CNC machining center needs to do these things well for metal cutting

First, the turning movement and the formed surface

Turning movement: In the cutting process, the workpiece and the tool must be cut relative to each other to remove excess metal. The movement of the excess metal on the workpiece by the turning tool on the lathe is called turning motion, which can be divided into main movement and advancement. Give exercise.

Feed motion: The new cutting layer is continuously put into motion. The feeding motion is the motion along the surface of the workpiece to be formed, which can be continuous or intermittent. For example, the horizontal lathe continuously moves during the turning tool's movement, and the workpiece's feeding motion on the head planer is intermittent.

The surface formed on the workpiece: During the cutting process, the machined surface, the machined surface, and the surface to be machined are formed on the workpiece. A machined surface is a new surface that has formed from the removal of excess metal. The surface to be processed refers to the surface on which the metal layer is cut. The machined surface is the surface on which the turning edge of the turning tool is being turned. CNC machining part

Main motion: directly cut off the cutting layer on the workpiece and transform it into chips, thus forming the movement of the new surface of the workpiece, called the main motion. When cutting, the rotational motion of the workpiece is the main motion. Usually, the speed of the main motion is higher, and the cutting power consumed is more significant. CNC  turning part

 
Second, the cutting amount of the machining center refers to the cutting depth, feed rate, and cutting speed.

(1) Cutting depth: ap = (dw - dm) / 2 (mm) dw = diameter of the unmachined workpiece dm = diameter of the machined workpiece, the depth of cut is what we usually call the amount of knife.

Selection of cutting depth: The cutting depth αp should be determined according to the machining allowance. When roughing, except for the remaining allowance, the roughing allowance should be cut off as much as possible. This not only can ensure the product of cutting depth, feed rate ƒ, and cutting speed V large under the premise of ensuring a certain degree of durability, but also can reduce the number of passes, and want to learn UG numerical control programming in QQ group 304214709 can receive data. In the case of excessive machining allowance, insufficient rigidity of the processing system, or insufficient blade strength, it should be divided into two or more passes. At this time, the cutting depth of the first pass should be taken larger, which can account for 2/3 to 3/4 of the total allowance, and the cutting depth of the second pass should be smaller to obtain the finishing process—smaller surface roughness parameter values ​​and higher machining accuracy.

When the surface of the cutting part has hard-hardened materials such as cast, forged, or stainless steel, the cutting depth should exceed the hardness or chill layer to avoid cutting the cutting edge on the problematic or chill layer.

(2) Selection of feed amount: the relative displacement of the workpiece and the tool in the direction of the feed motion, in units of mm per revolution or reciprocation of the workpiece or tool. After the depth of cut is selected, a more significant feed rate should be chosen as much as possible. A reasonable feed rate value should ensure that the machine and tool are not damaged by too much cutting force. The deflection of the workpiece caused by the cutting force does not exceed the allowable value of the workpiece precision, and the surface roughness parameter value is not too large. When roughing, the limit of the feed is mainly the cutting force. When semi-finishing and finishing, the limit of the feed is primarily the surface roughness.

(3) Selection of cutting speed: The instantaneous speed of a point on the tool's cutting edge relative to the surface to be machined in the main moving direction during the cutting process; the unit is m/min. When the cutting depth αp and the feed amount ƒ are selected, the maximum cutting speed is selected based on some, and the development direction of the cutting process is high-speed machining.

 

Third, the roughness mechanical concept

In mechanics, roughness refers to the smaller pitches' micro-geometric properties, peaks, and valleys on the machined surface. It is one of the problems of interchangeability research. Surface roughness is generally formed by the processing methods employed and other factors, such as friction between the tool and the part's surface during processing, plastic deformation of the surface layer metal during chip separation, and high-frequency vibration in the processing system. Due to the difference between the processing method and the material of the workpiece, the surface to be processed leaves a mark with a difference in depth, density, shape, and texture. Surface roughness is closely related to mechanical properties, wear resistance, fatigue strength, contact stiffness, vibration, and noise of mechanical parts. It has an essential impact on mechanical products' service life and reliability.

 

Fourth, the rough representation

After the part's surface has been machined, it looks smooth and uneven. Surface roughness refers to the microscopic geometric features of the smaller pitches and tiny peaks and valleys on the surface of the machined part, which are generally formed by the processing method and other factors taken. The function of the surface of the part is different, and the required surface roughness parameter values ​​are also different. The surface roughness code is marked on the part drawing to illustrate the surface characteristics that must be achieved after finishing the surface. There are three types of surface roughness height parameters:

1. Outline arithmetic mean deviation Ra

The arithmetic mean of the absolute distance between the point on the contour along the measurement direction (Y direction) and the reference line over the length of the sample.

2, micro unevenness 10 points height Rz

Refers to the sum of the average of the five most considerable contour peak heights and the average of the five most enormous contour valley depths within the sampling length.

3, the maximum height of the contour Ry

The distance between the highest peak line and the profile's bottom line over the sample's length.

Ra. is mainly used in the general machinery manufacturing industry.

 

Fifth, The effect of roughness on the performance of the part

The surface quality after machining the workpiece directly affects the workpiece's physical, chemical, and mechanical properties. The work performance, reliability, and service life of the workpiece depend primarily on the surface quality of the central part. Generally, essential critical parts' surface quality requirements are higher than ordinary parts because parts with good surface quality will significantly improve their wear, corrosion, and fatigue resistance.

 

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