Stepper motor D shaft to Lego axle adapter

Question

I am working on a prototype and I have a need for a motor shaft to Lego axle adapter for use with a stepper motor.

My overall project entails controlling a stepper motor using C# via USB connection to make very small rotations which will adjust the height of a specimen stage (constructed from Legos) for a stereo microscope.

I need adapters similar to 6mm D shaft to Lego axis adapter Free 3D print model but for 4 mm dia motor D shaft and 5 mm dia motor D shaft

The purpose of the adapter is to allow very small and slow rotations.

I do not want to own the model designs, ideally they can be given away for free (similar to the link above).
I need several of the adapter pieces; 3 of each (4 mm and 5 mm) printed and what would be a fair price for this?
I have no idea what type of material should be used to print these, I think Acrylonitrile Butadiene Styrene (ABS) would do.

score 5 · Accepted Answer · answered Jun 09 '22 at 07:13

OpenSCAD would be well suited for creating something made up of relatively simple shapes, where different dimensions are needed for some parts of the shapes - like the diameters and offsets of your stepper motor shafts.

A solution in OpenSCAD could look something like this:

outer_diameter = 8.5;   //Outer diameter of the adapter
stepper_length = 12;    //Length of the stepper shaft
stepper_diameter = 4;   //Diameter of the stepper shaft
stepper_d_offset = 1.6; //Offset from the center of the shaft to the plane of the D
//4mm shaft: d = 4, offset = 1.6
//5mm shaft: d = 5, offset = 2
//6mm shaft: d = 6, offset = 2.5
thickness_mid = 2;      //Thickness of the massive section between stepper and lego shafts
lego_length = 10;           //Length of the lego shaft
lego_diameter = 4.9;        //Outer diameter of the lego shaft
lego_internal_width = 1.9;    //Width of the slots for the shaft
lego_corner_radius = 0.5;
cutout_size = lego_diameter;
cutout_translate = cutout_size / 2 + lego_internal_width / 2;
$fn = 128;               //Accuracy / resolution of circles
eps = 0.01;
module fillet_square(width, radius) {
    translate([radius - width / 2, radius - width / 2, 0])
        minkowski() {
            square(width - 2 * radius);
            circle(radius);
        }
}
color(0,0.5)
union(){
    linear_extrude(height = stepper_length + eps) {
        difference() {
            circle(d = outer_diameter);

            difference() {
                circle(d = stepper_diameter);
                translate([0, stepper_d_offset + stepper_diameter / 2, 0]) {
                    square(size = stepper_diameter, center = true);
                }
            }
        }
    }
    translate([0, 0, stepper_length]) {

        linear_extrude(height = thickness_mid) {
            circle(d = outer_diameter);
        }
    }
    translate([0, 0, stepper_length + thickness_mid - eps]) {

        linear_extrude(height = lego_length + eps) {
            difference() {
                circle(d = outer_diameter);
                difference() {
                    circle(d = lego_diameter);
                    translate([cutout_translate, cutout_translate, 0]) {
                        fillet_square(cutout_size, lego_corner_radius);
                    }
                    translate([cutout_translate, -cutout_translate, 0]) {
                        fillet_square(cutout_size, lego_corner_radius);
                    }
                    translate([-cutout_translate, cutout_translate, 0]) {
                        fillet_square(cutout_size, lego_corner_radius);
                    }
                    translate([-cutout_translate, -cutout_translate, 0]) {
                        fillet_square(cutout_size, lego_corner_radius);
                    }
                }
            }
        }
    }
}

You can then export your .stl file (or any other format) for 3D-printing from OpenSCAD.

Stepper motor D shaft to Lego axle adapter

1 Answers1