Small high speed CNC vertical lathe is mainly used to process shaft, disc sleeve and other rotary parts. It can automatically complete the cutting of internal and external cylindrical surfaces, conical surfaces, circular arcs, threads and other processes through program control, and perform grooving, drilling, expanding, reaming and other work. More processing procedures can be completed in one clamping process, which improves the processing quality and production efficiency. Therefore, it is suitable for the processing of complex shaped rotary parts.
The screw pitch (lead) value of the command in the thread processing program section is equivalent to the feed speed F expressed in the feed rate (mm/r). If the spindle speed of the machine tool is selected too high, the converted feed speed (mm/min) must be much higher than the normal value.
The thread turning is realized through the synchronous operation function of the spindle, that is, the thread turning requires a spindle pulse generator (encoder). When the spindle speed is too high, the positioning pulse sent by the encoder (that is, a reference pulse signal sent by the spindle every revolution) may cause the thread of the workpiece to be disorderly buckled due to “overshoot” (especially when the quality of the encoder is unstable).
When small high-speed CNC vertical lathe is used to process threads, the spindle speed shall be determined according to the following principles:
1. Under the condition of ensuring production efficiency and normal cutting, lower spindle speed should be selected;
2. When the import length in the thread processing program segment δ 1 and cut out length δ 2. Consider that it is sufficient, that is, when the feed distance of the thread exceeds the length of the thread specified in the drawing by a large amount, the spindle speed can be appropriately higher;
3. When the allowable working speed specified by the encoder exceeds the large speed of the spindle specified by the machine tool, the spindle speed can be selected as high as possible;
4. In general, the spindle speed (n screw) during thread turning shall be determined according to the calculation formula specified in the machine tool or NC system manual. The calculation formula is mostly:
N screw ≤ n allowable/L (r/min), where n allowable – allowable working speed of encoder (r/min);
L – thread pitch of workpiece thread (or lead, mm).