Shape
setting of nitinol is one element of the complete nitinol
product manufacturing package at Norman Noble,
Inc.
It is an important function in the manufacturing process,
but one that is not widely available.
We are one of the few companies that offer Nitinol shape setting.
But, we are the only contract manufacturer to provide
all elements of nitinol manufacturing: micro machining Nitinol,
shaping Nitinol and electropolishing Nitinol.
What
is Shape Setting?
NiTi shape setting is the process by which the final, specified
shape of the metal is configured and programmed. This requires
specific thermal physics for each device depending on the end use
and end-use environment. Shape setting must also take into account
the type of nitinol being used, which may require different processing
temperatures and exhibit different characteristics. “Superelastic” and “shape
memory” types of nitinol are generally available in Nitinol
wire, ribbon, strip, Nitinol sheet, tubing or bar form.
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The Shape Setting Process
One of the most important challenges in the shape setting process
is determining the proper heat treatment parameters to achieve the
shape and properties of the part. Nitinol shape setting requires
thermal manipulation of the nickel-titanium from martensite to austenite.
The process requires a specific austenite start temperature (As Temperature)
and finish temperature (Af Temperature); and a specific martensite
start temperature (Ms Temperature) and finish temperature (Mf Temperature).
The parameters for this phase transformation
usually need to be determined experimentally for
each part. Norman Noble’s expert technicians
perform all research and development tasks prior
to production to insure that all shape and use requirements
are met.
To set shape nitinol, machined nitinol is constrained on a mandrel,
or custom fixture. This mandrel can be made by Norman Noble or provided
by
the customer. Once the nitinol is fixed on the mandrel, its shape
is set with a specific heat treat. Either Norman Noble or the customer
can specify the type of heat treat used: fluidized bed, with Alumina
media; convection air furnace; or salt bath furnace. Rapid cooling
is then used to return the metal to its original form. |
