In the process of milling, the reasonable selection of feed rate is an important factor to ensure processing efficiency, processing quality, and tool life. The feed rate not only affects the formation of chips but also directly influences key parameters such as cutting force, cutting heat, and surface roughness. Therefore, scientifically determining the feed rate of milling processing is of great significance for improving processing performance.



1. Definition and Classification of Feed Rate



During the milling process, the feed rate is usually expressed in the following ways:



1. Feed per tooth (fz): The feed distance moved by each tooth of the milling cutter per revolution, with the unit of mm/z.



2. Feed per revolution (fn): The displacement of the workpiece relative to the milling cutter per revolution of the cutter, which is equal to the feed per tooth multiplied by the number of teeth, i.e., fn = fz × Z.

　　3. Feed speed (vf): The linear displacement of the workpiece relative to the milling cutter per unit time, usually in mm/min, with the calculation formula of vf = fz × Z × n.



Among them, n is the spindle speed (r/min), and Z is the number of cutting teeth.



2. Factors affecting the selection of feed rate

　　1. Material characteristics: The hardness, strength, and toughness of the material to be processed have a direct impact on the selection of the feed rate. For example, when processing high-strength alloy steel, a smaller feed rate should be selected to avoid rapid tool wear.



2. Tool material and geometric parameters: Hard alloy tools have higher wear resistance than high-speed steel tools, allowing for the appropriate increase of feed rates; at the same time, the geometric parameters such as the front angle and rear angle of the tool will also affect the cutting performance.



3. Processing type: In rough processing, the main goal is to remove excess material, and larger feed rates can be selected; while in finishing processing, the goal is to ensure surface quality, and the feed rate should be appropriately reduced.

　　4. Machine tool performance and rigidity: The power, rigidity, and stability of the feed system of the machine tool determine whether it can withstand larger feed rates.



5. Cooling and lubrication conditions: Good cooling and lubrication can reduce cutting heat and friction, allowing for the use of larger feed rates.



3. Methods for determining the feed rate



1. Experience method: Set the feed rate based on the operator's experience and data from similar processing conditions in the past. This method is simple and quick, but has poor accuracy and consistency.



2. Lookup method: Refer to the cutting parameter table provided by the tool manufacturer, and find the recommended feed rate based on conditions such as material type, tool material, and milling type. This is one of the most commonly used methods in industry.



3. Formula calculation method: Estimate through cutting theory formulas and correct them based on actual processing conditions. For example:



$$



f_z = \frac{v_f}{n \times Z}



$$



5. Automatic setting of CNC system: Modern CNC machine tools can automatically calculate recommended feed rates based on input material and tool information, improving the degree of automation of processing.

　　4. Matters needing attention



In actual processing, it is recommended to first adopt a conservative feed rate for trial cutting, observe the cutting state, surface quality, and machine tool load before making adjustments. At the same time, it should be avoided that the feed rate is too large, causing tool chipping or broken teeth, or too small to affect processing efficiency.



Conclusion



In summary, reasonably determining the feed rate in milling processing is a comprehensive consideration of materials, tools, equipment, and processing requirements. Only by fully understanding the influence of each factor and combining theoretical and practical experience for reasonable selection can an efficient, stable, and high-quality processing effect be achieved. With the development of CNC technology and intelligent processing, the selection of feed rates in the future will be more intelligent and precise.