We have tracked the key short interest changes as of October 15 in the following 3D printer and services companies: 3D Systems Inc. (NYSE: DDD), Stratasys Ltd. (NASDAQ: SSYS), The ExOne Co. (NASDAQ: XONE) and Proto Labs Inc. (NYSE: PRLB).

Germany’s Voxeljet A.G. (NYSE: VJET) held its initial public offering on October 17, and we will add it to short interest coverage in our next report. Voxeljet’s IPO was a huge success for the company. Shares went off at $13 and closed Thursday night at $33.75.

Short interest in 3D Systems rose 2.1% to 27.64 million shares. Some 28.9% of the company’s stock is short.

Short interest in Proto Labs decreased by 8.2% to 2.77 million shares, or 13.7% of the company’s float.

Stratasys saw short interest drop 8.9% in the first two weeks of October to 2.52 million shares, or about 7.8% of the company’s float.

Short interest in ExOne rose 11.8% to 3.63 million shares. About 35.6% of the company’s shares are now held short.

After piling on ExOne in mid-September, short sellers eased off on the company a bit. Still, it was the only one of the four to see double-digit rise in short interest in the two-week period ending October 15. The anticipation — and ultimate success — of Voxeljet’s IPO probably gets most of the blame, because the two companies focus primarily on the industrial and commercial markets for their products.