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How to Form Memory Wire Nitinol

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Picture of How to Form Memory Wire Nitinol
Memory wire, a.k.a. Nitinol, a.k.a. Muscle Wire, a.k.a. Flexinol, is a nifty metal alloy (mixture) of Nickel (NI) and Titanium (TI). The NOL stands for Naval Ordinance Laboratory, where the memory properties were discovered by William J. Buehler and Fredrick Wang. If you are interested in buying Nitinol or the history and its many uses, check out these links:
http://www.robotshop.com/flexinol-en.html
http://www.musclewires.com
http://en.wikipedia.org/wiki/Nickel_titanium
 
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Step 1: Material List

Read all instructions first!
Materials needed:
Metal tweezers or clamps of some sort
Flame
Water and container
Rod for a spiral, anything else you would need for different shapes
Body heat or battery holder pack
Nitinol wire, ($20 to $30 per meter)

Step 2: Annealing Explination

Picture of Annealing Explination
  Nitinol, the non-brand-specific name, comes in an as-drawn form, which is what a Maker would want, because it allows one to set the memory. As-drawn refers to the drawing (not picture drawing) process, which is how a bar of alloy is continually pulled through reduced sized openings until it is a wire. When I received the Muscle Wire, it was very springy and difficult to bend. This is because the drawing down process presses the atoms in the metal closer and closer together. To make the wire easier to form, it has to be annealed.

  Annealing the wire is the same type of annealing that is used for all other metals, as well as glass. The material is brought to a temperature that allows the atoms to relax and rearrange, but not too hot as to deform or melt. A way to anneal wire is to heat it to a dull red glow along the entire length, and then quench it by putting it into water. It would be a good idea to find a container that will fit your metal, I used a bread pan. It is also possible to anneal the wire while it is looped, although it will try to straighten out at first. It is not necessary to use a pickle, for you jewelry smiths out there, although it would help to clean the wire. I chose not to, simply because I do not have the setup for that.
pride1567 days ago

You know the transformation can be triggered with electricity too! I guess the internal resistance creates the heat needed to flip phase, but... it can be done that way too $.02

Where would I go about getting the wire I need?
click on the links the author left on the intro step

Fort Wayne Metals, Memry, NDC, Johnson-Matthey- in that order

codeandpixels4 months ago

Hey, nice Instructable.

I bought some nitinol wire, after contacting them to see if what they sell is comparable to Flexinol and will contract when heated, and they said it would if I train it that way. Unfortunately, "As drawn", it seems to work opposite of what I would like, increasing in length when heated. can find lots of info about training the wire to a shape, but I can't find anything about training it to contract.

Since you mentioned an increase/shrink cycle that is used to make Flexinol, I was wondering if you have any more info about that process.

"Constrain it—it has to be under load. Then you heat treat it at 500 degrees Celsius and water quench or fast-cool it."

Pickledkitty (author)  codeandpixels4 months ago
From what I remember, the cycling that is used to produce Flexinol is so that the end product stays the same contraction rate instead of getting longer over time. Unfortunately this was quite a while ago, and I no longer have the websites that I got the information from if they are not listed in the Instructable.

Thanks! My attempts to train it by heating it (I used a candle flame) and letting it cool several times under tension haven't worked, so I may have to call it a loss and shell out for the pre-trained muscle wire.

Phoenix171 year ago
I am not an expert, but quenching is more for tempering or hardening, depending on the initial temperature.

Does this wire have different or unusual properties? in my experience and general knowledge suggests to anneal a metal to make it as plyable as possible, you want to give it the maximum amount of time to cool (ie cool as slowly as possible).

I have made a number of knives in the past and I prefer something like 1080 steel, raised to not quite white hot, then oil quenched until cool; then raise to approximately purple and oil quench again. This hardens and then tempers the worked steel.
Doulos3 Phoenix177 months ago
Nitinol does have some unusual properties. Nitinol can recover to its set shape from 8-10% strain when activated at its transition temperature. In relation to this instructable, Nitinol's transition temperature can also be raised when above about 500 degrees Celsius. At that high of a temperature, the Nitinol recrystallizes and will be "set" into a shape after quenching. So it is a kind of tempering per say. This stuff is pretty cool though, I've seen and heard of this thing being used in artificial arteries, temperature dependent shades, actuators, and even 1 kW motors. Some differences between Nitinol and other SMAs include a lower frequency response and a higher force imparted with Nitinol. It is a pretty cool metal though.
Kinnishian1 year ago
You are annealing it when you heat it and gradually cool, but some of the language seems to ambiguously refer to the quenching as part of the annealing, when it is quite the opposite (the quick cooling forces the atoms into a stressed formation.)

Cool instructable!
nicko01 year ago
hey ! your a lamp worker! ? are u using memory wire and glass in jewelry or something?
Edgar1 year ago
Gizmo makers around the World will thank you for this...
Went to my Blog:
http://faz-voce-mesmo.blogspot.pt/2013/05/a-newsletter-da-cncking-e-carradas-de.html
Treknology1 year ago
The temperatures quoted should be double-checked when you order your wire. Activation and Programming temperatures vary depending on the alloy-mix.

If you're able to use strong enough means to shape your wire initially, I also recommend by-passing the annealing steps. As shown, the author ended up with a shorter piece of wire than originally intended so, it should only be considered if really necessary.
dfields11 year ago
Nice movie! Elegant the way the wire moves.
oops, must have missed that. Thank you!
Cool, creative
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