Around the time the iPad came out more than two years ago, Microsoft executives got an eye-opening jolt about how far Apple would go to gain an edge for its products.

Microsoft learned through industry sources that Apple had bought large quantities of high-quality aluminum from a mine in Australia to create the distinctive cases for the iPad, according to a former Microsoft employee involved in the discussions, who did not wish to be named talking about internal matters.

The executives were stunned by how deeply Apple was willing to reach into the global supply chain to secure innovative materials for the iPad and, once it did, to corner the market on those supplies. Microsoft’s executives worried that Windows PC makers were not making the same kinds of bets, the former employee said.

The incident was one of many over the last several years that gradually pushed Microsoft to create its own tablet computer, unveiled last week. The move was the most striking evidence yet of the friction between Microsoft and its partners on the hardware side of the PC business. It is the first time in Microsoft’s almost four-decade history that the company will sell its own computer hardware, competing directly with the PC makers that are the biggest customers for the Windows operating system.

In the last decade, Apple has become one of the mightiest, richest and most successful companies in the world, in part by mastering global manufacturing. Apple and its high-technology peers — as well as dozens of other American industries — have achieved a pace of innovation nearly unmatched in modern history.

However, the workers assembling iPhones, iPads and other devices often labor in harsh conditions, according to employees inside those plants, worker advocates and documents published by companies themselves. Problems are as varied as onerous work environments and serious — sometimes deadly — safety problems.

Employees work excessive overtime, in some cases seven days a week, and live in crowded dorms. Some say they stand so long that their legs swell until they can hardly walk. Under-age workers have helped build Apple’s products, and the company’s suppliers have improperly disposed of hazardous waste and falsified records, according to company reports and advocacy groups that, within China, are often considered reliable, independent monitors.

More troubling, the groups say, is some suppliers’ disregard for workers’ health. Two years ago, 137 workers at an Apple supplier in eastern China were injured after they were ordered to use a poisonous chemical to clean iPhone screens. Within seven months last year, two explosions at iPad factories, including in Chengdu, killed four people and injured 77. Before those blasts, Apple had been alerted to hazardous conditions inside the Chengdu plant, according to a Chinese group that published that warning.

“If Apple was warned, and didn’t act, that’s reprehensible,” said Nicholas Ashford, a former chairman of the National Advisory Committee on Occupational Safety and Health, a group that advises the United States Labor Department. “But what’s morally repugnant in one country is accepted business practices in another, and companies take advantage of that.”

Apple is not the only electronics company doing business within a troubling supply system. Bleak working conditions have been documented at factories manufacturing products for Dell, Hewlett-Packard, I.B.M., Lenovo, Motorola, Nokia, Sony, Toshiba and others.

In an effort to compete with the iPad, Amazon Wednesday unveiled their new tablet computer called the Kindle Fire, which will retail for $199. It’s expected to sell well among parents who always buy the wrong thing.

There are two types of companies: those that work hard to charge customers more, and those that work hard to charge customers less. Both approaches can work. We are firmly in the second camp.