Application of FANUC 18iT System in High-precision Turning Center

The CGH46O high-precision CNC turning center developed by Beijing Machine Tool Research Institute is suitable for industries such as automotive, aerospace, military manufacturing and precision machinery manufacturing. The machine tool can complete machining processes such as car, milling, drilling, tapping, etc. in order to meet the processing requirements of high-precision, small-batch complex parts under the condition of one-time loading of processing disc parts.

1 Main features and key technologies of machine tools

The machine bed is inclined at an angle of 45°. It adopts a cylindrical rib structure and a high-quality cast iron bed, which not only facilitates heat dissipation from chip removal, but also makes the machine tool have a very high overall rigidity. The high stability of the structure design and debugging technology inhibits trace amounts. The vibration at the time of feeding basically eliminates the low-speed creep of the rectangular guide. The X, Z axis of the machine tool has high accuracy of the rolling guide pair, equipped with FANUC α series AC servo motor, and each servo axis adopts HEIDENHAIN linear scale for full closed loop control. The machine tool spindle adopts a high-precision gas hydrostatic spindle. During actual production, it must be ensured that the internal air float structure of the machine tool spindle has enough rigidity to ensure the complete manufacturing precision of the air float gap, so that the spindle can have high rigidity to meet the machine tool spindle as the Cs. Requirements for the stiffness of milling and drilling conditions when using the shaft. The machine tool is equipped with 12 workstation power cutter heads, of which 3 stations are equipped with power heads. The cutterhead has the characteristics of not only lifting the cutterhead but also achieving continuous indexing, selecting the nearest cutter, shortening the time of tool change, and high positioning accuracy. In this way, it is possible to complete the operations such as milling the plane on the outer circle, milling the arc groove on the end face, drilling the holes in the axial and radial directions, and tapping at the same time without removing the workpiece. The system can also have polar coordinate interpolation. Make up functions, processing square workpieces or grooves, etc.

2 CNC machine configuration system <br> <br> CNC system uses ultra-small ultra-thin, FANUC 18i CNC system has a high-speed 64-bit microprocessor with a network interface for complex precision lathe axis control function. The system has rich servo control functions and advanced contour interpolation technology, and can achieve smooth position movement control through CNC nano interpolation and high-speed and high-precision servo. The input/output unit uses FANUC I/O Unit MODELA. The input module is configured as AID16C; the output module is configured as AOD16C. Due to the full closed loop control of the X and Z axes, the FANUC raster interface must also be configured. The feedback resolution of the full closed-loop control scale is 0.1 μm. FANUC Czi high-precision magnetic pulse encoders are also used to perform Cs contour control of the spindle. The machine also configures the second spindle as the power axis of the power cutter head for milling, drilling and other functions.

3 Main Applications of FANUC 18iT System

3.1 Input/Output Module Settings FANUC I/O Unit The MODEL-A module is a general-purpose I/O module connected to the FANUC I/O Link. The address of the input/output signal must be set when editing the PMC program (X, Y ). AID16C is an input module. It needs to set the X address, and AOD16C is the output module. Set the Y address. When setting, pay attention to the correct setting of the group number, base number, and module name in the I/O module setting screen.

3.2 Setting of the Linear Scale <br> After the machine has been operated in a semi-closed loop, it performs full closed-loop control and debugging. Some servo parameters need to be adjusted when debugging. The X and Z axis grating feedback signals are respectively connected to JF101 and JF102 of FANUC grating interface. In the axis setting screen of FSSB, the separate interface board Ml must be set. The X axis Ml is set to 1 and the Z axis Ml is set. Is 2. In addition, some servo parameters need to be modified. For example, the 1st bit of parameter 1815 must be set to 1. On the servo parameter setting screen, parameters such as "flexible gear ratio", "position feedback pulse number", and "reference counter capacity" should be set correctly.

3.3 Setting of the Cs Contour Control Axis When performing the Cs contour control, the FANUC servo serial spindle can perform position control and interpolation in the same way as the X and Z axes. The machine can perform high-precision Cs contour control with the FANUC Czi high-precision magnetic pulse encoder mounted on the spindle of the machine tool. When installing a pair of magnetic heads of Czi high-precision magnetic pulse encoders, clearance and balance adjustments are required (Table 1).

Table 1 Parameter Settings and Meaning

Parameter number

Parameter bit

Setting value

Parameter significance

1006

O

l

Set the serial spindle controlled by Cs contour as rotation axis

1022

-

0

Set the axis attribute of the serial spindle of the Cs contour control to the rotation axis

1023

-

-1

Set serial spindle to Cs contour control axis

3704

7

l

Cs contour control effective for serial spindle

The gap between the sensor head and the magnetic teeth should be around 0.1mm. Actually, a strong signal can be obtained between 0.1mm and 0.12mm. The other two sensor heads must be in the diametrical direction to ensure that the C-axis rotates and the signals obtained in a 360-degree direction are uniform. After adjusting, it is better to observe the Lissajous figure of the X and Y signals with an oscilloscope, and the observed figure should be a full circle. It is required that the circle should keep the same size when the main shaft rotates, and the small change cannot be ignored. Otherwise, the gap is not uniform, or the two sensor heads are not in the diameter direction. After adjusting, set the parameters in Table 1 as well. In addition to the above setting adjustment, the function signals of the Cs contour control must also be processed in the PMC program to achieve the correct Cs contour control function.

3.4 Servo Adjustment <br> After the various functions of the machine tool are operated stably, in addition to the mechanical precision adjustment, the machine's servo adjustment function is also used to adjust the machining accuracy of the machine tool. Typical functions include N-pulse suppression, adjustable gain when stopped, mechanical speed feedback, and mechanical resonance suppression. The system can be used to make full use of the servo adjustment function to achieve a multiplier effect.

4 Conclusion

The CGH46O high-precision CNC turning center can realize sub-super precision machining by adopting technologies such as precision mechanical installation adjustment, CNC servo adjustment and pitch error compensation.

Table 2 Main technical parameters of the machine

Item Technical Parameters Spindle Rotation Accuracy 0.07μm Slide Linearity X-axis: 1.7μm/
150mm,
Z-axis: 2.2μm/300mm Control System Resolution 0.1μm Positioning Accuracy X-axis: ±0.6μm, Z-axis: ±0.83μm Precision Index of Machined Part (Non-Ferrous Metal) Roughness Ra0.02μm Roundness 0.26μm

We believe that by taking full advantage of our technological superiority and combining with the world's most advanced numerical control technology, we are able to manufacture first-class equipment with excellent performance that can meet the requirements of precision and ultra-precision machining.