Proto Labs (NYSE:PRLB) will report its third-quarter earnings results on Thursday, Oct. 23, before the opening bell. The past four quarters haven't been particularly good to Proto Labs shareholders, who now hold a stock worth 15% less than it was at this time last year. However, Proto Labs is still a strong company with enviable momentum on most financial fronts, and its Q3 report could go a long way toward alleviating investor concerns.

The company expects to generate between $54 million and $57 million in revenue, which will result in adjusted earnings in the range of $0.44 to $0.48 per share. Wall Street analysts are generally on the optimistic side. Their third-quarter consensus calls for $55.7 million in revenue and $0.47 in earnings per share, good for year-over-year growth rates of 33% on the top line and 27% on the bottom line.

These expectations are easily achievable, as Proto Labs' quarterly revenue has grown by an average of 29% over the past four quarters, with adjusted EPS growth averaging 24% over the same four quarters. Let's take a look at some of the key opportunities, and some potential challenges, that could impact Proto Labs' third quarter and make the difference between so-so and stupendous.

Will Proto Labs keep building stronger ties with more customers?
One of the biggest factors in Proto Labs' favor over the last few years is that it's not only been adding customers at a brisk clip, it's also been generating significantly more revenue from each customer over time:

Sources: Proto Labs earnings reports.

Over the past two years, Proto Labs has added nearly 50% more unique developers to its roster of clients, but it's also managed to increase the amount each developer typically spends on its services by 20%. That's exactly the sort of customer relationships investors should want from a company that serves a highly specific market need, and Proto Labs has delivered.

The only real concern investors might have about this progress is that Proto Labs' average revenue per developer does not increase on a consistent basis, as it's actually tended to flatten out for one or more consecutive quarters before spiking higher again. Will the third quarter show another move higher, or will Proto Labs' developer customers hold back on their spending? That answer will have a major impact on the company's top and bottom lines on Thursday.

Will Proto Labs' customer growth follow a familiar pattern?
Digging deeper into Proto Labs' reports on customer spending provides us an interesting glimpse into the ebb and flow of its revenue mix. The company's ability to add new customers has been relatively consistent for the past few years, but those new customers tend to spend more in the latter half of the year than they do in the first half:

Sources: Proto Labs earnings reports.

As you can see, new customer spending as a percentage of Proto Labs' revenue has hit peaks in the fourth quarter of 2012 and the third quarter of 2013. If this pattern holds up through 2014, we should see a healthy uptick in new customer spending reported on Thursday as well. Proto Labs' financial statements don't follow this metric back very far, but for as long as it's been a public company, it's enjoyed a surge in spending from its new customers in the third and fourth quarters. If this pattern doesn't hold up, it will likely result in some disappointment on Thursday -- but there's no reason to believe that this will happen.

Will Proto Labs' spending normalize after its recent spike?
Proto Labs spent more on capital expenditures in the second quarter than it ever has before, and free cash flow predictably plummeted as a result:

Sources: Proto Labs earnings reports.

Company executives explained this spending during their second-quarter earnings call by pointing out that they've built two new manufacturing facilities -- one in Minnesota and one in England -- which have collectively cost $19.5 million of the $31.6 million in capital expenditures so far this year. The rest of this spending (roughly $6 million per quarter) is in line with the third and fourth quarters of 2013, and company execs expect full-year capital spending to top out at around $40 million, which would drop third- and fourth-quarter spending totals back down to earlier levels. Barring unforeseen circumstances, it's likely that the second quarter's spike won't be repeated in the near future. Investors should hope that it doesn't, as that spike brought cash on hand down to its lowest level since Proto Labs went public at the start of 2012.

We'll be covering Proto Labs' third-quarter earnings in depth on Thursday, so check back early for all the analysis you'll need to understand this exciting young company's latest progress.

Alex Planes holds no financial position in any company mentioned here. Follow him on Twitter @TMFBiggles for more insight into investing, markets, economic history, and cutting-edge technology.

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