Choosing a universal testing machine starts with one number: capacity. Get it right and the machine will serve your laboratory for years, running tensile, compression and bending tests across a wide range of materials. Get it wrong and you either overload the frame, damage the force sensor, or tie up a large budget in a machine that never works near its rated load. Capacity selection is not a one-line calculation, but it follows a few straightforward rules. This guide walks through the materials and specimens you test, the standards you quote, and the drive technology that suits each load range, with real CHENJI universal testing machine models as reference points.
Start with the Materials and Specimens You Test
Capacity is the maximum force a universal testing machine can apply, rated in newtons (N) or kilonewtons (kN). The force your test actually needs depends on two things: the strength of the material and the cross-section of the specimen. The rough relationship is force = tensile strength × cross-sectional area. A 500 MPa steel coupon with a 100 mm² cross-section needs about 50 kN, while the same geometry in a 40 MPa rubber sample needs only 4 kN. That is why one machine family covers very different applications.
- Rubber, plastics, films, wires and small springs usually stay below 5 kN. A compact single-column frame such as the WDW-5 5 kN Single Column Universal Testing Machine with Convenient Operation fits this range with a small footprint and easy operation.
- Small metal coupons, fasteners and springs up to 10–20 kN suit bench-top electronic machines like the WDW-10 10 kN Electronic Universal Tensile Strength Testing Machine.
- Standard metal specimens, rebar and structural sections commonly need 100–500 kN, which is the band covered by the WDW-100 kN 200 kN 300 kN 500 kN Electronic Loading Universal Tensile Strength Testing Machine.
- High-strength and large-section testing moves into the 600–1000 kN class, where hydraulic frames such as the WEW-D Series 30 Ton 300 kN / 60 Ton 600 kN / 100 Ton 1000 kN Hydraulic Loading Universal Testing Machine and the WAW-1000A 1000 kN Computer Control High Capacity Hydraulic Universal Testing Machine provide the stiffness and power that large samples demand.
Match Capacity to Test Standards and Add Working Margin
Once you know the maximum force your specimens can produce, apply a working margin. A common rule of thumb is 20–50% above the highest expected load, because materials vary between batches, specimens are sometimes larger than planned, and some standards call for test rates that push the force higher. Also check the low end: force measurement accuracy is usually quoted as a percentage of the rated capacity, so a 1000 kN machine is the wrong tool for a 200 N sample. If your workload spans a wide range, choose a frame that accepts multiple interchangeable sensors rather than buying several machines.
The table below maps typical materials to sensible capacity bands.
| Material / Specimen | Typical Force | Machine Family | Example |
|---|---|---|---|
| Rubber, plastic, film, thin wire | 0.2–5 kN | Single-column electronic | WDW-5 |
| Small metal coupons, springs, bolts | 5–50 kN | Double-column electronic | WDW-10 / WDW-100 |
| Rebar, plate, standard metal coupons | 100–500 kN | Electronic or hydraulic | WDW 100–500 kN series |
| Structural steel, high-strength alloys | 600–1000 kN | Hydraulic | WEW-D series / WAW-1000A |
Electronic or Hydraulic: Match the Drive to the Load
Within the same capacity class, the drive system changes how the machine behaves. Electronic universal testing machines use a servo motor and ball screw drive. They offer wide speed control, high displacement accuracy and clean, quiet operation, which makes them the default for laboratories testing metals, plastics, rubber and composites up to a few hundred kilonewtons. The Electronic Universal Testing Machines series page lists the available models and speed ranges.
Hydraulic universal testing machines apply force through a hydraulic cylinder. They deliver very high forces in a compact frame, withstand heavy-duty cycles, and are the conventional choice at 300 kN and above for structural steel, rebar, concrete accessories and high-strength fasteners. The Hydraulic Universal Testing Machines series page covers microcomputer-controlled WEW variants and the servo-controlled WAW range.
Checklist Before You Buy
- List every material, specimen size and test standard you will run, not just today’s workload.
- Calculate the maximum force (strength × area) and add 20–50% margin.
- Check the low end of the range for small samples; prefer multi-sensor frames if the span is wide.
- Confirm speed range, grip types and fixtures for your specimen shapes.
- Ask for standards support (GB, ISO, ASTM) and clean data export for traceable reports.
Frequently Asked Questions
What capacity universal testing machine do I need?
Estimate the highest force your specimens can produce using force = tensile strength × cross-sectional area, then add 20–50% margin. A 5 kN single-column machine suits rubber, plastic and thin wire; 10–100 kN electronic frames handle small metal coupons and springs; 100–500 kN machines cover rebar and plates; and 600–1000 kN hydraulic frames are for structural steel and high-strength alloys.
Can one universal testing machine handle both small and large specimens?
Yes, if the frame accepts interchangeable force sensors. A multi-sensor electronic machine can test a 200 N film sample and a 50 kN metal coupon on the same frame. Avoid extreme spans, however, because a frame stiff enough for 1000 kN is rarely accurate enough for gram-level samples.
Should I choose an electronic or hydraulic universal testing machine for metals?
Up to roughly 300 kN, electronic machines offer better speed control and accuracy for most metal tests. Above that, hydraulic machines provide the force and rigidity needed for large structural specimens, rebar and high-strength materials, often at a lower cost per kilonewton.
Ready to Choose the Right Capacity?
Send CHENJI your specimen details and the standards you quote, and our engineers will recommend the right universal testing machine capacity and configuration for your laboratory.