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.

If you're following the 3-D printing space, you know volatility is par for the course. That said, shares of industry juggernaut 3D Systems Corporation (DDD -7.10%) have been particularly strong over the past two trading days, rising 4.5% on Friday and then tacking on another 4.4% on Tuesday (the market was closed on Monday) for a total two-day rise of 9.1%.

3D Systems' stock closed at $77.14 on Tuesday, so it's now higher than it was earlier in the month before investors pummeled the stock after the company announced much-weaker-than-expected preliminary full-year 2013 earnings results and 2014 earnings guidance.

Here are the likely reasons for the recent strength in 3D Systems' stock:

3D Systems-Hasbro partnership
3D Systems Corp. (DDD) announced on Friday that it's teaming with toy giant Hasbro (HAS -0.77%) to exclusively co-develop and commercialize innovative play 3-D printers and platforms later this year.

Certainly, "play 3-D printers" would appeal to some families interested in providing play experiences for their children that are both fun and educational. Additionally, if a family's first 3-D printer is a 3D Systems/Hasbro (I'd imagine they'll be co-branded) play 3-D printer, it's probably likely the family will be more prone to buy a 3D Systems' printer when it's ready to move up to a "real" 3-D printer. So, this partnering seems like a good move for 3D Systems.

My guess would be that the play 3-D printer might allow kids and their families to use basic design software to design something and then print it out of Hasbro's PLAY-DOH.

This Hasbro collaboration is yet another example of 3D Systems partnering with dominant companies across a wide range of industries. For instance, 3D Systems recently announced it was teaming with Hershey Company (HSY 2.86%), which is the largest chocolate producer in North America, to produce 3-D printed edibles and a new class of 3-D printers to produce edibles. In November, 3D Systems announced it was partnering with tech behemoth Google on Project Ara. The goal of Project Ara is to create a large-scale 3-D printing manufacturing platform capable of producing customizable open-source modular smartphones.

3D Systems prints first 3-D printed hybrid robotic exoskeleton
3D Systems Corp. (DDD) announced on Tuesday that it teamed with Ekso Bionics to produce the first ever 3-D printed hybrid exoskeleton robotic suit, which recently debuted at a Singularity Univ.-hosted event in Budapest. The suit was made for Amanda Boxtel, whose skiing accident in 1992 left her paralyzed from the waist down.

The hybrid 3D printed robotic suit enabled Amanda to stand and walk, assisted with crutches, during the event. "After years of dreaming about it, I am deeply grateful and thrilled to be making history by walking tall in the first ever 3D printed Ekso-Suit, made specifically for me," she said.

3D Systems' designers scanned Amanda's thighs, shins, and spine so the suit would be custom fit for Amanda. A 3-D printer then produced the Ekso suit from the scans. Mechanical actuators and controls, which Ekso Bionics manufactured, were then integrated with the 3-D printed portion of the suit.

This heartwarming story underscores a key strength of 3-D printing:  3-D printing allows for products to be custom-made to fit individuals, which is of critical importance when we're talking about medical devices, such as exoskeletons, various orthopedic implants, dental implants, and the like. Traditional manufacturing techniques can't always produce such exact-fitting devices.