How to Specify a Custom Spring

A custom spring specification should describe how the spring fits, how it moves and what load or torque it must deliver at defined operating positions. A photograph or a few external dimensions alone may not explain the requirements of the assembly.

Start with the spring type, a controlled drawing or reference sample, the operating conditions and the expected quantities. Identify which requirements are fixed and which may be reviewed with the manufacturer.

Provide the wire size, relevant diameters, free dimensions and end or leg geometry. Include the available installation space and the dimensions of mating components where they affect fit.

For a compression spring, distinguish its outside diameter from the diameter of the hole it fits into. If a guide rod is used, include the rod dimensions. Specify the free length and any relevant working lengths or solid-height restriction.

For a torsion spring, show the leg geometry, reference angle, working direction and the available space around the body and legs.

For a compression spring, state the required force at identified working lengths and the allowed tolerance. For an extension spring, identify the reference points used to measure extension and the required forces at the specified positions.

For a torsion spring, state the torque at defined angular positions and make the direction of movement clear. A description such as “stronger” should be translated into a measurable functional requirement.

Describe the expected movement, frequency of operation, target service life and installation conditions. Include the temperature range and relevant exposure to moisture, chemicals or other environmental conditions.

If a life or performance test is required, supply the test conditions and acceptance criteria. A cycle target without the associated operating conditions is incomplete.

Specify the required material grade and finish, or ask for a material proposal based on the application. Identify which characteristics require inspection and what reports or approval samples are needed.

Provide sample quantities, forecast production demand and delivery requirements. Drawing changes should be controlled by revision so the quotation and approval samples refer to the same requirements.

Send your drawing, load or torque requirements and expected quantities to tenghungkuo@anli-metal.com. ANLI reviews the spring design, process and quotation against the requirements of each application.