Questions loom about whether consumer desktop 3-D printers, such as the Stratasys (NASDAQ:SSYS) MakerBot or the 3D Systems (NYSE:DDD) Cube, are a sustainable revenue streams. Are these printers here to stay? Or are they just fads? If one inventor's enthusiasm for fused deposition modeling, or FDM, desktop 3-D printers is any indication of the sustainability of the category, we may only be scratching the the surface of their potential in the marketplace.

Why it matters
Both the Stratasys MakerBot and 3D Systems Cube lines make up a significant portion of the two companies' revenue streams.

MakerBot Replicator 2, desktop 3-D printer. Source: MakerBot.

Investors widely view Stratasys' acquisition of MakerBot this year as a massive success. Today, MakerBot revenue now accounts for about 9% of Stratasys' revenue. And Stratasys CEO David Reis said in the company's third-quarter press releases that he was "especially pleased by the contribution made by MakerBot." Even more, Reis refers to the desktop 3-D printer category as "one of the fastest-growing segments within our industry." And it's the MakerBot acquisition, he says, that makes Stratasys the "clear leader" in the category.

The 2012-launched Cube line already accounts for about 10% of 3D Systems' revenue. And the line has seen staggering growth, from just $3.3 million in revenue in the third quarter of 2012 to $13.15 million in Q3 today.

Mini Metal Maker creator lauds FDM desktop 3-D printers
Springing on to the 3-D printing community basically overnight, the inventor of the world's first desktop 3-D printer for metal, David Hartkop, has much to say about MakerBot's FDM technology. In fact, the MakerBot inspired the creation of his own printer.

From the heart of the maker culture, Hartkop says these consumer printers are here to stay.

Hartkop went as far as to say that the MakerBot and other desktop FDM printers are often the "centerpiece" for an "emerging do-it-yourself culture."

Fad or here to stay?
Do you agree with Hartkop? Are desktop 3-D printers here to stay? Are we just scratching the surface of their potential in the consumer market?