How to Design Living Hinges for CNC Machined Parts
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How to Design Living Hinges for CNC Machined Parts
Living hinges are thin, flexible sections of material that connect two rigid segments, allowing them to bend repeatedly without breaking. While commonly associated with injection molding, they can also be successfully machined, offering unique design opportunities for CNCproduced parts. For a company specializing in onestop CNC machining services, mastering living hinge design is a significant valueadd, enabling the creation of sophisticated, integrated assemblies from a single piece of material.
cnc machining center Material Selection is Paramount
The success of a CNCmachined living hinge is critically dependent on material choice. Not all materials possess the necessary fatigue resistance. The ideal candidates are tough, semicrystalline plastics with high elongation at break.
Polypropylene (PP) and Polyethylene (PE): These are the gold standards for living hinges, offering exceptional fatigue life and flexibility.
Nylon (PA): A strong alternative, though it can be stiffer and may require careful design to prevent cracking.
Acetal (POM): Can be used but has a more limited flex life compared to PP or PE.
cnc machining online
Materials to avoid are brittle plastics like standard Acrylic (PMMA) or Polystyrene (PS), as they will crack upon the first bend.
Key Design Principles for Machined Hinges
Unlike molded hinges, which can have ultrathin sections, CNC machining has practical limitations. The design must account for the tool's ability to cut the hinge accurately.
1. Hinge Thickness: This is the most critical dimension. For CNC machining, a typical hinge thickness ranges from 0.5mm to 1.0mm (0.020" to 0.040"). This is thin enough to be flexible but thick enough to be machined reliably without tool breakage or excessive deflection.
2. Hinge Length: The hinge should run the full length of the part that needs to bend. A longer hinge distributes the bending stress more effectively.
3. Generous Radii: All transitions from the hinge to the rigid panels must incorporate generous fillet radii. Sharp corners act as stress concentrators and are the primary point of failure. A radius equal to or greater than the hinge thickness is a good starting point.
4. Machining Considerations: The hinge is best machined from both sides (using a ballnose end mill) to create a consistent, symmetrical thin section. This also helps eliminate stress concentrations from tool marks. The tool path should be parallel to the hinge's bending axis for a smooth, uniform flexing region.
Benefits for Your Product Development
Integrating a living hinge into a CNC machined part consolidates multiple components into one, eliminating the need for separate hinges, pins, and assembly labor. This simplifies the Bill of Materials (BOM), reduces overall cost, and creates a more reliable, monolithic product. It is an ideal solution for prototypes, lowvolume production, and specialized enclosures, lids, or containers.
By leveraging expert design for manufacturability (DFM) and selecting the appropriate materials, your business can deliver innovative, highvalue parts that solve complex design challenges. Partnering with a skilled CNC service provider ensures your living hinge designs are not only functional but also optimized for performance and longevity.
Living hinges are thin, flexible sections of material that connect two rigid segments, allowing them to bend repeatedly without breaking. While commonly associated with injection molding, they can also be successfully machined, offering unique design opportunities for CNCproduced parts. For a company specializing in onestop CNC machining services, mastering living hinge design is a significant valueadd, enabling the creation of sophisticated, integrated assemblies from a single piece of material.
cnc machining center Material Selection is Paramount
The success of a CNCmachined living hinge is critically dependent on material choice. Not all materials possess the necessary fatigue resistance. The ideal candidates are tough, semicrystalline plastics with high elongation at break.
Polypropylene (PP) and Polyethylene (PE): These are the gold standards for living hinges, offering exceptional fatigue life and flexibility.
Nylon (PA): A strong alternative, though it can be stiffer and may require careful design to prevent cracking.
Acetal (POM): Can be used but has a more limited flex life compared to PP or PE.
cnc machining online
Materials to avoid are brittle plastics like standard Acrylic (PMMA) or Polystyrene (PS), as they will crack upon the first bend.
Key Design Principles for Machined Hinges
Unlike molded hinges, which can have ultrathin sections, CNC machining has practical limitations. The design must account for the tool's ability to cut the hinge accurately.
1. Hinge Thickness: This is the most critical dimension. For CNC machining, a typical hinge thickness ranges from 0.5mm to 1.0mm (0.020" to 0.040"). This is thin enough to be flexible but thick enough to be machined reliably without tool breakage or excessive deflection.
2. Hinge Length: The hinge should run the full length of the part that needs to bend. A longer hinge distributes the bending stress more effectively.
3. Generous Radii: All transitions from the hinge to the rigid panels must incorporate generous fillet radii. Sharp corners act as stress concentrators and are the primary point of failure. A radius equal to or greater than the hinge thickness is a good starting point.
4. Machining Considerations: The hinge is best machined from both sides (using a ballnose end mill) to create a consistent, symmetrical thin section. This also helps eliminate stress concentrations from tool marks. The tool path should be parallel to the hinge's bending axis for a smooth, uniform flexing region.
Benefits for Your Product Development
Integrating a living hinge into a CNC machined part consolidates multiple components into one, eliminating the need for separate hinges, pins, and assembly labor. This simplifies the Bill of Materials (BOM), reduces overall cost, and creates a more reliable, monolithic product. It is an ideal solution for prototypes, lowvolume production, and specialized enclosures, lids, or containers.
By leveraging expert design for manufacturability (DFM) and selecting the appropriate materials, your business can deliver innovative, highvalue parts that solve complex design challenges. Partnering with a skilled CNC service provider ensures your living hinge designs are not only functional but also optimized for performance and longevity.