eprintid: 218
rev_number: 17
eprint_status: archive
userid: 7
dir: disk0/00/00/02/18
datestamp: 2009-05-05 14:52:05
lastmod: 2015-05-29 19:49:37
status_changed: 2009-05-05 14:52:05
type: report
metadata_visibility: show
item_issues_count: 0
creators_name: Budd, C J
creators_name: Hewitt, Ian
creators_name: Mitchell, Sarah
creators_name: Coles, Chris
creators_name: Rankin, James
creators_name: Rodrigues, David
creators_name: O’Brien, Mick
creators_name: McKee, Sean
creators_name: Vynnycky, Michael
creators_name: King, John
creators_name: McGinty, Sean
title: Laser Welding of a Stent
ispublished: pub
subjects: materials
subjects: medicine
studygroups: esgi62
companyname: Boston Scientific
full_text_status: public
abstract: We consider the problem of modelling the manufacture of a cylindrical Stent, in which layers of a plastic material are welded together by a Laser beam. We firstly set up the equations for this system and solve them by using a Finite Element method. We then look at various scalings which allow the equations to be simplified. The resulting equations are then solved analytically to obtain approximate solutions to the radial temperature profile and the averaged axial temperature profile.
problem_statement: Stents are widely used in surgery as a means of reinforcing a damaged blood vessel. They typically comprise short cylindrical combinations of several plastic materials, a few centimetres in length and about 670μ in radius. As part of the manufacturing process these materials have to be welded together.
The problem of doing this welding efficiently using a laser was brought to ESGI62 by Boston Scientific.

Laser welding works by drawing a cylindrical covering of a shrink plastic material over another smaller cyliner of Pebax, and subjecting this combination to an incident laser light. At the centre of the assembly is a mandrel which acts both as a support for the plastic materials and a significant heat sink. The laser provides localised heating on the surface which is then conducted through the material causing a weld at the interface between the shrink plastic and the Pebax, when a thin layer of the Pebax melts. To obtain an even distribution of heat, the whole material is spun rapidly at 500rpm, and it is drawn slowly past the point of laser illumination.

The problem posed to the Study Group was to model this process and to try to determine analytical solutions for the temperature.
date: 2008
citation:   Budd, C J and Hewitt, Ian and Mitchell, Sarah and Coles, Chris and Rankin, James and Rodrigues, David and O’Brien, Mick and McKee, Sean and Vynnycky, Michael and King, John and McGinty, Sean  (2008) Laser Welding of a Stent.  [Study Group Report]     
document_url: http://miis.maths.ox.ac.uk/miis/218/1/stent-1.pdf