Extension springs are helical springs that create a controlled pulling force between two points, storing energy and returning the mechanism to its starting position. Maktel produces extension springs from 0.20 to 9.00 mm wire diameter for automotive, defence, appliance, machinery, electrical-electronic, lock and mechanism applications, from prototype to high-volume series production.
Design considerations
We evaluate coil geometry, initial tension, F1/F2 working forces, working travel, maximum extension, hook loads and installation geometry together. Cycle count, fatigue life, temperature and corrosion conditions guide the design and material selection.
Hooks and end types
We produce English and German-type hooks, full and half loops, extended and side hooks, custom end fittings and geometries built to your drawing — hook geometry is a critical design factor affecting load transfer and fatigue performance.
Material, heat treatment and surface finishing
We use EN 10270-1 DH class patented cold-drawn wire, EN 10270-2 Cr-Si high-tensile wire, oil-tempered wire, high-tensile stainless wire and project-specific alloyed spring wire. Depending on the application we apply stress relieving, shot peening, Cr+3 zinc plating, black oxide, nickel plating, cataphoretic coating and passivation; for high-tensile springs the coating-material relationship is assessed separately to preserve mechanical properties.
Production and quality control
Production is CNC controlled; dimensions, spring force and hook geometry are checked, and tests required by the customer specification are applied. Approved extension springs are packed and prepared for shipment in line with traceability requirements.
