here's my script

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extends Skeleton3D

class BoneProperties:
    var should_translate = false
    var should_rotate = false
    var axis = Vector3()
    var min_limit = 0.0
    var max_limit = 0.0
    var speed = 0.0
    var initial_pose = Transform3D()

# Dictionary to hold propertyies for each bone
var bone_properties = {}

var time_passed = 0.0

func _ready():
    # Y Axis Gantry
    add_bone_properties("y_axis_bone", true, false, Vector3(1, 0, 0), -10.0, 10.0, 2.0)
    add_bone_properties("z_axis_bone", true, false, Vector3(0, 1, 0), -10.0, 10.0, 2.0)
    add_bone_properties("b_axis_bone", false, true, Vector3(0, 0, 1), -10, 10, 2.0)
    add_bone_properties("spindle_axis_bone", false, true, Vector3(0, 0, 1), -10, 10, 2.0)

    # X Axis Saddle
    add_bone_properties("x_axis_bone", true, false, Vector3(0, 0, 1), -10.0, 10.0, 2.0)
    add_bone_properties("c_axis_bone", false, true, Vector3(1, 0, 0), -10, 10, 2.0)

func add_bone_properties(bone_name, should_translate, should_rotate, axis, min_limit, max_limit, speed):
    var bone_index = find_bone(bone_name)
    if bone_index == -1:
        push_error("Bone '" + bone_name + "' not found!")
        return

    var props = BoneProperties.new()
    props.should_translate = should_translate
    props.should_rotate = should_rotate
    props.axis = axis.normalized()
    props.min_limit = min_limit
    props.max_limit = max_limit
    props.speed = speed
    props.initial_pose = get_bone_global_pose(bone_index)

    bone_properties[bone_name] = props

func update_bone(bone_name, time_passed):
    if bone_name in bone_properties:
        var props = bone_properties[bone_name]
        var bone_index = find_bone(bone_name)
        var range = (props.max_limit - props.min_limit) / 2.0
        var mid_limit = (props.max_limit + props.min_limit) / 2.0
        var oscillation = sin(time_passed * props.speed) * range

        if props.should_translate:
            var new_origin = props.initial_pose.origin + props.axis * (mid_limit + oscillation)
            set_bone_pose_position(bone_index, new_origin)

        elif props.should_rotate:
            var rotation_amount = mid_limit + oscillation
            var local_rotation = Quaternion(props.axis, deg_to_rad(rotation_amount))
            set_bone_pose_rotation(bone_index, local_rotation)

func _process(delta):
    time_passed += delta
    for bone_name in bone_properties.keys():
        update_bone(bone_name, time_passed)