How to perform screw compensation on the machine tool of Siemens 840D CNC system - News - Global IC Trade Starts Here Free

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The machine tool of Siemens 840D system carries out the screw compensation. To enter the compensation interface, it mainly lies in the compilation of compensation files. Pay attention to the following points:
1. Modify the parameter MD38000 of the axis to be compensated, that is, the screw pitch error compensation point (SRAM). After modification, the user memory area inside the NC will be newly allocated when the system is powered off, and the user data of all buffers will be Deleted and newly allocated, such as: drive data, MMC data, tool compensation, partial programs, machine compensation tables, and so on.
Therefore, before modifying MD38000, you must make a backup before NC reset.
2. Export compensation data, generate ARC file or MPF program,
In the tree view of hmi's "DataOut" window, select "NC-active-data" → "Meas-system-error-comp" → "Measurement" System error compensation—axis 1” (axis x corresponds to the axis number of the axis to be pitch compensated), output the file to “Document” in the format “with CR+LF punched tape” and name it (here named “ AX1_EEC").
Note: The premise of this operation is that "NC-active-data" has been selected in "Data Selection", otherwise the corresponding compensation file cannot be found in "DataOut".
3. Enter the compensation data, edit the ARC file and select "Archive" → "AX1_EEC" in the tree view of the "DataOut" / "DataIn" / "Data Management" window. Open the file with the "input" key, enter the compensation data, save and close the editor.
Note: The check code should be deleted when editing the patch file.
The example compensation file contents are as follows:
%_N_AXIS1_EEC_INI
$AA_ENC_COMP[0,0,AX1]=0.024//
$AA_ENC_COMP[0,1,AX1]=0.020
$AA_ENC_COMP[0,2,AX1]=0.015
$AA_ENC_COMP[0,3,AX1]=0.014
......
$AA_ENC_COMP[0,9,AX1]=-0.004
$AA_ENC_COMP_STEP[0,AX1]=100.0//compensation interval: 100mm
$AA_ENC_COMP_MIN[0,AX1]=-100.0//Compensation starting position: 100mm
$AA_ENC_COMP_MAX[0,AX1]=-1000.0//Compensation termination position: 1200mm
$AA_ENC_COMP_IS_MODULO[0,AX1]=0
M17
Note that in the above compensation value, the absolute value is directly added. The positive and negative directions of the laser setting are the same as the positive and negative directions of the machine tool movement. The compensation value is the measured error value, which is corrected for positive and negative for negative.
4. Import the compensation data ARC file to the system setting MD32700=0, and make the data take effect.
Select "ReadStart-upArchive" in the "Series Start-up" window →
"AX1_EEC" and start running the compensation data ARC file.
5. Compensation data is valid. Set MD32700=1, NCKReset. After the axis returns to the reference point, the new pitch compensation value takes effect.
6. Pitch compensation
The pitch compensation function of the 840D CNC system is an absolute compensation method, and the pitch compensation is performed on the axis. We set the compensation starting point position a, the compensation end point position b, and the compensation interval distance c, then the number n of intermediate points that need to be interpolated, where n=1+(ba)/c.
The specific steps are as follows:
1) Set the axis data MD38000MM_ENC_COMP_MAX_POINTS[t]=n. Modifying this parameter will cause the NCK memory to be reallocated. So after the modification, you should make a backup of the NC under the service menu. (t=axis number of the compensated axis)
2) After the NCK reset is performed on the system, the “M4400” alarm will appear, indicating that the axis parameters are lost. At this time, the NC backup load under the 1) step is loaded into the NC system.
3) Copy "CEC_DATA" under the Nc-Active-Data menu to a newly created backup document directory *.MDN.
4) Find and open the compensation file form in the new directory, and change the corresponding compensation point directly in the table according to the data measured by the surveyor. Save and close the editor.
5) Set the axis parameter MD32700ENC_COMP_ENABLE=0 and load the modified compensation table into the NC system.
6) Set the axis parameter MD32700ENC_COMP_ENABLE=1 to do an NCK reset.
7) The axis returns to the reference point and the new compensation data is valid.
You can see the data changes under "Diagnostics" ------ "Servicedisplay" ------ "ServiceAxis" interface.
Pitch compensation acquisition compensation data generally passes through the laser detection instrument, usually going through two steps, one single step, two more steps. The former is to establish a compensation curve based on the machine axis error, and the latter is to detect the backlash of the shaft, positioning accuracy, repeatability, and positional deviation.
Taking the actual operation of PAMAφ140 after an electrical transformation as an example, the X-axis travel is -50mm~5870mm, the compensation starting point position is a=0, the compensation end point position is b=5800, and the compensation interval distance is c=200, then interpolation is required. The number of intermediate points is based on n = 1 + (ba) / c, that is, n = 30, and the number of cycles p = n - 2, that is, p = 28.
Before the single step, the reference point must be returned to the axis to ensure the uniqueness of the reference point.
After the process is completed, the error value detected by the laser interferometer can be edited into the compensation table. Generally speaking, in the full-closed mode of operation with the grating ruler as the detecting element, the compensation data should not be larger than 1 mm. In the semi-closed mode of operation with the motor's own encoder as the detection component, the compensation data is not subject to this limitation and can be filled in according to the actual situation. Many machine tools may change the gear ratio after long-term use due to gear wear and other reasons. It is recommended to check the gear ratio of the motor with a laser interferometer before making compensation, especially for the shaft with only semi-closed mode. To reduce the compensation error.
Finally we axis back to the reference point. In the axis adjustment interface of the 840D diagnosis section, it can be clearly seen that the pitch compensation is effective in one direction, and the data of the pitch compensation is valid in the reverse direction.