Solenoid force testing

Case study

Large solenoid tension test with pulley system

Large solenoid compression test on adjustable fixture for multiple designs

Solution

Twin-column tensile tester suitable for large solenoids
Custom fixture designed to accept multiple test specimens

Benefits

Capability to force test complete range of solenoids on one machine
Allows testing in vertical and horizontal orientation to simulate actual use

Requirement

Solenoids are used in many applications across a wide range of industries. From compact to heavy-duty, these components are fundamental to devices from small switches to large security-gate locks. They have the same operating principle of an electromagnet - a magnetic field is induced when an electrical current passes through a wire-coil – but solenoids can only operate in binary ‘on’ or ‘off’ states. When the magnetic field is present, a ferrous plunger is pulled into the housing to enable the functionality of these devices. Linear ‘push-type’ or ‘pull-type’ solenoids may operate as either ‘energize-to-hold’ or ‘energize-to-release’, where the electric current causes the plunger to push against, or be overcome by, a release spring. This duality of operation enables their implementation in ‘fail-safe’ or ‘fail-secure’ components like fire doors.

Mecmesin customers have used our force test systems to measure the important quality characteristics of their solenoids. When a fixed current is applied to the solenoid, the actuator can be pushed and pulled by the tester to identify its force/stroke curve and determine whether it is applying the correct force over its range of movement. The effect of friction within mechanical parts can be clearly seen by the amount of hysteresis in the force/stroke curve.

By using appropriate fixtures, suppliers of holding solenoids, access control devices, electrical anti-creep devices, electromagnetic security locks, actuators and proportional (positioning) solenoids can quickly and easily measure the force-to-stroke characteristics of their products.

One manufacturer required the capability to test not only their lightweight units, but also an electromagnetic bolt-lock designed to secure against mechanical loads up to 20 tonnes. The diverse range of solenoids presented one challenge, but additionally, as the customer offers a custom-design service, it was essential that Mecmesin’s test equipment provided the flexibility to test different physical sizes of unit. As these products are installed for use in both horizontal and vertical orientations, it was important that the fixtures supplied were easily interchangeable to save time when testing.

Solution

To perform tension and compression tests in both vertical and horizontal orientations, a set of fixtures were designed by Mecmesin’s Special Engineering department. A twin-column MultiTest system enabled high forces to be applied and ensured a large enough test space for the multiple-sample fixture.

The horizontal tension test used a custom threaded bolt with eyelet (provided by the manufacturer) screwed into the solenoid’s plunger. This enabled a cable, passing round a pulley, to apply the tension force to the plunger horizontally as the test stand’s crosshead moved vertically.

This versatile fixture set allowed the manufacturer to calculate the force/stroke characteristics between the extremes of the stroke; at rest and when energised. Force against stroke graphs form an essential part of the published technical data for supplier product catalogues, enabling this customer to design bespoke solenoids to specification and confidently meet their own customer’s requirement.