Reliability Design of Electrically Driven Titanium Wire (SMA) (7) Contact Surface Design

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Reliability Design of Electrically Driven Titanium Wire (SMA) (7) Contact Surface Design [Copy link]

【Foreword】

Shape memory alloy (SMA), also known as morphological memory alloy and titanium-nickel memory alloy, is composed of Ti (titanium)-Ni (nickel) materials. It is a wire made through multiple processes, which we call titanium wire for short. The titanium wire can be driven to move by circuits.

Compared with traditional motors and electromagnets, titanium wire is a new type of power component.

Titanium wire drive technology has been put into use in aerospace, intercontinental missiles, drones, mobile phones, automobiles, robots and other scientific and technological fields.

This article shares and popularizes the reliability design of titanium wire drive technology, making it easier for everyone to quickly and effectively transform it into scientific and technological achievements in the fields of mechanical and electronic industrial design.

Section 7 [Contact surface design ]

1. [Contact surface design]

We mentioned in Sections 4 and 6 that when driving the titanium wire through a rotating shaft or fulcrum structure, we recommend that the shaft diameter be designed to be 30 times larger than the titanium wire diameter. This can reduce the resistance of the drive mechanism and reduce the damage to the titanium wire caused by axial strain.

1) When the shaft diameter is too small, the titanium wire strain not only brings resistance to the drive mechanism, but also causes certain strain damage to the titanium wire. The smaller the shaft diameter, the greater the resistance brought by the drive mechanism, and the easier it is for the titanium wire to break.

2) When the driving mechanism adopts fulcrum drive, the fulcrum should be designed with R angle, not right angle or acute angle.

If the fulcrum is centered, there is no friction between the titanium wire and the driving fulcrum, and the size of the R angle does not need to be considered;

If the fulcrum is not centered and friction occurs between the titanium wire and the driving fulcrum, you need to refer to the first item and design the radius of the driving fulcrum to an appropriate R angle.

2. [Parting surface of contact surface]

During the contact design process of the drive mechanism, we need to consider the parting surface of the contact surface, especially the parting surface of metal materials.

After the design of our drive mechanism parts is completed, they enter the mold design and mold processing and production links. The parting surface will cause the parts to have the phenomenon of mold line, flash, burr, cross section, etc. during the die-casting process of the mold.

Therefore, during the structural design process, we need to prepare the draft angle in advance to avoid the intersection of the parting line and the titanium wire.

If it is unavoidable, we can add polishing and grinding process to batch parts.

3. [Mold ejector pin]

During the mold production process, our drive mechanism parts may have concave and convex surfaces caused by the ejector pins, which may cause the drive mechanism to jam or the titanium wire to be scratched or broken. This is a problem that is easily overlooked.

4. [Surface treatment of contact surface]

The surface process of the contact surface is required to be smooth, avoiding frosted surfaces, as well as the phenomena such as mold lines, flashes, burrs, and cross-sections that need to be avoided as mentioned in point 2.

Especially for parts made of harder materials, if the surface process uses frosted surface, it is easy to cause the titanium wire to break.

For example, in a ceramic shaft, the titanium wire is prone to breakage after about 5,000 to 8,000 drive operations.

If it cannot be avoided, we need to polish and grind the contact surface.

5. [Moving parts of the driving mechanism]

The four issues mentioned above also apply to the moving parts of our drive mechanism.

If the later process is not handled properly, it will easily lead to increased resistance, jamming, and blocking of the drive mechanism, thereby reducing the driving ability of the drive mechanism.

Therefore, after completing the design work, we need to pay further attention to the above-mentioned situations that may occur during mold design and mold manufacturing, and take precautions in advance.

In order to make the driving titanium wire practical in industrial applications, Brother Cai has compiled and compiled

"Cai Ge talks about titanium wire video"

《Common Circuit Control Schemes for SMA》

《Computational Model of Electrically Driven Titanium Wire (SMA)》

《Reliability Design of Titanium Drive Wire (SMA)》

Ten common structural models of electrically driven titanium wire (SMA)

A series of resources are provided for your reference. Welcome your attention and exchanges. Please like, collect and forward!

Produced by Titanium Wire Technology

Author Cai Ge talks about titanium wire