In our factory specializing in precision machining with Swiss-type lathes, CNC milling of extremely small parts is a highly challenging process. These parts are widely used in fields such as minimally invasive medical devices and micro-electronic components. Due to their tiny size (typically less than 1mm) and intricate structures, they are extremely prone to deformation or breakage during machining, requiring special processes and equipment. Below are the key points for achieving high-precision milling of micro-parts.
I. Special Selection of Equipment and Tools
Machining extremely small parts demands ultra-precise machine tools. Prioritize ultra-precision 5-axis CNC milling machines equipped with nanometer-scale optical encoders, capable of achieving positioning accuracy of ±0.1μm and repeatability of ±0.05μm to meet the demands of high-precision complex surface machining. The machine must also feature high rigidity and low vibration, often enhanced by air-isolation bases to reduce environmental interference.
For tools, micro-mills with diameters ranging from 0.05 to 0.5mm are essential, primarily made from single-crystal diamond or ultra-fine-grain carbide. For example, a 0.1mm single-crystal diamond ball-nose mill can achieve a mirror finish of Ra 0.05μm when machining micro stainless steel gears. The tool edge radius must be controlled below 0.5μm to minimize cutting resistance.
II. Precision Clamping and Positioning Techniques
Clamping of micro-parts must avoid mechanical damage and deformation. Common methods include vacuum chucks and micro-gripping systems:
Vacuum Chucking: Generates negative pressure through micron-scale air holes to hold parts, suitable for regular planar components like micro-sensor substrates.
Micro-Gripping Systems: Utilizes piezoelectric ceramic-driven tweezers or probes for sub-micron positioning, ideal for irregularly shaped parts. Before clamping, inspect the part surface under a microscope to ensure no debris interferes with positioning accuracy.
III. Extreme Optimization of Process Parameters
To minimize cutting heat and vibration, process parameters must be strictly controlled:
Spindle Speed: Operates at 100,000–200,000 r/min to rapidly remove material and reduce heat accumulation.
Feed Rate: Maintained at 50–200 mm/min to avoid excessive friction between the tool and part.
Cutting Depth: Limited to no more than 5μm per pass, using layered milling to gradually approach the final dimensions. Cryogenic Minimum Quantity Lubrication (MQL) is employed, spraying a mixture of -20°C liquid nitrogen and minimal lubricating oil onto the cutting zone to cool the tool and reduce friction.
IV. Real-Time Machining Monitoring
During machining, microscopic vision systems and force sensors are used for real-time monitoring:
Microscopic Vision: A 1000× magnification microscope continuously observes tool wear and part status. If tool edge chipping is detected, machining stops immediately for tool replacement.
Force Sensors: Monitor cutting force fluctuations. If the force exceeds the threshold by 10%, the feed rate is automatically adjusted to prevent part damage.
V. Case Study: Machining a Micro Medical Device Part
Take a 0.8mm-diameter medical micro-catheter connector as an example:
Equipment: Ultra-precision 5-axis milling machine with a 0.2mm carbide end mill.
Clamping: Vacuum chuck fixes the raw material with ±0.5μm positioning accuracy.
Machining: Spindle speed at 150,000 r/min, feed rate 120 mm/min, 10-layer milling with 3μm depth per layer.
Inspection: Atomic Force Microscopy (AFM) measures surface roughness to ensure Ra 0.1μm.
Using these techniques, our factory has successfully controlled the machining accuracy of micro-parts within ±1μm, with a yield rate exceeding 98%. For custom micro-precision machining needs, feel free to contact us for tailored solutions.