Weekly Ecommerce Automation articles, videos and tips by Marcus Schappi.

👉 Finger Manipulator MK1

Published on 16 Jan 2020


We need a manipulator (we’re calling it “👉 the finger”) that can manipulate a product from a gravity-fed shelf and into picking bin.

Whilst a simple single servo with metal horn worked in our previous experiment it had the following issues:

  • Limited range of movement
  • Not powerful enough to manipulate heavy product
  • Each slot would need an individual servo motor

Limited Range of Movement

The limited range of movement meant that the lip to prevent the product from sliding out of the shelf had to be very low.

The consequence of a “low lip” is that the chances of multiple product accidently being dispense increases.

Actuator Not powerful enough to manipulate heavy product

The actuator sometimes needs to move all products in a slot to dispense one unit. When the products are heavy, sometimes a servo actuator (in an unleveraged configuration) doesn’t have enough power to move the product.

Each needs an actuator

With each slot needing an actuator the chances of hardware failure increase.


Design a version of the finger that:

  • Has a larger range of movement
  • Has more torque/power to manipulate a heavy product from a shelf


One of my favourite sites is 507movements.com, a site that is an online edition of the classic technical reference Five Hundred and Seven Mechanical Movements by Henry T. Brown. You should check the site out, they even animate some of the movements.

Browsing the website I found movement 114 which we could use to translate the circular movement of a continuous rotation servo to a linear movement.

With some simple modifications we could increase the width of the finger and cut the whole design out on the laser cutter.



Whilst this design provides good a linear movement, we actually need a more oval like movement.

Our initial plan was to either use the XY-platform to provide the vertical movement necessary, or add more mechanics.

We feel that there is a simpler solution out there.