Common machining methods and characteristics

Commonly used mechanical metal cutting processing methods mainly include turning, milling, drilling, boring, planing, broaching, grinding and so on.

Turning

Definition: The cutting method in which the rotation of the workpiece is the main movement and the turning tool is the feed movement.

The main movement of turning is the part rotation movement, and the linear movement of the tool is the feed movement, which is especially suitable for processing the rotary surface.

Process characteristics of turning:

1. It is easy to ensure the position accuracy of each processing surface of the workpiece (coaxiality requirements, perpendicularity requirements)

2. High production efficiency

3. Low production cost

4. A wide range of materials suitable for processing

Application of turning:

In single-piece small batch production, various shafts, discs, and sleeve parts are mostly processed by horizontal lathes or CNC lathes with a wide range of adaptability. Parts with large diameters and short lengths are mostly processed by vertical lathes. When mass production of small and medium-sized shafts and sleeve parts with internal holes and threads is more complicated, the turret lathe should be used for processing.

Processing range of turning:

Turning is the main processing purpose of machining the rotating body. The outer circle, end face, taper, turning surface, threading, spring winding, etc. can be processed on the lathe. In addition, drilling, reaming, reaming, tapping, etc. can also be used. The machining accuracy of turning is generally IT8-IT7, and the surface roughness is Ra6.3-1.6μm; when finishing turning, the machining accuracy can reach IT6-IT5, and the roughness can reach Ra0.4-0.1μm. (Refer to different materials, the results may be a bit different)

There are many types of lathes. According to the structure and use, they can be divided into horizontal lathes, vertical lathes, profiling and multi-tool lathes, automatic and semi-automatic lathes, instrument lathes, and CNC lathes. Among them, horizontal lathes are the most widely used and the others are The basis of this type of lathe, the commonly used horizontal lathes are C6140 , C6132A and so on. Generally, there are such lathes in the following picture in the factory that engages in mechanical processing.

Milling

Definition: The cutting method in which the milling cutter rotates as the main movement, and the workpiece or the milling cutter makes the feed movement. Milling is one of the main processing methods for planes.

Process characteristics of milling:

1. High production efficiency: The milling cutter is a typical multi-tooth cutter. And the cutting edge involved in cutting has several teeth participating in the work at the same time when milling. And there is no idle return stroke like planing, and the cutting speed is also high. However, it is more productive than milling to process long and narrow planes or long straight planes.

2. The cutter teeth have better heat dissipation: the cutter teeth of the milling cutter can get a certain amount of cooling within a period of time away from the workpiece, the heat dissipation conditions are good, and the tool life is long.

3. There is impact during milling: the cutting of each tooth of the milling cutter is intermittent, and the number of teeth involved in the cutting during the milling process changes, and the cutting thickness also changes. Therefore, the cutting force changes, resulting in an impact during the cutting process.

    The main applications of milling:

    Milling is mainly used to process planes (including horizontal planes, vertical planes and inclined planes), grooves, forming surfaces and cutting. The machining accuracy can generally reach IT9-IT7, and the surface roughness is Ra1.6-3.2μm. In single-piece and small-batch production, vertical milling machines (horizontal and vertical) are often used for processing small and medium-sized workpieces . Gantry milling machines can be used when processing medium and large-sized workpieces.

Drilling

Definition: The method in which the drilling tool moves relative to the workpiece and makes an axial feed movement to machine holes on the workpiece.

Drilling is one of the most basic hole processing methods. Drilling is usually carried out on drilling machines and lathes, but can also be carried out on boring machines and milling machines.

Drilling application:

In single-piece and small-batch production, small holes (D<13mm) on small and medium-sized workpieces are usually processed by bench-type drilling machines (D<50mm) and vertical drilling machines are commonly used; the holes on large and medium-sized workpieces should be processed by radial drilling machines. Machining, the holes on the revolving workpiece are processed on a lathe. In batch and mass production, in order to ensure processing accuracy, improve production efficiency and reduce processing costs, drilling dies, multi-axis drills or modular machine tools are widely used for hole processing. For small and medium diameter holes (D<50mm) with high precision and small roughness, after drilling, it is often necessary to use reaming and reaming for semi-finishing and finishing.

Features of drilling processing:

    (1) Drilling is a method of drilling holes in a solid workpiece with a drill. The commonly used drill is a twist drill. When drilling, first select the drill bit according to the size of the hole. Generally, when the hole diameter is less than 30mm, it can be drilled at one time; when it is larger than 30mm, a small hole should be drilled first, and then a reaming drill is used to enlarge it. (2) Hole reaming is a processing method that expands an existing hole, called reaming. Twist drills can be used for reaming only to expand the diameter of the hole. While expanding the diameter of the hole and improving the accuracy of the hole shape and position, a special reaming method is used. The machining accuracy of the reamer drill is generally IT10～IT8, and the surface roughness is Ra6.3～3.2μm. Reaming can be used as the final processing of less demanding holes, or as a pre-processing before finishing (such as reaming). (3) Reaming is a finishing method that uses a reamer to remove a trace metal layer on the hole wall after reaming or semi-finishing boring to improve the dimensional accuracy of the hole and reduce the surface roughness value. The machining accuracy can reach IT7～IT6, and the surface roughness is Ra0.8～0.4μm. There are two types of reamers: hand reamer and machine reamer. The working part of the hand reamer is longer and the working part of the machine reamer is shorter. (4) Countersinking refers to the method of processing conical counterbores, cylindrical counterbores and end bosses on the machined holes. The tools used for countersinking are collectively referred to as countersinking.

    Boring

    Definition: The cutting processing method in which the boring tool rotates as the main movement and the workpiece or the boring tool is the feed movement. Boring processing is mainly carried out on milling and boring machines. Boring is the further processing of forging, casting or drilling holes. Boring can be divided into rough boring, semi-finish boring, and fine boring. The rough boring precision can reach IT12～IT11, and the surface roughness is Ra25～12.5μm. The precision of semi-finish boring can reach IT10～IT9, and the surface roughness is Ra6.3～3.2μm. The precision of fine boring can reach IT8～IT7, and the surface roughness is Ra1.6～0.8μm.

Boring application

    Boring can carry out rough machining, semi-finishing and finishing of through holes and blind holes on the workpiece. It is suitable for processing the holes and hole system on the workpiece with complex structure and large size such as box body and frame.

Characteristics of boring processing

    A boring tool can be used to process holes of various diameters within a certain range, especially large-diameter holes, which is almost the only method to choose from (wire cutting is also possible).

Planing

Definition: The cutting method in which the planer and the workpiece reciprocate in a straight line relative to the horizontal direction.

    Planing is one of the main methods of plane processing, and it is the most commonly used processing method for plane processing of single-piece small batch production. Common planer machine tools include bullhead planer, double planer and slotting machine.

Technological characteristics of planing:

    1. Good versatility: According to cutting movement and specific processing requirements. The price is low, and the structure of the planer is simpler than that of a lathe and a milling machine. Adjustment and operation are also more convenient. The single-edged planer used is basically the same as the turning tool. It is easy to manufacture and install the sharpening, simple shape, can process vertical and horizontal planes, and can also process T-shaped grooves, V-shaped grooves, dovetail grooves, etc.

    2. Low production efficiency: The main movement of planing is a reciprocating linear movement. In addition, when the tool cuts in and cuts out, it is affected by the inertial force when there is a reverse impact. A surface often limits the increase in cutting speed. The length of the cutting edge that the single-edge planer actually participates in is limited, and it can be processed after multiple strokes. The basic process time of processing discontinuity is longer, and the planer does not cut when it returns to the stroke.

   3. The processing accuracy is not high: the precision of planing can reach IT8～IT7, and the surface roughness is Ra1.6～6.3μm. But when a wide knife is used for fine planing, that is, when multiple pieces or multiple knives are processed on a planer, use a wide blade planer to cut off a very thin layer of metal on the surface of the workpiece at a very low cutting speed, and the flatness is not greater than 0.02/1000, surface roughness Ra0.4～0.8μm.

The processing range of planing:

    Due to the characteristics of planing, there are many applications in maintenance workshops and mold shops, and planing is mainly used in single-piece small batches

In mass production, planing is mainly used to machine flat surfaces, but it is also widely used to machine straight grooves. The maximum planing length of the bullhead planer is generally not more than 1000mm, so it is only suitable for processing medium and small workpieces. The planer is mainly used to process large workpieces, or to process multiple medium and small workpieces at the same time. Slotting machine, also known as vertical bullhead planer, is mainly used to process the inner surface of the workpiece, such as keyway, spline groove, etc., can also be used to process polygonal holes, such as square holes, hexagonal holes, etc., especially suitable for processing blind holes or shoulders with obstacles的内面。 The inner surface.