Yamaha YK-X Series, User Manual

Page: 131 / 178

5-9
CHAPTER 5 Periodic Inspection
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
8
(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
8
/(n
×
60
×
h
×
D
×
N
×θ
) years
where 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
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.
n : 10
θ
: 0.25
N : 80
h : 24 hours per day
D : 240 days per year
Replacement period = 8.4
×
10
8
/(n
×
60
×
h
×
D
×
N
×θ
)
= 8.4
×
10 8 /(10
×
60
×
24
×
240
×
80
×
0.25)
= 12.2 years
Robot model
YK500XG, YK600XG
YK600XGH, YK700XG, YK800XG, YK900XG, YK1000XG
80
80
80
80
30
50
X-axis Y-axis R-axis
Table 5-1 Harmonic drive speed reduction ratio
Table 5-2 Bolt tightening torque
Bolt size Tightening torque (kgfcm) Tightening torque (Nm)
M3 button head bolt 14
20
1.4
M3 20 2.0
M4 46 4.5
M5 92 9.0
M6 156 15.3
M8 380 37
M10 720 71
M4 set screw 2.0
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).