How to do a good job of precision automatic lathe machining


Precision automatic lathe processing needs to be done in the right way in order to get the job done. Also only to adapt to the continuous development of enterprises, then, how to do a good job of precision automatic lathe processing? Take a look at the following article.
How to do a good job of precision automatic lathe machining
A. Analysis of the content of the part drawing
Analysis of the geometric conditions of the machining contour: the main analysis of the part drawing is the primary work in the process preparation, which directly affects the production of parts and processing results. Mainly includes the following purposes are for the unclear size of the drawing and the closed dimensional chain to deal with. Analyze the dimensional tolerance requirements on the part drawing to determine the machining process to control its dimensional accuracy, such as the selection of tools and the determination of cutting dosage.
Analysis of shape and position tolerance requirements: for CNC cutting processing, the shape and position of the part error is mainly affected by the accuracy of the machine tool mechanical motion sub. In turning, such as the direction of motion along the z coordinate axis and its spindle axis is not flat shape, it can not guarantee the cylindricity of the shape tolerance requirements; and such as the direction of motion along the X coordinate axis and its spindle axis is not perpendicular, it can not guarantee the perpendicularity of the position tolerance requirements. Therefore, it is necessary to consider the options for technical processing before programming.
Analysis of the surface roughness of the part requirements, material and heat treatment requirements, the requirements of the blank, the requirements of the number of pieces is also the process arrangement and the determination of the tool route is not negligible parameters.
Second, a reasonable determination of the tool route, and make automatic lathe machining the shortest
Determine the work of the tool route is the focus of the processing program, due to finishing cutting program tool route is basically along the order of its parts contour, so the main content is to determine the roughing and empty travel tool route. Tool path refers to the tool from the point of the tool to start moving, until the return to the point and end of the processing program after the path. Including the cutting path and the tool introduction, cutting out and other non-cutting empty travel. Make the shortest route can save the whole process of execution time, but also reduce some unnecessary tool consumption and machine tool feed mechanism sliding parts of the wear. Figure 1 below shows the three turning taper method, with rectangular cycle command for processing, to analyze the alignment route reasonable determination.
This method is after each feed, the turning tool moving trajectory parallel to the cone bus, with each feed eating tool, Z-phase size increases by a certain percentage, and general turning processing cone method is the same, so that beginners easy to understand. z-directional size is calculated according to the formula C = D - d / L derived. If C is 1:10, it means that 1 mm is removed from the diameter X and 10 mm is added to the length Z. According to this ratio can be very simple to make, and can ensure the same amount of margin for each turning to make a uniform cut. Figure 1b shows the taper angle changing method, which is to keep the Z dimension as the drawing size with each X-direction feed, and each cut changes the size of the taper angle, only the last cut is the size of the taper angle required by the drawing. This cone turning method can not need to carry out each Z direction size calculation, but in the processing due to the same Z direction size, so that the processing route is longer, while the cutting allowance is not uniform, affecting the surface size and roughness of the workpiece, generally suitable for cone surface is short, the allowance is not large in the cone. Figure 1c for the step processing cone method, this processing method is every time the tool path parallel to the axis of the workpiece, processing many small steps, the last turning tool along the cone bevel for the tool, this processing method to do 1:1 scale chart first, otherwise easy to car waste workpiece, because it is step-like, so the residual is not uniform, affecting the quality of cone surface processing.
Obviously, among the above three cutting routes, if the starting point is the same, the parallel method of turning cone route is the most reasonable, and this method is commonly used in production for processing.
Third, reasonable call g command to make the least program segments
According to each individual geometric elements (i.e., straight line, diagonal line and arc, etc.) are prepared in accordance with the corresponding processing procedures, which constitute the processing procedures of each program that is the program segment. In the preparation of machining programs, it is always desired to achieve the machining of parts with the least number of program segments, so as to make the program concise, reduce the chance of errors and improve the efficiency of programming work.
As the CNC lathe device generally has the function of linear and circular interpolation, except for the non-circular curve, the number of program segments can be obtained from the geometric elements of the component and each program determined by the process line, and the principle of making the least number of program segments should be considered at this time. The selection of a reasonable G command can make the program segments reduced, but also to take into account the shortest route to the tool. For example, if the parts in Fig. 1 above are machined, if the blanks are all bars, you can use the linear interpolation command G01 for programming, or the rectangular cycle command G90 for programming, or the compound cycle command G71 for programming, all of which can process the workpiece.
For the machining of non-curved trajectories, the number of required main program segments is known only after calculations are performed under the condition that its machining accuracy is guaranteed. In this case, a non-circular curve should be divided into several main program segments (mostly straight lines or circular arcs) according to the approximation principle, and the number of segments of the divided main program should be the minimum when its accuracy requirements can be met. In this way, not only can greatly reduce the calculation workload, but also reduce the input time and memory capacity of the number of possession.
Fourth, the reasonable arrangement of "back to zero" route
In the production of more complex contour of the processing program, in order to make its calculation process as simple as possible, not only is not easy to make mistakes, but also easy to check, the end point of the tool after each knife processing through the implementation of the "back to zero" instruction (that is, return to the tool point), so that the full return to the tool point position, and then in the implementation of subsequent procedures. This will increase the distance of tool travel and reduce productivity. Therefore, in the reasonable arrangement of the "back to zero" route, should make the end of the previous tool and the start of the next tool between the distance as short as possible, or zero, that is, to meet the requirements of the shortest route.
Fifth, the reasonable choice of cutting amount
Automatic lathe processing CNC turning cutting amount is an important parameter that indicates the main motion of the machine body and the size of the feed motion, including the depth of cut, spindle speed, feed rate. Their selection corresponds to the basic requirements of general turning, but the parts processed by CNC lathes are often more complex, and the cutting amount should be adjusted at any time in combination with the actual processing of the parts after the initial determination according to certain principles, and the adjustment method is to use various multiplier switches on the operation panel of CNC lathes to make adjustments at any time to achieve a reasonable configuration of the cutting amount, which should have a certain amount of actual production for the operator. processing experience.
Sixth, the details of the programming problem processing
1, pay attention to the reasonable use of G04
G04 is a pause instruction, the role of the tool in a command time to temporarily stop processing. The instruction is often ignored because it does not do the actual cutting movement. However, it is good for ensuring the machining accuracy and changing the movement in the groove, drilling, etc. It is often used in the following cases: (1) groove cutting, drilling in order to ensure the size and roughness of the bottom of the groove, hole bottom should be set G04 command. (2) When the running direction is changed greatly, G04 command should be set between the changing running direction command. (3) When the running speed changes greatly, the G04 command should be set when the running command is changed. (4) Use G04 for interrupted processing. According to the cutting requirements of rough machining, the continuous motion trajectory can be arranged in sections, and each adjacent section is separated by the G04 command. During machining, after each segment of tool feed, a short delay time (0.5 seconds) is set to pause, followed by a segment of feed until the end of machining. The number of segments, depending on the requirements of the broken cutting, when the broken cutting is not ideal, to increase the number of segments.
2、Rough and finish machining separate programming
To improve the accuracy of the parts and ensure productivity, the last cut of the turning workpiece contour is usually completed by the finishing tool for continuous processing, therefore, rough and finish machining should be made separately. And, the tool in and out of position to consider properly, try not to cut in and out of the continuous contour or change tools and pause, so as not to cause elastic deformation due to sudden changes in cutting force, resulting in a smooth connection on the contour of the scratch, sudden changes in shape or stagnant tool marks and other defects.
3, the production often take the median size of the part requirements as the basis for programming size. If you encounter than the minimum production unit specified by the machine tool is smaller than the value, should try to its maximum entity size and rounding. Such as the drawing size of ? 80 + 00, 026 is written X80.013.
4, production as far as possible in line with the principle of overlap of the points. That is to say, the origin of the programming and the design of the benchmark, the position of the tooling point as far as possible to overlap, to reduce the processing errors caused by the non-overlap of the benchmark. In many cases, if the dimensional reference on the drawing is not the same as the dimensional reference required for production, the dimensions of each reference on the drawing should be converted to the dimensions in the programming coordinate system first. When the need to master the control of certain important dimensions of the allowable variation, but also through the size chain to get the solution, and then the next step in the production work.
5、Crafty use of cutting knife chamfering. To cut off the surface with a chamfered parts, in batch turning processing is more common, in order to facilitate the cut and avoid turning off the chamfer, can be cleverly used to cut off the knife at the same time to complete the car chamfering and cutting two processes, the effect is better. At the same time, the cutting tool has two tips, in the programming, we should pay attention to which tip and the width of the tool to prevent errors in the processing of the tool.
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