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Key Considerations When Selecting Compression Springs

Types of Compression Spring Ends

open, closed, ground, and ungrouded ends. These configurations can impact the spring rate, despite constant factors like wire size, coil count, and outer diameter (OD).

Characteristics of Closed Ends

Closed-end compression springs stand upright on flat surfaces due to closed terminal coils, favored for their simplicity and cost efficiency, as they demand less processing. For springs with high slenderness ratios, additional rod or shaft support may be necessary.

Features of Ground Ends

Ground end compression springs, a variant of closed-end springs, have precisely ground ends to align with spring dimensions. This precision comes with increased production time and costs. The ground ends ensure proper slenderness ratios, allowing effective operation without extra rod or shaft support.

Benefits of Double Closed Ends

Double closed end compression springs boast two closed terminals, similar to closed and squared ends. Produced akin to extension and torsion springs, all coils are in contact. These ends enhance stability, offering higher slenderness ratios, necessitating reinforced ends to prevent buckling, often at lower costs than their closed or ground counterparts.

Details on Open End

Open end compression springs are less common due to stability concerns without rod or shaft support. With open and spaced coils, these springs suit applications prioritizing minimized solid height.

Material Concerns for Compression Springs

Popular spring materials include carbon steel and exotic alloys. Music wire, high carbon steel, is commonly used, while stainless steel 302, though less strong, offers superior corrosion resistance.

Nickel alloys are selected for extreme temperature tolerance, corrosive resistance, and non-magnetic properties, available under various brand names. Copper alloys, such as phosphor bronze and beryllium copper, are prized for excellent electrical conductivity and corrosion resistance.

Physical Aspects of Compression Springs

Outer Diameter (OD): For springs inserted into holes, consider the outer diameter. If surrounded by internal components, measure their dimensions. OD expands under compression, essential to consider if used in tubes or bores. The OD measures across the outer coil edges.

Manufacturing processes can restrict spring OD, impacting required assembly space. Manufacturers offer work-in-hole diameters based on anticipated OD expansion and tolerances, crucial when ordering custom springs or choosing from catalogs.

Inner Diameter (ID): For springs fitting over shafts or mandrels, account for the inner diameter. A minimum clearance of ten-thousandths of an inch prevents friction. The ID calculates by deducting twice the wire diameter from the OD.

Free Length: Ensure the spring's free length exceeds available space for a preloaded state, maintaining position. Free Length, the spring length without compression or force, measures from end to end or tip to tip.

Solid Height: Wire diameter and total coil count dictate solid height, crucial to ensure loaded heights do not exceed or undercut the solid height.

Environmental factors, temperature, and moisture exposure influence spring performance. Costlier materials withstand higher temperatures, increasing spring expenses.

Spring Pitch: Pitch refers to space between adjacent coils, from center to center. Calculate by measuring coil gaps and adding wire thickness.

Active Coils: These are the coils in compression springs that compress and deflect under load, contributing to the spring's movement.

Total Coils: This includes both active coils and non-deflecting, closed coils devoid of pitch.

Noting total and active coil counts is important. Closed or ground-end springs have inactive ends, whereas open-end springs boast fully engaged active coils.