Selection of mould design variables in direct stereolithography injection mould tooling

Harris, Russell A.; Newlyn, H; Dickens, Phill

doi:10.1243/0954405021520193

Cited by 17 publications

(11 citation statements)

References 3 publications

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“…These include polyester (PE), polypropylene (PP), polystyrene (PS), polyamide (PA), polycarbonate (PC), polyetheretherketone (PEEK), acrylonitrile-styrene acrylate (ASA) and acrylonitrilebutadiene-styrene (ABS) [5][6][7][8][9].…”

Section: Stereolithography Tooling For Injection Mouldingmentioning

confidence: 99%

Crystallinity control in parts produced from stereolithography injection mould tooling

Harris¹,

Hague²,

Dickens³

2003

Proc. Instn Mech. Engrs, Part L: J. Mat

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• This is an article from the journal, Proceedings of the Institu- This item was submitted to Loughborough's Institutional Repository (https://dspace.lboro.ac.uk/) by the author and is made available under the following Creative Commons Licence conditions.For the full text of this licence, please go to: http://creativecommons.org/licenses/by-nc-nd/2.5/ Crystallinity control in parts produced from stereolithography injection mould tooling R A Harris*, R J M Hague and P M Dickens Rapid Manufacturing Research Group, Loughborough University, Loughborough, UK Abstract: The use of moulds produced by stereolithography (SL) for injection moulding provides a quick route to manufacturing a low volume of parts without expensive hard tooling. However, these parts have been shown to exhibit different material property characteristics than those produced from metal tooling. The aim of the present work is to research methods that would allow SL moulds to produce parts of similar material property characteristics to those from conventional metal tools. This work has identi ed that the different part characteristics are due to differing levels of crystallinity developed in the parts from the comparative mould varieties (SL and metal). These crystallinity differences have been associated with the cooling rates imparted owing to the thermal properties of the mould material. The latter part of this work concerns controlling and manipulating this degree of crystallinity. After a discussion of possible methods, two approaches are taken to modifying the crystalline content of parts produced by SL moulds. One of the approaches is material based, the other concerns the injection moulding process. Differential scanning calorimetry (DSC) is used to quantify the resulting levels of crystallinity in the parts. The results show that by process modi cation it is possible to produce parts by SL moulding that possess a similar crystalline content to those moulded from metal tooling. The use of modi ed materials allows parts created in SL and metal tools to be of a consistent crystalline content. The work concludes that not only are SL moulds capable of producing parts that are more like those from metal moulds but also present some unique opportunities that have been demonstrated to be unachievable in metal moulds.

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Section: Stereolithography Tooling For Injection Mouldingmentioning

confidence: 99%

Crystallinity control in parts produced from stereolithography injection mould tooling

Harris¹,

Hague²,

Dickens³

2003

Proc. Instn Mech. Engrs, Part L: J. Mat

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“…The SL moulds were manufactured by a 3D Systems SLA350 machine, using Vantico 5190 resin. The build layer thickness was 0.05mm, as this has previously been demonstrated as an optimal value in extending the working life of SL moulds [6].…”

Section: Mould Designmentioning

confidence: 95%

“…The draft angle used to ease part removal from the mould was 1.5. This value has previously been shown to be an optimum value for reducing potential damage to SL tools upon part ejection [6].…”

Section: Mould Designmentioning

confidence: 99%

The structure of parts produced by stereolithography injection mould tools and the effect on part shrinkage

Harris

Hague

Dickens

2004

International Journal of Machine Tools and Manufacture

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Stereolithography (SL) tooling for plastic injection moulding provides a low cost and quick alternative to hard tooling methods when producing a small quantity of parts. However, work by the authors has shown that a different rate of polymer shrinkage was experienced in semi-crystalline parts when produced from SL moulds as compared to those from conventional metal tooling methods.Different shrinkage means the parts are not truly the same as those that would be produced by metal tooling and highlights a disadvantage to SL tooling. This work associates the increased shrinkage experienced to a greater percentage crystallinity developed in the parts due to their thermal history during processing. In these experiments the cooling rate, which is imparted due to the 2 heat transfer characteristics of the mould has been identified as the controlling factor of a parts % crystalline content and the cause of shrinkage anomalies.The morphology analysis results show that there is 30% more crystallinity developed in the nylon (PA66) parts produced in SL moulds than those produced from aluminium moulds. The results also reveal different characteristics during thermal analysis that may also be due to the thermal history imparted by the mould. The work utilises the thermal analysis technique Differential ScanningCalorimetry (DSC) to quantify the different levels of crystallinity in the parts. The thermal characteristics of the mould are demonstrated by real-time data acquisition.

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“…There is also a possibility of surface smoothening over the life of molds which can be good for tool life, but they can lead to excessive flashing. 3D-printed tool designers have recommend having draft angles of about 5% in polymer molds for the ease of ejection of parts; higher draft angles will lead to easier part ejections [24].…”

Section: Failures Due To Injection Pressurementioning

confidence: 99%

Categorization of Failures in Polymer Rapid Tools Used for Injection Molding

et al. 2019

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Background—Polymer rapid tooling (PRT) inserts for injection molding (IM) are a cost-effective method for prototyping and low-volume manufacturing. However, PRT inserts lack the robustness of steel inserts, leading to progressive deterioration and failure. This causes quality issues and reduced part numbers. Approach—Case studies were performed on PRT inserts, and different failures were observed over the life of the tool. Parts molded from the tool were examined to further understand the failures, and root causes were identified. Findings—Critical parameters affecting the tool life, and the effect of these parameters on different areas of tool are identified. A categorization of the different failure modes and the underlying mechanisms are presented. The main failure modes are: surface deterioration; surface scalding; avulsion; shear failure; bending failure; edge failure. The failure modes influence each other, and they may be connected in cascade sequences. Originality—The original contributions of this work are the identification of the failure modes and their relationships with the root causes. Suggestions are given for prolonging tool life via design practices and molding parameters.

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Selection of mould design variables in direct stereolithography injection mould tooling

Cited by 17 publications

References 3 publications

Crystallinity control in parts produced from stereolithography injection mould tooling

Crystallinity control in parts produced from stereolithography injection mould tooling

The structure of parts produced by stereolithography injection mould tools and the effect on part shrinkage

Categorization of Failures in Polymer Rapid Tools Used for Injection Molding

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