Replacing The Harmonic Drive; Replacement Period - Yamaha YK-X Series User Manual

5

Replacing the Harmonic Drive

The YK-XG series robots listed in Table 5-1 use a harmonic drive as the speed
reduction gear for the X, Y and R axes. Harmonic drives need to be replaced after
a specified operation time. Use the guideline explained below to determine the
replacement period and replace the harmonic drive periodically. Since the YK-
XG series robots listed in Table 5-1 use long-life harmonic grease, it is not neces-
sary to replace the harmonic grease.
5-1

Replacement period

The harmonic drive replacement period is determined by the total number of
turns of the wave generator used in the harmonic drive. It is recommended to
replace the harmonic drive when the total number of turns has reached 8.4×10
(at ambient operating temperatures of 0°C to +40°C). This means that the re-
placement period will differ depending on the following operating conditions. If
the robot operation duty ratio is high or the robot is operated in environments at
higher temperatures, the harmonic drive should be replaced earlier.
Replacement period = 8.4×10
where
For example, when the robot is used under the following conditions, the replacement
period for the X-axis harmonic drive of the YK500XG can be calculated as follows.
Replacement period = 8.4×10
YK500XG, YK600XG
YK600XGH, YK700XG, YK800XG, YK900XG, YK1000XG
Recommended "Screw Lock": LOCTITE 262 (made by Henkel Corporation)
Use only YAMAHA genuine bolts or JIS B 1176 hex socket head bolts
(strength class: JIS B 1051 12.9).
n : Number of axis movements per minute
θ
: Average turn per axis movement
N : Speed reduction ratio
h : Operation time per day
D : Operation days per year
n : 10
θ
: 0.25
N : 80
h : 24 hours per day
D : 240 days per year
= 8.4×10
= 12.2 years
Table 5-1 Harmonic drive speed reduction ratio
Robot model
Table 5-2 Bolt tightening torque
Bolt size
M3 button head bolt
M4 set screw
M3
M4
M5
M6
M8
M10
5-9
CHAPTER 5 Periodic Inspection
8
/(n×60×h×D×N×θ) years
8
/(n×60×h×D×N×θ)
8
/(10×60×24×240×80×0.25)
Tightening torque (kgfcm)
14
20
20
46
92
156
380
720
X-axis Y-axis R-axis
80 80 30
80 80 50
Tightening torque (Nm)
1.4
2.0
2.0
4.5
9.0
15.3
37
71
8