> For the complete documentation index, see [llms.txt](https://delta-robotics.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://delta-robotics.gitbook.io/docs/hardware/nitinol/wire.md).

# Wire

Delta Robotics Nitinol wire, specs, force and resistance data, cycle life, control, and cooling, plus how to make it move without ruining it on day one

At Delta Robotics, we sell wire that moves. Not electrically, though it does that too, but physically: our Nitinol wire contracts when you heat it, then relaxes back into shape as it cools. It is a tiny, silent robot muscle. This page covers what the wire does, its numbers, and how to keep it working past day one.

{% hint style="warning" %}
The wire reaches its activation temperature of about 90 C and draws several amps to tens of amps depending on diameter. Keep hands clear while it is powered and use adequately rated wiring. See [Safety essentials](/docs/get-started/safety.md) for the full hazards.
{% endhint %}

## What you are working with

Here is what is in the box:

* **Material:** Nickel-Titanium (Nitinol, a shape memory alloy)
* **Form:** Straight annealed
* **How it works:** Joule heating (run current through it)
* **Lengths:** 1 ft, 5 ft, 10 ft (custom lengths on request)
* **Diameters:** 0.5 mm, 1.0 mm, 2.0 mm
* **Activation temp:** about 90 C

By default the wire is trained straight. To make it curl, bend, or hold another shape, see [How to Train Nitinol](/docs/learn/how-to-train-nitinol.md).

## Wire specifications

The wire activates around 85 to 95 C. The data below combines manufacturer specs, lab tests, and extrapolation. We are still validating these numbers across lab and field tests; if you spot something off, tell us.

| **Property**               | **0.5 mm** | **1.0 mm**            | **2.0 mm**             |
| -------------------------- | ---------- | --------------------- | ---------------------- |
| Resistance (Ω/m)           | \~4.3 Ω    | \~1.1 Ω *(estimated)* | \~0.27 Ω *(estimated)* |
| Heating Pull Force (g)     | \~3,560 g  | \~14,240 g *(est.)*   | \~56,960 g *(est.)*    |
| Cooling (Bias) Force (g)   | \~1,424 g  | \~5,696 g *(est.)*    | \~22,784 g *(est.)*    |
| Contraction Current (\~1s) | \~4 A      | \~16 A *(est.)*       | \~64 A *(est.)*        |
| Cooling Time (90 °C, air)  | \~14 s     | \~40 s *(est.)*       | \~100 s *(est.)*       |
| Max Recommended Strain     | **5%**     | **5%**                | **5%**                 |

> *1.0 mm and 2.0 mm wire specifications are extrapolated from 0.5 mm data using math, standard assumptions, and coffee.*

## Cycle life

Less strain means longer life. For wire you want to keep, stay in the 3 to 4 percent range.

| **Strain** | **Cycle Life**       |
| ---------- | -------------------- |
| 2%         | 1,000,000+ cycles    |
| 4%         | 100,000+ cycles      |
| 6%         | 10,000–20,000 cycles |
| 8%         | 2,000–5,000 cycles   |
| >8%        | Not recommended      |

## Control it with the TF Node Controller

All of our wire works with the TF Node Controller, which drives Nitinol with regulated current instead of a raw supply.

* Pre-made wire profiles (coming soon)
* USB and serial control, so you can script it
* Built-in current and resistance sensing
* 60 A output, enough to drive even 2 mm wire to an under-one-second contraction

The Node runs on an Arduino Minima, talks over CAN, and supports up to 127 devices from one USB cable. It also let us shape-set wire electrically before we had a furnace. See the [TF Node Controller](/docs/hardware/thermoflex/tf-node-controller.md) page for specs and control modes.

## Cooling

The wire can only cycle as fast as it cools, so cool it faster to move faster.

* **Air cooling to room temperature:** about 14 s for 0.5 mm, 40 s for 1.0 mm, and 100 s for 2.0 mm, in still air. A fan helps.
* **Liquid cooling:** up to 100 times faster. An integrated cooling system is in development.

## Mounting and wiring

Mounting methods, electrical connections, pre-tension guidance, and the experimental soldering process now live on their own page: [Mounting and wiring](/docs/hardware/nitinol/mounting-and-wiring.md).

## Sources and references

* Fort Wayne Metals: [Shape Memory Nitinol](https://www.fwmetals.com/what-we-do/materials/nitinol/shape-memory-nitinol) and the [NiTi Actuator Wire Datasheet (PDF)](https://www.fwmetals.com/media/pbmke3zt/0-3-mm-acuator-data-sheet.pdf)

## Related pages

* [Spring](/docs/hardware/nitinol/spring.md): The coiled version of this wire.
* [Mounting and wiring](/docs/hardware/nitinol/mounting-and-wiring.md): Anchor and connect the wire correctly.
* [TF Node Controller](/docs/hardware/thermoflex/tf-node-controller.md): Drive the wire with precise current.
* [How to Train Nitinol](/docs/learn/how-to-train-nitinol.md): Give the wire a new shape.