What happened

Shares of ExOne Company (NASDAQ:XONE) soared 30.4% in May, according to data from S&P Global Market Intelligence. The industrial 3D printing specialist's stock has gained 41.2% in 2017 through June 2. 

For context, shares of diversified 3D printing leaders 3D Systems and Stratasys climbed 29.2% and 8.6%, respectively, in May, and are up 51.9% and 67.8% this year through June 1. The S&P 500 returned 1.4% in May and has returned 9.9% so far this year.

XONE Chart

Data by YCharts.

So what

We can attribute ExOne stock's powerful monthly performance to the company's release of its first-quarter 2017 earnings on May 10. On that day, the stock jumped 7.6%, and it tacked on 15.3% the next day following the company's analyst conference call.

For the quarter, revenue grew 29% to $10.9 million, net loss widened 24% to $6.8 million, and loss per share expanded 20% to $0.42. Investors were likely pleased with the solid increase in revenue, which included a 95% jump in revenue from sales of 3D printers. Five printers were sold in the quarter, versus one in the year-ago quarter. Moreover, investors were probably encouraged by the 19% sequential growth in backlog to $23.5 million, and management's statement that the company is on track to achieve its goal of positive adjusted earnings before interest, taxes, depreciation, and amortization (EBITDA) by year's end.

A man working next to ExOne's large S-Max 3D printer.

ExOne's S-Max 3D printer. Image source: ExOne.

Now what

Current ExOne investors are surely pleased with a 30% gain in one month and a year-to-date gain of 41%. However, I wouldn't advise new investors to jump in without abandon.

There were some positives in the earnings release and on the conference call. However, the company has yet to prove it has a sustainable business model and can turn a profit. Moreover, analysts don't expect it to be profitable five years out. ExOne is worth watching since it's involved in the metals space, which is the fastest-growing space within the 3D-printing realm. In fact, Stratasys just invested in a potential ExOne competitor, Desktop Metal. (Although there should only be partial overlap in their target applications and markets.) However, investors should not assume that profitability is a sure thing at some point in the future. 

Investors should look at ExOne's results through a wider time lens than one quarter. Its quarterly revenue and other metrics will be very "lumpy" due to the small number of high-priced 3D printers it sells.

Beth McKenna has no position in any stocks mentioned. The Motley Fool recommends 3D Systems and Stratasys. The Motley Fool has a disclosure policy.