Eight common faults and solutions in CNC machine tool machining

The metal cutting tool cuts off the excess metal on the workpiece through the NC machine tool, so as to form the workpiece. CNC machine tools, tool system and tool management are the basis of giving full play to the machining efficiency of CNC machine tools and ensuring machining quality. Therefore, the common faults and solutions in NC machining are directly related to the cutting tools. The following are some faults often encountered in the NC machining process, and there are many solutions. Therefore, if you don't have enough experience to directly find the problem entry point, you can also use the "elimination method" for comparison. These faults and detection methods have been processed and tested, which can be used as a reference for problems encountered at work.

1. The workpiece size is accurate and the surface finish is poor

Cause of failure

The tool tip is damaged and not sharp;

The machine tool resonates and is placed unsteadily;

The machine tool crawls;

Poor processing technology.

Solution:

If the tool is not sharp after being worn or damaged, regrind the tool or select a better tool to set the tool again; If the machine tool resonates or is not placed stably, adjust the level, lay the foundation and fix it stably; The reasons for mechanical crawling are that the carriage guide rail is severely worn and the lead screw ball is worn or loose. The machine tool should be maintained. After going to and from work, the iron wire should be cleaned and lubricating oil should be added in time to reduce friction; Select the coolant suitable for workpiece processing, and try to select a higher spindle speed when it can meet the processing requirements of other processes.

2. Large and small taper head of workpiece

Cause of failure
The placement level of the machine tool is not adjusted well, one high and one low, resulting in unstable placement;
When turning a long shaft, the contributing material is relatively hard and the cutting tool is deep, resulting in the phenomenon of tool yielding;
The ejector pin of tailstock is not concentric with the main shaft.

Solution:
Use the level gauge to adjust the levelness of the machine tool, lay a solid foundation, fix the machine tool and improve its toughness; Select a reasonable process and appropriate cutting feed to avoid the tool being forced to yield. Adjust the tailstock.

3. The phase light of the driver is normal, and the size of the machined workpiece is large and small

Cause of failure:
The machine tool carriage runs at high speed for a long time, resulting in the wear of screw rod and bearing;
The repeated positioning accuracy of the tool holder has deviation in long-term use;
The carriage can accurately return to the processing starting point every time, but the size of the processed workpiece still changes. This phenomenon is generally caused by the spindle. The high-speed rotation of the spindle causes serious bearing wear, resulting in the change of processing size.

Solution:
Use the dial indicator to lean against the bottom of the tool holder, edit a fixed cycle program through the system, check the repeated positioning accuracy of the carriage, adjust the screw clearance and replace the bearing; Check the repeated positioning accuracy of the tool rest with a dial indicator, adjust the machinery or replace the tool rest; Use a dial indicator to check whether the workpiece returns to the starting point of the program accurately after processing. If it is possible, overhaul the spindle and replace the bearing.