end-effector Design

Single Pen Gripper

For black/white drawings, we designed and manufactured a custom end effector capable of gripping a large variety of pens through a pseudo-grub screw mechanism. We place the pen holding mechanism on rails with springs, which allows the pen to draw a consistent line despite inaccuracies in the z-coordinate and varying drawing surface height.

The individual parts were printed from PLA plastic, and standard fasteners are used to assemble the end effector. Furthermore, to reduce frictional forces during drawing, linear ball bearings were press-fitted into the plastic, which also reduce inaccuracies in the xy-plane.

CAD model

Side view of working prototype

Diagonal view of working prototype

Pen Carousel Gripper

To facilitate fully autonomous multi-color drawings, we designed a four-pen carousel gripper. By choosing a set of pens that span the full color space (e.g. CMYK), the capabilities of the robot are now expanded to draw images with any color.

A passive mechanism actuated by the 7th joint of the robot changes the height of a single pen at a time by 12 mm, such that the robot only draws with a single color at a time. Similar to the single pen end effector, the carousel gripper also features springs and rails to ensure consistent lines.

Demonstrations of the pen changing mechanism are shown below, as well as an alternative control-based method, which modifies the end effector angle relative to the paper in order to achieve multi-color drawings without any moving parts.

Changing Pens

Modified Drawing Angle

Page updated

Google Sites

Report abuse