Internal Support Fixtures vs. External Clamping Fixtures in CNC Machining

DALIAN, China - May 25, 2025 - PRLog -- Principle of Operation and Structure

Internal Support Fixtures:

These fixtures primarily clamp the inner surface of the workpiece through an internal supporting structure. They are commonly used for processing parts such as shafts, pipes, or components with internal holes. For example, hydraulic internal hole universal fixtures use quick-change bases and internal hole expanding sleeves to accommodate workpieces of different sizes, ensuring stability with the base reference surface and providing a part ejection function. CNC internal support fixtures work by driving components like cylinders to move downward and secure the workpiece. Multiple workpieces can be clamped simultaneously on the same fixture. CNC slide-rail-based internal support fixtures consist of an installation base, a drive unit (such as pneumatic or electric cylinders), and internal support tooling. The drive unit controls the pin's rise and fall to adjust the clamping force on the workpiece.

External Clamping Fixtures:

These fixtures fix the workpiece by clamping its outer surface. They are widely used in operations such as milling, drilling, and grinding. For example, a hydraulic universal fixture for clamping outer diameters utilizes a quick-change locking nozzle design that allows for replacement in 10 seconds. It is equipped with a dust cover and an end-face positioning system, with a maximum clamping force of up to 40KN.

Applicable Scenarios

Internal Support Fixtures:

These are suitable for processing parts with internal hole structures that need to be fixed from the inside, ensuring the precision of internal hole machining. Examples include internal milling of pipe fittings and internal hole machining of shaft components.

External Clamping Fixtures:

These are suitable for a wide range of parts, whether regular or irregular in shape, as long as they can be securely clamped from the outside. They are commonly used for milling flat parts, drilling irregularly shaped components, and other similar tasks. External clamping fixtures are widely used in various machining processes, such as milling, drilling, grinding, etc.

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