1 Introduction
FANUC system is one of the commonly used control systems for CNC machine tools, and its control commands are divided into single cycle commands and multiple cycle commands.
2 programming ideas
The essence of the program is to find out the characteristics of the tool trajectory, and realize the repeated statements in the program through a mathematical algorithm. According to the above part characteristics, we find that the X coordinate value gradually decreases. Therefore, you can use the FANUC system to X change the wear value, customize the turning cycle machining, control the tool each time from the part contour distance of the tool with a fixed value, and process it in each machining cycle before the modification and then use the system condition to jump, return Modify the statement accordingly. After the roughing cycle is completed, determine the workpiece to determine the amount of finishing, modify the tool compensation parameters, and then jump to complete the turning.
3 Correctly select the starting point of the cycle
When the cycle program ends, 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 safely returns to the starting point at the end of the cycle. When the cycle command is programmed, it is easy to use and deal with potential safety hazards that cause major problems. Of course, safety cannot be guaranteed. The starting point is set too far from the workpiece, resulting in a long and empty tool path. affect processing efficiency. Is it safe to return to the start of the cycle, the start of the cycle program, the tool position at the end of the last line of the finishing process, the shape of the workpiece at the end of the cycle, the shape of the tool holder and other tool mounting positions. In either case, it is ultimately possible to ensure that the cycle does not interfere with the rapid retraction by changing the starting position of the cycle program. You can use the mathematical calculation method, the CAD software to query the base point coordinate method to determine the reasonable and safe starting position of the cycle, or in the program debugging stage, use the single-stage operation and low-rate feed, try to cut, and modify the program starting point coordinates step by step. Identify a reasonably safe starting location. After considering the above factors, it is necessary to determine the starting point of the cycle, and special attention should be paid to: if the machining and cutting are added to the measurement and debugging program before processing, such as the machine tool runs to the Nth line, the spindle stops, and the program is paused. After the measurement, retract to the appropriate position. position, and then manually or manually enter the position near the workpiece, automatically execute the finishing cycle command, and then the starting point of the cycle program is the point. If you choose an incorrect position, there may be interference. Before the program line, add instructions to quickly enter a reasonable starting position of the loop program to ensure safety.
4 Reasonable Combinations of Loop Instructions
Usually, the finishing G70 command is used in conjunction with the roughing G71, G73, G74 commands to complete the rough machining of the workpiece. However, in the case of a workpiece with a concave structure, for example, if the FANUCTD system G71 cycle command is used for roughing, roughing is performed with G71, because the command performs roughing according to the contour in the last cycle. For example, use the G71 cycle command of the FANUCTC system to perform rough machining, and set the depth of the finishing edge margin to be less than the depth of the concave structure. The trimming allowance is insufficient, and the workpiece is scrapped.
To solve this problem, we can use the roughing method of G71 and G73, that is, first use the G71 cycle to remove most of the cutting edge, then use the G73 cycle to remove the concave structure with the machined edge, and finally use the G70 cycle to finish or still use G71 And G70 machining, the depth of the concave-convex structure left in the roughing stage exceeds the finishing allowance, in G70 machining, use to change the X-direction length compensation value of the tool or set the wear compensation method, after machining, for example, in G71 , set the finishing allowance in the X direction to 3.5, after the roughing is finished, set a positive value input in the corresponding tool X direction compensation (for example, 0.5 is the finishing allowance), the tool is recovered and filled, and processed according to the G70 command , carry out semi-finishing, cutting depth 3, after semi-finishing, set the X direction compensation of the corresponding tool to -0.5 for cumulative input, call the tool again, process according to G70 command, execute
Finishing, the cutting depth is 0.5. In order to keep the machining program consistent, and for the semi-finishing and finishing stages, the X-direction tool settings are also called different compensation numbers.
5 CNC lathe programming skills
5.1 Setting the initial state of the CNC system with a safety block
When writing a program, the planning of safety blocks is very important. Before starting the tool and spindle, in order to ensure the safety of machining, please set the starting or initial state in the starting block. While CNC machines are set to defaults after power-up, there should be no opportunity for programmers or operators to rely on system defaults due to the ease of change. Therefore, when writing NC programs, develop a safe program to set the initial state of the system and good programming habits, which can not only ensure the absolute safety of programming, but also operate in debugging, tool path inspection and size adjustment, etc. The program is more convenient to use. At the same time, it also enhances program portability, as it does not depend on the default settings of specific machine tools and CNC systems. In the FANUC system, when machining parts with small diameters, the safety block can be set as: G40G97G99G21.
5.2 Use the M command skillfully
CNC lathes have multiple M commands, and the use of these commands is related to the needs of machining operations. Correct and clever use of these M commands, these parts will bring a lot of convenience. After completing the 5-Axis Machining, add M05 (spindle stop rotating) M00 (program stop); command, which allows us to easily measure the size of the part to ensure the machining accuracy of the part. In addition, after the thread is completed, use the M05 and M00 commands to facilitate the detection of thread quality.
5.3 Reasonably set the starting point of the cycle
Before using these cycle commands, FANUCCNC lathe has many cycle commands, such as simple canned cycle command G92, compound canned cycle command G71, G73, G70, thread cutting cycle command G92, G76, etc., the tool must first be positioned to the beginning of the cycle The starting point of the cycle not only controls the safety distance of the tool approaching the workpiece and the actual depth of cut for the first roughing, but also determines the distance of the hollow stroke in the cycle. The starting point of G90, G71, G70, G73 commands is usually set at the corner of the workpiece closest to the start of roughing, the X direction is generally set to X (rough diameter), and the Z direction is generally set to 2-5mm from the workpiece. The start direction of thread cutting cycle commands G92 and G76 is usually set outside the workpiece. When machining external threads, the X direction is generally set to X (thread diameter + 2). When machining internal threads, the X direction is generally set to X (thread diameter -2) and the Z direction is generally set to the thread 2-5mm.
5.4 Use wear skillfully to ensure the dimensional accuracy of parts
Tool compensation is divided into geometric offset and wear offset. Geometric offsets determine the position of the tool relative to the program origin, and wear offsets are used for precise sizing. In order to prevent waste when machining parts on CNC lathes, wear compensation values can be entered before machining parts. When setting the part wear compensation value, the sign of the wear compensation value should have the allowance of the CNC component. When machining the outer ring, a positive wear offset should be preset. When machining holes, a negative wear offset should be preset. The size of the wear offset is preferably the size of the finishing allowance.
6 Conclusion
In short, before the CNC lathe machining operation, the writing of instructions is the foundation, and it is the key to the operation of the lathe. We must do a good job in the writing and application of the instructions.
Post time: Aug-09-2022