Actuator Fabrication
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
- 1 Forum Threads
- 2 Electromagnetic Actuators
- 3 Electrostatic Actuators
- 4 Pneumatic
- 5 Hydraulic
- 6 Thermal
- 7 Electroactive Polymers (EAP)
- 8 Piezoelectric
- 9 Shape Memory Alloy (SMA)
- 10 Interfacing and Control
- 10.1 Interfacing with fluidics
- 10.2 Scratch-built solenoid valves
- 10.3 Scratch-built solenoid clutches
- 10.4 Magnetorheological (ferrofluid) valves and clutches
- 10.5 Electrorheological valves and clutches
- 10.6 SMA valves and clutches
- 10.7 Electroactive Polymer valves and clutches
- 10.8 Thermally actuated valves and clutches
- 10.9 Piezoelectric valves and clutches
- 10.10 Electrostatic valves and clutches
- 11 Fluidic (fluid logic) and Pure-Mechanical Systems
Forum Threads
Printable actuators are a popular topic in the forums. For reference here are some of the threads:
Electromagnetic linear actuated beds
Electromagnetic Actuators
The fabrication of traditional electromagnetic motors uses materials that:
- conduct electricity very well (materials with a low resistivity). See the List of conductive materials.
- that are magnetic (materials with a high remanent magnetisation). See the List of magnetic material.
- that can be easily magnetised and demagnetised (materials with a high relative permeability). See the List of magnetic material.
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
Amazing electromagnet electric 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
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
Building a printable stepper for a next generation Tommelise
First thrust plate for a printable stepper motor milled
Solenoids and Electromagnets
Electromagnet with castable coils on Thingiverse
Electromagnet Demispool on Thingiverse
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:
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
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 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...
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
Electroactive Polymers (EAP)
Basic info on Electroactive Polymers
A paper about 3D printing electroactive polymers:
Freeform fabrication of ionomeric polymer-metal composite actuatros
Piezoelectric
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
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.
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
Printable Fluidic Logic Element
Scientific American Article on Fluidics
Tippetts Fountains short introduction to fluidics
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:
