CNC Knowledge: CNC lathe thread programming cutting, now you will understand it in seconds

There are four standard threads that can be turned on a CNC lathe: metric, inch, modulus and diameter. Regardless of which thread is turned, a strict movement relationship must be maintained between the lathe spindle and the tool: that is, a turn of. the spindle (i.e. the workpiece (one lathe), the tool should move uniformly over the distance of one step (from the workpiece). The following is an analysis of ordinary threads to improve our understanding of ordinary threads in order to better deal with ordinary threads.

1. Dimensional analysis of ordinary yarns

Processing ordinary threads on a CNC lathe requires a series of dimensions. The calculation and analysis of dimensions required for ordinary thread processing mainly includes the following two aspects:

1. Workpiece diameter before thread processing

Considering the expansion of the thread processing profile, the diameter of the workpiece before thread processing is D/D-0.1P, that is, the main diameter of the thread minus the pitch of 0, 1. Generally, it is 0.1 to 0.5 smaller than the main diameter. of the wire depending on the deformation capacity of the material.

2. Feed quantity of wire processing

The wire feed amount can refer to the bottom diameter of the wire, which is the final feed position of the wire cutter.

The small diameter of the thread is: the large diameter – 2 times the height of the thread = 0.54P (P is the pitch);

The feed amount for thread processing should be continuously reduced, and the specific feed amount is selected according to the tool and work material.

2. Installation and adjustment of ordinary threading tools

If the turning tool is installed too high or too low, when the tool reaches a certain depth, the flank surface of the turning tool will resist the workpiece, increasing friction and even bending the workpiece, causing chewing of the tool if it is too much; low, the tool Chips are not easily evacuated. The direction of the radial force of the turning tool is toward the center of the workpiece. In addition, the gap between the feed screw and the nut is too large, resulting in cutting depth. to continually and automatically deepen, thereby lifting the workpiece and causing the tool to chew. At this time, the height of the turning tool should be adjusted in time so that the tool tip is at the same height as the workpiece axis (the tip of the tailstock can be used to adjust the tool). During rough turning and semi-finishing turning, the tool tip position is approximately 1% D higher than the exit center of the workpiece (D represents the diameter of the workpiece being turned). machining).

The part is not firmly clamped. The rigidity of the workpiece itself cannot withstand the cutting force during turning, resulting in excessive deflection, which changes the center height of the turning tool and the workpiece (the workpiece is lifted) , causing a sudden increase in height. the cutting depth and causing the tool to chew, at this time the workpiece should be clamped tightly and the tip of the tailstock can be used to increase the rigidity of the workpiece.

Tool setting methods for ordinary threads include the trial cutting method and automatic tool setting with a tool adjuster. You can use the tool directly to test the tool, or you can use G50 to set the workpiece zero point and use the workpiece offset to set the. zero point of the part for tool adjustment. The requirements for tool setting in thread processing are not very high, especially there are no strict restrictions on the tool setting in the Z direction, which can be determined according to the requirements programming.

3. Programming ordinary threads

In current CNC lathes, there are generally three processing methods for threading: G32 direct cutting method, G92 direct cutting method and G76 oblique cutting method. Due to different cutting methods and different programming methods, processing errors are also caused. different. We must carefully analyze the operation and use and strive to process high-precision parts.

1. G32 single cutting method. Since both sides of the cutting edge work at the same time, the cutting force is large and cutting is difficult. Therefore, both cutting edges are easy to wear while cutting. When cutting threads with a larger pitch, due to the greater cutting depth, the blade wears out faster, which leads to an error in the pitch diameter of the thread. However, the tooth shape accuracy is higher, so it is generally used for small threads. pitch thread processing. Because the tool movement and cutting are all completed by programming, the processing program is long; Because the cutting edge is easy to wear, frequent measurements should be taken during processing.

2. G92 simple cutting method simplifies programming and improves efficiency compared to G32 control.

3. G76 oblique cutting method, due to single edge processing, the processing blade is easily damaged and worn, making the processed thread surface uneven and the tool tip angle changes, this which results in poor tooth shape accuracy. However, because it works with a single cutting edge, the tool load is low, chip evacuation is easy, and the cutting depth decreases. Therefore, this processing method is generally suitable for processing large pitch threads. Since this processing method can easily remove chips and has better cutting edge processing conditions, this processing method is more practical when the thread accuracy requirements are not high. When processing higher precision threads, two-tool machining can be used. First, use G76 processing method for rough turning, then use G32 processing method for fine turning. However, it should be noted that the starting point of the tool must be accurate, otherwise it will be easy to deform randomly and cause parts to be scrapped.

4. After the yarn processing is completed, you can judge the yarn quality by observing the yarn profile and take timely measurements. When the wire crest is not sharp, increasing the cutting amount of the knife will increase the wire diameter. The increase depends on the plasticity of the material. When the tooth crest has been sharpened, increasing the cutting amount of the knife will proportionally reduce the main diameter. According to this characteristic, the amount of wire cutting should be processed correctly. avoid disposal.

4. Ordinary wire detection

For general standard threads, threaded ring gauges or plug gauges are used to measure. When measuring external threads, if the “top end” ring gauge of the thread simply screws in, but the “stop end” ring gauge does not screw in, it means that the processed thread meets the requirements, otherwise he is not qualified. When measuring internal threads, use a thread stamp and measure in the same manner. In addition to measuring threaded ring gauge or plug gauge, other measuring tools can also be used for measurement. Use a thread micrometer to measure the diameter of the thread pitch. Use a caliper to measure the thickness of the trapezoidal thread pitch and the thickness of the worm screw. Tooth thickness of the pitch diameter. Use a measuring needle according to the three needles. The measurement method measures the pitch diameter of the thread.