Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of fiber-laser specialist IPG Photonics (Nasdaq: IPGP) look dim today, falling as much as 12.5% on above-average trading volume.

So what: The company reported great but not tremendous earnings on Monday and took some lumps in Tuesday trading. Analyst reactions have been positive with two raised target prices, and there's no obvious reason why IPG should be falling again today, but there you have it -- Mr. Market isn't exactly known for his rationality.

Now what: We might be looking at some major IPG owners in the process of taking some profits off the table, or perhaps the talking heads on MSNBC and Bloomberg TV are making trouble while I'm not watching. Either way, there's nothing inherently wrong with IPG today, and like I said, that quarterly report was actually impressive.

It's not even a sector effect: Direct rivals Coherent (Nasdaq: COHR), GSI Group (Nasdaq: GSIG), and Newport (Nasdaq: NEWP) are all chugging along today with either mild drops or moderate price spikes. IPG remains a core stock in the Rule Breakers portfolio, and it makes sense to treat this irrational drop as a buy-in opportunity.

Interested in more info on IPG Photonics? Add it to your watchlist.

Fool contributor Anders Bylund holds no position in any of the companies discussed here. IPG Photonics is a Motley Fool Rule Breakers selection. The Fool owns shares of IPG Photonics. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool is investors writing for investors.