3.6. Allowable Load of Wrist Axis

The load, which will be applied to the mechanical interface of robot's wrist axis, is restricted by allowable weight, allowable load torque and allowable moment of inertia.

Allowable weight :

Table 3‑2 Allowable weight

Robot model	Allowable weight
HA006	58.8 N (6kgf) or less
HA020	196 N (20kgf) or less
HA010L	98 N (10kgf) or less

Allowable load torque

Table 3‑3 Allowable load torque

Robot model	Allowable load torque
	R2 axis rotation	B axis rotation	R1 axis rotation
HA006	11.8 N·m (1.2 kgf·m) or less		5.9 N·m (0.6 kgf·m) or less
HA020	39.2 N·m (4 kgf·m) or less		19.6 N·m (2 kgf·m) or less
HA010L	24.5 N·m (2.5 kgf·m) or less		10.5 N·m (1.1 kgf·m) or less

Allowable moment of inertia

Table 3‑4 Allowable moment of inertia

Robot model	Allowable moment of inertia
	R2 axis rotation	B axis rotation	R1 axis rotation
HA006	0.17kgm²(0.017kgf m·s²)		0.06kgm²(0.006kgf·m·s²)
HA020	0.75kgm²(0.075kgfms²)		0.25kgm²(0.025kgfms²)
HA010L	0.64kgm²(0.064kgfms²)		0.15kgm²(0.015kgfms²)

Refer to the Table [3-2]~[3-4] so that the load does not exceed the allowed condition.

[Fig. 3.9]~[3.10] shows the allowable range where the material point can be located when you think that the assembled load has a material point. But because the actual load (End Effector) rarely is on the material point, calculate the moment of inertia of each axis to make the evaluation. The following shows an example of considering the assembling load as the material point.

(Ex) Robot type is【 HA006 】 and the weight of the load is 40Kg

n Allowable center location from center of R1 axis

① Allowable center location from allowable torque

LR1 ≤ (Allowable torque) / (Load weight)

LR1 = 88.3 N·m / (40Kg×9.8 m/s2) = 0.225 m

② Allowable center location from allowable moment of inertia

LR1 ≤ (Allowable moment of inertia/Load weight)1/2

= (1.62 kg·m2 / 40 kg )1/2 = 0.201 m( ＜ 0.225 m)

From the above results, the distance from the center of R1 axis is limited by the allowable moment of inertia and must be within 0.201 m.

n Allowable center location from center of B axis

(The center of the B axis of this robot is on the same axis and also the allowable load torque and allowable moment of inertia have the same B axis and R2 axis values. Therefore if the allowable conditions of B axis are satisfied, the same will be satisfied for R2 axis.)

① Allowable center location from allowable torque

LB ≤ (Allowable torque) / (Load weight)

LB = 176.5 N·m / (40Kg×9.8 m/s2) = 0.450 m

② Allowable center location from allowable moment of inertia

LB ≤ (Allowable moment of inertia/Load weight)1/2

= (6.48 kg·m2 / 40 kg )1/2 = 0.402 m( ＜ 0.450 m)

From the above results, the distance from the center of B axis is limited by the allowable moment of inertia and must be within 0.402 m.

n Torque Map

Figure 3.10 Wrist axis torque map [HA006]

Figure 3.11 Wrist axis torque map [HA020]

Figure 3.12 Wrist axis torque map [HA010L]

3.6. Allowable Load of Wrist Axis​

3.6. Allowable Load of Wrist Axis