For shareholders of The ExOne Company (XONE), days like today are hard to stomach.

Shares of ExOne plunged more than 16% this morning after the additive manufacturing specialist's first-quarter results badly missed expectations. Revenue fell 8% year over year to $7.3 million, which translated to a wider net loss of $0.38 per share. Analysts, on average, were looking for a net loss of just $0.12 per share on sales of $9.87 million.

Now, with ExOne having officially fallen short of estimates in every single quarter since going public early last year, shares are trading within spitting distance of a new 52-week low.

Perspective is in order
Then again, quarters like this are exactly why ExOne avoids providing quarterly guidance. 

Remember, ExOne focuses on selling high-end industrial 3-D printers with an exceedingly large per-unit price tag. In short -- and this early in ExOne's long-term story -- this means dealing with long sales cycles and chunky quarterly revenue.

To be sure, one-third of last quarter's revenue -- or $2.4 million -- came from the sale of just three 3-D printers, including one S-Max unit and one S-15 machine sold to European customers, and a single M-Flex unit sold in the United States. By comparison, last year's first quarter saw five machines sold -- including four 3-D printers and one laser machine -- for $4.2 million.

But this doesn't mean ExOne is a failing business.

First, keep in mind ExOne's first-quarter sales from 3-D printed products, materials, and production service centers actually rose by 37% year over year to $3.7 million. In addition, while ExOne consistently opts not to predict its quarterly performance, as analysts insist on doing, it continues to expect full-year 2014 revenue to grow 40%-50% to a range of $55 million-$60 million -- the mid-point of which sits just above analysts' consensus for 2014 sales of $56.98 million.

To be fair, ExOne did reduce its 2014 gross margin guidance to between 40% and 43%, down from the previous expected range of between 43% and 46%. But ExOne also explained that it's the result of developmental costs associated with its new ExCast initiative, which could generate an additional $50 million to $60 million in revenue next year alone. And that's why fellow Fool Blake Bos recently insisted ExCast is "of utmost importance for the company to succeed over the long-term, satisfy investor's expectations, and drive the stock price higher."

Foolish takeaway
Don't get me wrong. I'll readily admit it hurts to see stocks we recommend fall this much in a single day. But in ExOne's case, I see nothing to indicate its long-term story is broken. As a result, if shares continue to remain depressed over the next few days, I intend to add ExOne to my personal portfolio as soon as the Fool's trading restrictions allow.