In CNC machining, the milling method refers to the trajectory planning method when the tool completes the milling of the workpiece. In the processing of the same part, various milling methods can meet the size and accuracy requirements of the part, but the processing efficiency is not the same.
The Classification of milling Tools
The milling methods can be divided into 4 categories:
(1) Unidirectional Milling
(2) Reciprocating Milling
(3) Circular Milling
(4) Compound Milling
A compound pass is a mix of the first three passes. One-way or reciprocating passes are used, which are all milling passes in terms of machining strategies. Therefore, according to the different processing strategies, the milling method can be divided into row milling, circular milling and other special methods. Row cuts and loop cuts are commonly used.
The line milling method is beneficial to the maximum feed rate of the machine tool, and the milling surface quality is also better than that of the ring milling process. However, when a complex plane pocket has multiple bosses to form multiple inner contours, an additional tool lifting action is often generated, that is, somewhere in the tool path, or to avoid interference between the tool and the boss, or for To return the tool to the remaining unprocessed area, lift the tool to make it a certain height from the machining plane, and then translate to the beginning of another tool path, and then continue the milling action.
The line milling tool path is mainly composed of a series of straight line segments parallel to a certain fixed direction, and the calculation is simple. Suitable for simple pocket finishing or roughing with large allowance removal.
In ring milling, the tool travels along a path with similar boundary contours, which is composed of a set of closed curves, which can ensure that the tool maintains the same milling state when milling parts. Since the loop milling process is to construct the current loop track graph through continuous offset to calculate the next loop track, the calculation is complicated and time-consuming. It is suitable for the processing of complex cavities and curved surfaces.
6 Keys for CNC Milling Improvement
1. The shape and geometric elements of the workpiece itself
The shape and geometric elements of the workpiece itself include the geometric shape of the processing domain, the size and location of the island and so on. This is an inherent characteristic of the workpiece itself, and it is an immutable factor, but it is the fundamental factor that determines the way of milling.
2. Process route
The process route is a direct process to achieve the purpose of processing, and is the direct basis for the selection of the milling method. The process route determines the sequence of processing domains, the merging and splitting of islands, the division of roughing, semi-finishing, and finishing, etc. There are many technological routes to achieve the goal, which determines the different choices of the milling method.
3. Workpiece material
The workpiece material is also one of the factors that determine the milling method. The workpiece material is a direct processing object and does not directly affect the milling method, but it will affect the selection of tool material, size, processing method, etc., thereby indirectly Affects the way of milling. The shape and size of the workpiece blank will cause whether the distribution of the machining allowance of each part of the workpiece is uniform. At the same time, for the workpiece with optional blank, the difference in the size and shape of the blank will change the clamping method, the redistribution of the processing area, etc., which will affect the processing. strategy, leading to different ways of taking the knife.
4. The clamping and fastening method of the workpiece
The clamping and fastening method of the workpiece also indirectly affects the milling method. Change, the vibration affects the way of the tool.
5. Selection of tools
The selection of tools includes tool material, tool shape, tool length, number of tool teeth, etc. These parameters determine the area and frequency of contact between the tool and the workpiece, thus determining the volume of the milling material per unit time and the machine tool. Load, its wear resistance and tool life determine the length of milling time. Among them, the tool size (ie diameter) has a direct impact on the way of milling tools. Due to the selection of tools with different diameters, the size of the residual area will be affected, resulting in changes in the machining trajectory, resulting in different milling methods.
6. Machining domain selection
In the milling process, when a complex plane cavity has multiple bosses to form multiple inner contours, additional tool lifting actions are often generated for line milling; for circular milling, it will cause machining. Track lengthened. This additional tool lifting action or the lengthening of the machining path will seriously reduce the efficiency of the milling process. Therefore, how to minimize the number of such situations is a major concern for us.
The entire CNC milling area is divided into several sub-areas according to the processing needs, and each sub-area is processed separately. The tool lift occurs between the sub-areas. At the same time, these processing sub-areas are merged or divided according to the milling method, or even ignored. This different selection of processing areas not only reduces the number of tool lifts, but also does not make the processing path relatively longer, and at the same time, the most reasonable milling method can be adopted for the new area, which improves the processing efficiency.