe safety precautions and wear appropriate personal protective equipment.
Temperature Control:
- Control the temperature during machining to avoid deformation due to overheating.
Waste Management:
- Properly dispose of waste generated during the machining process, adhering to environmental principles.