The machining process specification is one of the process documents that specifies the machining process and operation methods of parts. It is a process document written in the prescribed form under specific production conditions, which is used to guide production after approval. The mechanical processing technology regulations generally include the following contents: the process route of workpiece processing, the specific content of each process and the equipment and process equipment used, the inspection items and methods of the workpiece, cutting amount, time quota, etc.

In the production process, the process of changing the shape, size, position, and properties of the production object to become a finished or semi-finished product is called a process. It is the main part of the production process. The process can be further divided into casting, forging, stamping, welding, mechanical processing, assembly and other processes. The mechanical manufacturing process generally refers to the sum of the mechanical processing process of parts and the assembly process of machines. Other processes are called auxiliary processes, such as transportation, storage, power supply, equipment maintenance, etc. A process is composed of one or several sequentially arranged processes, with each process consisting of several steps. 1、 Mechanical processing technology 1: During turning, the workpiece rotates to form the main cutting motion. When the tool moves along the parallel axis of rotation, it forms inner and outer cylindrical surfaces. The cutting tool moves along a diagonal line that intersects with the axis, forming a conical surface. On a copying lathe or CNC lathe, the tool can be controlled to feed along a curve, forming a specific rotational surface. By using formed turning tools, rotating surfaces can also be machined during lateral feed. Turning can also process threaded surfaces, end planes, and eccentric shafts. The machining accuracy of turning is generally IT8-IT7, and the surface roughness is 6.3-1.6 μ M. When precision turning, it can reach IT6-IT5, and the roughness can reach 0.4-0.1 μ M. The productivity of turning is high, the cutting process is relatively smooth, and the cutting tools are relatively simple. Do you understand the eight major processes of mechanical processing? What is the processing flow like? 2: The main cutting motion of milling is the rotation of the tool. When milling horizontally, the formation of the plane is formed by the edges on the outer surface of the milling cutter. During end milling, the plane is formed by the end face edge of the milling cutter. Increasing the speed of the milling cutter can achieve a higher cutting speed, resulting in higher productivity. However, due to the impact caused by the cutting in and out of the milling cutter teeth, the cutting process is prone to vibration, which limits the improvement of surface quality. This kind of impact also intensifies the wear and damage of the cutting tools, often leading to the fragmentation of hard alloy blades. During the general time of cutting off the workpiece, a certain amount of cooling can be obtained, so the heat dissipation conditions are better. According to whether the main motion speed direction during milling is the same or opposite to the workpiece feed direction, it is further divided into forward milling and reverse milling. The horizontal component of milling force is the same as the feed direction of the workpiece, and there is usually a gap between the feed screw and the fixed nut of the workpiece table. Therefore, cutting force can easily cause the workpiece and worktable to move forward together, causing a sudden increase in feed rate and causing cutting. When milling workpieces with surface hardness such as castings or forgings, the teeth of the milling cutter first come into contact with the hard skin of the workpiece, which intensifies the wear of the milling cutter. Reverse milling can avoid the phenomenon of movement that occurs during forward milling. During reverse milling, the cutting thickness gradually increases from zero, and as a result, the cutting edge undergoes a stage of squeezing and sliding on the hardened machined surface, accelerating tool wear. Meanwhile, during reverse milling, the milling force lifts the workpiece upwards, which can easily cause vibration, which is a disadvantage of reverse milling. The machining accuracy of milling can generally reach IT8-IT7, and the surface roughness is 6.3-1.6 μ M. Ordinary milling can generally only process flat surfaces, and fixed curved surfaces can also be machined using forming milling cutters. CNC milling machines can use software to control several axes in a certain relationship through the CNC system, milling complex surfaces. In this case, ball end milling cutters are generally used. CNC milling machines are of great significance for processing complex shaped workpieces such as blades, mold cores, and cavities in turbomachinery. 3: When planing, the reciprocating linear motion of the tool is the main cutting motion. Therefore, the cutting speed cannot be too high and the productivity is low. Planing is smoother than milling, and its machining accuracy can generally reach IT8-IT7, with a surface roughness of Ra6.3-1.6 μ m. The precision planing flatness can reach 0.02/1000, and the surface roughness is 0.8-0.4 μ M. 4: Grinding involves the use of grinding wheels or other tools to process workpieces, with the main motion being the rotation of the grinding wheel. The grinding process of a grinding wheel is actually a comprehensive effect of the cutting, engraving, and sliding effects of the abrasive particles on the surface of the workpiece. In grinding, the abrasive particles themselves gradually become dull from being sharp, resulting in a decrease in cutting effectiveness and an increase in cutting force. When the cutting force exceeds the strength of the adhesive, the blunt abrasive particles fall off, exposing a new layer of abrasive particles, forming the "self sharpening" of the grinding wheel. But chips and abrasive particles will still block the grinding wheel. Therefore, after grinding for a certain period of time, it is necessary to use diamond turning tools or other tools to trim the grinding wheel. Do you understand the eight major processes of mechanical processing? What is the processing flow like? During grinding, due to the many cutting edges, the machining process is smooth and accurate. The grinder is a precision machining machine tool, with a grinding accuracy of IT6-IT4 and a surface roughness of Ra of 1.25-0.01 μ m. Even up to 0.1-0.008 μ M. Another characteristic of grinding is the ability to process hardened metal materials. Therefore, it is often used as the final processing step. During grinding, a large amount of heat is generated and sufficient cutting fluid is required for cooling. According to different functions, grinding can also be divided into outer circle grinding, inner hole grinding, flat grinding, etc. 5: Drilling and boring are the most commonly used methods of hole machining on drilling machines, where the drill bit is used to rotate and drill holes. The machining accuracy of drilling is relatively low, generally only reaching IT10, and the surface roughness is generally 12.5-6.3 μ M often uses reaming and reaming to perform semi precision machining and precision machining after drilling. Expanding holes is carried out using an expanding drill, and reaming holes are processed using a reamer. The precision of hinge machining is generally IT9-IT6, and the surface roughness is Ra1.6-0.4 μ M. When expanding or reaming, the drill bit and reamer generally follow the axis of the original bottom hole, which cannot improve the accuracy of the hole position. Boring holes can be aligned with the correct position of the hole. Boring can be done on a boring machine or lathe. When boring holes on a boring machine, the boring tool is basically the same as the turning tool, but the difference is that the workpiece does not move, while the boring tool rotates. The machining accuracy of boring holes is generally IT9-IT7, and the surface roughness is Ra6.3-0.8mm.. Drilling, boring, machining, and lathe machining 6: Gear surface machining. Gear surface machining methods can be divided into two categories: forming method and generating method. The machine tool used for machining tooth surfaces using the forming method is generally a regular milling machine, and the cutting tool is a forming milling cutter, which requires two simple forming movements: the rotational motion of the cutting tool and the linear movement. The commonly used machine tools for generating tooth surfaces include hobbing machines, slotting machines, etc. 7: The cutting process of complex surface machining for three-dimensional surfaces mainly adopts the methods of profile milling and CNC milling, or special machining methods (see Section 8). Prototype milling must have a prototype as a reference. During processing, the ball shaped imitation head is constantly in contact with the prototype surface under a certain pressure. The motion of the profiling head is transformed into inductance, and the machining amplification controls the motion of the three axes of the milling machine, forming a trajectory of the tool head moving along the surface. Milling cutters often use ball end milling cutters with the same radius as the copying head. The emergence of CNC technology has provided more effective methods for surface machining. When machining on a CNC milling machine or machining center, it is achieved by using a ball end milling cutter to machine point by point according to coordinate values. The advantage of using a machining center to process complex surfaces is that there is a tool library on the machining center, equipped with dozens of cutting tools. The rough and fine machining of curved surfaces can be carried out using different cutting tools for different curvature radii of concave surfaces, and appropriate cutting tools can also be selected. At the same time, various auxiliary surfaces such as holes, threads, grooves, etc. can be machined in one installation. This fully ensures the relative positional accuracy of each surface. 8: Special machining methods refer to a series of machining methods that use chemical, physical (electrical, acoustic, optical, thermal, magnetic) or electrochemical methods to process workpiece materials, which are different from traditional cutting methods. These processing methods include chemical machining (CHM), electrochemical machining (ECM), electrochemical mechanical machining (ECMM), electrical discharge machining (EDM), electrical contact machining (RHM), ultrasonic machining (USM), laser beam machining (LBM), ion beam machining (IBM), electron beam machining (EBM), plasma machining (PAM), electro-hydraulic machining (EHM), abrasive flow machining (AFM), abrasive jet machining (AJM), liquid jet machining (HDM), and various composite machining. 2、 The mechanical processing technology process refers to the processes directly related to the transformation of raw materials into products during the production process. It includes rough manufacturing, part processing, heat treatment, quality inspection, and machine assembly. The manufacturing of cutting tools and fixtures required to ensure the normal operation of the process, as well as the adjustment and maintenance of machine tools, are auxiliary processes. The process of gradually changing the shape, size, relative position, and performance of the blank in a certain order using mechanical processing methods until it becomes a qualified part is called the mechanical machining process. Technicians determine the process to be adopted based on product quantity, equipment conditions, and worker quality, and write relevant content into process documents. This type of document is called a process specification. In order to facilitate the formulation, implementation, and production organization management of process regulations, it is necessary to divide the process into different levels of units. They are processes, installations, workstations, steps, and cutting tools. The process is the basic unit in the manufacturing process. The machining process of parts consists of several processes. In a process, there may be one or several installations, each installation may include one or several workstations, each workstation may include one or several steps, and each step may include one or several cutting paths.

(1) The part of a process in which one or a group of workers continuously complete one or several workpieces at the same time on a workplace or machine is called a process. The basis for dividing processes is whether the work location has changed and whether the work process is continuous. For example, when machining a batch of shafts on a lathe, each shaft can be continuously roughened and precision machined, or the entire batch of shafts can be roughened first and then precision machined sequentially. In the first scenario, processing only includes one process; In the second scenario, due to the interruption of the continuity of the machining process, although the machining is carried out on the same machine tool, it becomes two separate processes. Process is the fundamental unit that constitutes a manufacturing process and is also the fundamental unit of production planning. (2) The process of installing a workpiece in a machining process to occupy a correct position on the machine tool or in a fixture and being clamped is called clamping. Sometimes, the workpiece needs to be clamped multiple times on the machine tool to complete the work content of a process. Installation refers to the part of the process that is completed after the workpiece is clamped once. For example, when machining a shaft on a lathe, first process part of the surface from one end, then turn around and then process the other end. At this time, the process includes two installations. (3) When a workstation uses an indexing (or shifting) fixture, a rotary worktable, or a multi axis machine tool for processing, the workpiece needs to pass through several positions in sequence after being clamped on the machine tool. The part of the process completed by the workpiece at each position occupied by the machine tool is called a workstation. Simply put, the part of the process completed by the workpiece relative to the machine tool or tool at each machining position is called a workstation. In order to reduce the clamping error and time loss caused by multiple clamping, various rotary workbenches, rotary fixtures, or mobile fixtures are often used, so that the workpiece is processed in several different positions in one clamping. (4) The part of the process that is continuously completed under the condition that the machining surface remains unchanged and the machining tools remain unchanged is called a work step. Also commonly referred to as "feed" in production. The entire process consists of several steps. Each process can include one or several steps. Each work step typically includes one work itinerary, but can also include several work itineraries. In order to improve productivity, using several cutting tools to simultaneously process several machining surfaces is called a composite step, which can also be regarded as a single step, such as using a combination drilling machine to process porous box holes.

(5) The part of the work step completed by machining a tool on the machining surface in one go is called cutting. For example, if the metal layer to be cut off for shaft parts is very thick, it needs to be cut in several times, and each cutting is called a cutting pass. Therefore, completing a feed motion of the tool while keeping the cutting speed and feed rate constant is called a single tool feed.