💬 SOP - How to Measure on a Metallic Surface
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xxSOP - How to Measure on a Metallic Surface

Document Classification: Confidential
Reference:	​SOP-INX-01 	​
Owner: 	​	​Gerardo Cerros 	​	Version: 	​1.0
Approved by: 	Lisandro Robles	​	​Approval date: 	10.21.2025
 Areas covered by the procedure: 
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Relevant documentation to explore more details:

  • Measuring with CMA R.Op. Spherical Spectro and applicable to the X-Rite Ci6x


Purpose

This SOP outlines the procedure for using a spectrophotometer to measure the colors printed on metal cans for color control. The measurements will be taken on the flat sample and if possible, at three different angles (0°, 45°, and 90°) and averaged to ensure accuracy, OR the measurement can be taken directly on cylindrical can (straight wall or necked can) using a Tabletop, and if possible at three different points (top – mid – bottom).

Scope

This procedure applies to all personnel responsible for color quality control in the printing process on metal cans.
Equipment and Materials:
  • Spherical Spectrophotometer + Tabletop for cans (Model: CMA R.Op.UV or X-rite Ci6x)
  • Metal cans with printed colors
  • Cleaning cloth (lint-free)
  • Calibration tile (provided by the spectrophotometer manufacturer)

Procedure

  1. Preparation

    1. Ensure the spectrophotometer is calibrated according to the manufacturer's instructions using the calibration tile.
    2. Clean the surface of the metal can with a lint-free cloth to remove any dust, fingerprints, or other contaminants.

  3. Measurement Setup

    1. Turn on the spectrophotometer and allow it to warm up or to be at room temperature.
    2. Set the spectrophotometer to the appropriate measurement mode for metal surfaces.
      1. Illuminant D50 and Observer Angle at 2°
      2. SCI/SCE (Specular Component Included AND Specular Component Excluded)
      3. Define on the software or the Spectro the number of measurements to average
      4. Aperture 8mm or 4mm, depending on the measurement surface.

  5. Taking Measurements

    1. Position the spectrophotometer at a 90° angle relative to (“stamping direction”) the surface of the metal can.
    2. Ensure the measurement aperture is in full contact with the can surface to avoid any light leakage.
      1. Automatic Record the measurement made by the software.
    4. If required: Repeat the measurement at a 45° and 90° angle.
      1. Rotate the spectrophotometer or the can as necessary to achieve the measurement angle.
      2. Ensure the measurement aperture is in full contact with the can surface.
      3. Use the spectrophotometer's software to compute the average
      4. Automatic Record the measurement made by the software.

  7. Cleaning and Maintenance

    1. After completing the measurements, clean the spectrophotometer’s measurement aperture with a lint-free cloth.
    2. Store the spectrophotometer in a its original case, dry place as per the manufacturer’s recommendations.

Safety and Quality Control

  • Always handle the spectrophotometer and metal cans with care to prevent damage.
  • Ensure the work area is clean and free from contaminants that may affect the accuracy of the measurements.
  • Regularly check the calibration of the spectrophotometer to maintain measurement accuracy.

Troubleshooting

  • If the spectrophotometer gives inconsistent readings, recalibrate the device and repeat the measurements.
  • If the measurements are still inconsistent, inspect the spectrophotometer and the metal can for any damage or contamination.
  • Control Spectro last revision date as per manufacturer requirements.

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