Improving The Cutting Surface Precision - Mitsubishi MELDAS MDS-C1 Instruction Manual

4-3-3 Improving the cutting surface precision

If the cutting surface precision or roundness is poor,
these can be improved by increasing the speed
loop gain (VGN1, VIA) or by using the disturbance
observer function.
<Examples of faults>
• The surface precision in the 45° direction of a
taper or arc is poor.
• The load fluctuation during cutting is large,
causing vibration or surface precision defects
to occur.
POINT
(1) Adjusting the speed loop gain (VGN1)
If the speed loop gain is increased, the cutting surface precision will be improved but the machine
will resonate easily.
The final VGN1 setting should be approx. 70 to 80% of the maximum value where resonance does
not occur. (Refer to "4-2-2 (1) Setting the speed loop gain")
(2) Adjusting the speed loop leading compensation (VIA)
The VIA has a large influence on the position trackability, particularly during high-speed cutting
(generally F1000 or more). Raising the setting value improves the position trackability, and the
contour precision during high-speed cutting can be improved. For high-speed high-precision
cutting machines, adjust so that a value equal to or higher than the standard value can be set.
When VIA is set lower than the standard value and set to a value differing between interpolation
axes, the roundness may worsen (the circle may distort). This is due to differences occurring in the
position trackability between interpolation axes. The distortion can be improved by matching the
VIA with the smaller of the values. Note that because the position trackability is not improved, the
surface precision will not be improved.
(Refer to "4-2-2 (2) Setting the speed loop leading compensation")
No. Abbrev. Parameter name
SV005 VGN1 Speed loop gain 1
SV008 VIA Speed loop lead
compensation
4. Servo Adjustment
Adjust by raising the speed loop gain equivalently to improve cutting surface
precision, even if the measures differ. In this case, it is important how much the
machine resonance can be controlled, so adjust making sufficient use of
vibration suppression functions.
Set the speed loop gain.
Set this according to the load inertia size.
The higher the setting value is, the more accurate the control will be,
however, vibration tends to occur.
If vibration occurs, adjust by lowering by 20 to 30%.
The value should be determined to be 70 to 80% of the value at the time
when the vibration stops.
Set the gain of the speed loop integration control.
The standard setting is "1364". During the SHG control, the standard
setting is "1900". Adjust the value by increasing/decreasing it by about
100 at a time.
Raise this value to improve contour tracking precision in high-speed
cutting. Lower this value when the position droop vibrates (10 to
20Hz).
Y
Explanation
4 - 14
X
Setting range
1 to 999
1 to 9999