Technical Guideline GOOD CREASABILITY DRAFT

Transcription

1 Technical Guideline GOOD CREASABILITY

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3 Contents 1 Introduction Terminology and standards referenced Procedure 2 2 Assessment of the creasability of folding carton board Creasing trials Preliminary treatment of samples and test conditions Printing of the samples Creasing trials under standard conditions Creasing trials under stricter conditions Evaluation of creasing trials Visual evaluation Technical evaluation Suitable equipment 7

4 INTRODUCTION / ASSESSMENT OF THE CREASABILITY OF FOLDING CARTON BOARD 1 Introduction The Technical Guideline Good Creasability describes methods for the practical evaluation of the creasability of folding cartonboard. It relates directly to the Technical Guideline Quality Characteristics of Cartonboard and applies to the board grades defined in it (with the exception of liner grades). What is involved here is the initial version of the Technical Guideline, which is the outcome of a project carried out by Fachverband Faltschachtel Industrie in co-operation with Professor Dr Martin Angerhöfer, Munich University of Applied Sciences, Packaging Technology Programme. FFI has assumed responsibility for validating the technical data outlined in this document with its market partners for a second version of the Technical Guideline. 1.1 TERMINOLOGY AND STANDARDS REFERENCED The terminology defined in DIN Standard (May 2008) applies. 1.2 PROCEDURE With the help of the methods outlined in Chapter 2, creasing trials are carried out under practical conditions, with subsequent visual and technical evaluation. Folding carton board is given a good creasability classification when the defined conditions are satisfied. 2

5 2 Assessment of the creasability of folding carton board Creasing time, i.e. the time from when the creasing rule engages the surface of the board to the time when the cutting & creasing machine reaches its bottom dead centre, depends primarily on the sheet output and the thickness of the board. In the case of sheet outputs that are standard in practice and the board grades to which this guideline applies, creasing time amounts to to 0.03 seconds. It has been demonstrated in normal production conditions that the creasing time has a substantial impact on creasing quality. This means that equipment needs to be used for creasing trials with which a creasing time of between and 0.03 seconds is possible. Reliable and practically viable visual evaluation of creases to determine cracks in the surface of the board is only possible with printed surfaces. Board samples that are to be tested must therefore be printed before creasing trials are carried out. 2.1 CREASING TRIALS Preliminary treatment of samples and test conditions The board samples that are to be tested must be given preliminary treatment under the conditions specified in DIN EN Standard 20187, at a temperature of (23 ± 1) C and a relative humidity level of (50 ± 2)%. Creasing trials as well as visual and technical evaluation of them must be carried out under the same standard conditions (23 ± 1) C and a relative humidity level of (50 ± 2)% Printing of the samples The board sample must be offset printed solidly with the colour cyan before creasing trials are carried out. This can be done on a commercial offset printing machine or on test printing equipment Creasing trials under standard conditions With the help of a laboratory cutting & creasing unit, 3 samples per board grain direction are creased with 4 different creasing parameters in each case. This means that there are 24 samples in total. The sample dimensions and the location of the creasing rules can be found in Illustration 1, Diagram 1. The laboratory cutting & creasing unit must guarantee a creasing time between and 0.03 seconds. In all creasing trials, creasing tool thickness is determined by the recommendations made by the board manufacturer. The counter die is configured as a steel counter plate. The hardness of the rubber material next to the cutting rules is Shore 35. The creasing channel width and immersion depth are varied as specified below (immersion depth is defined in DIN Standard as Eintauchtiefe ): Creasing parameter 1 Creasing channel width: Recommendation made by the board manufacturer minus 10% (rounded off to 0.05 mm) Immersion depth: 0 mm Creasing parameter 2 Creasing channel width: Recommendation made by the board manufacturer Immersion depth: 0 mm Creasing parameter 3 Creasing channel width: Recommendation made by the board manufacturer plus 10% (rounded off to 0.05 mm) Immersion depth: 0 mm Creasing parameter 4 Creasing channel width: Recommendation made by the board manufacturer Immersion depth: -0.1 mm 3

6 ASSESSMENT OF THE CREASABILITY OF FOLDING CARTON BOARD Creasing trials under stricter conditions Arrangements can be made to carry out additional creasing trials under stricter conditions, i.e. with a shorter distance between adjacent creasing rules. The tooling required for this is shown in Illustration 1, Diagram EVALUATION OF CREASING TRIALS Visual evaluation The sample strip is folded manually through 180 in the direction of the creasing bead at the central creasing line and is fixed in this position using a suitable clamp. The ends of the clamp are located 5 mm from the centre of the creasing line Technical evaluation Technical evaluation of the creasing trials is carried out using a measuring instrument that records the bending moment curve over the bending angle for creased and uncreased samples, with what is known as the folding factor being determined as a result. The samples are bent with a speed of 90 /s in a range from 0 to 90. The force sensor of the measuring instrument is located at the position indicated in Illustration 1, Diagrams 1 and 2. The folding factor indicates the relative reduction in the bending work between uncreased and creased board and is calculated as follows (cf. also Illustration 2): The average of the 3 samples per board grain direction and crease parameter setting is calculated. A board grade is given a good creasability classification if all 8 averages of the folding factors range at least between 45 and 55%. Figures higher than 55% are considered to be very good and can be arranged individually for special applications. Figures higher than 65% must be avoided, although they can be agreed individually for special applications. The folded crease is checked with the naked eye to determine the presence of any breaks in the coating or cracks in the top layer. A board grade is given a good creasability classification, when none of the 24 samples has any breaks in the coating or cracks in the top layer that are visible to the naked eye. Bending work of the creased sample (B) FOLDING FACTOR 100% 100% Bending work of the uncreased sample (A) 4

7 80 mm 20 mm 10 mm ILLUSTRATION 1 Schematic drawing Creasing trial creasing quality test Scale 1:0.5 Source: FFI e.v. 24 mm 40 mm 30 mm Diagram 1 Standard conditions 80 mm 20 mm 20 mm Creasing line Force measuring position Test instrument clamping area 30 mm 30 mm 24 mm Diagram 2 Stricter conditions 5

8 ASSESSMENT OF THE CREASABILITY OF FOLDING CARTON BOARD ILLUSTRATION 2 Calculation of the folding factor Source: Karl Marbach GmbH & Co. KG, Heilbronn, Germany The folding factor indicates the relative reduction in bending work between uncreased and creased board. It is defined as follows: FOLDING FACTOR 100% B A 100% Area A under the curve of the uncreased sample Area B under the curve of the creased sample 600 mn 550 mn 500 mn 450 mn 400 mn 350 mn A 600 mn 550 mn 500 mn 450 mn 400 mn 350 mn 300 mn 250 mn 200 mn 150 mn 100 mn 50 mn 0 mn mn 250 mn 200 mn 150 mn 100 mn 50 mn 0 mn B

9 2.3 SUITABLE EQUIPMENT Suitable equipment for carrying out creasing trials and for making technical evaluations of the results in accordance with this guideline is available on the market. The laboratory cutting & creasing unit and crease bend tester supplied by Marbach, Heilbronn, Germany, are one example (cf. Illustration 3). ILLUSTRATION 3 Illustrations of a laboratory cutting & creasing unit (picture on the left) and a crease bend tester (picture on the right). 7

10 Reproduction only permitted with the author s approval. All rights reserved. No claim is made that this document is complete. Although FFI has done everything in its power to make sure that the information in this document is accurate, FFI cannot accept any liability for corporate decisions taken on the basis of this document. The user of this information alone is responsible for such decisions.

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12 Fachverband Faltschachtel-Industrie e.v. Kleine Hochstraße Frankfurt am Main Germany Telefon: +49 (0) Fax: +49 (0) info@ffi.de Date: June 2015 photo sources: Skrock Fotografie, Karl Marbach GmbH & Co. KG