Understanding Calibration Blocks: An Essential Tool in Precision Engineering

Understanding Calibration Blocks: An Essential Tool in Precision Engineering

Calibration blocks are a mainstay of non-destructive testing (NDT). They’re used to detect flaws within a component and can be utilised with various testing methods, including ultrasonic testing (UT), eddy current testing (ET), phased array (PA), advanced ultrasonic testing (A-UT) and time of flight diffraction (TOFD).

There are different blocks within each of these categories. For example, blocks for UT consist of at least 12 varieties, each of which is either standard models or customised for a particular need. The blocks used will depend on the item to be tested, its material, shape and form.

What is a calibration block?

A calibration block is a highly refined, shaped block against which the shape and form of an object is tested. It’s made of a similar material – for instance, carbon steel, titanium or aluminium. It’s important that they’re created from a tough, strong substance to ensure they remain unchanged during multiple testing processes. They provide a highly precise benchmark that’s used to define the accuracy and correctness of the test subject.

What is the purpose of a calibration block?

A calibration block sets the standard of a part. No matter which testing method is used, the data returned provides an accurate report of the integrity of the part. The information gathered includes aspects such as material depth, surface damage and more.

Expected defects are machined into the calibration block. This simulates particular anomalies to be tested for. Whatever NDT is performed, the returned results provide intimate knowledge of the part. With this knowledge, the necessary adjustments and tweaks can then be carried out to ensure true mechanical operation.

Why calibration blocks are so important for maintaining the precision of CNC machinery

Regular testing with calibration blocks is a key element to precise and repeated CNC machining results. Even the slightest defect can ruin a production run. The more complex or intricate a part, the lower the tolerance for error. Regular calibration is crucial to ensure the accuracy of produced parts over the medium term.

The process of CNC machine calibration generally looks like this:

  • Testing: Using calibration blocks and the chosen form of NDT, the machine is evaluated. Errors and defects are identified
  • Adjustment: Any necessary adjustments or repairs are carried out, returning the machining process to the correct alignment
  • Retest: A further calibration is carried out to ensure any anomalies have been corrected

The process should be accurately documented for future testing reference.

The regularity of calibration is individual to the machine and/or parts. Degraded tolerance is strong evidence that immediate re-calibration is needed. Even if zero issues are noted, it’s recommended that gaps between calibration should be no longer than a year – but ideally, calibration tests at a maximum of six monthly intervals will ensure the best accuracy.

The whole reason for precision CNC machining is just that – precision. Therefore, the more regularly calibration is performed, the better. In addition to minimum standards or alteration in part tolerance, calibration should also be carried out after any repair or change is made to the machine.

Whether you carry out testing tasks in-house or utilise the services of an external contractor, regular calibration brings the following advantages:

  • Higher accuracy and precision: Early detection of minor defects and misalignments is essential for quality control
  • Customer satisfaction: The consistent production of parts that are fit for purpose equals value for money for customers and enhances your reputation
  • Reduces waste: The more accurate the parts produced, the less material is wasted
  • Reduces costly reworking: Creating precise parts the first time removes the need for reformatting/reworking inaccurate parts
  • Increased machine longevity: Regular calibration reduces machine wear and tear. In turn, this reduces breakdown and repairs
  • Increased compliance: The more accurate the parts, the better they conform to industry regulations

SixDe utilises a wealth of precision engineering expertise to design and manufacture both off-the-shelf and customised calibration blocks. Our highly successful, solutions-focused approach to even the most complex of challenges extends throughout our entire portfolio.

From design to manufacturing, we offer a one-stop solution for all your precision engineering needs.

Contact us today to find out more.