Tool selection and cutting amount determination in CNC machining (3)

November 01, 2022

2. Determining the feed rate The feed rate is an important parameter in the cutting amount of CNC machine tools. It is mainly selected according to the machining accuracy and surface roughness requirements of the parts and the material properties of the tools and workpieces. The maximum feed rate is limited by the machine stiffness and the performance of the feed system. The principle of determining the feed rate: When the quality requirements of the workpiece can be guaranteed, in order to increase the production efficiency, a higher feed rate can be selected. Generally, it is selected in the range of 100-200mm/min; when cutting or processing deep holes or machining with high-speed steel tools, it is better to choose a lower feed speed, generally in the range of 20-50mm/min; when processing precision, surface When the roughness requirement is high, the feed speed should be selected to be smaller, generally in the range of 20--50mm/min; when the tool is in the idle stroke, especially when the distance is “return to zero”, the CNC system setting of the machine can be set. The highest feed rate.

3. Determine the amount of back-feeding knife. The amount of back-feeding knife is determined according to the rigidity of the machine tool, workpiece and tool. Under the condition of stiffness, the amount of back-feeding should be equal to the machining allowance of the workpiece, which can reduce the number of passes. ,Increase productivity. In order to ensure the quality of the machined surface, a small amount of finishing allowance can be left, generally 0.2 to 0.5 mm. In short, the specific value of the cutting amount should be determined by analogy according to the machine tool performance, relevant manuals and practical experience.

At the same time, the spindle speed, depth of cut and feed rate can be adapted to each other to form the optimum cutting amount.

The cutting amount is not only an important parameter that must be determined before the machine tool is adjusted, but also whether the value is reasonable or not has a very important influence on the processing quality, processing efficiency, production cost and the like. The so-called "reasonable" cutting amount refers to the cutting amount that utilizes the cutting performance of the tool and the dynamic performance of the machine tool (power, torque) to obtain high productivity and low processing cost while ensuring the quality.

references:

1. Taiyuan Metal Cutting Tool Association. Metal Cutting Practical Tool Technology. Beijing: Mechanical Industry Press. 2002

2, machine tool processing skills training. China Labor Press. May 1996, 3, gorgeous Juan, Xu Wei. Teaching reform of CNC machining technology exploration

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