Medical Design Briefs - February 2021 - 16

TECHNOLOGY LEADERS Test & Measurement

* A superior ball recirculation model
can attain metrics like these:
* Maximum speed: 1 m/s
* Maximum acceleration: 50 m/s2
(about 5 g's)
When even greater velocities are
called for, a top-flight system with a nonrecirculating ball cage could reach:
* Maximum speed: 3 m/s
* Maximum acceleration: 300 m/s2
(about 30 g's)
Naturally, especially in the second
example, very high speeds bring somewhat lower levels of resolution.

A robotic multichannel pipette device delivers a liquid for medical and pharmaceutical research and testing.

demonstrates long experience in directsystem design, and whose system can
work with any controller you choose.
4. Pick Precision
Obviously, the demands of your
machine design will determine the level
of precision you need. Today, your
choice includes systems with resolution
down to well below a human hair, which
has a diameter of 75 μm. For example,
an advanced ball recirculation model
could have:
* Maximum digital resolution: 0.1 μm
* Accuracy over 1000 m down to ±10 μm
* Repeatability: ±0.1 μm (unidirectional), ±0.2 μm (bidirectional)
For even greater precision on even
more compact dimensions, a nonrecirculating model like the one mentioned earlier offers extreme rigidity. Its
ball cage design maximizes load capacity
in all directions, eliminating the cage

creep normally associated with highspeed movement. No reset strokes are
needed during production, for instance.
The results are exceptional stiffness,
high load capacity, and very smoothrunning performance, as well as outstanding precision. A system like this can
achieve:
* Maximum digital resolution: 0.1 μm
* Accuracy: ±3 μm
* Repeatability: ±0.1 μm (unidirectional),±0.2 μm (bidirectional)
Note: In the near future, look for
some advanced systems like these to add
absolute positioning capability. So even
if your system loses power, the last position is safely maintained.
5. Select for the Speed You Need
The best modern distance measuring
systems can achieve impressive velocities
to match an application's needs such as
high productivity.

The compact Schneeberger Miniscale Plus integrated encoder system, with ball
recirculation and 0.1 μm resolution, provides high rigidity and precision for carriage lengths and rails from 7 to 42 mm in width and up to 1 m in length.

The ultra-compact MSQscale integrated encoder system, with exceptional rigidity
in a ball cage non-recirculating design and resolution as low as 0.1 μm, offers the
highest speed and acceleration for stroke lengths from 0.33 to 130 mm.

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6. Trust Experience
The linear motion field offers a large
number of suppliers. But the hard reality is that product quality varies; some are
startups - and even established suppliers may be late entrants in the distance
measurement system segment.
The more important that precise
measurement is to your medical product
and the results it delivers, the more
important it is to source an experienced
supplier. Look for a maker with a proven
record for technological excellence, as
well as thousands of successful installations of high-performance linear motion
components and systems.
Consider the factors described above
as a guide to determining the linear distance measuring system that will go the
distance for your device - and the
demanding marks that you and it must
meet.
This article was written by Ross
Blumenthal, Vice President for Sales and
Marketing with Schneeberger Corp. He has 35
years of experience specifying and engineering
solutions in automation engineering and
motion control. For more information, visit
http://info.hotims.com/79410-342.

Medical Design Briefs, February 2021

http://info.hotims.com/79410-342 http://www.medicaldesignbriefs.com

Medical Design Briefs - February 2021

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