What is five-axis machining?
Five-axis machining, as the name suggests, is a type of CNC machine tool machining. It involves three translation axes (x , y , and z) plus any two rotary axes, and is considered the only means of machining impellers, blades, marine propellers, heavy-duty generator rotors, steam turbine rotors, and large diesel engine crankshafts. Five-axis machine tools, also known as five-axis machining centers, can machine different sides of a workpiece without changing its position on the machine tool, greatly improving the machining efficiency of prismatic parts.
△ A five-axis machining process for a " stainless steel banana " showcased by an international machine tool brand.
Five-axis machine tools have various mechanical structures, but they mainly fall into the following categories:
Compared to traditional three-axis machine tools, five-axis machine tools have many advantages, such as improved cutting conditions, avoidance of tool interference, one-time clamping, improved machining quality and efficiency, simplified production management, and shortened new product development cycle.
Due to the high price of five-axis machine tool systems and the difficulty in creating NC programs, they are difficult to apply to the general public. However, with the breakthrough development of computer-aided design ( CAD ) and computer-aided manufacturing (CAM) systems, domestic five-axis machine tools have also made breakthrough progress.
True or false five-axis
A CNC machine tool with five linked axes cannot be simply called a five-axis machine tool. Similarly, a CNC system that can control five axes cannot be called a five-axis CNC system.
To determine whether it is a true five-axis machine tool and a five-axis CNC system, the first thing to do is to see if it has RTCP functionality.
RTCP , short for Rotational Tool Center Point , literally means " rotational tool center . " RTCP has the following characteristics:
1. Perform feed control based on the actual cutting point of the tool;
2. Forward-looking control for five axes;
3. Capable of handling vertical, tilted, and eccentric milling heads;
4. " Virtual Spindle " : Orients a specific axis to the tool axis to perform drilling and retraction operations;
5. Coordinate rotation and/or coordinate transformation for five axes;
6. Rotation of the reference coordinate system ( G194 ): Applied to machining programs and those movements originating from JOG or handwheels;
Machine tools without RTCP interpolation function perform interpolation calculations on the tool rotation center, i.e., the tool axis point. However, machine tools with RTCP function enabled use the tool tip point. The difference in machining effect is shown in the figure below:
RTCP calibration
The machining and assembly of mechanical components can cause deviations between the rotary axes and the theoretical design. For example, theoretically, the two rotary axes of a dual-rotary-table five-axis machine tool are usually designed to intersect and be perpendicular, with no spatial distance between them. However, in reality, they may not intersect or be perpendicular.
RTCP parameters are structural parameters that describe the relative positions of two rotary axes of a five-axis machine tool. The measurement accuracy of the five-axis structural parameters directly determines the quality of the RTCP function, thus affecting the positioning accuracy of the tool center point. Therefore, the precise measurement of the structural parameters of a five-axis machine tool is of great significance.
Traditional manual measurement has the following defects and limitations:
( 1 ) It is difficult to measure the axial direction of two rotation axes. It is assumed that the two axes are parallel to the corresponding coordinate axes and orthogonal to each other. This is the premise of the manual measurement method. However, in reality, the two axes are not necessarily parallel to the coordinate axes, nor are they necessarily orthogonal to each other. This measurement premise cannot be guaranteed, which will lead to measurement errors.
( 2 ) When measuring the structural parameters of the dual rotary table RTCP , the drive axis is required to rotate 90° in the positive or negative direction . Not all machine tools have this angle stroke.
( 3 ) The operation steps are complicated, the degree of automation is low, and the quality of the measurement results is often closely related to the experience of the machine tool testers.
To address the limitations and inaccuracies of manual measurement, maximize the automation and standardization of measurements, and achieve precise control of the center point of a rotary tool, Shenzhen Zowell's high-performance trajectory motion control card ADT-09 series has developed an RTCP fitting calibration algorithm. Through data processing in the measurement module, it can accurately calculate the direction and offset of the rotation axis, overcoming the limitations of manual measurement of the rotation axis direction and insufficient accuracy, and achieving precise control of the center point of the rotary tool.
The ADT-09 series RTCP model also supports non-orthogonal five-axis machine tool structures, supporting various situations such as arbitrary direction of the rotation axis, orthogonal and non-orthogonal, intersecting and non-planar rotation axes.
ZW3D ADT-8969G1 Motion Control Card
Application Case Sharing
So how does the Zowell ADT-09 series motion control card leverage its RTCP function in specific applications ?
When RTCP meets visual dispensing
How to achieve dual-station, high-precision, and high-efficiency glue dispensing for mobile phone mid-frame tilting at any angle?
Typically, in dispensing processes, to control factors such as the amount of adhesive, the dispensing nozzle must maintain a fixed height above the workpiece. For planar dispensing, only the Z- axis height needs to be maintained to achieve trajectory control and dispensing valve control. However, in situations like the following, a complete solution becomes impossible—
The ADT-09 series withstood this test, cleverly utilizing the customer's vision system and laser height measurement system to obtain high-precision calibration data. Combined with calibration error compensation functions specifically designed for five-axis equipment, such as pitch compensation and AC orthogonal compensation, it uses the RTCP algorithm to realize a dual-station, high-precision, and high-efficiency dispensing system for mobile phone mid-frame tilt at any angle.
When RTCP meets Focal
How to control a Focal laser height meter to follow and collect the outline of a mobile phone at equal intervals?
This project uses the 5D RTCP algorithm to control the Focal laser height gauge to follow and collect the outline of the mobile phone at equal intervals. The 5- axis platform A- axis is in a 0°/45° orientation, allowing the Focal to scan around the outline of the front surface of the mobile phone. The 3D simulation software can use the Focal data to fit and depict the actual 3D effect to observe the flatness of the front and sides of the mobile phone.
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