Metal Machining -8 Machining methods from Highfive Electronics
HIGHFIVE’s high-precision machining center has more than 40 sets of precision CNC machining equipment, providing CNC lathes, milling machines, machining centers, and turning-milling composite external processing.
1. Metal Machining-Milling
The main cutting motion is the rotation of the processing tool. When processing on a horizontal milling machine, the plane is formed by the cutting edge on the outer surface of the milling cutter. When processing on a vertical milling machine, the plane is formed by the end edge of the milling cutter. Yes, increasing the speed of the milling machine tool can effectively obtain a higher cutting speed, so the efficiency of production and processing is higher.
However, because the cutter teeth of the milling cutter cut into and cut out of the device to form an impact, vibration is prone to occur during the cutting process, which limits the quality of surface processing. Such impacts also aggravate tool wear and damage to tools and often lead to the embrittlement of cemented carbide tools.
During the time period of cutting in and out of the workpiece, a certain amount of cooling can be obtained, so the heat dissipation conditions are relatively good. According to the direction of the main motion speed during milling, the direction of the main movement speed is opposite or the same as the feed direction of the workpiece, which can be divided into up milling and Down milling two kinds;
A, Up milling
It can avoid the movement phenomenon that occurs during down milling. During up milling, the cutting thickness gradually increases from zero. Therefore, the cutting edge begins to go through a stage of squeezing and sliding on the hardened machined surface, which intensifies the wear of the tool, and at the same time, When up-milling, the milling force will lift the workpiece, which is easy to cause vibration, which is the disadvantage of up-milling;
B, Down milling
The horizontal separation of the milling force is the same as the feed direction of the workpiece. There is generally a gap between the workpiece mounting table and the feed screw and the fixed nut. Therefore, the cutting force is likely to cause the workpiece and the workpiece mounting table to move forward together, allowing the workpiece to move forward. The sudden increase in feed rate causes the phenomenon of “knife hitting”.
When milling workpieces with a hardness on the surface such as castings and forgings, the down-milling cutter teeth first base the workpiece on the hard skin layer, which accelerates the wear of the milling cutter.
The accuracy of milling processing can generally achieve IT8-IT7, and the surface roughness can generally achieve 6.3-1.6um. Ordinary milling processing can generally only be applied to plane processing, and a relatively fixed surface can also be processed with a forming milling cutter.
A CNC milling machine can use software to control several axes through the CNC system to perform linkage according to a certain relationship, and milling is more complicated. For curved surfaces, ball-end milling cutters are generally used at this time.
The CNC milling machine has special significance for processing complex workpieces such as impeller products and mechanical pages, mold cores, and cavities.
2. Metal Machining-Turning
Using rotary turning to form a turning movement. When the tool moves along the parallel axis of rotation, an inner and outer cylindrical surface is formed, and the tool moves along the oblique line that intersects the axis to form a tapered surface. On CNC lathes, controlling the tool to feed along a curve can form a specific rotating surface.
Using forming tools, it can also process rotating curved surfaces during the lateral feed. Turning is often used in threaded surface, end surface, and eccentric shaft processing. The accuracy of turning to process is generally IT8-IT7, and the surface roughness is 6.3-1.6um.
When precision turning, it can achieve IT6-IT5, and the roughness can achieve 0.4-0.1um. Turning processing has the characteristics of high processing efficiency, stable processing, and simple tools.
3. Metal Machining-Grinding
Grinding is the processing of a workpiece with a grinding wheel or other abrasive tools. This type of processing is relatively common. Its main movement is the rotation of the grinding wheel. The grinding process of the grinding wheel is actually the cutting, engraving, and sliding of the surface of the workpiece by the abrasive particles.
The comprehensive performance of this kind of effect, during the grinding process, the abrasive grain itself is gradually blunt from sharp, which makes the cutting effect worse and the cutting force becomes larger.
When the cutting force exceeds the strength of the binder, the blunt abrasive grains fall off, exposing a new layer of abrasive grains, forming the “self-sharpening” of the grinding wheel. However, cutting and crushing abrasive particles will still block the grinding wheel. Therefore, after grinding for a period of time, the grinding wheel needs to be corrected with a diamond turning tool.
When grinding, because there are many blades, the processing is relatively stable and the processing accuracy is relatively high. A grinding machine is a finishing machine. The grinding accuracy can achieve IT6-IT4, and the surface roughness Ra can achieve 1.25-0.01um. It can reach 0.1-0.008um.
Another feature of grinding is the ability to process hardened metal materials. Therefore, grinding is often used as the final processing procedure. During grinding, the heat generated is relatively large, and sufficient cutting fluid is required for cooling. According to different functions, grinding is generally divided into three processes: inner hole grinding, cylindrical grinding, and flat grinding.
4. Metal Machining-Complex Surface Processing
Three-dimensional surface cutting processing mainly adopts copy milling and numerical control milling methods or special processing. Copy milling must have a prototype as a model. During the processing, the ball head is a copy head, which always contacts the prototype surface with a certain pressure. The movement of the profiling head is transformed into inductance, and the machining amplification controls the movement of the three axes of the milling machine to form the trajectory of the cutter head along the curved surface.
Most milling cutters use ball-end milling cutters with the same radius as the profiling head. The emergence of CNC technology provides a more effective method for surface processing. When processing on a CNC milling machine or machining center, the ball-end milling cutter is used to point by point according to the coordinates.
Value processing is complete. The advantage of using a machining center to process curved surfaces is that there is a tool magazine on the machining center, and the tools are generally more than a dozen or even more.
For rough machining and finishing of curved surfaces, different tools can be used for different curvature radii of concave curved surfaces, and appropriate tools can also be selected. At the same time, various auxiliary surfaces, such as holes, threads, slots, etc., can be machined in one clamping. , This advantage fully guarantees the relative position accuracy of each surface.
5. Metal Machining-Planing
When planing processing, the reciprocating linear motion of the purchased tool is the main cutting motion. Therefore, the speed of the planning process will not be very high, and the production efficiency will naturally be lower. Therefore, the planning process will be more stable than the milling process.
The accuracy can generally achieve IT8-IT7, the surface roughness can achieve Ra6.3-1.6um, the flatness of fine planing processing can even reach 0.02/1000, and the surface roughness is 0.8-0.4um;
6. Metal Machining-Tooth Surface Processing
Gear tooth surface processing methods are generally divided into two types, forming method and generating method. The machine tool used in the forming method to process the tooth surface is an ordinary milling machine, and the tool is a forming milling cutter, which requires two simple forming motions, the rotary motion and the linear motion of the tool.
Commonly used machine tools for tooth surface processing by the generative method are generally gear shapers and gear hobbing machines.
7. Metal Machining-Drilling and Boring Processing
On a drilling machine, rotating a hole with a drill bit is a commonly used method for aperture processing. The accuracy of drilling is relatively low, generally, only IT10 can be reached, and the surface roughness is generally 12.5-6.3um. The manufacturer’s general practice is to drill After processing is completed, reaming and reaming are carried out for semi-finishing and finishing.
Reaming uses a reaming drill, and reaming is generally processed with a reamer. The reaming accuracy is generally IT9-IT6, and the surface roughness is Ra1.6-0.4um. Whether it is reaming or reaming, the drill and reamer generally follow the axis of the original hole bottom hole, which cannot improve the position accuracy of the hole.
Boring can correct the position of the hole. Generally, it can be done directly on a boring machine and a lathe. When boring on a boring machine, the boring tool is basically the same as the turning tool. The difference is that the workpiece does not move, the cutting tool rotates, and the accuracy of boring processing Generally IT9-IT7, the surface roughness is Ra6.3-0.8mm.
8. Metal Machining- Special Processing
The so-called special processing method refers to the general term of a series of processing methods that use chemical, physical or electrochemical methods to process workpiece materials, which are different from traditional cutting processing methods.
These processing methods mainly include chemical processing (GHM), Electrochemical machining (ECH), electrochemical machining (ECMM), electric discharge machining (EDM), electrical contact machining (RHM), ultrasonic machining (USM), laser beam machining (LBM), ion beam machining (IBM), electronics Beam machining (EBM), plasma machining (PAM), electro-hydraulic machining (EHM), abrasive flow machining (AFM), abrasive jet machining (AJM), liquid jet machining (HDM) and various complex machining, etc.
Metal Machining Principles
The determination of the processing route generally follows the following principles.
① It should be able to guarantee the accuracy and surface roughness of the workpiece to be processed.
② Make the processing route the shortest, reduce the idle travel time, and improve the processing efficiency.
③Simplify the workload of numerical calculation as much as possible and simplify the processing procedure.
CNC machining (3 photos)
④ For some reusable programs, subroutines should be used.
CNC advantages and disadvantages
Numerical control processing refers to processing with numerical control processing tools. CNC index-controlled machine tools are programmed and controlled by CNC machining languages, usually G codes.
The CNC machining G code language tells the Cartesian position coordinates of the machining tool of the CNC machine tool and controls the feed speed and spindle speed of the tool, as well as the tool changer, coolant, and other functions.
Compared with manual machining, CNC machining has great advantages. For example, the parts produced by CNC machining are very accurate and repeatable; CNC machining can produce parts with complex shapes that cannot be completed by manual machining.
Numerical control machining technology is now widely promoted. Most machining workshops have CNC machining capabilities.
The most common CNC machining methods in typical machining workshops are CNC milling, CNC lathe, and CNC EDM wire cutting (electric discharge wire cutting).