The Properties of HDPE
HDPE (High-density Polyethylene) or PEHD polyethylene High-Density) is a tough, flexible plastic polymer with good electrical insulation, excellent chemical resistance, impact resistance, and a higher tensile strength. HDPE is an ideal choice when a finished product’s rigidity is crucial.
HDPE plastic material exhibits stronger intermolecular forces due to the minimal branching of its chemical makeup. Unlike low-density polyethylene plastic material, HDPE can withstand extreme temperatures without deformation. Although HDPE is not inherently self-lubricating as PTFE, it is non-toxic. Hence, it is compatible with food processing and packaging applications.
Although the molding process of HDPE plastic materials causes variation in its physical properties, here are common HDPE mechanical properties:
- Melting Temperature: 130°C (266°F)
- Tensile Strength: 2,900 PSI (20MPa)
- Elongation of HDPE (Break): 600% – 1350%
- Impact Strength: 69 J/m
- Elongation of HDPE (Yield): 9 – 18%
- Flexural Modulus: 970 -138 MPa
- Glass Transition Temperature: 130°C
- Hardness (Shore D): 62.3
- Heat Deflection: 185°F (85°C )
- Flammability Rating: 80.6
- Operating Temperature 120°C/248°F
The Most Common Processes of Machining HDPE
High-density polyethylene is compatible with various machining processes due to its favorable material properties. Here are common HDPE machining processes:
- CNC Milling
- CNC Routing
- CNC Drilling
- CNC Turning
Benefits of Precision Machined HDPE Parts
Due to the versatility of this high-density polyethylene, manufacturers across different industries use the engineering thermoplastic for different parts. Here are some of the expected benefits
- Lightweight: Machined HDPE parts can replace parts made with heavier materials without compromising their performance or longevity.
- Incredible Strength: Precision HDPE parts usually exhibit excellent impact resistance and can withstand harsh weather and working conditions.
- Food Safety and Recyclability: Precision-machined HDPE parts are made from food-grade materials. They align with sustainability goals since they reduce non-biodegradable waste and plastic production.
- Cost-Effectiveness: Precision-machined HDPE parts are more cost-effective than other plastics due to their low raw material cost and ease of machining.
- Non-Toxic: HDPE machined parts are non-toxic, making them well-suited for certain applications, such as food processing equipment and packaging.
Types of HDPE Plastic Materials
HDPE is a versatile plastic material available in different variants, each with unique properties for specific applications. Here are the commonly used HDPE types:
Standard HDPE
Standard HDPE is the basic HDPE form and the most widely used HDPE material in CNC machining. It is economical and offers an outstanding balance of strength and ductility. This HDPE plastic is best suited for general-purpose industrial and consumer goods applications since it can resist several chemicals and exhibits high impact strength. More importantly, Standard HDPE is easy to machine and weld.
HDPE with UV Stabilization
This HDPE type contains additives that protect it from UV light degradation. These additives make it suitable for outdoor applications where sunlight exposure is significant. For example, it is ideal for playground equipment, piping systems, and outdoor furniture. These products benefit from the enhanced durability and longevity provided by the UV-resistant additives.
Cross-linked HDPE (PEX)
PEX is an enhanced type of HDPE chemically linked polymer chains. It can retain its mechanical properties when exposed to thermal stress, making it durable in high-demand environments. Cross-linking HDPE helps improve its chemical, thermal, and crack resistance. Hence, PEX is widely used in applications that demand higher temperature ratings, such as underfloor heating systems and hot water pipes.
High-Molecular-Weight HDPE (HMW HDPE)
This type of HDPE possesses a higher molecular weight than standard HDPE, allowing it to exhibit outstanding impact strength and abrasion resistance. HMW HDPE is perfect for producing significant components requiring high durability, like automotive fuel tanks, marine structures, and industrial wear parts.
Ultra-High-Molecular-Weight HDPE (UHMWPE)
UHMWPE is a HDPE variant famous for its abrasion resistance and extreme toughness. It has a longer polymer chain that makes it a tough engineering plastic. Besides, it is much denser than standard HDPE and is widely used in high abrasion applications like lining chutes, ballistic plates, medical implants, conveyor belts, and gears.
HDPE with Fiber Reinforcement
Using fibers such as carbon or glass to reinforce HDPE plastic enhances its mechanical properties, such as strength and stiffness. HDPE with reinforcement is ideal for applications that require optimized structural integrity, including construction materials and automotive components.
Applications of Machined HDPE Parts
HDPE machined parts are often used for different purposes due to their safety, cost-effectiveness, recyclability, corrosion-resistant performance, and durability. Here are typical applications of machined HDPE parts:
- Home Appliances: Machined HDPE parts are found in home appliances due to their thermal stability and good electrical insulation properties. Electrical device housings, handles, and knobs are typical examples of machined HDPE parts.
- Food Containers: HDPE is an FDA-approved material with good chemical resistance. It is durable, easy to clean, bacteria-resistant, and low in weight. Machined HDPE food containers include jars, trays, bottles, and cups.
- Electrical: Since HDPE exhibits low dielectric constant and loss tangent, it is perfect for conduit protectors for communication or electrical cables and coax cable inner insulators.
- Automotive: HDPE’s low moisture absorption and corrosion resistance make it suitable for creating lightweight vehicle fuel tanks.
- Toys: HDPE material is suitable for making toys and playground equipment due to its low cost, non-toxicity, and moisture resistance.
- Construction: HDPE materials, especially HDPE pipe grade, are ideal for producing different types of pipes since they are highly resistant to corrosion and exhibit high tensile strength.
HDPE Machining: Tips and Tricks
HHDPE is a commonly used CNC machining material that can pose numerous setbacks if the processing parameters are inappropriate. We’ll explore helpful tips for successful HDPE machining in this section:
Choose the Appropriate Cutting Tools and Speed
Machining HDPE parts with the right tools and speed is essential to ensure the best results. Using clean tools with sharp edges helps make clean and precise cuts on the HDPE material. High-density polyethylene machining is best done with high processing speeds. Therefore, practice regular replacement or sharpening of damaged or worn-out tools.
Sub-Assemblies
Designing precision HDPE parts as separate components is recommended since HDPE materials are available in different sizes. Since HDPE doesn’t work well with adhesives, you can use mechanical fasteners to secure these components firmly in an assembly.
Clear Generated Chips Regularly
The chips produced while CNC machining HDPE material into desired shapes may clog the machine. Experts recommend using compressed air and vacuum systems to remove chips and prevent clogged machinery effectively. They also help ensure a precise, smooth surface finish and reduce debris.
Consider Annealing
The heat generated during the HDPE machining process can cause surface cracks and internal stress in the HDPE machined parts. This issue is primarily common when machined material is cold. However, annealing the material before routing and milling operations helps mitigate these complications.
Conclusion
CNC HDPE machining helps create precise and top-quality plastic components for applications requiring high strength and low weight. Despite the vast benefits of machining this engineering for different industries, understanding the HDPE machining process helps achieve the best results for your project. This article has discussed everything you need to know to elevate your HDPE machined parts!
AT-Machining is a leading plastic machining expert in China with the resources to transform your design idea into functional parts. Our professionals work with HDPE and other machining plastics according to customers’ preferences and specifications. Our skilled engineers leverage modern machining facilities and CNC machines to produce different machined HDPE parts with close tolerances. Submit your CAD file today; we offer instant quotes and reliable DfM feedback.
