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W28 – Leaflet | IGT Roughness

W28 - IGT Roughness
AMSTERDAM - Multi-purpose printability tester
Version: 2023-05

Introduction

There are many factors determining the final quality of a printed image. Among these roughness, or rather, the degree of smoothness of the substrate, is one of the most important. There are many methods and devices to determine the roughness; however, they all have their limitations. The determination of roughness described in this leaflet is a dynamic method, which is executed while maintaining the conditions of the printing process as closely as possible.

Principle

A small drop of IGT roughness solution (with an accurately determined volume) is rolled out between two identical paper surfaces at high speed. Due to the high speed only the surface recesses of the paper will be filled. The area of the resulting blot on the paper is measured and the roughness of the paper is calculated as the volume of solution per square meter of paper (cm³/m²).

The speed in this test is high, so that the time of contact between the roughness solution and the paper is very short and the solution cannot penetrate into the paper pores. To prevent initial penetration of the solution into the paper, the spot of application is closed with a lacquer. The amount of roughness solution needed to carry out the test depends on the roughness of the paper to be tested: with very smooth papers 1 mm³ may be sufficient, while for very rough papers a volume of up to 6 mm³ may be necessary.

IGT Roughness, stain

Method of operation

Standards

This method has been standardized in the Dutch standard NEN 1839:2013 nl

Materials

  • [409.010.705.414] Micro syringe
  • [409.006] Dispenser BP .600/1 for micro syringe
  • [409.004.000] IGT roughness solution
  • [409.005.000] IGT Lacquer
  • [402.331.720] Printing disc aluminium
  • [404.001.006] Rubber packing
  • [409.007] Nomogram
  • 5 strips of substrate to be tested, dimensions 55 x 340 mm
  • 5 strips of substrate to be tested, dimensions 55 x 205 mm
  • ruler
  • lint free rags
  • water and ethanol

Testing conditions

Standard test atmosphere according to ISO 187 (23,0 ± 1,0 °C and 50 ± 2% RH)

Sample Conditioning

Be aware of the fact that a different way of conditioning of the samples can have influence on the results.

Standard settings

  • Printing speed: increasing, end speed 3 m/s
  • Printing force: 1000 N
  • 1–6 mm³ roughness solution
  • Checkbox Scan activated (Not applicable for Basic type Amsterdam)
  • Camera lamp high (Not applicable for Amsterdam Basic type)

Preparation

  1. Cut paper strips of 55 x 340 and mark with top and/or bottom side, machine and/or cross direction and a code for the paper.
  2. Cut paper strips of 55 x 205 and mark with top and/or bottom side, machine and/or cross direction and a code for the paper.
  3. Apply a spot of lacquer at 60 mm from the start of the shorter strip of paper and let dry.
  4. Select method IGT Roughness.
  5. If desired, touch the checkbox Scan to scan and save (not applicable for Basic type Amsterdam).
  6. Mount the rubber packing on the sector.
  7. Mount the strip of the paper with the side to be tested upward on the sector.
  8. Mount the syringe in the dispenser and fill with the blue coloured testing liquid:
    • Insert the needle of the syringe with the plunger downward into the test liquid.
    • Fill the syringe with the liquid by moving the plunger upward, downward and upward for several times.
    • Clean the outside of the needle with a rag and ethanol.
  9. Mount the strip of 55 x 205 mm with some tape on the aluminium disc with the seam aligned with the pin at the back of the disc.
  10. Observe that the dried lacquered spot is positioned left from the pin.
  11. Place the disc on the first printing shaft.

Execution

  1. Touch the button [Print] and press both side buttons to rotate the sector and first shaft into the start position and release.
  2. To create a drop of 1 – 6 mm³ of the testing liquid press the knob on the dispenser one time for each mm³ and release gently on the spot of lacquer.
  3. Press both side buttons to make the print and release side buttons when the display says DONE.
  4. Take both samples from the sector and mark the length and the width in the centre of the length of the stain with a pen.

If the camera was activated

The print is scanned and analysed. After that the camera moves upward. Save or discard the results.
To perform a next test, mount a new samples on the sector and aluminium disc; touch the button [Print] again or touch [Back] to start from the beginning. It is recommended to perform the test at least five times per sample.

After finishing all tests, press [Back] and clean and store all parts as described in the manuals.

Cleaning

1. Clean the syringe and needle by flushing it with water several times.
3. Clean the aluminium disc with some ethanol on a lint free rag.
4. Make sure the Amsterdam is clean and if necessary clean with some ethanol on a lint free rag.

Assessment

If a scan was made

The results are automatically analysed and shown in the display: stain length in mm, area in mm²  and roughness in mm³/m².

Test result

Magnification of the scan via touch screen is possible.

If satisfied, touch the textbox [Batch] on the left of the display to save both data and image with the help of the pop-up keyboard that automatically appears. Afterwards the data and images can be transferred to a USB stick. For the correct procedure please refer to the manual of the Amsterdam. Data are saved in a CSV format that can be loaded into Excel. Images are saved as PNG files. The data will relate the results to a specific image to enable you to combine both.

If no scan was made

Measure both the length (a) of the stain and the width (b) in the centre of the length of the stain to the nearest 0,5 mm.

Find the corresponding positions (a) and (b) in the nomogram and connect the two points with a straight line. The intersection with the R-axis gives the roughness in 0,01 cm³/m² for a drop volume of only 1 mm³.

Multiply the value of the R-axis with the number of mm³ of the drop volume used and divide this value by 100. The dimension of the roughness is cm³/m².

Repeat this calculation for every test strip and calculate the average and if desired the standard deviation. In some cases it may be useful to mention the highest and lowest values as well.

Explanatory notes to the nomogram – calculation example

Assume a certain paper is tested with a volume V of 2 mm³.
Assume the resulting stain has a length (a) of 70 mm, and a width (b), measured in the middle of the length of 13 mm.
From the nomogram the value for 100 R at 1 mm³ = 65 is found.
The roughness R is: R = (V x 65):100 = (2 x 65):100 = 1,3 cm³/m²

The area of the stain may be approximated using the formula:
A = 0,85 x l x b

Herein is:
A = area of the stain in mm³
l = length of the stain in mm
b = width of the stain in mm

The roughness is calculated with the formula:
R = (V x 1000 ) : 2 A

Herein is:
V = volume in mm² of roughness solution
A = area in mm² of stain

NOTES

  1. The stain should be symmetrical vis-à-vis the longitudinal axis.
  2. If a nomogram value in excess of 150 is reached when a drop smaller than 6 mm³ was used, a larger drop volume must be chosen.

Randstad 22 - 02

1316 BX Almere

The Netherlands

P.O.box 22022

1302 CA Almere

The Netherlands

+31 20 40 99 300 +31 20 40 99 339 info@igt.nl
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