How to determine the processing plan for the most

2022-10-03
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How to determine the processing scheme for NC lathe programming (I) the principle of determining the processing scheme

the processing scheme is also known as the process scheme. The processing scheme of NC machine tools includes the formulation of working procedures, working steps and cutting routes

in the process of machining with CNC machine tools, due to the complexity and diversity of machining objects, especially the ever-changing shape and position of contour curves, and the influence of various factors such as different materials and batches, when formulating machining schemes for specific parts, we should make specific analysis, treat them differently, and deal with them flexibly. Only in this way can the processing plan be reasonable, so as to achieve the purpose of high quality, high efficiency and low cost

the general principles for formulating the processing plan are: rough first and then fine, close first and then far, inside first and then outside, minimum program segments, shortest cutting route, and special treatment under special circumstances

(1) rough first and then finish

in order to improve production efficiency and ensure the finish machining quality of parts, the rough machining process should be arranged first, and a large amount of machining allowance before finish machining should be removed in a short time, while trying to meet the uniformity requirements of finish machining allowance

after the rough machining process is arranged, the semi finish machining and finish machining after tool change should be arranged. Among them, the purpose of arranging semi finish machining until the polygonal aperture ring can just fill the field of vision is to arrange semi finish machining as a transitional process when the uniformity of the allowance left after rough machining cannot meet the requirements of finish machining, so as to make the finish machining allowance small and uniform

when arranging the finishing process that can be carried out with one or more knives, the final contour of the part shall be formed by continuous machining with the last knife. At this time, the forward and backward position of the processing tool should be considered properly, and try not to arrange cutting and cutting out or tool change and pause in the continuous contour, so as to avoid elastic deformation caused by the sudden change of cutting force, resulting in surface scratches, sudden changes in shape or residual knife marks and other defects on the smooth connecting contour

(2) close first and then far

the distance between the machining part and the tool setting point is the distance between the machining part and the tool setting point. In general, especially in rough machining, it is usually arranged that the part close to the tool setting point is processed first, and the Part 305 far from the tool setting point is processed after the expanded perlite thermal insulation product position, so as to shorten the moving distance of the tool and reduce the empty travel time. For turning, it is beneficial to maintain the rigidity of blank parts or semi-finished parts and improve their cutting conditions

(3) inside first and then outside

for parts that need to process both the inner surface (inner mold and cavity) and the outer surface, when formulating its processing plan, it is usually arranged to process the inner mold and cavity first and then the outer surface. This is because it is difficult to control the size and shape of the inner surface, the rigidity of the tool is relatively poor, the durability of the tool tip (edge) is easily affected by cutting heat, and it is difficult to remove chips in processing

(4) the shortest tool path

the work focus of determining the tool path is mainly used to determine the rough machining and empty travel. The tool path should also have the function of heat dissipation and separation of impurities and air in the oil, because the tool path in the finishing cutting process is basically carried out along the contour sequence of its parts

the tool path generally refers to the path that the tool moves from the tool setting point (or the fixed origin of the machine tool) until it returns to the point and ends the machining program, including the path of cutting and non cutting empty travel such as tool introduction and cutting out

on the premise of ensuring the processing quality, making the processing program have the shortest tool path can not only save the execution time of the whole process of adding 70 gypsum hollow strip, but also reduce some unnecessary tool consumption and the wear of the sliding parts of the machine tool feed mechanism

in addition to relying on a lot of practical experience, the optimized process plan should also be good at analysis, which can be supplemented by some simple calculations when necessary

the above principles are not immutable. For some special cases, flexible and variable schemes need to be adopted. For example, some workpieces must be finished first and then rough machined to ensure their machining accuracy and quality. These all depend on the continuous accumulation and learning of the actual processing experience of programmers

(II) relationship between processing route and machining allowance

under the condition that CNC lathes have not reached universal use, generally, excessive allowance on blank parts, especially the allowance containing forged and cast hard skin, should be arranged to be processed on ordinary lathes. If it is necessary to process with a numerical control lathe, pay attention to the flexible arrangement of the program. Arrange some subroutines to cut the parts with excessive allowance first

(1) processing route for step cutting of large allowance blanks

(2) end position of the tool during layered cutting

(III) spindle speed during thread turning

when the CNC lathe processes threads, due to the change of its transmission chain, in principle, its speed as long as it can ensure that the tool moves a pitch along the direction of the main feed axis (mostly Z axis) every revolution of the spindle, it should not be limited. However, when NC lathes process threads, they will be affected by the following aspects:

(1) the pitch (lead) value of the instruction in the thread processing program section is equivalent to the feed speed f expressed in the feed rate (mm/r). If the spindle speed of the machine tool is selected too high, the converted feed speed (mm/min) must greatly exceed the normal value

(2) at the beginning/end of its displacement, the tool will be constrained by the frequency rise/fall of the servo drive system and the interpolation calculation speed of the numerical control device. Because the frequency rise/fall characteristics can not meet the processing needs and other reasons, the pitch of some threads may not meet the requirements due to the "lead" and "lag" generated by the main feed motion

(3) turning thread must be realized through the synchronous operation function of spindle, that is, turning thread requires spindle pulse

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