Derui chamberFoam material testing for furniture and mattress laboratories
A foam sample that recovers after a short compression can still change after sustained compression or repeated loading. Compression set and dynamic fatigue evaluate different responses. This guide explains how to select the method, control the specimen and measurements, and connect the test scope with suitable laboratory equipment.
Quick answer: Compression set evaluates residual deformation after a defined compression and recovery procedure. Dynamic fatigue evaluates changes after repeated loading. Choose the applicable method and edition, then confirm the fixture, loading conditions, measurements and reporting formula. Neither result should be converted into a universal furniture service life or quality grade.
1. Compression Set and Dynamic Fatigue Are Different Tests
Compression set
The sample is held at a specified compression for a defined period and environment, released and measured after the required recovery. The result describes remaining deformation under those conditions.
Dynamic fatigue
The sample undergoes repeated loading. The evaluation compares relevant properties before and after that loading, such as thickness and hardness under a defined measurement procedure.
The tests complement one another when both are relevant to the material specification. A satisfactory result in one does not establish performance in the other. Results from raw foam specimens also should not be treated as a complete evaluation of an assembled chair, sofa or mattress.
2. Select the Standard, Test Item and Material Scope
ASTM D3574 includes several methods for flexible polyurethane foam. ISO 1856 concerns compression set of flexible cellular materials, while ISO 3385 concerns fatigue under constant-load pounding. Identify the exact method before comparing results or purchasing fixtures.
| Reference | Relevant evaluation | Planning check |
|---|---|---|
| ASTM D3574, Test D | Compression set with maintained deflection. | Confirm specimen preparation, compression, exposure, recovery and the calculation for the requested edition. |
| ASTM D3574 fatigue methods | Different repeated-loading procedures, including constant-force and constant-deflection pounding methods. | Specify the test item; a reference to D3574 alone does not identify the fatigue procedure. |
| ISO 1856 | Compression set. | Confirm material scope, selected method and its conditioning, exposure and reporting requirements. |
| ISO 3385 | Fatigue by constant-load pounding, including assessment of thickness and hardness changes. | Confirm the specimen, loading and measurement procedure. Do not assume identical conditions to an ASTM method. |
A constant-force setup and a constant-deflection setup control different variables. Use the method named by the buyer or responsible laboratory. Any proposed equivalence between standards needs a documented comparison of procedures, not just a similar machine description.
3. Plan a Controlled Compression Set Evaluation
The fixture must maintain the required plate separation and specimen arrangement throughout the exposure. Where the procedure uses spacers or limiters, their dimensions establish the gap; increasing clamp force is not a substitute for the specified compression.
- Identify and prepare the samples.Record material, batch, cutting direction, specimen dimensions and the number required by the method. Apply the specified preparation and conditioning.
- Measure the initial thickness.Use the required measuring arrangement and contact conditions. Identify each sample so its final measurement can be paired with its initial value.
- Set and maintain the compression.Confirm the plate gap, spacer arrangement, parallelism and specimen placement. Record the selected compression rather than treating fixture capacity as a test requirement.
- Apply the specified exposure.Follow the required time and environment, including an oven where the selected procedure requires it. Record actual conditions and interruptions.
- Release, recover and calculate.Follow the specified handling and recovery timing, then measure and calculate using the method’s formula and reporting basis.
For a compression set setup involving an oven and compression fixture, review the DR-J204 Foam Compression Set Tester with Laboratory Oven against the selected method, specimen arrangement and temperature requirements.
Sample quantity and capacity are separate: the method specifies how many samples must be evaluated. The fixture’s usable plate area and arrangement determine how many it can accommodate. Confirm both before ordering.
4. Plan Dynamic Fatigue Around the Required Loading Control
Define the specimen support, loading head, loading control, operating rate and completed loading required by the method. Confirm how the machine establishes and verifies the controlled variable.
- Measure the initial properties using the prescribed procedure.
- Position the specimen and loading assembly consistently, with safe access and guarding.
- Run the required sequence and retain count, settings, interruptions and observations.
- Apply the specified recovery and final measurement conditions.
- Compare the relevant properties and identify the exact method in the report.
The DR-J802 Foam Dynamic Fatigue Tester is a product to discuss for repeated-compression work. Confirm the proposed loading control, fixture, specimen fit and records for your actual procedure.
A fatigue test does not measure density by itself. If density is part of the material specification, determine it separately with the appropriate specimen and method.
5. Keep Thickness Loss, Compression Set and Hardness Change Distinct
Before reporting a percentage, confirm the reference value in the denominator. “Thickness loss” and “compression set” should not automatically be used as names for the same calculation.
Illustrative thickness calculation
If a sample measures 25 mm initially and 23.5 mm after recovery under the same measuring conditions, the difference is 1.5 mm. Relative to the initial thickness, that is 6%. This arithmetic example does not establish the required compression set formula or an acceptance limit.
Illustrative hardness comparison
If the same measurement procedure gives 200 N before fatigue and 170 N afterwards, the difference is 30 N, or 15% of the initial value. Use this calculation only where it matches the reporting procedure and agreed measurement basis.
Use the compression set formula required by the selected method, including its reference dimensions. For hardness change, compare measurements made at the same specified conditions rather than combining different indentation methods or settings.
Where indentation force measurements are required, review the DR-J801 Foam IFD Hardness Tester against the required loading foot, support, measuring range and procedure. Confirm whether this function is included in the fatigue package or needs separate equipment.
Apply acceptance criteria from the governing material specification or agreed buyer requirements. Avoid assigning “premium,” “acceptable” or “failed” grades to arbitrary percentages.
6. Check the Setup Before Diagnosing a Material Problem
| Unexpected observation | Checks that help interpretation |
|---|---|
| Large residual thickness change | Confirm initial measurement, plate gap, specimen placement, exposure and recovery timing before attributing the change to material composition. |
| Hardness changes with little thickness change | Review the measurement procedure, support, specimen condition and recorded loading. These properties need not change by the same proportion. |
| Different results within a batch | Check sample location and orientation, geometry, preparation, identification and equipment conditions. |
| Interrupted or irregular fatigue run | Record the interruption and loading actually completed. Follow the approved procedure for continuation, repeat testing or reporting a deviation. |
A test result alone does not prove a specific cell-structure mechanism or prescribe a formulation change. Review the specimen and supporting evidence, then document any material or process change before comparing further tests.
7. Specify the Equipment and Records You Need
- Compression fixture: plate geometry, gap-setting accessories, specimen arrangement and handling needs.
- Exposure equipment: required environment, usable space and condition verification for the selected procedure.
- Fatigue assembly: loading control, head and support geometry, adjustment range and operating sequence.
- Measurement equipment: thickness and hardness functions, ranges, measuring conditions and relevant calibration records.
- Data and reports: sample identity, initial and final values, loading or exposure records, calculations and deviations.
- Laboratory installation: utilities, access, guarding, operating instruction and maintenance arrangements.
Keep the sample register and record raw measurements as well as calculated values. A report should identify the material, specimen preparation, method and edition, actual conditions, recovery, results and the source of acceptance criteria.
8. Send a Useful Foam Testing Equipment Enquiry
Provide the foam type, specimen dimensions, required methods and editions, compression or loading requirements, exposure conditions, sample throughput, measurement and export needs, and available laboratory utilities.
If both compression set and fatigue are needed, list them separately. Ask the supplier to identify included fixtures and measurement functions, optional accessories and work requiring another instrument.
9. Frequently Asked Questions
Is compression set the same as dynamic fatigue?
No. Compression set examines residual deformation after a defined compression and recovery. Dynamic fatigue evaluates changes following repeated loading.
Can one fixed temperature, time and cycle count cover all methods?
No. Use the conditions of the selected procedure and edition, together with any documented buyer additions.
Are constant-force and constant-deflection fatigue interchangeable?
No. They control different variables. Confirm the method before selecting equipment or comparing results.
Can the original-thickness percentage always be called compression set?
No. Check the selected method’s formula and reference dimensions. State the calculation clearly rather than changing the result’s name.
Does a fatigue machine automatically measure hardness loss?
Only if the required measurement function and procedure are supplied. Confirm the measuring assembly and whether a separate instrument is needed.
Do these results predict the life of a finished sofa or mattress?
They describe material response under defined laboratory conditions. Product construction and use add other influences; do not treat a material result as a complete finished-product durability evaluation.
Related Equipment and Laboratory Planning
- Foam testing equipment — explore equipment for different material evaluations.
- Furniture testing equipment calibration checklist — plan measurement checks and records.
- How to set up a furniture testing laboratory — connect the test scope with equipment and utilities.
Method References
Consult the ASTM D3574 catalogue, BSI’s entries for ISO 1856 compression set and ISO 3385 constant-load fatigue, and Instron’s D3574 method overview. Use the applicable standard and approved procedure for detailed settings and calculations.
