Firstcut Helps Put the
Muscle in Moxy
Roger Schmitz has a simple formula for designing
a great new product: build and test; build and
test; then build and test some more. That’s what
he and the development team at Fortiori Design
in Spicer Minnesota have been doing since he first
conceptualized the Moxy muscle oxygen sensor
in the fall of 2010. Schmitz is quick to admit that
there are already ways to measure an athlete’s
metabolic state—the metabolic cart that measures
gases exhaled into a mask and blood lactate
meters that run a blood sample through a desktop
machine—but neither is very practical for use in
actual training activities like running or cycling.
“We had requested quotes
from other machine shops, all
of which were more expensive
and a lot slower. Even their
quotes took longer.”
Another drawback of those methods was that
they measured overall oxygenation rather than
that of specific muscles, like leg muscles for a
bicyclist. Schmitz knew that individual muscle
oxygenation could be assessed using near
infrared spectroscopy (NIRS), which measures
the scattering of light shone into the body at a
specific location, but that technology required
prohibitively-expensive optics. He believed,
however, that the proper algorithm could
accomplish the same result with a simpler, less
expensive optics and that the entire system could
be made into an affordable, wearable unit.
© Proto Labs 1999–2012
“We took a lean startup approach, aiming to
come up with a ‘minimum viable product’ and
advance step by step from there to develop the
device we would take to market,” says Schmitz.
“Our first prototype was a sensor worn next
to the skin and connected by wire to a laptop
that ran the algorithm. We needed to shield
the electronic components of the sensor from
EMI (electromagnetic interference). That would
normally be done by treating an injection-molded
plastic shell with an EMI-blocking coating, but
that treatment would have been prohibitively
expensive for a small number of prototypes.
Instead, we had Proto Labs’ Firstcut division
machine the two half shells of our prototype from
aluminum, which naturally blocks EMI. Firstcut
also made our plastic optics holder.”
Schmitz designed Moxy using Pro/Engineer and
SolidWorks software. The first time he uploaded a
3D CAD model to Firstcut’s online quoting engine,
it identified several design issues. Some of the
Close up of black domed radio transmitter atop Moxy Monitor sensor device.
Proto Labs, Inc., 5540 Pioneer Creek Dr., Maple Plain, MN 55359 USA | 877.479.3680
holes were too deep, there was a minor aspect
ratio problem, and some inside corners needed to
be radiused.
“We made the necessary changes and sent a
revised model that Firstcut machined for us,”
he says. “We had requested quotes from other
machine shops, all of which were more expensive
and a lot slower. Even their quotes took longer.
The aluminum case parts we got from Firstcut
were very cool. It was a complex shape, contoured
to fit the wearer’s body on the outside and shaped
to fit the electronics inside, but Firstcut’s ballend mills had no problem with it. We called the
resulting device Moxy1 and used two prototypes
to test runners on a treadmill and adjust our
algorithm until we were getting consistent, stable
results. Our next goal was to eliminate the wire
and the laptop to come up with a wearable device.
“Another nice thing about Firstcut
is that they could handle the
draft in our designs, which
most machine shops can’t.”
“We appreciate the short lead
times and transparency in quoting
at both Proto Labs divisions.”
The company is now in the final stages of
development with a team of about a dozen and
partnership with a professional training facility
in San Diego. “We’re getting the final bugs
worked out,” says Schmitz. “Moxy needs to be
100 percent waterproof, both to withstand sweat
and, ultimately, to be used by swimmers, so the
shell will have to be fully gasketed. The next
prototype version of the shell will be injectionmolded plastic with an EMI-blocking coating, and
the entire device will be extensively drop-tested,
vibration-tested, water-tested, and lifecycle-tested.
We figure we’ll have to build and break between
50 and 70 units before we really know that it’s
bulletproof. We’ll use Proto Labs’ Protomold
division, which I’ve used before with great
success, for molded plastic parts. We appreciate
the short lead times and transparency in quoting
at both Proto Labs divisions and expect to easily
meet our goal of bringing a fully-tested product
to market in summer of 2013.”
Moxy2 added a microcontroller to the sensor to
do the calculations that had previously been done
on a laptop. It had a radio transmitter outside
the EMI- shielded shell to send the results to
a TI Chronos wristwatch for display, using its
own battery for onboard power. The new model
required revised shells, which were again
machined from aluminum stock by Firstcut.
“Since we weren’t tied to the laptop anymore we
could start doing serious real-world testing,” says
Schmitz. “We figured we’d need about 20 copies,
but because Firstcut’s turnaround was so fast we
initially ordered just four and waited on the other
16 until we’d identified additional changes that
could be incorporated into the next version.
Moxy Monitor System: Front and back of sensor shown with watch display.
Another nice thing about Firstcut is that they
could handle the draft in our designs, which most
machine shops can’t. Draft isn’t really needed in
machined parts, but when we go into full-scale
production it will be required for molded or die
cast parts and we wanted our prototypes to be as
close to production designs as possible.”
© Proto Labs 1999–2012
Proto Labs, Inc., 5540 Pioneer Creek Dr., Maple Plain, MN 55359 USA | 877.479.3680