1 Preface
FANUC system is one of the commonly used control systems for CNC machine tools. Its control instructions are divided into single-cycle instructions and multi-cycle instructions.
2 Programming Ideas
The essence of the program is to discover the characteristics of the tool path and implement repeated instructions in the program via mathematical algorithms. According to the above part characteristics, we find that the value of the X coordinate gradually decreases. You can therefore use the FANUC system to modify the declaration accordingly. After the roughing cycle is completed, the part is determined to determine the amount of finishing, the tool compensation settings are changed, and then the jump is completed to complete the turning.
3 Choose the starting point of the cycle carefully
At the end of the cycle program, the tool automatically returns to the starting position of the cycle program execution at the end of the cycle. Therefore, it is necessary to ensure that the tool returns safely to the starting point at the end of the cycle. When programming cycle instructions, it is easy to use and carries major safety risks. Of course, security cannot be guaranteed. is placed too far from the workpiece, resulting in multiple and empty tool paths that affect processing efficiency. Whether it is safe to return to the start of the cycle, to the starting position of the cycle program, to the tool position at the end of the last line of the finishing process, to the shape of the part at the end cycle, tool holder shape and other tool mounting locations. In both cases, it is ultimately possible to ensure that the loop does not interfere with rapid retraction by changing the starting position of the loop program. You can use mathematical calculation methods, the query base point coordinate method of CAD software to determine the reasonable and safe starting position of the cycle, or during the debugging stage of the program, use one-stop operation. step and feed at low magnification, try cutting and modifying the program. starting point coordinates step by step Determine a reasonably safe starting location. After considering the above factors, it is necessary to determine the starting point of the cycle. Particular attention should also be paid: if the measuring and debugging program is added to machining and cutting before processing, for example on the machine tool. works up to the Nth line, the spindle stops and the program is paused after measurement, it retracts to the appropriate position, and then manually or manually enters the work. Position yourself near the workpiece, automatically execute the finishing cycle command, then the cycle program starting point is the point. Selecting an incorrect position may cause interference. It is best to add the command before the finishing cycle and before the program line. enter quickly. A reasonable starting position for the cycle program to ensure safety.
4 Reasonable combination of loop instructions
Usually, the G70 finishing command is used in combination with the G71, G73 and G74 roughing commands to complete the rough machining of the part. However, in the case of a part with a concave structure, for example, if the G71 cycle command of the FANUCTD system is used for roughing, the roughing is carried out with G71 because the command performs the roughing according to the contour of the last cycle. For example, use the FANUCTC G71 system cycle command for rough machining and set the finishing edge margin to be less than the depth of the concave structure in the rough machining step. roughing (such as using the FANUCTC G71 system cycle control for rough machining). , the concave structure on the cutting side will be cut. If the cutting allowance is insufficient, the part will be scrapped.
In order to solve this problem, we can use the rough machining method of G71 and G73, that is, first use the G71 cycle to remove most of the cutting edges, and then use the G73 cycle to remove the concave structure with machined edges, and finally, use G70 cycle for finishing or always use G71 and G70 processing, the depth of concave and convex structure left in step roughing exceeds finishing tolerance In G70 processing, use the length compensation value in the X direction or the tool setting for. change Wear compensation method, after machining, for example, in G71, set the finishing allowance in the X direction to 3.5. After roughing, set a positive value in the corresponding tool’s X direction compensation (for example, 0.5 is the finishing allowance), recycle. and fill the tool, process according to the G70 command, implement semi-finishing, cutting depth 3, after semi-finishing, the corresponding tool X direction compensation is set to -0.5 cumulative input , recall the tool, process according to command G70, execute
Finishing, cutting depth is 0.5. In order to maintain the consistency of the machining program, the tool setting values in the X direction for the semi-finishing and finishing steps are also called different compensation numbers.
5 CNC Lathe Programming Skills
5.1 Use safety blocks to set the initial state of the CNC system
When writing a program, planning security blocks is very important. Before starting the tool and spindle, in order to ensure processing safety, please set the start or initial state in the start block. Although CNC machines are set to default upon power-up, a programmer or operator should not have the option of relying on system defaults due to the ease of modification. Therefore, when writing CNC programs, it is recommended to develop a safe program to set the initial state of the system. This will not only ensure absolute programming safety, but also work in debugging, tool path inspection and size adjustment. . The program is more convenient to use. At the same time, it also improves the portability of the program because it does not rely on the default settings of specific machine tools and CNC systems. In the FANUC system, when processing small diameter parts, the safety block can be set to: G40G97G99G21.
5.2 Use the M command skillfully
CNC lathes have several M instructions, and the use of these instructions is tied to the needs of the machining operation. By using these M controls correctly and intelligently, these parts will bring a lot of convenience. After finishing the workpiece, add the instruction M05 (spindle stops rotating) M00 (program stops), which allows us to easily measure the size of the workpiece to ensure the machining accuracy of the piece. Additionally, after the thread is finished, use the M05 and M00 commands to make it easier to detect thread quality.
5.3 Reasonably set the starting point of the cycle
Before using these cycle instructions, FANUCCNC lathe has many cycle commands, such as G92 simple fixed cycle instruction, G71, G73, G70 compound fixed cycle instruction, threading cycle instruction G92, G76, etc. The tool must first be positioned at the start. of the cycle The cycle start point not only controls the tool’s safety distance from the workpiece and the actual cutting depth of the first blank, but also determines the hollow stroke distance of the cycle. The start point for instructions G90, G71, G70 and G73 is generally set at the corner of the part closest to the start of rough machining. The X direction is usually set to X (roughing diameter) and the Z direction is usually set. 2 to 5 mm from the part. The starting direction of G92 and G76 thread cycle instructions is usually set outside the workpiece. When processing external threads, the X direction is usually set to X (thread diameter + 2). When processing internal threads, the X direction is usually set to X (thread diameter – 2), and the Z direction is usually set to 2-5mm thread.
5.4 Intelligent use of wear to ensure dimensional accuracy of parts
Tool compensation is divided into geometric offset and wear offset. The geometric offset determines the position of the tool relative to the program origin, and the wear offset is used for accurate sizing. When processing parts on a CNC lathe, in order to avoid waste, the wear compensation value can be entered before processing the parts. When setting the wear compensation value of the workpiece, the sign of the wear compensation value must have a margin for the machined workpiece. When machining the outer ring, a positive wear offset must be predefined. When machining holes, a negative wear offset must be predefined. The size of the wear offset is preferably the size of the finishing allowance.
6Conclusion
In short, before performing CNC lathe processing operations, writing instructions is the basis and key of lathe operations. We must do a good job writing and following the instructions.
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