A process control system for cryogenic CNC elastomer machining

Dhokia, Vimal; Newman, Stephen T.; Crabtree, Paul; Ansell, Martin P.

doi:10.1016/j.rcim.2011.02.006

Cited by 19 publications

(6 citation statements)

References 16 publications

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“…Traditional machining of a polymer using high-speed routing tools produces fine particulate swarf as demonstrated in a previous study. This is considered to be undesirable as the surface being machined is being damaged, resulting in micro tears and serration throughout the surface, leading to inferior products [29]. Production of cleancut, non-serrated, or segmented chips indicates an improved machined surface.…”

Section: Cryogenic Machining Analysismentioning

confidence: 99%

Adiabatic shear band formation as a result of cryogenic CNC machining of elastomers

Dhokia¹,

Newman²,

Crabtree³

et al. 2011

Proceedings of the Institution of Mechanical Engineers, Part B:

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The traditional method for producing polymer-based products is the use of moulding technologies such as injection moulding. CNC machining methods are predominantly used for metal part manufacture. The use of CNC machining methods for direct machining of polymers has been discussed in previous studies, particularly for hard polymers such as polypropylene. The CNC machining of soft elastomers, such as ethylene vinyl acetate (EVA), even at significantly reduced temperatures presents a number of challenges, with one being the formation of a machining phenomenon termed adiabatic shear bands, which can lead to increased part surface roughness and reduced part quality. The adiabatic shear band is an area on a chip where the ductile properties of the material being machined have been exceeded and the heat generated does not have sufficient time to be removed. This can lead to permanent material damage resulting in reduced fatigue resistance. The adiabatic shear formation has the potential to be even more evident with the machining of elastomers, leading to rapid material degradation, poor surface finish characteristics, and reduced material attenuation. In this paper the state of the art in cryogenic manufacturing is described and the concept of cryogenic CNC machining of elastomers is discussed. The experimental work consists of machining EVA and Neoprene utilizing the described cryogenic CNC machining facility. Sample chips are taken from the experimental testing and analysed using a scanning electron microscope to illustrate the adiabatic shear band formation in some cases. It is observed that in order to reduce this effect, correct machining parameters corresponding to the elasticity values need to be used and the glass transition temperature needs to be maintained.

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Section: Cryogenic Machining Analysismentioning

confidence: 99%

Adiabatic shear band formation as a result of cryogenic CNC machining of elastomers

Dhokia¹,

Newman²,

Crabtree³

et al. 2011

Proceedings of the Institution of Mechanical Engineers, Part B:

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“…Cryogenic liquid nitrogen improved the surface roughness of machined PDMS with machined temperature lower than −143 • C. In addition, the problems of adhesion and shrinkage in machining PDMS were also solved with correct amount of liquid nitrogen flow. A similar technique was applied by Dhokia et al, in machining elastomer [48]. With the technique of cryogenic liquid nitrogen machining, formation of adiabatic shear band was reduced in milling ethylene vinyl acetate (EVA) and Neoprene [49].…”

Section: Cryogenic Machining Of Viscoelastic Polymers and Elastomersmentioning

confidence: 99%

Roles of Cryogenic Cooling in Turning of Superalloys, Ferrous Metals, and Viscoelastic Polymers

Yap

2019

Technologies

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Cryogenic machining is a relatively new technique in machining. This concept was applied on various machining processes such as turning, milling, drilling etc. Cryogenic turning technique is generally applied on three major groups of workpiece materials—superalloys, ferrous metals, and viscoelastic polymers/elastomers. The roles of cryogen in machining different materials are unique and are summarised in this review article. Finally, the challenges in using cryogenic machining in industries are also highlighted.

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“…Above the glass transition temperature the viscous element will dominate the response, while below this temperature the elastic element will dominate [9]. Many polymers have glass transition temperatures below room temperature, so favourable elastic-dominated behaviour can be obtained using low temperature, or cryogenic, machining [10], though this often requires careful consideration of contraction rates [11], and a process control system to maintain the appropriate temperature [12].…”

Section: Viscoelastic Behaviour Of Polymersmentioning

confidence: 99%

Characterising the machining of biomedical grade polymers

Aldwell

Hanley²,

O’Donnell

2014

Proceedings of the Institution of Mechanical Engineers, Part B:

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The manufacture of polymer components for biomedical applications is an area which has received much attention from polymer scientists, with high levels of wear resistance achieved, but relatively little research has been done into the machining operations required to manufacture the complex geometries used in total joint replacement. Traditional metal cutting theories have been shown to be insufficient for analysis of polymer machining, as polymers exhibit viscoelastic behaviour, and unique chip formation mechanisms. This paper details an experimental investigation into the effect of tooling and machining parameters on the cutting forces, surface roughness and chip formation in Ultra High Molecular Weight Polyethylene, a common material used in biomedical applications. This research quantifies the relative importance of each parameter, the chip formation mechanisms and resulting surface roughness for the given machining parameters, and provides new insight into applied research on the machining of polymers.

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A process control system for cryogenic CNC elastomer machining

Cited by 19 publications

References 16 publications

Adiabatic shear band formation as a result of cryogenic CNC machining of elastomers

Adiabatic shear band formation as a result of cryogenic CNC machining of elastomers

Roles of Cryogenic Cooling in Turning of Superalloys, Ferrous Metals, and Viscoelastic Polymers

Characterising the machining of biomedical grade polymers

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