CNC machining refers to the machining performed with CNC machining tools. CNC index-controlled machine tools are programmed and controlled by CNC machining language, usually G code. The CNC machining G code language tells the CNC machine tool which Cartesian position coordinates to use for the machining tool, and controls the tool feed rate and spindle speed, as well as tool changer, coolant and other functions.
General CNC machining usually refers to computer digital control precision machining, CNC machining lathes, CNC machining milling machines, CNC machining boring and milling machines, etc.
CNC milling produces excellent machined parts from metals magnesium alloys, aluminum alloys, stainless steel and plastics.
For cylindrical parts such as pins, shafts, and spacers, or parts with general rotational symmetry, "turn" them on a CNC lathe.
|Processing Type||Minimum Wall Thickness||Aperture||Minimum size||Maximum size|
|3-axis CNC milling||1mm||+/- 0.025 mm||1mm x 2mm x 2mm||1100mm x 800mm x 650mm [x,y,z]|
|4-axis CNC milling||1mm||+/- 0.025 mm||1mm x 2mm x 2mm||1100mm x 800mm x 650mm [x,y,z]|
|5-axis CNC milling||1mm||+/- 0.025 mm||1mm x 2mm x 2mm||1100mm x 800mm x 650mm [x,y,z]|
Machining tolerance is +/- 0.001mm. Thickness >0.51mm; Undercut: Square Profile, Full Radius, Dovetail Profile
|Processing Type||Minimum Thickness||Minimum diameter||Maximum size||Angle|
|2-axis CNC turning||0.25mm||0.2mm||260mm*1100mm||30°|
For cylindrical parts such as pins, shafts, and spacers, or parts with general rotational symmetry, "turning" them on a lathe is often the easiest and most cost-effective option. Machining tolerance is +/- 0.01mm.
The CNC lathe feed processing path refers to the path that the turning tool starts to move from the tool setting point (or the fixed origin of the machine tool) until it returns to this point and ends the processing program, including the cutting processing path and the cutting-in and cutting-out of the tool Equal non-cutting idle travel path.
The feed route of finishing is basically carried out along its part contour sequence. Therefore, the key point of determining the feed route is to determine the feed route of rough machining and idle travel.
In CNC lathe processing, the determination of the processing route generally follows the following principles.
①Should be able to ensure the accuracy and surface roughness of the workpiece to be processed.
②Make the processing route the shortest, reduce the idle travel time, and improve the processing efficiency.
③ Try to simplify the workload of numerical calculation and simplify the processing program.
④For some repetitive programs, subroutines should be used
CNC machining has the following advantages:
①The number of tooling is greatly reduced, and complex tooling is not required for machining parts with complex shapes. If you want to change the shape and size of the part, you only need to modify the part processing program, which is suitable for new product development and modification.
②Stable processing quality, high processing precision and high repeatability, which meet the processing requirements of aircraft.
③The production efficiency is high in the case of multi-variety and small batch production, which can reduce the time for production preparation, machine tool adjustment and process inspection, and the cutting time is reduced due to the use of the optimal cutting amount.
④It can process complex profiles that are difficult to process by conventional methods, and even process some unobservable processing parts.
The disadvantage of CNC machining is that the machine tool is expensive and requires a high level of maintenance personnel.
1. Analyze the machining drawings and determine the machining process
According to the processing drawings provided by the customer, the technicians can analyze the shape, dimensional accuracy, surface roughness, workpiece material, blank type and heat treatment conditions of the parts, and then select the machine tool, tool, determine the positioning and clamping device, processing method, processing sequence and cutting amount.
In the process of determining the machining process, the command function of the CNC machine tool used should be fully considered, the efficiency of the machine tool should be fully utilized, and the processing route should be reasonable, the number of tool passes and the processing time should be short.
2. Reasonably calculate the coordinate value of the tool path path
According to the geometric size of the machined part and the programmed coordinate system, the movement path of the tool path center is calculated, and all the tool position data are obtained.
The general CNC system has the functions of linear interpolation and circular interpolation. For the contour processing of planar parts with relatively simple shapes (such as parts composed of straight lines and circular arcs), it is only necessary to calculate the starting point and end point of geometric elements. , the center of the arc (or the radius of the arc), the coordinate value of the intersection or tangent point of two geometric elements. If the CNC system has no tool compensation function, the coordinate value of the motion path of the tool center should be calculated.
For parts with complex shapes (such as parts composed of non-circular curves and curved surfaces), it is necessary to use straight line segments (or arc segments) to approximate the actual curve or surface, and calculate the coordinates of its nodes according to the required machining accuracy value.
3. Write part CNC machining program
According to the tool path of the part, the tool movement path data and the determined process parameters and auxiliary actions are calculated. The programmer can write the part processing program segment by segment according to the function instructions and block format specified by the CNC system used. When writing, keep in mind:
First, the standardization of program writing should be easy to express and communicate;
Secondly, on the basis of being fully familiar with the performance and instructions of the CNC machine tools used, the skills of using each instruction and the skills of programming blocks.