In the field of machining, after CNC machining process methods and division of processes, the main content of the process route is to rationally arrange these processing methods and processing sequence. In general, CNC machining of mechanical parts includes cutting, heat treatment and auxiliary processes such as surface treatment, cleaning and inspection. The sequence of these processes directly affects the quality, production efficiency and cost of the parts. Therefore, when designing CNC machining routes, the order of cutting, heat treatment and auxiliary processes should be reasonably arranged, and the connection problem between them should be solved.
In addition to the basic steps mentioned above, factors such as material selection, fixture design and equipment selection need to be considered when developing a CNC machining route. Material selection is directly related to the final performance of parts, different materials have different requirements for cutting parameters; The fixture design will affect the stability and accuracy of the parts in the process of processing; Equipment selection needs to determine the type of machine tool suitable for its production needs according to the characteristics of the product.
What do we have to do before arranging the CNC machining process route?
1, the processing method of precision machinery parts should be determined according to the characteristics of the surface. On the basis of familiar with the characteristics of various processing methods, mastering the processing economy and surface roughness, the method that can ensure the processing quality, production efficiency and economy is selected.
2, select the appropriate drawing positioning reference, according to the principle of crude and fine reference selection to reasonably determine the positioning reference of each process.
3, When developing the machining process route of the parts, it is necessary to divide the rough, semi-fine and finishing stages of the parts on the basis of the analysis of the parts, and determine the degree of concentration and dispersion of the process, and reasonably arrange the processing sequence of the surfaces. For complex parts, several schemes can be considered first, and the most reasonable processing scheme can be selected after comparison and analysis.
4, determine the processing allowance and process size and tolerance of each process.
5, select machine tools and workers, clips, quantities, cutting tools. The selection of mechanical equipment should not only ensure the quality of processing, but also be economical and reasonable. Under the conditions of mass production, general machine tools and special jigs should generally be used.
6, Determine the technical requirements and inspection methods of each major process.Determining the cutting amount and time quota of each process is usually decided by the operator for a single small batch production plant. It is generally not specified in the machining process card. However, in the medium batch and mass production plants, in order to ensure the rationality of production and the balance of rhythm, it is required that the cutting amount must be specified, and must not be changed at will.
cnc machining process arrangement
First rough and then fine
The processing accuracy is gradually improved according to the order of rough turning - semi-fine turning - fine turning. The rough lathe can remove most of the machining allowance of the workpiece surface in a short time, thereby increasing the metal removal rate and meeting the requirement of the uniformity of the allowance. If the residual amount left after the rough turning does not meet the finishing requirements, it is necessary to arrange a semi-finishing car for finishing. The fine car needs to ensure that the outline of the part is cut according to the drawing size to ensure the processing accuracy.
Approach first and then far
Under normal circumstances, the parts close to the tool should be processed first, and then the parts far away from the tool to the tool should be processed to shorten the moving distance of the tool and reduce the empty travel time. In the process of turning, it is beneficial to maintain the stiffness of the blank or semi-finished product and improve its cutting conditions.
The principle of internal and external intersection
For parts that have both an inner surface (inner cavity) and an outer surface to be processed, when arranging the processing sequence, the inner and outer surfaces should be roughed first, and then the inner and outer surfaces should be finished. Must not be part of the surface of the part (outer surface or inner surface) after processing, then processing other surfaces (inner surface or outer surface).
Base first principle
Priority should be given to the surface used as the finishing reference. This is because the more accurate the surface of the positioning reference, the smaller the clamping error. For example, when machining shaft parts, the center hole is usually machined first, and then the outer surface and end face are machined with the center hole as the precision basis.
The principle of the first and the second
The main working surface and assembly base surface of the parts should be processed first, so as to find out the modern defects on the main surface in the blank early. The secondary surface can be interspersed, placed on the main machined surface to a certain extent, before the final finishing.
The principle of the face before the hole
The plane outline size of the box and bracket parts is large, and the plane is generally processed first, and then the hole and other sizes are processed. This arrangement of processing sequence, on the one hand with the processed plane positioning, stable and reliable; On the other hand, it is easy to process the hole on the machined plane, and can improve the processing accuracy of the hole, especially when drilling, the axis of the hole is not easy to deviate.
Conclusion
When developing the machining process of parts, it is necessary to select the appropriate processing method, machine tool equipment, clamp measuring tools, blank and technical requirements for workers according to the production type of parts.