NG-SHM Class D – Servo-Hydraulic Universal Testing Machine

The NG-SHM Class D is a servo-hydraulic universal testing machine for high-force work: tension, compression, bending and shear on fasteners, rebar, chain, welds and castings.

Force capacity runs from 600 kN to 2000 kN across three models, and the machine is calibrated to Class 1 or Class 0.5 of ISO 7500-1. The actuator is mounted above the frame, which leaves one large space underneath for every test type and gives room for long specimens with high elongation.

We supply it to laboratories that test components rather than prepared coupons, where the specimen geometry varies and the failure is sudden. The design of the cylinder, the grips and the hydraulic power unit all follow from that requirement.

It sits in the same family as the rest of our servo-hydraulic machines, which differ mainly in how the test space is arranged.

Mounting the actuator above the test space leaves a single large working area underneath, so tension, compression, bending and shear are all performed in the same place without a second zone taking up frame height.

The arrangement also serves axis alignment and shock absorption, and the test space is adjusted from the actuator itself. Alignment is not a detail on a tensile machine: a specimen loaded off axis reports a lower strength and often breaks outside the gauge length, which invalidates the result.

The practical benefit is room for specimens that stretch a long way before they fail, which is exactly what ASTM E8 tension testing on ductile steel produces.

For laboratories with limited ceiling height, the single zone layout also keeps the overall frame shorter than a dual zone machine of the same capacity.

Single zone means every test type finishes in one space: tension, compression, bending and shear all use the same working area under the actuator.

The trade is footprint against setup time. A single zone keeps the machine compact and the workflow short, but fixtures are changed when the test type changes, because there is no second space standing ready with platens already rigged.

For a laboratory that runs long batches of one test type, that is the right trade: the fixture goes in once and stays. For a laboratory that alternates constantly between pulling and crushing, the dual zone Class B suits that pattern better.

We are happy to work through the actual mix of testing with you before the layout is chosen, because it is not a decision that can be changed afterwards.

Three models are offered: SHM605 at 600 kN (134,885 lbf), SHM106 at 1000 kN (224,808 lbf) and SHM206 at 2000 kN (449,617 lbf).

Capacity should be chosen from the strongest specimen you expect, with headroom above it, and with the lower end of the verified range in mind as well. A machine sized for the heaviest test that might ever arrive will push routine work toward the bottom of its range, where the permitted error is largest in relative terms.

Test space, stroke and specimen ranges grow with the capacity, so the model decision usually settles the fixture question at the same time.

Send us the specimen you break most often, its size and the standard you test to with a quotation request and we will confirm the capacity and the grips together.

The machine is calibrated to Class 1 or Class 0.5 of ISO 7500-1.

That class is the number that matters on a testing machine. It states how far the indicated force may deviate from the true force, and it is what makes a result defensible when a customer or an auditor asks. Class 0.5 halves the permitted error of Class 1.

Which class a laboratory needs is normally set by its accreditation and by the specifications it reports against. Where a testing house serves several customers, the stricter class is the safer purchase because it satisfies both.

The equivalent North American verification procedure is ASTM E4, and we can prepare the machine for either.

Force and extension both range from 1% to 100% of full scale, with accuracy better than ±1% or ±0.5% depending on the calibration class. Extension resolution is 1/350,000 of maximum extension.

The 1% lower limit is the figure that catches people out. Below it the reading falls outside the verified range of the machine, so capacity should be matched to the work rather than bought as large as the budget allows.

Resolution and accuracy are different properties. Resolution describes the smallest step the system can show; accuracy describes how close the value is to the truth. Both matter, and a fine resolution on a poorly verified machine proves nothing.

We can supply the machine with verification in place so that it enters service ready to produce reportable results.

Elongation is measured on the specimen itself. An extensometer is clipped to the gauge length, which is what ASTM E8 and ISO 6892-1 expect for modulus and yield results.

Crosshead travel is not a substitute. It includes the take-up of the grips and the elastic stretch of the frame, and on a short specimen that error is large enough to move a yield figure by a margin a customer would notice.

The machine measures crosshead position with an encoder, and that measurement is used for control and for positioning, but the two numbers answer different questions and should not be confused in a report.

Tell us the standards you report to and we will quote a suitable extensometer with the frame.

A quality encoder provides the displacement measurement and gives the control loop its accuracy.

Position feedback is what allows the machine to hold a rate rather than a valve opening. Without it a hydraulic machine can only be driven at a fixed command, and the actual speed then changes as the specimen yields and the load falls away.

It is also what makes displacement control usable as a test mode in its own right, which some component tests and most compression work require.

It is not the same measurement as elongation on the specimen, which is read by an extensometer on the gauge length.

Force loading speed runs from 0.02% to 2% of full scale per second.

Standards limit the rate because the yield strength a metal reports depends on how quickly it is loaded. ISO 6892-1 defines those limits for room temperature tensile testing, and a machine has to sit inside them for the whole elastic region rather than on average.

Holding a slow steady rate is harder for a hydraulic machine than moving quickly, which is why the servo valve, the encoder feedback and the pressure regulation on this machine are specified the way they are.

If your specification names a stress rate, send it over and we will confirm that the model you are considering covers it for your specimen sizes.

Actuator speeds are 230, 230 and 7.9″ (200 mm)/min upward on the SHM605, SHM106 and SHM206, and 310, 360 and 12.2″ (310 mm)/min downward.

These are positioning speeds rather than test speeds. Stroke is 58, 68 and 30.7″ (78 cm) across the three models, so on a long specimen the travel between tests is a real part of the working day and worth considering where throughput matters.

The test rate itself is set by the method in the software and by the force loading speed range, not by the maximum actuator speed.

The two differential circuits in the hydraulic unit include one that returns the piston quickly after a test, which is what keeps that dead time down.

Maximum tension space is 60, 70 and 31.5″ (80 cm) on the three models, and maximum compression space is 42, 46 and 21.3″ (54 cm).

Column spacing is 18.7″ (47.5 cm) on the SHM605, 22.6 × 14″ (57.5 x 35.5 cm) on the SHM106 and 30.3 × 18.5″ (77 x 47 cm) on the SHM206. Those figures set the widest fixture the frame will accept, which is often the real limit rather than the specimen itself.

Check the tension space against your longest specimen including the grips, not the specimen alone. Wedge grips and an extensometer take up room that is easy to forget at the specification stage.

Our team will check the numbers against your actual test pieces as part of the quotation.

Two columns on the SHM605, four on the SHM106 and the SHM206.

Columns guide the moving parts and carry the reaction. More of them on the larger frames is what keeps the load path straight when the force more than triples, and alignment is what a tensile result depends on: a specimen loaded off axis reports a low strength and often breaks outside the gauge length.

The column arrangement also sets the width of the working space, so it decides which fixtures fit as well as how the frame behaves under load.

Both figures, spacing and count, are quoted per model so the frame can be matched to the fixtures a laboratory already owns.

Round specimens are covered from Ø10 to Ø40 mm on the SHM605, Ø15 to Ø55 mm on the SHM106 and Ø15 to Ø70 mm on the SHM206.

Flat specimens run 2 to 30 mm thick, 2 to 40 mm and 10 to 70 mm across the same three models. Anything outside those ranges is a grip question before it is a frame question, because it is the jaws that have to hold the section without slipping or crushing it.

Where a laboratory tests a wide spread of sizes, more than one set of jaws is normal and is cheaper than compromising at either end of the range.

Send the section and the standard with a request for pricing and we will confirm which jaws are needed.

The machine uses advanced wedge type hydraulic tensile grips, which hold high strength material without slipping.

A wedge grip tightens as the load rises, so the clamping force follows the test instead of being set once by hand at the start. On high strength steel that is the difference between a break in the gauge length and a specimen that pulls out of the jaws with no usable result.

Where the break happens is not a detail: ISO 6892-1 expects failure inside the gauge length for the result to count, and a grip failure wastes the specimen and the preparation behind it.

Grips are quoted with the frame because the correct jaw depends on the specimen rather than on the machine.

The hydraulic unit runs two differential circuits. One of them grips the specimen at low pressure first and only then applies the extra-high pressure.

That sequence matters on components with thin walls, on tube, and on any specimen where full clamping force applied instantly would deform the section before the test begins. A deformed grip area changes the result and can move the failure to the jaw.

The same circuit releases the pressure automatically when the specimen breaks, so the grips are not left loaded after a failure and the broken halves can be removed safely.

Together the two behaviours allow the same machine to hold a hardened bolt and a thin walled section without a change of technique.

The system is built with a 25 MPa high pressure part and a 50 MPa super high pressure part. The main cylinder works at about 25 MPa and the clamping cylinder at about 48 MPa, both driven by a single motor and pump.

Separating them means the clamping force does not have to come from the same pressure that drives the test. Clamping needs high pressure over a small area; the test needs controlled pressure over a large one, and forcing both from a single stage compromises one of them.

Using one motor and pump for both keeps the power unit compact and the maintenance simple, which matters in a laboratory rather than a plant room.

It is one of the reasons the machine holds grip force steady through a long test without a separate clamping unit standing beside it.

The unit runs a pressure servo: a logic valve holds system pressure no more than 1 MPa above cylinder pressure, so the pump delivers what the cylinder is asking for instead of running at full pressure all day.

The differential pressure is adjustable, which keeps the test free of shaking while saving energy and heat at the same time. Oil that is not pressurised unnecessarily does not have to be cooled afterwards.

The gear pump keeps noise at or below 70 dB, total system heating power is 2 kW, and the semi-open unit carries an air-cooling device that starts automatically at the temperature set on the oil gauge.

For a laboratory the practical result is a machine that can stand in the same room as the people using it rather than behind a wall.

Triple filtration brings particles down below 5 microns before the oil reaches the servo valve.

Contamination is the usual cause of servo valve trouble, and the valve is what the control accuracy and the service life of the whole system depend on. A valve damaged by dirty oil does not fail cleanly: it degrades, and the symptoms look like control problems long before anyone suspects the oil.

Filtration is therefore maintenance that pays for itself rather than a specification line. Oil condition and filter changes belong in the laboratory routine alongside verification.

We can advise on the service interval that suits your duty cycle when the machine is commissioned.

Above the rated pressure the relief valve overflows and protects the system.

It is the hydraulic equivalent of a fuse: the excess energy goes somewhere harmless rather than into the frame, the fixture or the specimen. On a 2000 kN machine that matters to the operator as much as to the equipment.

Overload protection is one part of a wider picture that also includes the guided cylinder, the pre-loaded connection in the load path and the automatic pressure release when a specimen breaks.

As with any high-force equipment, we recommend that these functions are covered in operator training at installation rather than read about later.

The piston and rod are forged as one body, so there is no joint to fail under impact, and the rod is plated with nickel and chrome up to 0.1 mm thick against corrosion and wear.

The rod is sized for stiffness so that lateral loading does not bend it, and a halite guidance ring resists lateral force at low friction. Sealing is by U-shaped components with a double ring, held to zero leakage.

These are the parts that decide how long a hydraulic machine holds its accuracy under repeated high loads. A cylinder that develops play or leakage does not stop working; it quietly changes what the machine measures.

The same cylinder design is used on the Class DP frames.

The piston and guide sleeve wearing ring is produced by a copper melting process, which NextGen rates at five times the life of the usual polymer ring.

It is a maintenance figure rather than a performance one. The wearing ring is a consumable on any hydraulic cylinder, and how often it has to be changed decides how much downtime the machine costs over its working life.

For a laboratory running production release testing, downtime is the expensive part rather than the parts themselves, because specimens and schedules do not wait for a cylinder rebuild.

Service intervals depend on duty cycle, and our team can advise on what to expect for your pattern of use.

The joint between the piston rod and the upper grip is pre-loaded to zero clearance.

Any free play in that connection would appear at the start of the curve as false compliance, and on a stiff specimen it would move the modulus. It would also produce a small shock every time the load reverses, which is the last thing wanted in a machine measuring to half a percent.

Removing it is why the connection is pre-loaded rather than simply bolted together, and it is one of the details that separates a machine built for measurement from one built only to apply force.

The guided cylinder and the one-body forged piston serve the same purpose from the other end of the load path.

The machine runs our GenTest software, which records the curve and produces the report against the method you selected.

Method-driven testing is what keeps a result reproducible across operators. The control steps, the calculations and the report template are all part of the method rather than of the operator's habits, so two people on two shifts produce results that can be compared.

It also matters when a result is questioned months later: the method, the raw curve and the report are one record rather than three files that have to be matched up by date.

The same software runs the rest of our universal testing machines, so a laboratory with several frames keeps one set of methods.

Power consumption is 5 kW, 8.5 kW and 12 kW across the three models. Frames measure 29.1 × 15.7 × 111″ (74 x 40 x 282 cm), 34.3 × 25.6 × 129″ (87 x 65 x 327 cm) and 47.2 × 35.4 × 150″ (120 x 90 x 382 cm).

The hydraulic power units are 19.7 × 34.6 × 36.4″ (50 x 88 x 92.5 cm), 28 × 44.5 × 43.3″ (71 x 113 x 110 cm) and 47.2 × 35.4 × 43.3″ (120 x 90 x 110 cm) and stand separately from the frame, so the floor plan has to allow for both plus the hose run between them.

Frame weights are 6,613 lbs (3,000 kg), 13,227 lbs (6,000 kg) and 19,841 lbs (9,000 kg). Floor loading and ceiling height therefore come first in the layout, followed by the route into the building for installation.

We will go through the site requirements with you as part of the quotation rather than after the order is placed.

The semi-open structure of the hydraulic power unit opens at the rear through two doors for maintenance and part replacement.

Plan the installation with that access kept clear. Oil, filters and seals are the recurring items on any hydraulic machine, and a power unit pushed into a corner turns a routine service into a lifting operation.

Access matters for the frame as well, particularly around the grips, where jaw changes and cleaning are part of normal operation rather than occasional maintenance.

Where a laboratory runs a preventive maintenance programme, we can set out what the machine needs and at what interval so it can be scheduled alongside verification.

Compression platens are 5.9″ (150 mm) on the SHM605 and 7.9″ (200 mm) on the SHM106 and SHM206.

Platen size limits the compression side of the working space. A block or a casting wider than the platen cannot be loaded squarely, and an off-centre compression test loads the columns and the cylinder as well as the specimen.

Which platen ships with a machine depends on the model and on the compression work it is bought for, so it is specified with the rest of the configuration rather than fixed in advance. Laboratories testing concrete cubes, castings or large blocks usually take the largest platen the frame allows.

Tell us what you compress and we will confirm the platens with the offer.