In the goods inwards department of manufacturers and distributors, checking the thickness of purchased material is one of the most important quality controls. Plate, tube, bar, sections: the thickness declared by the supplier does not always match the actual figure, and a reading outside tolerance can compromise subsequent machining, the strength of the finished product and the commercial margin. This guide shows how to set up systematic thickness quality control with Dakota NDT instruments.
Why check thickness at goods inwards
- Commercial tolerances: most rolled steel products allow tolerances from ±0.05 to ±0.5 mm depending on thickness and class; material at the lower limit means losing machining allowance
- Compliance with design specifications: on structural components, pressure parts and critical applications, thickness is a contractual compliance parameter
- Verification of conformity certificates: the certificate declared by the supplier has to be compared with direct measurements on statistically representative samples
- Prevention of downstream problems: an error at goods inwards propagates and is amplified in the processes that follow
- Regulatory assurance: for products destined for tanks, pressure vessels and regulated structures, thickness control is a supplier quality requirement
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Typical material types at goods inwards
- Plate in carbon steel, stainless steel, aluminium and alloys: thicknesses from 0.5 to 50 mm
- Tubes and piping: diameters from DN 10 to DN 500, wall thicknesses from 1 to 30 mm
- Sections: L, T, U and box sections with different wall thicknesses on each side
- Bars and flats
- Forged or cast components
Dakota instruments for goods-inwards quality control
For goods-inwards quality control the most suitable Dakota NDT instruments are the CX series, which offers an excellent balance between cost and functionality:
- CX2: ideal for measurements on a single repetitive material (carbon steel or another fixed one), for quick checks in production
- CX4: adds Echo-Echo ThruPaint™ mode and Velocity Mode to handle different materials and painted surfaces
- CX8-DL: includes a 100,000-reading data logger and B-Scan, ideal for anyone who has to produce formal material acceptance reports
For applications calling for micrometric precision (aerospace, racing automotive, precision components) the PMX Precision series with 0.001 mm resolution is preferable.
Typical goods-inwards inspection procedure
- Document check: verification of 3.1 or 2.2 certificates, packing list and delivery note
- Sampling plan: define how many pieces to measure per batch (for example √n + 1, or criteria specific to the quality system)
- Calibration of the instrument: on a reference block suited to the expected material
- Measurement on every sample piece: at least 3 measuring points, stored in the data logger if using the CX8-DL
- Comparison against tolerance: check that the average and minimum thickness fall within the declared tolerance
- Recording of the result: accepted, rejected, accepted by concession
- Production of the acceptance report: with DakMaster™, directly in PDF or Excel
Benefits of ultrasonic measurement for goods-inwards QC
- Non-destructive: no marks are left on the item under examination
- Fast: a few seconds per point, hundreds of readings in an hour
- Repeatable: with a calibrated instrument, repeatability is of the order of a hundredth of a millimetre
- Traceable: NIST-MIL-STD calibration of the Dakota instruments, archiving in DakMaster™
- Economical: a single CX instrument covers a wide range of materials and applications, avoiding investment in multiple dimensional gauges
- Versatile: it also works where access from two sides is impossible (for example tubes already assembled on arrival)
Integration with the quality system
Companies certified to ISO 9001, ISO/TS 16949 (automotive), EN 9100 (aerospace) or equivalent have to demonstrate the traceability of acceptance inspections. The Dakota instrument and the DakMaster™ software provide the required elements:
- Factory calibration traceable to NIST and MIL-STD-45662A
- Record of the instrument’s periodic calibrations
- Data logger with unique identification of batch and operator
- Signable reports with complete traceability elements
- Compliance with the ASTM E797 and EN 14127 measurement standards
For advice on setting up Your goods-inwards quality control with Dakota instruments, contact our technical department.