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On Polishability of Tool Steels
Halmstad University, School of Business, Engineering and Science, Mechanical Engineering and Industrial Design (MTEK), Functional Surfaces.ORCID iD: 0000-0002-9084-819X
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

One of the world’s fastest growing industries is the plastic industry. Today’s ever increasing demands of high quality products, shorter lead times and reduced costs push development and research forwards. Moulds for plastic injection moulding need to have a functional surface to meet demands on demoulding and wear properties, but also to produce the required final surface quality, which for ‘standard mould qualities’ of high gloss applications means nearly defect free, shiny and smooth mould surfaces with roughness levels in the nm-range.

The aim of this thesis was to develop a metrology framework to quantitatively characterise these mould surfaces in order to gain better understanding of which defect structures are critical at injection moulding, and how these are correlated to material properties and operating conditions in surface preparation of tool steels. In practice this means to capture surface features of some few nm in height/depth up to some hundreds of microns in lateral dimension within insert areas of cm2 and larger. Experiments combining polishers’ experience with steel producers’ as well as non-contact areal texture examinations of surface topography were performed to overcome and link practical skills to academic ones.

Based on areal surface metrology, defect classification and image analysis based surface characterisation, an evaluation procedure for polished tool steel surfaces was developed, initially tested and verified. The suggested method involves descriptions of relevant defect structures and acceptance levels for high gloss polished tool steels in the form of numerical parameter values based on interferometric measurements. It was also concluded that the cleanness of the steels was less important as long as it was kept within reasonable levels; the surface preparation strategy is a major factor influencing the mould surface quality e.g. it was found that a ‘several-step-strategy’ was favourable to avoid defect structures; not all ‘mirror-like’ mould surfaces had desirable topographies for injection moulding, therefore a well-defined mould surface assessment with numerical values describing mould surface quality is necessary to secure effective mould surfaces.

Place, publisher, year, edition, pages
Göteborg: Chalmers University of Technology , 2013. , 50 p.
Series
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny Serie, ISSN 0346-718X ; 3509
Keyword [en]
tool steels, polishability, surface characterisation, surface texture parameters, high gloss polishing, injection moulding
National Category
Manufacturing, Surface and Joining Technology
Identifiers
URN: urn:nbn:se:hh:diva-22175Libris ID: 13966873ISBN: 978-91-7385-828-1 OAI: oai:DiVA.org:hh-22175DiVA: diva2:621848
Public defence
2013-04-05, Virtual development laboratory, Chalmers University of Technology, Göteborg, 10:00 (English)
Opponent
Supervisors
Note

Includes pamphlet in Appendix I.

Available from: 2013-11-08 Created: 2013-05-17 Last updated: 2015-01-26Bibliographically approved
List of papers
1. Tool steel polishing and topography characterization
Open this publication in new window or tab >>Tool steel polishing and topography characterization
2007 (English)In: The Swedish Production Symposium in Göteborg 28-30 August 2007, 2007Conference paper, Published paper (Other academic)
Abstract [en]

Manual polishing is a common method to accomplish a mirror-like mould surface, although it is a cumbersome and time-consuming process. It is, thus, of great interest within the industry to find faster and better polishing techniques to decrease the costs and lead times. A key factor towards improved polishing techniques is to find ways to characterize polished surfaces; which parameters and instruments can be used and what is the definition of polishability? This paper summarises a study where three steel grades were analysed with five different measuring devices. The results showed that mechanical stylus instrumentations are not enough to describe very smooth surfaces, but measurement devices with better resolution are needed, such as interferometers.

Keyword
tool steel, polishing, 2D and 3D parameters, surface characterisation
National Category
Engineering and Technology
Identifiers
urn:nbn:se:hh:diva-2711 (URN)2082/3113 (Local ID)2082/3113 (Archive number)2082/3113 (OAI)
Conference
The Swedish Production Symposium 2007, 28-30 August 2007, Göteborg, Sweden
Available from: 2009-07-06 Created: 2009-07-06 Last updated: 2015-01-26Bibliographically approved
2. Surface characterisation of high gloss polished tool steels
Open this publication in new window or tab >>Surface characterisation of high gloss polished tool steels
2009 (English)In: Proceedings of the 8th International Tooling Conference: TOOL 09: Tool Steels – Deciding Factor in Worldwide Production: RWTH Aachen University, Aachen, Germany, June 2–4, 2009: Volume II / [ed] P. Beiss, C. Broeckmann, S. Franke & B. Keysselitz, Aachen: Mainz , 2009, 953-963 p.Conference paper, Published paper (Refereed)
Abstract [en]

It is well known that high quality tool steels, i.e. steels possessing low contents of defect structures, and the adoption of well developed polishing techniques are required to get satisfactory mould surfaces for plastic forming. However, there is still a lack of knowledge concerning how different defect structures on mould surfaces affect final plastic components, and how tool steel surfaces can be measured and analysed in convenient ways.

Based on non-contact 3D-surface texture analysis, three test moulds and corresponding injection moulded plastic plaques were characterised with the objective to study how defect structures on the mould surfaces were transferred into the final plastic components.

Surface structures, remaining scratches and to a certain extent pin-holes originated from the mould surface were all detected on the surface of the plastic components. However, more extensive studies need to be performed in order to understand why different defect structures on tool steels occur, how they can be avoided and, for different plastic products, which the critical limits are (in terms of amount, shape and size of the defects).

Place, publisher, year, edition, pages
Aachen: Mainz, 2009
Keyword
high gloss polishing, surface characterization, plastic components, injection moulding, surface defects
National Category
Engineering and Technology
Identifiers
urn:nbn:se:hh:diva-6153 (URN)3861307014 (ISBN)9783861307013 (ISBN)
Conference
The 8th International Tooling Conference, TOOL09: Tool Steels - Deciding Factor in Worldwide Production: RWTH Aachen University, Aachen, Germany, June 2-4, 2009
Available from: 2010-10-18 Created: 2010-10-18 Last updated: 2015-01-26Bibliographically approved
3. A quantitative method to estimate high gloss polished tool steel surfaces
Open this publication in new window or tab >>A quantitative method to estimate high gloss polished tool steel surfaces
2011 (English)In: Proceedings of the 13th International Conference on Metrology and Properties of Engineering Surfaces: 12 – 15 April 2011, Twickenham Stadium, UK / [ed] Richard Leach & Liam Blunt, Teddington: National Physical Laboratory , 2011, 35-39 p.Conference paper, Published paper (Refereed)
Abstract [en]

Visual estimations are today the most common way to assess the surface quality of moulds and dies; a method that are both subjective and, with today’s high demands on surfaces, hardly usable to distinguish between the finest surface qualities. Instead a method based on non-contact 3D-surface texture analysis is suggested. Several types of tool steel samples, manually as well as machine polished, were analysed to study different types of surface defects such as pitting, orange peel and outwardly features. The classification of the defect structures serves as a catalogue where known defects are described. Suggestions of different levels of ‘high surface quality’ defined in numerical values adapted to high gloss polished tool steel surfaces are presented. The final goal is to develop a new manual that can work as a ‘standard’ for estimations of tool steel surfaces for steel producers, mould makers, polishers etc.

Place, publisher, year, edition, pages
Teddington: National Physical Laboratory, 2011
Keyword
tool steel, replication, surface analysis, surface characterisation
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:hh:diva-21482 (URN)978-0946754-59-5 (ISBN)
Conference
13th International Conference on Metrology and Properties of Engineering Surfaces, 12-15 April 2011, Twickenham, UK
Available from: 2013-02-13 Created: 2013-02-13 Last updated: 2015-01-26Bibliographically approved
4. Factors influencing the surface quality of polished tool steels
Open this publication in new window or tab >>Factors influencing the surface quality of polished tool steels
2014 (English)In: Surface Topography: Metrology and Properties, ISSN 2051-672X, Vol. 2, no 3, 035004Article in journal (Refereed) Published
Abstract [en]

Today’s demands on surface quality of moulds for injection moulding of plastic components involve no/low defect contents and roughness levels in the nm-range for high gloss applications. Material properties as well as operating conditions influence the mould finish, and thus the final surface of moulded products. This paper focuses on how particle content and different polishing strategies influence final surface qualities of moulds. Visual estimations of polished tool steel samples were combined with non-contact 3D-surface texture analysis in order to correlate traditional assessments to more quantitative methods, and to be able to analyse the surfaces at nanometer-level.

It was found that steels with a lower proportion of particles, like carbides and oxides, gave rise to smoother polished surfaces. In a comparative study of polishers from different polishing shops, it was found that while different surface preparation strategies can lead to similar final roughness, similar preparation techniques can produce high-quality surfaces from different steel grades. However, the non-contact 3D-surface texture analysis showed that not all smooth polished surfaces have desirable functional topographies for injection moulding of glossy plastic components.

Place, publisher, year, edition, pages
Bristol: Institute of Physics Publishing (IOPP), 2014
Keyword
Polishing strategy, tool steels, surface quality, high gloss appearance
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:hh:diva-22174 (URN)2-s2.0-84979198888 (Scopus ID)
Available from: 2013-05-17 Created: 2013-05-17 Last updated: 2017-03-20Bibliographically approved
5. Quantitative evaluation of the surface finish of high gloss polished tool steels
Open this publication in new window or tab >>Quantitative evaluation of the surface finish of high gloss polished tool steels
2013 (English)In: Metrology and Properties of Engineering Surfaces, 2013: Proceedings of the 14th International Conference, Taipei, Taiwan, June 17-21, 2013, 2013, 207-218 p.Conference paper, Published paper (Refereed)
Abstract [en]

Standardised procedures to measure and estimate surface qualities of moulds for injection moulding of plastic components do not exist. Instead, steel producers as well as polishers and mould-users need to rely on master plaques for tactile comparisons and/or their own visual estimations for surface quality controls.

This paper presents an overview of various surface evaluation methods of steels, including existing standards and available surface metrology. A new method to evaluate high gloss polished tool steel surfaces, based on a 3D non-contacting measurement technique, is presented. The suggested method is based on defect extraction, and should be useful for both specifications and quality controls. Included defects were found to be quality criteria for polished tool steel surfaces. The surface acceptance levels and defect classification are based on interviews and questionnaires, as well as literature studies and visual estimations of test samples made by experienced polishers.

Keyword
tool steel, surface analysis, characterisation, high gloss, defects
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:hh:diva-22171 (URN)
Conference
The 14th International Conference on Metrology and Properties of Engineering Surfaces, Taipei, Taiwan, June 17-21, 2013
Available from: 2013-05-17 Created: 2013-05-17 Last updated: 2015-03-30Bibliographically approved

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