A robot arm for end-effector motion, wherein the robot arm comprises: - a first actuator configured to rotate an inner arm-assemblage about a first axis of rotation (29, 29A), the inner arm-assemblage being connected to an outer arm-linkage (17, 18; 18) pivotably arranged around a second axis of rotation, the outer arm-linkage being connected to an end-effector platform, thereby forming a first kinematic chain from the first actuator to the end-effector platform, which gives a first degree of freedom for positioning the end-effector platform; - a second actuator (5; 5b) configured to rotate the outer arm-linkage (17, 18; 18) around the second axis of rotation, thereby forming a second kinematic chain from the second actuator to the end-effector platform, which gives a second degree of freedom for positioning the end-effector platform; - a third actuator (6; 6b, 512) configured to rotate a shaft around a third axis of rotation (33; 99) such that the outer arm-linkage (17, 18; 18) is rotated via a joint (16; 161), thereby forming a third kinematic chain from the third actuator (6; 6b) to the end-effector platform, which gives a third degree of freedom for positioning the end-effector platform; - a fourth actuator (50; 150) and a fourth kinematic chain configured to transmit a movement of the fourth actuator to a corresponding orientation axis for an end-effector, the fourth kinematic chain comprising: an orientation linkage (52, 57, 59; 202, 204, 207, 209; 284, 286; 251, 256, 258) mounted to the inner arm-assemblage via at least one bearing (53, 55; 206), and an orientation transmission (64B, 64A, 216; 64C, 64D, 64E; 100, 64A; 281, 279, 275; 260, 262, 264, 266, 271, 270) mounted to the end-effector platform, wherein the orientation linkage comprises an end-effector rotation link (59; 209; 258; 281) and end-joints (58, 60; 208, 210; 257, 259; 257, 259; 282, 280) of the end-effector rotation link, each end-joint providing at least two degrees of freedom - a first actuator configured to rotate an inner arm-assemblage about a first axis of rotation (29, 29A), the inner arm-assemblage being connected to an outer arm-linkage (17, 18; 18) pivotably arranged around a second axis of rotation, the outer arm-linkage being connected to an end-effector platform, thereby forming a first kinematic chain from the first actuator to the end-effector platform, which gives a first degree of freedom for positioning the end-effector platform; - a second actuator (5; 5b) configured to rotate the outer arm-linkage (17, 18; 18) around the second axis of rotation, thereby forming a second kinematic chain from the second actuator to the end-effector platform, which gives a second degree of freedom for positioning the end-effector platform; - a third actuator (6; 6b, 512) configured to rotate a shaft around a third axis of rotation (33; 99) such that the outer arm-linkage (17, 18; 18) is rotated via a joint (16; 161), thereby forming a third kinematic chain from the third actuator (6; 6b) to the end-effector platform, which gives a third degree of freedom for positioning the end-effector platform; - a fourth actuator (50; 150) and a fourth kinematic chain configured to transmit a movement of the fourth actuator to a corresponding orientation axis for an end-effector, the fourth kinematic chain comprising: an orientation linkage (52, 57, 59; 202, 204, 207, 209; 284, 286; 251, 256, 258) mounted to the inner arm-assemblage via at least one bearing (53, 55; 206), and an orientation transmission (64B, 64A, 216; 64C, 64D, 64E; 100, 64A; 281, 279, 275; 260, 262, 264, 266, 271, 270) mounted to the end-effector platform, wherein the orientation linkage comprises an end-effector rotation link (59; 209; 258; 281) and end-joints (58, 60; 208, 210; 257, 259; 257, 259; 282, 280) of the end-effector rotation link, each end-joint providing at least two degrees of freedom an orientation linkage (52, 57, 59; 202, 204, 207, 209; 284, 286; 251, 256, 258) mounted to the inner arm-assemblage via at least one bearing (53, 55; 206), and an orientation transmission (64B, 64A, 216; 64C, 64D, 64E; 100, 64A; 281, 279, 275; 260, 262, 264, 266, 271, 270) mounted to the end-effector platform, wherein the orientation linkage comprises an end-effector rotation link (59; 209; 258; 281) and end-joints (58, 60; 208, 210; 257, 259; 257, 259; 282, 280) of the end-effector rotation link, each end-joint providing at least two degrees of freedom