caress the gaze: 3d printed structures using sma actuators

by:AIRWOLF     2020-06-15
This tricky problem is trying to provide a framework for designing dynamic, shape-changing objects using SMA actuators.
For me, the ultimate goal is to design an interactive wearable device called \"the touch of the gaze (
See the final result: www. behnazfarahi. com )
The information provided here is intended to demonstrate how to design a dynamic 3D printed object activated using an SMA actuator.
Applications can be wearable devices, buildings, industrial objects, etc.
The printer used in \"the touch of gaze\" is the Objet connecx500 3D printer.
This technology allows the manufacture of composite materials with different flexibility and density, and it is possible to combine materials with different material properties in many ways and deposit them in a single printing process.
However, you can also do some interesting dynamic prototypes using MakerBots or any 3D printer (
Some filaments such as PLA have interesting elastic properties, which makes it ideal for designing SMA actuators).
Gaze at the touch from Pier Vimeo 9.
Why is sports design important?
Since ancient times, human beings have been fascinated by the creation of artificial movements. they have developed mechanisms for the generation of mechanical movements, such as bullet bombs in ancient Greece or windmills in medieval Europe.
Historically, the 17 th century marks a significant increase in the phenomenon of automatic control of humans or animals, that is, self-control
Operate the machine.
However, none of these designs demonstrate the performance and behavior of biological movements caused by muscle function.
Muscle function stimulates many researchers and scientists to explore the potential of developing smart materials such as EAPs (Electro-Active polymer, SMAs (
Memory alloy)and so on.
There are many kinds of smart materials, but there are mainly three categories: discoloration materials, luminous materials and mobile materials.
Having said that, please note that although their performance is similar, none of these actuators end up with the complexity of actual muscle behavior.
You may have heard of muscle lines or shape memory alloys. This (
Seems magical)
When heated to the activation temperature and returned to the initial stage, the alloy metal changes its shape.
It can be converted into any specific form when it cools down.
In other words, it is called a shape memory alloy because it has a memory of its initial form.
Through special heat treatment, a piece of SMA can be made to \"remember\" a shape.
For example, a wire of length can be made to remember that it should be a letter \"a\" at temperatures above 70 °c\"
If you bend and deform this line at room temperature, it stays bent.
However, if you put it in a cup of water with a temperature of more than 70 °c, it immediately becomes the letter \"\".
In this tricky question, I first wanted to demonstrate how to design a variety of motion using SMA, and then show how 3D printing can help integrate motion into an object designed.
By the way, if you are interested in reading more information about living things
I recommend this book: Bionic: Bio-inspired technology, edited by Yoseph BarCohen. (
This book is written in this way: the way to design actuators that meet the requirements is to use a cell structure that can demonstrate interesting mechanical properties such as auxiliary behavior and activate them using SMA actuators.
What is the auxiliary material?
The auxiliary material exhibits unusual mechanical behavior due to negative Poisson\'s ratio.
In other words, when stretching, the forces applied by these materials perpendicular to them become thicker.
This is due to their special internal structure and when the sample is uni-axially loaded. (
Check this video: I also found this paper very useful for the design of the auxiliary structure, which not only provides a systematic approach to the design of the 2D auxiliary structure, does it also provide 3D auxiliary structures that can be activated?
How did the material survive?
Some interesting research from the MIT assembly lab is exploring the concept of living matter and 4D printing, which is very exciting.
Their research on 4D printing is a new way to print customizable smart materials.
However, in my study, due to the difficulty of embedding SMAs or replacing the resin material of the printer during the printing process, the actuator was assembled during the post-printing process.
Here are some of my attempts: This video shows an MIT project on smart issues: My first step is to try and understand 2D assisted design and its manufacturing and behavior.
As shown in the figure, the basic 2D structure has periodic boundary conditions:a)hexagon(b)square(c)triangle(source: )
By using the Objet connecx500 3D printer for multi-material 3D printing, different material properties are assigned to these parts of the structure to study their mechanical behavior.
As mentioned above, multi-material 3D printing allows the manufacture of composite materials with different flexibility and density, which can combine materials in many ways and deposit different material properties in one printing process.
Therefore, the design is started by distributing soft materials (
Tango black in Objet printer)
Joints and rigid materials (Vero White)
The middle part.
The result is an interesting contraction/expansion behavior.
Please note: There are different printing techniques in multiple versions
Material, but an easy way is to export various \"stl\" files to the printer. (
Basically, if you have two or more layers of objects, export them separately and assemble them for printing, assign various materials in 3D printer software such as Objet Studio.
Then, in Objet Studio, you have to select and insert everything and click assemble \".
The other way to do multi-material printing is bit map 3D printing, in which you send a series of PNG files that show a pixel gradient.
Monolith seems to be a very good software.
Modeling engine based on multi-model
3D printing materials. (
I haven\'t tried it myself, but here you can find it: intro)
After printing these prototypes, I started working on their mechanical behavior and the way to activate them using SMA actuators.
As you can see in this video, I use a wide variety of actuators in terms of the thickness of the SMA actuator, driving temperature, spring spacing, coil size, etc: next, I will demonstrate the basics of using SMA actuators.
It\'s fun to use SMA wires, but it\'s also tricky.
The SMAs is both quiet and lightweight, and is also known as a motor-less actuator.
They can do different movements, organic, gentle, beautiful viewing.
David Benjamin, Marcelo Coelho, Philip Beesley, Jei Qi, Rob Ley are all people who use these materials in the project.
I found the SMA spring to be perfect for use with the tension structure.
You can see one of my projects here that uses these actuators in dynamic tensile structures: You have to know what shape memory alloys are.
Choosing SMA as the driving material requires understanding the limitations and rules of using this material.
As mentioned above, it can deform when triggered by a specific activation temperature, and then \"remember\" its original shape.
SMAs is usually made as a wire.
Due to the small size, rugged and easy to trigger of these products, they can be used in many products.
Because they move silently and organically, they can become good tools for active sports.
These wires with smaller diameter usually account for 2% to 10% of their length.
The diameter of the wires is one of the really important factors driving them.
The larger diameter wire has a greater pull force than the lower diameter wire.
The Wire with large diameter also closes for a long time (
It takes longer for the wire to return to its original, uncontracted shape). Higher-
The wire resistance in diameter is lower and more power is needed.
Therefore, they are more likely to overheat and lose their initial ability to shrink.
0 wire.
006 \"or smaller can run continuously without worrying about overheating. High-temperature (90C)
Faster wire disconnectiontimes than low-temperature (70C)wires.
Where can you order SMAs?
You can order from different manufacturing companies: 1.
They list all the different variants of their product. 2.
It is a typical muscle Wire Company.
Check to see if there is a student/researcher discount on their product.
How much current does it take to activate them?
The trickiest part of using SMAs is to control the current so you don\'t overheat the wires.
If you overheat, you can even see smoke coming out and the SMA stops responding after a few times.
To find out how much current is needed, check the bending technical data sheet: one way, like any circuit, is to use Ohm\'s law: V (voltage)= I (current)x R (resistance).
So, let\'s imagine that you want to use 0.
Diameter \"wire, you have a 6 volt power supply, but you don\'t know how long the wire should be.
First of all, you know from the data sheet that what you need is 4000 mA or 4a. (
This is a lot in this case).
The resistance is 6/4 = 1 from Ohm\'s law. 5 ohms.
We know the wire itself is 0.
16 Ohm/inch resistor, which means we can activate: 1. 5/0. 16= 9. 37 inch.
You can connect it to Arduino using a transistor (
Example TIP 120)or relays.
How do you control speed?
This is an interesting thing I would like to explore further, but technically changing the power before the moving point changes the speed of motion.
In other words, if you activate the wire with 12 v, the full shrink speed is faster than 6 v.
All you need to do is make sure they don\'t overheat through this experiment. (
Here, I would like to thank my artist/mechanical engineer friend Paolo Salvagione for his help in designing various SMA actuators: one of the challenges of designing dynamic systems using SMAs or flexinol is, unlike a servo motor that can control its motion and position, you have less control over its motion.
In fact, precise SMA position control is possible but not easy.
A major drawback of the SMA wire is that its cooling and heating curvature are not equal.
You basically have to wait for the material to cool down.
Based on the following documents, when using an SMA actuator, there is no standard model that specifies the temperature, load and material geometry to achieve the desired performance;
Therefore, the convention is to derive the heat of the actuator model
Some or all mechanical performance experiments :(
The following article explains the issue in detail and provides active cooling and pre-cooling
To overcome SMA :~ Response time of ytt110030/data/SMA, stress system.
Based on this, I suggest there are three ways to design SMA actuators: 1)
Using weight/gravity, SMAYou can use gravity by simply adding some weight to the SMA actuator.
This is a good way to enhance the material.
Having said that, this is an experimental process that requires testing and testing to understand the force required to recover the SMA wire/spring.
Alternatively, if you can find the data sheet of the SMA you are using, you can calculate the exact force that the SMA can lift. 2)
With the bias spring, you can also push the SMA into the stretch state using the bias spring. 3)
Using material properties in this method, material behavior plays an important role in storing and releasing bending energy during the heating and cooling stages of the SMA line.
So it can help with the retracement process.
The mechanical properties of the inherently elastic material apply initial tension to the SMA line.
So by heating the wire, it will shrink in the structure and produce additional curvature.
If the structure is also elastic to push the SMA to stretch, then this will be a faster process.
In this project, this is the main focus of the study of the cell system.
As mentioned above, the material properties can provide sufficient force to recover the SMA actuator to the tensile state (initial)stage.
Below is a video showing a prototype developed by Paolo and I that shows a relatively equal cooling/heating time for the response of the SMA actuator.
As you can see, when the SMA is charged, it will shrink and bend the PLA members, and when there is no current, it will slowly return to the full length due to the mechanical power of the PLA.
The actuator in this video is composed of SMA spring wire, PLA member (
Print with MakerBot)
And transparent acrylic resin at the bottom.
To further develop this design, as you can see in this image, this method has been implemented to drive the cellular structure by assembling SMA actuators between rigid/hard material nodes. Therefore: 1)
The force will never be passed directly to the soft component, but always the transition from hard to soft force distribution. 2)
The material properties of the PLA plus honeycomb structure provide an interesting organic response through the heating/cooling cycle of the SMA.
This method of design movement can provide organic, silent, life
Just like the movement you designed. Ok.
Let\'s try to make a small prototype together.
You can apply this logic to anything you want to design.
Attached you can find 5 different STL files that need to be assembled and assigned with a variety of digital materials.
Imagine that you have a material gradient from soft to hard.
Using the Objet 3d printer, I go from \"still\" to \"hard \"(
TangoBlack> coast 60> Coast 85> Gray 40> gray 25> VeroWhite).
The logic is that no matter where you use force (SMA actuators)
Then the material needs to be stiff (
VeroWhite in this case)
Between nodes, the material gradually becomes soft.
In this way, you will have a softer transition for the distribution of forces, which is no different from the structure in nature.
After printing this piece, the SMA actuator needs to be connected.
To do this, I used a make bot to print connection members made from PLA that were later assembled into one piece and then I installed SMA (
See pictures).
Attach the STL file where you can also find the PLA file.
How do PLA parts connect to our cellular grid?
Use the nuts and bolts in the McMaster catalog/121. . .
You can connect your members together and you don\'t have to worry about their connection at all.
Also, please note that the SMA actuator cannot weld anything.
Therefore, both the wire connection and the joint need to use the curl tube (
You can find all kinds of these products here: I also used tiny eye terminals between SMA and screws.
As you can see in these photos, the next step is to design the form of these modules.
The animal and fish scale system inspired me a lot.
The design process therefore explores how the cell structure can be extended to 3D dimensions to create formal expressions.
All forms are generated using Locust calculations in Rhinos
It can be a new structure in itself-.
This is a highly iterative back and forth process between digital design and physical testing using a 3D printer.
3D printing and behavioral research/caressing eyes wrote this from Behnaz Farahi.
Here is the video of the final 3D printing process: The 3D printing process/the touch of the gaze of behfarfarahi on Vimeo.
I hope this project can provide a new way for the motion design of our daily objects, by introducing soft and Organic Motion in matter, which is not very based on traditional mechanical systems.
Hopefully I have provided a small step for the design of programmable objects. . . .
Good luck, happy!
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