3D Systems ( NYSE: DDD ) has made strong rally over the last few days. However, the stock started falling in the after-hours trading yesterday as the company announced an equity offering. It is disappointing for the shareholders that as the stock was gaining an upward momentum; this piece of news has brought the share price down. Since the start of the year, the 3-D printing sector has been under pressure and the recent rally by 3D Systems and Stratasys ( SSYS ) was being taken as the start of a sustained upward movement by the 3-D printers. Yesterday, the company announced that it will offer 5.95 million shares of common stock in a public offering. Furthermore, the underwriter has the option to buy 892,500 additional shares in the 30 days after the offering. According to the press release, the proceeds will be used to finance future acquisitions and working capital requirements. At the moment, the company has 103.5 million shares outstanding.