During NC machining, control signals are sent to the servo drive device through the digital operation of the CNC system, and the servo motor is driven to rotate, and then passed to the worktable through the mechanical feed device, so that the relative movement between the workpiece and the tool, and position detection at the same time The feedback device converts the actual relative movement between the workpiece and the tool into an electric signal and feeds it back to the CNC device. So what are the reasons for the instability of the CNC machining size?
1. The connection between the servo motor shaft and the screw is loose, causing the screw to be out of sync with the motor, causing a size error. When testing, just mark the coupling between the servo motor and the screw and move the table (or tool post) back and forth at a faster rate. Due to the inertia of the table (or turret), the coupling will make the coupling Significant relative movement of the two ends. This kind of failure usually manifests as the machining size only changes in one direction, and it can be eliminated only by tightening the coupling screws evenly.
2. Poor lubrication between the ball screw and the nut will increase the movement resistance of the table (or tool post), making it impossible to execute the movement instructions completely and accurately. This kind of failure usually manifests as irregular changes in the part size within a few wires, and the fault can be eliminated simply by improving the lubrication.
3. The movement resistance of the machine tool table (or tool post) is too large, which is generally caused by the tight adjustment of the inserts and poor lubrication of the surface of the guide rail of the machine tool. This failure phenomenon generally manifests as irregular changes in part size within a few wires. The inspection can be carried out by observing the size and change of the position deviation of DGN800-804. Usually, the difference is large when the forward and reverse directions are stationary. This type of failure is simply a matter of readjusting the inserts and improving rail lubrication.
4. The rolling bearings are worn or improperly adjusted, causing excessive movement resistance. This failure phenomenon also usually manifests as irregular changes in size within a few filaments. The inspection can be performed by the position deviation of DGN800-804, the method is the same as above. This kind of trouble only needs to replace the worn bearing and adjust it carefully, and the trouble can be eliminated.
The above is the content of CNC machining for you. If you want to know more, please call us for a consultation!
FAQ:
CNC machining size instability is mainly caused by mechanical connection looseness, poor lubrication, excessive movement resistance, or bearing wear, which affect the precision of the machine’s motion system.
If the coupling between the servo motor and screw becomes loose, the screw may not rotate in sync with the motor, leading to dimensional errors in the workpiece.
Mark the coupling and move the table or tool post rapidly. If the marks show relative movement, it means the coupling is loose and needs to be tightened evenly.
Poor lubrication increases friction and movement resistance, preventing accurate execution of movement commands. This results in irregular dimensional changes in the machined part.
Simply improving lubrication—by cleaning the mechanism and adding proper lubricating oil—can eliminate the issue and restore machining stability.
This usually occurs due to tight insert adjustment or poor rail lubrication. The solution is to readjust the inserts and improve guide rail lubrication.
You can check the position deviation values (DGN800–804) in the CNC system. Large deviations during forward and reverse motion indicate excessive resistance.
When rolling bearings are worn or improperly adjusted, they increase friction and cause random dimensional variations, typically within a few microns.
Replace worn bearings and carefully readjust the bearing clearance to ensure smooth and stable motion transmission.
Perform regular maintenance, ensure proper lubrication, tighten mechanical connections, and inspect motion components periodically to prevent size instability and ensure machining precision.
