Ergonomics - Atlas Copco

production of heavy vehicles such as trucks,
buses and off-road vehicles.
the working environment
The high torque nutrunner is usually preferred
in modern industrial situations as it
contributes to a good working environment.
The workstation can be stationary or on a
moving line. The tool has virtually no negative
impact on the working environment.
Weight can be a negative factor for the
operator, therefore in most applications the
tools are suspended from balancers.
Design for good ergonomics
During the 1970’s, production engineers
tried to replace impact wrenches with stalltype
nutrunners in order to reduce noise
and improve accuracy. However, operators
complained of the increased tightening
times (about three times longer than impact
wrenches). This was particularly noticeable
in assembly line production where the
entire balance of the line was changed.
A popular solution was a new tool design
incorporating two motors – a fast motor for
rapid nut run-down and an additional, slower
motor for the final tightening sequence.
Tools with reaction bars are heavier
than conventional tools. This must be
considered in tool installation, for example,
using balancers or articulating arms.
Safety
The major safety risk in operating these
machines is pinching, crushing, or severing
of the fingers. The forces acting between the
reaction bar and the workpiece are considerable
and could easily sever a finger. Thus,
all machines carry a warning label: “Never
hold the reaction bar while tightening”.
HanDle DeSiGn
Small machines usually have pistol grips.
Larger tools tend to be front-heavy due to
the extra gears required. A handle placed
under the machine, as near to the center
of gravity as possible, minimizes operator
discomfort.
external loaD
High torque nutrunners are heavy and
should therefore be suspended from balancers.
During tightening, the reaction forces
are absorbed by the reaction bar instead of
the handle. The reaction bar may make the
tool front-heavy, thus exposing the operator’s
wrist to bending torque.
WeiGHt
A high-torque machine, equipped with
transducers for measuring torque and angle,
is a heavy tool, therefore an articulating arm
is recommended. Since the larger machines
59