A 160T/4000 machine is the workhorse size in most fabrication shops, and the factory acceptance test is the last point at which a defect is somebody else's responsibility. The protocol below is deliberately measurement-based: every item produces a number that can be compared with the specification and repeated after installation.
1. The practical problem
Catalogues at this size look almost identical, while the machines behind them differ in frame construction, hydraulic layout and feedback. A buyer who accepts on appearance and a demonstration bend discovers the differences during the first production run: a ram that only holds parallelism when the load is centred, an oil circuit that overheats in summer, a safety circuit that requires workarounds to be productive. A structured test at the builder's plant converts those risks into documented measurements, and it matters more for an export order: the machine will be installed thousands of kilometres away, so any figure not measured and written down at the factory cannot be demonstrated later.
2. Failure mechanism
Most post-delivery disputes trace to one of three mechanisms. The first is insufficient structural stiffness, where deflection is larger than the crowning system can compensate and the error appears only on long parts. The second is inadequate synchronisation, where the ram is accurate with a centred load and loses parallelism when the load moves. The third is thermal, where the hydraulic system reaches temperatures that change valve response within a shift. All three are measurable in a few hours with a dial indicator, a digital protractor, a precision level and a thermometer.
3. Key parameters
Check the parameters that appear on the order against the nameplate: rated tonnage, distance between side frames, table length, throat depth, stroke, open height, ram speed and the control model. Then check the ones that are usually omitted: deflection compensation type and stroke, backgauge axes and repeatability, pump and motor rating, oil tank volume and cooler capacity, and the safety devices fitted.
| Test | Method | What it protects against |
|---|
| Ram repeatability | Twenty cycles to the same position, dial indicator or scale readout at both ends | Valve and feedback faults, hydraulic drift |
| Parallelism under load | Same test with the load offset from centre | Weak synchronisation, frame twist |
| Angle across a long strip | Five-point measurement at two or three tonnage levels | Deflection, crowning, tooling condition |
| Full-load capability | Rated tonnage on a short thick part in a wide die, pressure held briefly | Undersized hydraulics, pump or relief faults |
| Thermal behaviour | Temperature logged at start and after a representative running period | Undersized cooler, excessive pressure drop |
| Safety functions | Light curtain, guard interlock, emergency stops, reset logic tested separately | Non-compliant guarding, stopping distance |
4. Diagnosis and calculation method
- Run all tests with the oil at working temperature; a cold machine flatters both the hydraulics and the repeatability figures.
- Measure ram position at both ends rather than relying on the controller display alone.
- Use a workpiece of at least 3000 mm for the angle test, since the purpose is to expose deflection behaviour.
- Convert angle spread into a positional figure using the die geometry so the result can be compared with the machine specification.
- Ask for the deflection test record with the crowning at zero and at the recommended setting, so the compensation range is documented.
- File photographs or a short video of the key readouts with the report, signed by both parties.
5. Prevention
Write the test into the purchase contract rather than agreeing it at the end of the build. Specify the acceptance figures, the material and tooling to be used, who witnesses, and what happens if a figure is not met. Then repeat the same measurements after installation and again after thirty days, so that settling is documented rather than disputed. A buyer who has the factory numbers, the installation numbers and the thirty-day numbers can tell a transport problem from a foundation problem from a machine problem without argument. Machines built for this level of documentation include our 380V synchro servo 160T/4000 press brake and the wider 160 tonne CNC hydraulic press brake range, where the acceptance record is provided as part of the delivery.
6. FAQ
How long should a FAT take?
For a machine of this size, a structured test of the items above takes several hours including warm-up, and it is worth allowing a full day if a customer part is bent as well. Rushing the warm-up invalidates the hydraulic results.
Can the tests be done with the buyer's own material?
They should be, where the buyer's material is representative. Bending the material actually to be used reveals springback and tooling behaviour that a test strip of mild steel will not.
What if the machine passes FAT and fails after installation?
Then the comparison between the two records becomes the diagnosis: foundation and levelling, frame settling, calibration of feedback and transport damage are the usual candidates, and each appears differently in the data.
আপনার বার্তাটি 20-3,000 টির মধ্যে হতে হবে!