How can the shielding effectiveness of the metal housing of an HMI (Human Machine Delivery System) be guaranteed?

Ensuring the shielding effectiveness of the HMI metal enclosure hinges on controlling gaps, openings, and cable entry/exit points that allow electromagnetic leakage. Shielding effectiveness primarily depends on the enclosure material itself, typically aluminum alloy, steel plate, or galvanized steel. Higher conductivity and thicker materials generally provide better shielding. All joints between enclosure components must maintain good electrical continuity, achieved through the use of conductive gaskets, finger springs, or multi-point screw connections. Insulating varnish must be removed from the joint surfaces. For necessary display windows, transparent conductive film or metal mesh laminated glass should be used, with its conductive frame tightly connected to the enclosure.

Ventilation vents should be designed as waveguide arrays, i.e., an array of numerous small holes, with a cutoff frequency higher than the highest frequency requiring shielding. Openings for buttons, indicator lights, etc., should use plastic parts with a metallic coating or incorporate conductive bushings. All cable entry/exit points must use shielded cables and shielded connectors, or feedthrough filters and conductive sealing gaskets. The grounding terminal on the enclosure must be reliable, ensuring proper connection to the mounting cabinet. Shielding effectiveness can be evaluated through simulation during the design phase and verified through testing. Eintech offers a variety of conductive pads, shielding windows, and filter connector assemblies to help engineers build HMI metal housings with excellent shielding performance.