One, the difference is as follows:
1, the structure is different
Three-axis vertical CNC machining centers are three axes of linear motion in different directions, respectively up and down, left and right, and front and back, up and down is the direction of the spindle, which can rotate at high speeds; four-axis vertical machining centers are based on the three-axis addition of a rotary axis, that is, the horizontal plane can be rotated 360 degrees, not high-speed rotary The four-axis vertical machining center is based on the three-axis, that is, the horizontal plane can be rotated 360 degrees, not high-speed rotation.
2, the use of different ranges
Three-axis machining center machining center is the most widely used, three-axis machining center can be a simple plane processing, and can only be processed at a time on a single side, three-axis machining centers can be very good processing, aluminum, wood, disappearing mold and other materials.
The use of four-axis machining centers less than three-axis machining centers, it can make the product through the rotation to achieve multi-faceted machining, greatly improving the processing efficiency, reducing the number of clamping. Especially the processing of cylindrical parts more convenient. And can reduce the repeated clamping of the workpiece, improve the overall machining accuracy of the workpiece, and help to simplify the process, improve productivity. Shorten the production time.
Two, programming methods:
1, analyze the parts drawings
According to the parts drawings, through the parts of the material, shape, size and accuracy, surface quality, roughness, and heat treatment and other requirements to analyze, clarify the processing content and play request, select the appropriate CNC machine tool.
This step includes:
1) Determine the part should be arranged in which category or which machine tool for processing.
2) What kind of fixture or what kind of mounting position method.
3) Determine what kind of tool or how many tools to use for machining.
4) to determine the machining route, that is, the choice of the tool point, the program starting point (also known as the starting point of machining, machining starting point is often coincident with the tool point), the route of the tool, the end of the program (the end of the program is often coincident with the start of the program).
5) Determine the depth and width of cut, feed rate, spindle speed and other cutting parameters.
2, determine the process
In the analysis of the parts on the basis of drawings, to determine the parts of the machining process (such as determining the positioning method, the selection of fixtures and fittings, etc.) and machining routes (such as determining the tooling points, tool routes, etc.), and determine the amount of cutting. Processing involves more content, the main points are as follows:
1) Determination of machining methods and process routes In accordance with the principle of giving full play to the function of the CNC machine tool, to determine a reasonable machining methods and process routes.
2) tool, fixture design and selection of CNC machining tools to determine the comprehensive consideration of the processing method, cutting amount, workpiece materials and other factors to meet the requirements of easy adjustment, good rigidity, high precision, durability and so on. CNC machining fixture design and selection, should be able to quickly complete the workpiece positioning and clamping process to reduce auxiliary time.
And try to use a combination of fixtures to shorten the production lead time. In addition, the fixture used should be easy to install on the machine tool, easy to coordinate the dimensional relationship between the workpiece and the machine coordinate system.
3) the choice of tool point tool point is the starting point of the program execution, the choice should be to simplify programming, easy to find the right, easy to check in the process of machining, reduce machining errors as a principle.
The tool setting point can be set on the workpiece to be machined, can also be set on the fixture or machine tool. In order to improve the machining accuracy of the parts, the tool setting point should be set as far as possible in the parts of the design reference or process reference.
4) Determination of the machining route machining route to ensure that the precision of the machined parts and surface roughness requirements; try to shorten the tool route, reduce the empty tool travel; help to simplify the numerical calculations, reduce the number of program segments and programming workload.
5) the determination of the amount of cutting cutting, including the depth of cut, spindle speed and feed rate. The specific value of the cutting amount should be based on the provisions of the manual of the CNC machine tool, the material to be processed workpiece, processing content and other process requirements, and combined with empirical data to consider.
6) Determination of coolant Determine whether the machining process needs to provide coolant, whether or not you need to change the knife, when to change the knife.
Since the CNC machining center when machining parts. Work processes are very centralized. In a clamping, often need to complete roughing, semi-finishing and finishing. In determining the process should be carefully and reasonably arrange the machining sequence of each process to improve machining accuracy and productivity.
3, numerical calculation
Numerical calculation is based on the geometric dimensions of the parts and determine the machining route, calculate the input data required for CNC machining. General CNC systems have linear interpolation, circular interpolation and tool compensation functions. For the contour machining of parts with simple shapes (e.g., parts composed of straight lines and circular arcs), the starting point and end point of the geometric elements are calculated, as well as the center of the circular arc and the coordinate values of the intersection or tangent point of the two elements.
The shape of complex parts (such as non-circular curves, surfaces composed of parts), with a straight line segment or arc segment through the proximity of the node coordinate values calculated by the accuracy requirements. This situation requires the use of computers, the use of relevant software for calculation.
4, the preparation of machining programs
After the completion of the process and mathematical processing work, should be based on the use of machine tools, CNC system instructions, the format of the program segment, process, numerical calculations, as well as auxiliary operating requirements, in accordance with the CNC system program instructions and format requirements, segment by segment, the preparation of the parts machining program.
Prior to programming, programmers should understand the performance of CNC machine tools, functions and program instructions to write the correct CNC machining program.
5, program input
To write a good program, input to the CNC system, commonly used methods are the following two:
1) in the CNC milling machine operating panel for manual input;
2) the use of the DNC (data transfer) function, the first program into the computer, and then by the special CNC transmission software. The machining program into the CNC system . Then call up the execution . Or transfer while processing.
6, program verification
Prepared program, the program must be run to check. Machining program should generally be verified and test cutting to be used for formal processing. Can be used to empty the knife, idle drawing and other ways to check the correctness of the machine tool trajectory and action.
In the graphic display function and dynamic simulation function of the CNC machine tool or CAD/CAM software, with graphic simulation of tool cutting workpiece inspection method is more convenient. But these methods can only check out the movement trajectory is correct, can not check the machining accuracy of the machined parts.