Common Challenges of Plastic Machining
For many industries such as aerospace, automotive and medical industries, plastic machining plays a vital role in providing machined plastic components with precision. However, machining plastics presents challenges compared to metals. Mostly due to heat sensitivity, flexibility, and chipping. Understanding these challenges is crucial for ensuring high-quality finished products with minimal defects.
In this blog, we explore some of the most common challenges of plastic machining and how to address them.
Material Warping & Thermal Expansion
Material warping caused by heat is one of the biggest challenges. Plastics have a low melting point and tend to expand when exposed to heat. This can lead to dimensional instability, making it difficult to maintain precise specifications. To mitigate this, we make sure our machinists use sharp cutting tools, optimise feed rates, and use coolant or air blasts to reduce heat build-up during the machining process. Checking to make sure the material is clamped, and set-up properly as improper clamping can cause additional stress on the material during machining and result in warping.
Achieving Tight Tolerances
When under stress, plastics can often warp and deform, making it challenging to achieve tight tolerances. Any variations in temperature and material flexibility, no matter how small, can lead to slight changes in the final product’s dimensions, which can have a major impact on the final product’s functionality. To improve accuracy, it’s important to use appropriate material holding techniques, minimise heat generation, and account for material-specific shrinkage or expansion rates when machining.
Tool Wear & Selection
When machining plastics it’s important to select the right tool for the task. Using the wrong tools can cause excessive heat build-up, rough surface finishes, and increased tool wear which will cost more in the long run. Carbide or diamond-coated tools are often recommended due to their durability and ability to maintain sharp cutting edges. Additionally, making sure to choose the right cutting speeds and feeds can help extend tool life and improve machining efficiency. All skills our experienced machinist have learnt over the years.
Chip Control & Swarf Management
Unlike metals, when plastic is machined, the plastic chips do not break apart easily, leading to long, stringy swarf. This can become challenging by clogging cutting tools and interfering with the material surface quality. If these chips and swarf are not dealt with in the right way this can result in re-cutting of the chips, causing defects and inefficiencies in the product. To overcome this challenge, we try to use specialised cutting geometries, vacuum extraction systems, or compressed air to remove swarf effectively during machining.
Surface Finish & Post-Processing
When it comes to finishing some plastics are prone to micro-scratches or rough textures due to their softness. Using high-speed polishing, buffing, or flame polishing can enhance surface smoothness. It’s also important to select the right cutting parameters and minimise vibrations during machining as this often helps produce better surface finishes.
Fixturing & Holding Challenges
Due to their flexibility and lower rigidity, plastics can shift or deform under clamping pressure, affecting machining accuracy. To counteract this, we use vacuum fixtures, specialised soft jaws, or occasionally adhesive techniques to securely hold parts in place without introducing unwanted stress that could distort the material and impact the final product.
Material-Specific Considerations
Different types of plastics have different characteristics, meaning they require different approaches. For example:
- Acrylics can crack if machined too aggressively, necessitating slow feeds and sharp tools.
- Nylon absorbs moisture, which can alter its dimensions over time.
- Polycarbonate is highly impact-resistant but can be prone to stress-induced cracking.
Machining plastics presents distinct challenges that require careful consideration of material properties, tooling selection, and machining parameters. By addressing with the right techniques and equipment, plastic machining can yield durable and highly accurate components made from a number of different plastic materials, each with their own characteristics and suited for a variety of applications.
If you need expert plastic machining solutions, including CNC routing, CNC milling, and CNC turning, contact our team today to discuss your project and for a quote. Our team is ready to provide high-quality precision machining tailored to your project’s requirements.