Apple is running out of time if it is to meet its target of shipping the 21in iMac before the end of November. With the 30 November falling this Friday, Apple will have to ship the entry-level iMac before the end of the week.

The company announced the new thinner iMacs just over a month ago on 23 October. In the meantime customers haven't been able to pre-order the new model, or even purchase the soon to be superseded model from Apple.

Reports claim that the delay is down to problems with the new screen lamination process that requires high pressure welding. The screen lamination problems were first identified as a challenge by KGI Securities analyst Ming-Chi Kuo back in July. Kuo noted that the new screen lamination process for the new iMac is more difficult with the 27in model, and suggested that as a result it would launch 6-8 weeks after the 21.5in option. 

According to a report, the welding technique that Apple is using, and which enables the new iMac to be so thin, comes from a UK company based in Cambridge. TWI's Wayne Thomas invented the friction-stir welding process in 1991. The process doesn't require materials to be melted in order to be joined, instead the process uses frictional heat in order to soften and merge the edges.

Apple licensed the technology earlier this year, according to a report on The Register.

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