The clamping method for the machined parts on CNC machine tools also requires a reasonable selection of positioning reference and clamping scheme. When selecting precision reference, it is generally necessary to follow the two criteria of "consistent reference" and "overlapping reference". In addition to these two criteria, we also need to consider: a. completing all external surface processing in one positioning clamping as much as possible, therefore, selecting a positioning method that is convenient for all external surfaces to be processed. b. When the workpiece is clamped at once, it should be able to complete all external processing of the workpiece. c. When determining the placement position of the workpiece on the workbench, consideration should be given to the impact of processing at each workstation, tool length, and tool stiffness on processing quality. d. The fixtures used in control machining should be selected as much as possible, which are assembled from universal components and can be adjusted to shorten the production preparation cycle.
(1) Part clamping method and fixture selection
The clamping method for the processed parts on CNC machine tools should also be reasonably selected for positioning reference and clamping scheme. When selecting precision reference, it is generally necessary to follow the two criteria of "consistent reference" and "overlapping reference". In addition to these two criteria, we also need to consider:
a. Try to complete all surface processing in one positioning clamping, therefore, choose a positioning method that is convenient for processing all surfaces.
b. When the workpiece is clamped at once, it should be able to complete all external processing of the workpiece.
c. When determining the placement position of the workpiece on the workbench, consideration should be given to the impact of processing at each workstation, tool length, and tool stiffness on processing quality.
d. The fixtures used in control machining should be selected as much as possible, which are assembled from universal components and can be adjusted to shorten the production preparation cycle.
(2) Organization of processing sequence
When organizing the processing sequence, the basic principles must be adhered to, including "first surface, then hole", "first rough, then fine", etc. In addition to these basic principles, we should also follow the following principles:
a. Process according to the centralized process of cutting tools, to prevent the same tool from being repeatedly used, and to reduce the number and time of tool changes.
b. For hole systems with high coaxiality requirements, the machining of the hole system should be completed after a single positioning, and then the hole system in other coordinate orientations should be processed. This can eliminate errors generated during repeated positioning and improve the coaxiality of the hole system.
c. Select and determine the cutting point and tool change point. Once determined, it is not advisable to replace them.
