Actuator Fabrication

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An actuator is a device that takes energy in some form and converts it to perform some type of mechanical work. One of the most challenging and exciting frontiers in self-replicating machine research is the development of printable actuators - actuators that can be built using the constrained set of materials and processes available to a RepRap-style 3D printer. This page collects links to various resources that are relevant to this effort. Printable actuators are a big step towards a more self-replicating RepRap.

Where possible a link is provided to CAD models and/or a description that is clear enough such that a motivated experimenter could replicate the work. Currently only a few of these projects are truly "printable" in the pure sense. But even non-printable actuators that can be made by hand are relevant. Intrepid experimenters can figure out how to build by machine what they can build by hand. Some of the links go to academic papers or other sources of information that stop short of detailed design information, but still have useful information.

Feel free to add your own information, but please try to keep this page focused on projects that people can actually build.

Even better, do some experiments yourself and link to the results from this page!


Contents

Forum Threads

Printable actuators are a popular topic in the forums. For reference here are some of the threads:

Electromagnetic linear actuated beds

Printable Motors

Printable BLDC Motors

Using Air Motors

95% reprappable repraps

Artificial Muscles

Reprapping Engines

Full Mechanical Reprap

Wire Wound Stepper Motor

Reprapable linear drives

Electromagnetic Actuators

The fabrication of traditional electromagnetic motors uses materials that:

Rotary Motors

With Magnets

A possibly-printable Electric Motor on Thingiverse

Brushless DC Motor Parts v0.1 on Thingiverse

A pancake motor using printed circuit board coils: Flat brushless P.C.B motor experiment

Another Printed Circuit Motor

World's Smallest Brushless Motor

Build thread: submicro brushless motors

There are hundreds of variants of the famous Beakman motor: The Beakman Motor.

This page would not be complete without an entry on Bill McLennan's hand-made motor that won the first Feynman Prize: Small world's big achievement.

An example of a reed-switch motor: home made brushless motor.


Without Magnets

Jedlik Motor

Amazing electromagnet electric motor

Home-Made Electric Motor

homemade electric motor

Variable Reluctance Motor

DIY 3-phase AC Induction Motor


Linear Motors

With Magnets

Maglev Train Demonstration - Linear Synchronous Motor and Disc Magnets

Without Magnets

Daniel's Linear Induction Motor

Unique Electric Engine

Some of Forrest Higgs's Work on a Printable Linear Stepper

First steps towards printing a stepper motor

A design charette for a printed linear stepper motor, part 1

A design charette for a printed linear stepper motor, part 2

First try at cutting steel

Building a printable stepper for a next generation Tommelise

Going high risk steampunk

First thrust plate for a printable stepper motor milled

Vitamins and minerals


Solenoids and Electromagnets

Printing Electromagnet Spools

Electromagnet with castable coils on Thingiverse

Electromagnet Demispool on Thingiverse

Electromagnet coil motor


Ratchet Drives

Ratchet drives are mechanical transmissions that can be combined with short-travel actuators to allow long-distance precise motion.

A quick test of the printable stepper thrust plate

Stepping ratchet gear thing on Thingiverse

Binary mechanical controllerless Stepper motor

2 Way Ratchet Mechanism on Thingiverse

Plastic Experiment on Thingiverse

Pin Drive from Design of a Primitive Nanofactory


Solenoid-driven rotary motors

These things are just waiting to be turned into stepper motors:

Four Stroke Solenoid Motor

Homemade Solenoid Motor

Electric piston engine

A printable electric motor similar to the four stroke solenoid motor above.

Electrostatic Actuators

Electrostatic actuators in theory can deliver a force while barely using any power. However large electric fields are generally needed to obtain useful forces. This requires either large voltages (which are dangerous) or very small features. In traditional fabrication methods complexity is expensive and an actuator consisting of many small features is not an option. In 3d printing however complexity is almost free, which opens up the way for large scale electrostatic actuators.

Dielectric elastomer actuators

Dielectric Elastomer actuators consists of a flexible elastomer in between two electrodes. The elastomer makes it possible to apply larger electric fields than would be possible in air. Dielectric elastomer's have been shown to be capable of high energy densities. Often the elastomer's are pre-stretched to reduce the amount of air inside the material and improve the dielectric strength of the material.

In 2008 Jeremy Risner got his PhD at UC Berkeley on the investigation of Dielectric elastomer actuation for printable mechatronics. His PhD mainly focused on the development of structures that could prestretch conventional dielectric elastomer materials. Investigation of dielectric elastomer actuation for printable mechatronics


Duduta et al. from Harvard university managed to make an dielectric elastomer that had a strain of up to 7 percent. They did this by spin coating 37.7 micrometer thick layers of urethane acrylate oligomer and layers of conductive ink. Multilayer Dielectric Elastomers for Fast, Programmable Actuation without Prestretch


Air based electrostatic actuators

Rotary

Rotary 3-phase ink-jet printed electrostatic motor

Linear

Electrostatic Motor

Pneumatic

Reciprocating

Detailed plans for a wooden engine: Air Engine 2

This is a plastic pneumatic engine that looks almost printable: 2 Cylinder Air Engine

A clever way to seal a piston with ferrofluid: Ferrofluid Piston

A variety of functional LEGO engines: Lego 2 cylinder LPE engine, LEGO Pneumatic Engine (LPE) 3 cylinder inline

An engine made with drillpress, file, and solder: 4-cylinder swash plate air engine

A Printed Wobbler Engine

A printed reciprocating steam engine

Rotary Non-reciprocating

A laser-cuttable Simple Air Vane Motor on Thingiverse

RotaVac - A Rotary Vacuum Pump on Thingiverse

Development of three-chamber micro pneumatic wobble motor

A LEGO turbine my first lego turbine

Tesla Turbine V2 on Thingiverse


McKibben-style air muscles

robotic joint moved by pneumatic McKibben muscles

Silent Flexible Synthetic muscle - Pneumatic...

Air Muscle test 1


Hydraulic

Zach's lasercut peristaltic pump

Peristaltic Pump on Thingiverse

These might be printable or laser-cuttable: Gear Pump


Thermal

Automated Design for Micromachining: Heatuator

Desktop Fabricated Heatuators

Ink-jet heatuator

Bimetallic strip


Electroactive Polymers (EAP)

Basic info on Electroactive Polymers

Contractive EAP Actuator

A paper about 3D printing electroactive polymers:

Freeform fabrication of ionomeric polymer-metal composite actuatros

Piezoelectric

Piezomotor

PCB Motor Introduction

A paper about fabricating piezo actuators: Development of PZT and PZN-PT Based Unimorph Actuators for Micromechanical Flapping Mechanisms


Shape Memory Alloy (SMA)

Basic info on Shape memory alloy

SMA Shape Memory Alloy actuator

SMA Manipulator

Composable Flexible Small Actuators Built from Thin Shape Memory Alloy Sheets by E. Torres-Jara, K. Gilpin, J. Karges, R.J. Wood and D. Rus.

Interfacing and Control

One of the drawbacks of pneumatic, hydraulic and other non-electrical actuators is that they need to be controlled with valves (or clutches in the case of pure mechanical systems). Since we are typically using a computer for control, the valves/clutches must ultimately have an electrical interface. This is often accomplished with some type of solenoid. But if the motivation for using non-electrical actuators is to avoid the need for making coils, we haven't really solved the problem if we still need solenoid-driven valves and clutches.

In principle it is possible to build printable, electrically operated valves and clutches based on thermal, piezoelectric, SMA, electrostatic, electrorheological and other methods. Unfortunately it seems that there is a lot less activity in this area than there is for actuators in general. Some different categories are listed below as place-holders for future results. Maybe with enough material this section could be moved to a new article on transducers.

Interfacing with fluidics

One can interface with fluidic circuit and use the circuit to control actuators.

Fluidic tone and sound sensor can be used for acoustic interfacing.

Photofluidic interface

Putting a heating element in a fluidic amplifier can also be used for electrical interfacing.

Scratch-built solenoid valves

Home made two-way solenoid valve controlling air muscle

Scratch-built solenoid clutches

Magnetorheological (ferrofluid) valves and clutches

Electrorheological valves and clutches

SMA valves and clutches

Electroactive Polymer valves and clutches

Thermally actuated valves and clutches

Piezoelectric valves and clutches

Electrostatic valves and clutches

Fluidic (fluid logic) and Pure-Mechanical Systems

Main article: Mechanical Computer

For the truly ambitious among you, consider doing away with the computer entireley. There are several examples of functional fluidic and mechanical computing machines, both classical and modern. Fluidics and mechanical logic do have the disadvantage of requiring more power than electronics and having slow speeds. Power requirements for mechanical and fluidic control systems are expected to be more than the 60 watts prescribed in the Gada prize.

Required reading in this area is Chris Phoenix's design proposal for a fluidic controlled macro-scale machining self-replicator.

One should also be familiar with the Jacquard loom.


Detailed build information for fluidics is hard to find(on the internet at least), but here are a few sources:

A first try at building a fluidic amplifier

Programmable Water

Design and Performance of Two Integrated Circuits for Fluidic-controlled Pneumatic Stepping-motor System

Fluidic element overview

Printable Fluidic Logic Element

Scientific American Article on Fluidics

Tippetts Fountains short introduction to fluidics

Fluidic Full Adder

Fluidic Vortex Diode

Fluidic Vortex Amplifier


Books

"Fluidics Quarterly" provides useful information on fluidic element design

"Microfluidics: History, Theory and Applications" by William B. J. Zimmerman provides a good overview of fluidic circuit design.

"3D Microfluidic Devices Fabricated in Layered Paper and Tape" by Andres W. Martinez, Scott T. Phillips and George M. Whitesides [1]

There are several printable designs for machines that might be called "printable proto-computers", meaning that they have many of the buildings blocks needed to make a mechanical computer. Some examples of these are:

waterjet clock on Thingiverse

Wind-up Toy on Thingiverse


And if that isn't hard enough for you, you can always make things more interesting by hopping down a few notches in scale:

Two Types of Mechanical Reversible Logic.

Design of a Primitve Nanofactory