During homing the robot has to set his zero position. Zero position is choosen as the point where all three arms of the robot are in horizontal position.
The mechanical dimensions are given by L = 0.0175m, B = 0.015m, s = 0.004m. The upper limit can be calculated as follows:
(1) tan(β) = sin(β) / cos(β) = (B - y) / L (2) cos(β) = s / y
Substitute (2) into (1) to get:
(3) L * sin(β) - B * cos(β) = -s
Using following trigonometric formulas in (3):
(4) t = tan(β / 2) (5) sin(β) = 2 * t / (1 + t^2) (6) sin(β) = (1 - t^2 / (1 + t^2)
(7) (s + B) * t^2 + 2 * L * t + (s - B) = 0
t1 = 0.2736 -> β = 30.6° t2 = -2.1157 (neg. solution)
Hence, the maximum angle the axis can turn is 90° + β ≅ 120°.