Neometrix / Spring & Component Test Machines / Spring Testing Machine / NMX-SPT-37

NMX-SPT-37 · ENGINEERED-TO-ORDER CLASS — LOAD · MEASURE · RELEASE · RECORD

Spring Testing Machine. A spring's rate is the easy number. Whether it comes back is the one that decides its life.

Name: Spring Testing Machine
Brand: Neometrix
SKU: NMX-SPT-37

Anyone can read what a spring does while it is loaded. The load cell and a ruler will tell you that. What a load cell and a ruler will not tell you, on their own, is whether the spring comes all the way back once the load is gone.

So this machine does three things in order. It loads the spring smoothly and reads its rate. It releases the spring and reads what it has kept. And when the spring will be cycled in service, it does both again and again until the spring's fatigue life is a fact and not a guess.

Discuss a spring testing machine Capability note (PDF)

A spring testing machine: two slim steel columns supporting a crosshead, a plain unmarked coil spring resting on the lower platen, and a plain grey electronics cabinet beside the frame, and no people

Fig · 01 — A spring testing machine: a two-column load frame with a digital crosshead, a plain coil spring on the lower platen, and a control cabinet beside it — illustrative render.

The rate

read in one passthe slope of load against position

The set

read after releasedoes it come back to free length

The fatigue life

read over cyclesdoes it still come back the thousandth time

The fixture

matched to the motioncompression, extension or torsion

Status

quoted, engineered to orderno unit yet delivered

ISO 9001ISO 14001EN 13906 spring design referenceISO/IEC 17025 calibration reference

Overview

Why a spring is proved by what it does after the load is gone.

Because a spring that is right for stiffness alone is not proven for the job it will actually be asked to do.

Fig · 02 — The machine in one picture: load feeds measurement, which feeds the record, with the fixture and the calibration standing behind them.

A spring is never measured directly. Only load and position are.

What the machine is for

It tests compression, extension and torsion springs, whether newly made, received from a supplier, or removed from service, to find out what they actually do under load, not what the drawing says they should do.

Why the rate is the easy part

A spring is never measured directly. Only its load and its position are, and the rate is simply the slope of that line. A single smooth pass, read carefully, gives the rate.

Why the set is the harder part

A spring that has taken a permanent set will not return to its free length once the load is removed. That only shows up after the load is taken off and the spring is left to find its own length, which is why the machine does not stop at the top of the load.

Why fatigue is a third question

A spring that passes its rate and its set once can still fail the thousandth time it is loaded. A spring meant to be cycled in service has to be cycled on the machine before it is trusted to be cycled anywhere else.

Why the fixture changes with the spring

A compression spring is pushed between platens, an extension spring is pulled by its own end hooks, and a torsion spring is twisted about its axis. The fixture changes; the three questions asked of the spring do not.

Why the load cell is not fixed to the frame

A load cell sized for the heaviest spring a frame will ever see reads a light spring poorly. So the machine is built to take a load cell matched to the spring in front of it, not just to the frame's own maximum.

The test

Mount, zero, load, hold and read, release and recover, record and cycle.

Six steps in a fixed order. The last two are the ones a single reading under load cannot show.

FIG · 02SPRING TESTING MACHINE · MOUNT / ZERO / LOAD / HOLD & READ / RELEASE & RECOVER / RECORD & CYCLE — THE SPRING IS JUDGED BY WHAT IT DOES AFTER THE LOAD IS GONE

The step people underrate is the release. A spring that is never let go of is a spring that was never really tested.

Fig · 03 — Three spring types, three motions: compression, pushed between platens; extension, pulled by its end hooks; and torsion, twisted about its own axis — a drawing of the idea, with no values.

1 · Mount

The spring is fitted to a fixture matched to its own ends: platens, hooks or a torsion arm.

2 · Zero

The free length, or the free angle, is read before any load is applied, so every later reading has something to be measured against.

3 · Load

The load is applied smoothly to the chosen point and held, never jerked or bounced onto the spring.

4 · Hold & read

Load and position are read together, at rest, so the rate comes from a real reading, not an assumption.

5 · Release & recover

The load is removed and the spring is left to find its own length, which is where a permanent set shows itself.

6 · Record & cycle

The curve and the set are logged, and if the test calls for it, the whole cycle is repeated until a fatigue life is a fact.

Work content

What the machine contains, element by element.

Read it as a checklist: a machine missing a row will buy that row back later, usually as a result nobody can trust.

A plain unmarked coil spring clamped between two flat steel platens on a small test fixture, with a thin cable leading away from the top platen, and no people

Fig · 04 — A spring clamped in its fixture between two plain plates, ready for a compression test — illustrative render.

Element	What it does	What matters
Load frame	holds the fixture square and rigid	stiff enough that its own flex never enters the reading
Crosshead drive	moves the fixture smoothly to the load	screw or servo-driven, with no jerk at the start
Load cell	reads the force on the spring	matched to the spring under test, not fixed to the frame's maximum
Displacement transducer	reads position for compression and extension	fine enough to define the whole curve, not just the end points
Rotary encoder & torque cell	read angle and torque for torsion springs	a different pair of instruments for a different motion
Compression fixture	holds the spring between platens	parallel and square to the load
Extension fixture	holds the spring by its own end hooks	grips the hook, not the coil
Torsion fixture	holds the spring and applies a torque about its axis	the arm length is part of the calibration
Guarding	protects the operator	against the stored energy a broken spring can release
Control & data acquisition	runs the sequence and logs load and position together	the same sequence every time, against limits from the spring's own drawing
Calibration	keeps every reading trustworthy	traceable, and checked before it is relied on
Testing & documentation	prove the machine, then every spring	a calibrated machine, and a report for every spring

The element that decides whether a reading can be trusted is not a machine at all. It is the load cell. A frame with the wrong load cell for the spring in front of it is measuring with the wrong instrument, however good the frame.

Fig · 05 — One machine, three load ranges: a light spring, an ordinary spring and a heavy spring, all on the same frame.

Full specification — expand

Machine	A load frame with a screw or servo-driven crosshead; a load cell matched to the spring under test; a displacement transducer or, for torsion, a rotary encoder and torque cell; fixtures for compression, extension and torsion, matched to the spring's own ends; a control and data acquisition system; guarding against a sudden release of stored energy; and testing and documentation before handover
The One Idea	A spring's rate is the easy number. Whether it comes back is the one that decides its life
Why the Rate Is Easy	A spring is never measured directly - only the load and the position are - and the rate is simply the slope of that line, read in a single smooth pass
Why the Set Is Not	A spring that has taken a permanent set will not return to its free length once the load is removed, and that only shows up after the load is taken off and the spring is left to find its own length
Why Fatigue Is a Third Question	A spring that passes its rate and its set once can still fail the thousandth time it is loaded, so a spring meant to be cycled in service has to be cycled on the machine before it is trusted
Why Three Motions	A compression spring is pushed between platens, an extension spring is pulled by its end hooks, and a torsion spring is twisted about its own axis, so the fixture changes with the spring even though the three questions asked of it do not
Why the Load Cell Changes	A load cell sized for the heaviest spring a frame will ever see reads a light spring poorly, so the machine is built to take a load cell matched to the spring in front of it, not just to the frame's own capacity
Standards	EN 13906-1, EN 13906-2 and EN 13906-3 are the public references for the design of compression, extension and torsion springs, and ISO/IEC 17025 for calibration. None of them sets the limits for a particular spring: those come from the spring's own drawing and are set by the customer. Acceptance of the finished machine rests with the customer and their inspection authority
Configurations	A bench machine for one fixture and static tests, a fatigue rig built to cycle a spring for endurance, and a multi-mode rig that takes compression, extension and torsion fixtures on one frame
Scope Boundary	This is the machine built around a spring's own rate, set and fatigue life. It is not a general load frame for materials and components (see servo-hydraulic fatigue testing machine), not a single-blow toughness test (see materials impact testing machine), and not a test of a complete suspension unit (see hydro-gas suspension (HSU) validation system)
Status	Neometrix has quoted against successive spring testing machine requirements, and no delivered spring testing machine is claimed.

Configurations

One method, three ways to supply the machine.

The steps, the calibration and the record are shared. What changes is whether the machine cycles, and how many spring types it must take.

Bench machine

One fixture, static tests

A fixed machine with one fixture, for a laboratory that tests a single spring type: rate and set, on demand.

Fatigue rig

Cycled, for endurance

A machine built to cycle a spring, hour after hour, so that its fatigue life is a fact and not an assumption.

Multi-mode rig

Compression, extension, torsion

One frame with interchangeable fixtures, so a laboratory that sees all three spring types does not need three machines.

Fig · 06 — Three ways to supply the machine, one method: a bench machine, a fatigue rig, or a multi-mode rig.

And the part that is not equipment at all, yet decides all three: the test method — the written sequence, the limits taken from the spring's own drawing, and the rule for reading the set, so that every spring is judged the same way.

Where it is used

Wherever a spring has to be trusted before it goes into something else.

The common thread is a spring whose failure would be somebody else's problem, later and harder to trace.

Spring manufacturers

Where every batch, or a sample from it, is proved against its own drawing before it ships.

Incoming inspection

Where a spring is received from a supplier and checked before it is built into an assembly.

Vehicle and rail workshops

Where springs are tested new, or after time in service, as part of an overhaul.

Research and design

Where a new spring design is proved against its calculation before it is committed to.

FAQ

Common questions.

Longer answers, for readers who want the reasoning.

Q · 01 What does a spring testing machine actually measure?

Two things, directly: load and position. Everything else is worked out from them. The spring rate is the slope of the line those two draw as the spring is loaded - a straightforward calculation from a careful reading. The permanent set is the difference between the spring's free length before the test and its length once the load has been removed and it has been left to settle. For a torsion spring, position becomes an angle and load becomes a torque, but the same two-quantity idea holds. No instrument reads a spring's rate directly; it is always derived from load and position measured together.

Q · 02 Why does the release matter as much as the load?

Because a spring's job, in service, is not just to push or pull under load. It is to go back to where it started once the load is gone, ready for the next cycle. A spring can meet its rate perfectly while under load and still take a permanent set once released, especially if it has been loaded close to the point where its coils touch or its material is worked hard. That failure is invisible to a test that only reads the spring while it is loaded. It only shows up in the step most benches are tempted to skip: releasing the spring fully and reading what length, or what angle, it has actually kept.

Q · 03 Why do compression, extension and torsion springs need different fixtures?

Because they are loaded in different directions and by different features of the spring itself. A compression spring is squeezed between two flat, parallel platens, and its ends must sit square to the load or the reading is distorted. An extension spring is pulled apart by hooks or loops formed into its own ends, so the fixture has to grip the hook without damaging it, not the coil. A torsion spring is twisted about its own axis by an arm, and the arm's length becomes part of the calibration, because torque is force multiplied by that length. The three questions asked of the spring, rate, set and fatigue life, are the same in every case; only the hardware that applies and reads the load changes.

Q · 04 Why can one machine not just use its biggest load cell for every spring?

Because resolution is not free. A load cell reads best near the top of its own range and progressively worse near the bottom of it, so a load cell chosen for the heaviest spring a frame will ever see is a poor instrument for a light one - the reading is technically a number, but not a trustworthy one. A machine built to serve more than one class of spring is built to take an interchangeable or auto-ranging load cell, matched to the spring actually on the fixture, while the frame, the fixtures and the method stay the same. The frame's capacity sets the ceiling; the load cell in place on a given day sets how well the floor is read.

Q · 05 Is this the same as the fatigue testing machine, the impact tester, or the suspension-unit rig?

No, and the differences are worth stating precisely. The servo-hydraulic fatigue testing machine page is a general-purpose load frame for materials and components, not built around a spring's own end geometry or its free length. The materials impact testing machine page measures toughness with a single pendulum blow, not a load-deflection curve built up over a smooth cycle. The hydro-gas suspension (HSU) validation system page proves a complete suspension unit, gas and hydraulics together, not the raw mechanical spring that might sit inside one. This page does not replace any of them, and it does not claim what they claim a second time.

Q · 06 Has Neometrix built one of these?

We would rather answer this plainly than let a page imply otherwise. Neometrix has quoted against successive spring testing machine requirements, and no delivered spring testing machine is claimed. What stands behind the offer is adjacent: Neometrix engineers general-purpose load frames and their servo control (see the servo-hydraulic fatigue testing machine page) and precision instrumentation and data acquisition built around a single-blow test (see the materials impact testing machine page). The load cells, displacement transducers, torque cells and the frame's own drive are proven catalogue items and are chosen with the customer, not invented. What Neometrix engineers is the frame, the fixtures, the data acquisition, the calibration chain, the test method and the documentation. So the honest position is that the machine is engineered to order, the neighbouring disciplines are in the building, and the first machine of this exact kind will be built around the customer's own springs and drawings rather than lifted off a shelf.

Q · 07 Which standards apply, and who sets the pass criteria?

EN 13906-1, EN 13906-2 and EN 13906-3 are the public references for the design and calculation of compression, extension and torsion springs made from round wire and bar. ISO/IEC 17025 is the public reference for the competence and traceability of the calibration that makes the machine's readings trustworthy, and ISO 9001 for the quality system around the build. None of them sets the rate, the free length or the allowable set for a particular spring: those come from the spring's own drawing, and this page prints none of them. Acceptance of the finished machine, including its proving tests before handover, rests with the customer and whatever inspection authority they name.

Q · 08 What do you need from us to quote?

Six things, and most of them describe the spring rather than the machine. First, the spring types: compression, extension, torsion, or a mix. Second, the range: the lightest and the heaviest spring the machine must take, since that sets the frame and the load cells. Third, the tests: rate and set only, or fatigue as well. Fourth, the fixtures: any spring geometries that need a purpose-made fixture rather than a standard one. Fifth, the configuration: a bench machine, a fatigue rig, or a multi-mode rig. Sixth, the site: the power and floor space the laboratory can offer. From that we come back with a layout drawing, a written test method you can check, and a budgetary price.

The neighbouring test machines, and how they differ from this one.

Three neighbours in the same family of load, structural and component test equipment.

↗ The general load frame

Servo-Hydraulic Fatigue Testing Machine

A general-purpose load frame for tension, compression and fatigue of materials and components, not built around a spring's own geometry.

↗ A single blow, not a curve

Materials Impact Testing Machine

Pendulum impact testers that measure toughness by a single blow, not a load-deflection curve.

↗ The whole unit, not the spring

Hydro-Gas Suspension (HSU) Validation System

Proves a complete gas-and-hydraulic suspension unit, not the raw mechanical spring that a simpler unit might use.

Browse all Neometrix product lines.

Get a quotation

Tell us the spring, the range,
and whether it must be cycled.

The projects desk replies within two working days with a layout drawing, a written test method you can check, and a budgetary quotation. Write to [email protected] or use the form.

Enquire — spring testing machine Capability sheet (PDF) +91 7777 876 876

ISO 9001 / 14001 ENGINEERED-TO-ORDER CLASS — SPRING TESTING MACHINE MOUNT · ZERO · LOAD · HOLD & READ · RELEASE & RECOVER · RECORD & CYCLE — THE SPRING IS JUDGED BY WHAT IT DOES AFTER THE LOAD IS GONE ENGINEERED IN NOIDA · INDIA