When machining mechanical parts, if the workpiece is too high, roughing should be done in layers using different length tools. After roughing with a large tool, a smaller tool should be used to remove the remaining material. Use flat-bottomed tools for machining flat surfaces, and minimize the use of ball-end mills to reduce machining time; if there is a slope and it is an integer, use a tapered tool for machining.
At the same time, reasonably set tolerances to balance machining accuracy and computer calculation time, and perform multiple processes to reduce idle time. For high-hardness workpiece materials, choose climb milling; for low-hardness workpiece materials, choose conventional milling. Rough machining uses climb milling, and finish machining uses conventional milling; tool materials with good toughness and low hardness are suitable for rough machining, while tool materials with poor toughness and high hardness are suitable for finish machining.
In CNC machining, the clamping method of the workpiece should be scientifically selected, including the positioning datum and clamping scheme. When selecting the precision datum, the principles of "standard uniformity" and "standard overlap" should generally be followed. In addition to these two principles, it is also necessary to consider completing the machining of all surfaces in one positioning and clamping operation. Therefore, a positioning method that facilitates the machining of each surface should be selected.
When the workpiece is clamped once, it should be possible to machine all surfaces of the workpiece; when determining the placement position of the workpiece on the worktable, the machining of each station should be considered, as well as the influence of the length and rigidity of the tool on the machining quality. The fixtures commonly used in CNC machining should be assembled from general-purpose components and be adjustable to reduce production preparation time.
When allocating the machining sequence, basic principles must be followed, including "surface first, then holes" and "roughing first, then finishing." Process operations should be grouped by tool to prevent repeated use of the same tool, reducing tool change frequency and time.
For hole systems requiring high coaxiality, all machining of that hole system should be completed after one positioning before machining other hole systems at different coordinate positions. This eliminates errors caused by repeated positioning and improves the coaxiality of the hole system. The tool point or tool setting point should be carefully selected and, once determined, should not be changed.
