by Kyle Thompson, Product Line
Manager, Thomson Systems Group
Wheel-guided slides move heavy loads quickly and accurately
over long stroke lengths
Linear motion systems can make or break the productivity of industrial machines. If a sluggish linear axis
slows down an entire machine, cycle time
and throughput will suffer. So, why not simply speed up the machine’s linear axes?
That’s easier said than done, because the
need for speed usually has to be balanced
against travel length, accuracy, and load
requirements. Striking this balance can be
particularly difficult with large-format production and packaging machines that have
heavy payloads and need to operate quickly
to meet cycle time goals.
For a linear motion component that can
strike this balance, consider wheel-guided
linear slides. Wheel guides don’t always get
as much engineering attention as other types
of linear motion devices, but they should.
In the right application, wheel guides offer
the best balance of speed, load carrying capacity, and travel length. Recently developed
models also offer improved positioning accuracy, opening up new application possibilities.
Wheel-guided slides have a simple operating principle: Driven by a belt, the carriage
rides on a set of wheels that run within a precision guideway along the length of the guide.
Compared to other guides based on other
types of rolling elements,
wheel guides can reach
higher operating speeds
and accelerations. Wheel
guides can also accommo-
date high dynamic and moment loads.
The best wheel guides can reach speeds of
up to 10 m/s, and accelerations of up to 40
m/s2 — far faster than ball guides limited to
less than 5 m/s by the recirculation speed of
the balls. As for loads, the most robust wheel
guides can handle dynamic loads in a travel
direction of up to 5,000 N and moment loads
of up to 930 Nm.
Wheel guides also tend to offer longer
strokes than any other type of linear guides.
For example, wheel guides offering up to 11
meters of travel are available off the shelf.
While less accurate or repeatable than a
high-performance ball guide, wheel guide
accuracy has not proven to be much of an
issue in practice. Good wheel guides can
easily achieve positioning accuracy under 1
mm, more than enough for most of the applications they target.
Some newly developed wheel guides can
do even better in the accuracy department.
New models with precision guideways and
preloaded rollers offer a positioning accuracy
of ±0.05 mm with solid repeatability.
Belt-driven wheel guides have been
around for decades, yet many engineers rule
them out prematurely in the belief that their
application requires a screw- or belt-driven
ball guide. Many applications require every
iota of accuracy, repeatability, and stiffness
that a screw- or belt-driven ball guide can
However, there is a large class of linear
motion applications in which a ball guides
strike the wrong balance of technical fea-
tures. Applications that share one or more of
the following characteristics can favor wheel
• Machine productivity increases with
linear axis speed.
• Stroke requirements exceed a few meters.
• Dynamic and moment loads are high.
• Accuracy requirements are moderate.
Many types of filling, dispensing, and
packaging machines fall into this category,
as well as food processing machines. Factory
automation, material handling, printing, and
scanning systems are also a good fit.
In the right applications, wheel guides can
provide a cost-effective alternative to more
expensive ball guides while offering a performance boost over other belt-driven slides (see
Thomson offers a way to size and select
a linear system at www.linearmotioneer-ing.com. This online tool can configure
a complete system based on application
parameters. Outputs include downloadable
3D models, orderable part numbers, and
detailed specifications. A sort-and-filter
feature allows quick organization and comparison of all the solutions that fit specific
An Economical Belt-Driven Alternative
Wheel guides are not the only game
in town when it comes to economical
point-to-point linear motion. Another
popular belt-driven linear axis uses
prism slides to support and guide the
carriage. Made from an engineering
polymer, the prism slides run along
the linear unit’s extrusion rather than a
This elimination of a bearing reduces
cost, especially as stroke length increases. Like wheel guides, prism guides can
extend to strokes of 11 meters.
Prism-guided units don’t have all the
capabilities of a wheel-guided unit—in
terms of speeds, loads or accuracy. But
prism guides have some advantages of
the their own, including:
• Low noise.
• Shock load tolerance.
• Contamination resistance.
In applications not needing all the
capabilities of a wheel guides or applications with contamination or shock
loads, prism guides can offer the lowest
total installed cost of any type of guide.
Simple Belt Changes
The steel reinforced ATL belt that drives Thomson wheel
guides can replaced or re-tensioned externally—without the
time and expense of removing the load from the carriage.