Shape memory alloys (SMAs) exhibit exceptional actuator and sensory functionalities utilized in various industrial sectors, such as medical technology, aerospace, and automotive [
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4]. In these fields, where lightweight, silent operation and high performance are crucial requirements, they are gaining increasing significance. SMAs can be exploited as actuators with minimal additional components, resulting in weight and space savings compared to electromagnets. Commercially wrought SMAs are available in the form of wires, foils, sheets, and tubes. Wires with various thicknesses and distinct shape memory effects (SMEs) are readily available on the market. Despite attempts by the industry to establish standardized actuators, numerous customized actuator systems are being developed. In the case of actuators, Nickel–Titanium (NiTi) is predominantly used due to NiTi’s superior SMEs. The underlying mechanism for the SMEs is the reversible martensitic transformation, where the high-temperature phase austenite transforms into the low-temperature phase martensite on cooling/mechanical loading. Upon heating/unloading, the reverse transformation takes place. In most actuation applications, the extrinsic two-way effect is exploited, in which a constant force is applied and the phase transformation is triggered by heating, thereby realizing actuator movement. System integration of SMA wires often involves a firmly bonded or clamped connection (e.g., casting, crimping, adhesive bonding). However, these techniques have significant drawbacks. The intensity of the SME and the fatigue life of the actuator strongly depend on microstructure and surface condition [
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9]. Therefore, exposing the material to elevated temperatures or mechanical stresses/surface damage during processing can affect actuator performance. Moreover, conventional connections cannot be undone without causing harm to the actuator. Adhesive joints require additional surface treatments and the mechanical compatibility of these joints can be problematic [
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13]. Especially, the incorporation of wire actuators into engineering systems necessitates additional developmental steps as compared to standardized and pre-assembled actuators. To address these challenges, a novel approach based on a form-fit connection is investigated in the present study. The approach consists of melting the ends of conventional SMA wires to establish a sphere, which, due to its larger diameter, can be used as a form-fit connection element. In the present work, an experimental setup with an integrated high-speed pyrometer was used to control the surface temperature of the melt pool during sphere generation. A first proof of concept applying this technique without temperature control has already been published elsewhere [
14]. As an application example for such actuators with spherical ends, a connection to a printed circuit board can be realized by press-fitting the manufactured spherical end into a coated hole, providing a mechanical anchorage and an electrical connection. In general, lasers are important tools for processing and welding NiTi SMAs since they apply the energy locally at high densities and thus minimize the size heat-affected zones, HAZs [
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19]. However, the successful laser processing of NiTi strongly relies on precise control of process temperatures. Particularly with smaller material volumes, such as wires, the risk of uncontrolled overheating exists, as the usage of constant laser power does not provide control of the temperature due to the high process dynamics. This may lead to unintentional vaporization of nickel, which has a significantly lower vaporization temperature of 2730 °C compared to the vaporization temperature of titanium with 3260 °C [
20]. Alternatively, there are different material characteristics, such as microstructure and transformation behavior, which are strongly dependent on the thermal history of the material. Modern pyrometers allow real-time monitoring and control of temperatures, preventing excessive heat accumulation and potential material damage. In scientific research and comparative studies, the inclusion of an advanced pyrometer enhances the consistency and reliability of experimental data [
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24]. Researchers can establish a standardized framework for assessing laser processing parameters by precisely measuring and documenting process temperatures, facilitating meaningful comparisons, and promoting reproducibility across different studies. The present work addresses the performance of temperature-controlled fused spherical shape memory wire actuators in terms of mechanical, thermal, and functional properties.