Stepper Capstan Winches

The chief actuation system for the course projects is a four-axis stepper-motor driven capstan winch set. The primary construction material is laser-cut 6mm plywood. The enclosure houses four NEMA17 stepper motors and an Arduino with CNC shield and four A4988 drivers. An external 12VDC power supply is required for the motors, and a USB cable from the Arduino to a host computer.

Download the SolidWorks CAD files.

All designs and documentation available under a Creative Commons Attribution-ShareAlike License (CC BY-SA 4.0) .

Renderings

../_images/stepper-capstan-winch-oblique.PNG

Four-axis capstan winch set.

../_images/capstan-winch-parts.PNG

Laser-cut part outlines. All are 6 mm plywood except the power connector plate. Not shown: optional rear cover. PDF of outlines.

../_images/large-capstan-hub.JPG

Capstan hub fabricated using 3D printing. This mounts on a Pololu hub to connect to the stepper motor shaft. The nominal diameter is 40 mm. With a typical stepper motor maximum rotation rate of 300 RPM, the maximum line speed is 628 mm/sec. The hub is sized to use a #81 rubber band (2 x 1/2 inch) as a traction surface.

../_images/stepper-capstan-winch-back.PNG

Rear view, showing location of steppers and Arduino.

../_images/stepper-capstan-winch-bottom-oblique.JPG

Oblique view showing bottom. The cutouts are for adjusting the eyebolts which route the lines.

../_images/stepper-capstan-winch-face-view.JPG

Front view. The letters are marked with a partial-power cut.

../_images/stepper-capstan-winch-rear-oblique.JPG

Rear view.

../_images/stepper-capstan-winch-side.PNG

Side view. The Arduino USB connector is exposed via a cutout. A barrel plug connector is installed on a small panel behind the power cutout.

../_images/stepper-capstan-winch-top.PNG

Top view.

Components

A partial parts list follows.

Size

Description

Vendor

Vendor Ordering

5mm x M3

mounting hub for 5 mm shaft, M3 holes on 12.7 mm circle, for stepper motors, includes 1.5 mm hex key for set screw

Pololu

1998

NEMA17

stepper motor, 76 oz-in (5.5 Kg-cm), 1.5 Amp/phase, M3 mounting holes, 5mm shaft

Automation Technology

KL17H248-15-4A

M3 x 10

socket head cap screw, 2.5 mm hex socket

McMaster-Carr

91290A115

M3 x 14

socket head cap screw, 2.5 mm hex socket

McMaster-Carr

91290A119

M3 x 18

socket head cap screw, 2.5 mm hex socket

McMaster-Carr

91290A121

M3

nut, 2.3 mm thick, 5.5 mm wide

McMaster-Carr

91828A211

8-32

Routing Eyebolt with Nut, 8-32 Thread

McMaster-Carr

9489T112

8-32

nut, zinc-plated, 1/4” width, 3/32” height

McMaster-Carr

90760A009

81

#81 Rubber Band (e.g. broccoli produce band)

Band-It Rubber Co