The WSJ revealed some iPhone 6 production numbers as Foxconn struggles to meet demand from pre-orders: the company is operating around 100 production lines around the clock, has 200,000 workers dedicated to production of the iPhone 6 and iPhone 6 Plus – and is manufacturing 540,000 units a day.

“We have been churning out 140,000 iPhone 6 Plus and 400,000 iPhone 6 every day, the highest daily output ever, but the volume is still not enough to meet the preorders,” said a person familiar with the matter …

The split between the two models also provides some insight into what pre-order customers have ordered, suggesting that more than a third of orders are for the larger iPhone 6 Plus. The real number could be far higher, as production of the larger model is being held back by very poor yield rates for the 5.5-inch screen.

The output rate of 5.5-inch is still only around 50%-60%, which means display makers have to scrap almost half of the substandard output, said a person at a display component supplier. The person said the output rate of the 4.7-inch display is better at 85%.

The high failure rates reflect the complexity of the new screens, in which the touch sensors are integrated into the display itself rather than being a separate layer as on earlier iPhone models – part of the secret to the thinness and lightness of the new phones.

The far lower yield rates for the iPhone 6 Plus displays explains why they went to 3-4 week delivery almost immediately when pre-orders opened, and why Apple excluded the larger model from employee reservations.

Apple announced a record 4 million pre-orders in the first 24 hours, and both models have been receiving rave reviews in the tech press.

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