In recent years, the demand for heatable plastic surfaces has grown steadily in many areas. Examples can be found in the automotive sector in particular: Especially in the winter months, camera systems, headlights, lidar systems or elements of radar sensor technology, which are required for autonomous and semi-autonomous driving, regularly freeze up. For example, the LED technology used in modern headlamp systems does not generate enough radiant energy (cold emitters), which means that additional heating is required to defrost the headlamp covers. Integrated heating wires, which automatically ensure defrosting at low temperatures, provide a remedy here. In recent years, integrated heating wires have established themselves as a versatile option for heating plastic surfaces. They stand out from alternatives such as vaporized surfaces, for example, because they do not affect radar or lidar systems.
To ensure that heating wires can be installed invisibly, it is important to conceal them in existing plastic elements. Manufacturer logos and parts of the front and rear bumpers are ideal for this. However, these usually have curved surfaces, which requires a process with three-dimensional alignment for attaching the wires.
Previous solutions usually involved first applying the heating wires to a film, which was then overmolded. However, this method only works with slightly curved surfaces. Three-dimensionally shaped surfaces cannot be mapped using this method, which also limits the design of the plastic elements to be heated.
With 3D wire embedding, there are very few limits to the design of plastic covers. 3D wire embedding technology XYZ, newly developed by MackSmaTec, integrates heating wires into already designed plastic surfaces by applying wire geometries directly to the front or rear of sensor covers, front grilles, emblems or bumpers. Not only does this ultimately lead to more precise results, it also saves a considerable amount of time and money. With a diameter of between 50 and 100µm, the wires are barely visible. Reflections can also be prevented by a black coating.
How does 3D wire embedding work?
3D wire embedding is an innovation compared to the conventional wire embedding process, which is used, for example, in the production of antennas in chip cards. A new addition is the ability to utilize additional degrees of freedom using a 6-axis robot. This enables a depth dimension in wire embedding and the robot's ability to react to curved/uneven surfaces: the robot can adapt the inclination of the wire embedding head to the surface to be processed. This is important because the wire-embedding process can only work if the sonotrode is aligned perpendicular to the surface being processed. To make this possible, the MackSmaTec wire-laying head was combined with a robot from ABB, which is equipped with the so-called Integrated Force Control package, which makes it possible to always generate the same contact pressure - thus compensating for unevenness or deviations between the workpiece and the 3D contour.
Excursus: What does Integrated Force Control mean and what are the advantages?
With the Integrated Force Control package, robot developer ABB has created a solution that enables robots to react actively to their environment. This is based on tactile sensors that constantly provide information about the environment. This information ensures that the robot adjusts its speed or deviates from the specified path, for example. Thanks to Integrated Force Control, it is therefore possible to machine complex contours.
wire embedding as such is carried out using theultrasonic wire embedding technology developed by MackSmaTec. This works with an innovative ultrasonic technology that enables a fast and precise process: an ultrasonic generator is used to generate electrical vibrations at 70 kHz, which are converted into mechanical vibrations by a piezo crystal. The sonotrode amplifies these vibrations, resulting in molecular and interfacial friction on the substrate. The friction between the sonotrode, wire and substrate or plastic surface leads to partial melting of the latter. The heating wire is then placed into the molten plastic via the wire feedthrough in the sonotrode and thus integrated directly into it.
The penetration path of the wire is regulated by the contact pressure of the sonotrode on the surface. Precise force control is essential for a stable process. Thanks to ABB's Integrated Force Control, the robot can also react actively to uneven surfaces and adjust its path or the alignment of the wire-laying head accordingly. This makes it possible to process concave and convex contours with the 3D wire-embedding process.
What are the advantages of 3D wire embedding?
The advantages of innovative 3D wire embedding technology lie firstly in the ability to process three-dimensional surfaces quickly and without intermediate steps. The 3D wire embedding contour can either be programmed as a curve in space using the RobotWare robot control software or read in as a path from a 3D CAD file. The compact design of the robot cell is a further advantage. In addition, the process may also be used in other sectors in the future and can be used wherever heated plastic surfaces are required. This means that more cost-intensive and time-consuming methods can be replaced.
