Pneumatic motion control helps machine shops stay competitive
By Steve Whyte, Parker Hannifin Pneumatics Division
is perhaps the biggest challenge for small and mid-sized machine shops
and factories. In order to compete, some business managers are
transitioning to more economical automated production. They are
increasingly dependent on the use of investment-intensive machine tools
that are unmanned and often operational around the clock.
Understanding the need to maximize machine capabilities, machine
builders have had to develop innovative ways to automate machining
centers. For example, engineers at Lang Technik GmbH have developed an
inexpensive pneumatic holding and feed system that supports unmanned
machine operation on the second and third shifts.
A vertical lift conveys clamped workpieces to a coil-shaped holding
tower that stores them for later shifts. When the pieces are required,
they slide down the coil and the automated system places the next
un-machined workpiece on the clamping jig of the machine tool.
A part storage system for automated machine centers, the Eco
Tower from Lang Technik.
In the process, the automated handling system performs horizontal,
vertical, and swivelling movements. The system requires a combination of
precision movement and motion control plus high load-bearing capacity.
In designing the system Lang had multiple choices for motion control.
The first option considered was a multi-axis robotic arm. Robotics have
the ability to be reprogrammed for different tasks, but that
functionality comes at a premium cost, and it was not required in the
application. A second option was an electromechanical design, using
linear motors to drive the actuators that moved parts into position.
This approach offered high levels of precision and high throughput, but
added cost for functionality that was not essential. The third option
was pneumatic operation. For relatively heavy loads and simple, reliable
operation, pneumatic motion control is hard to beat.
The design engineers at Lang chose pneumatic rodless linear actuators
with heavy duty guides. The robust yet simple construction of the
pneumatic linear drives offered a favourable price-performance ratio.
The integrated guide rails allow the cylinders to be used at high
torques up to 1400 Nm and loads up to 18,000 (N).
An example of a pneumatic drive with integrated guide rails,
the Parker OSP-P rodless actuator from Parker Hannifin.
Lang found this pneumatic solution to be far more cost-effective than
articulated-arm robots with the additional advantage that this feed
system offers operational flexibility. When required, the machine
operator can shift the automated part handling system to a park position
and work at the machine tool manually without any obstructions..
Pneumatic linear drives place low demands on internal plant
infrastructure as compressed air is commonly available. The relatively
simple design of limit switches and pneumatic valves means that
maintenance can be performed easily contributing to reduced operating
costs. In addition, the pneumatic linear drives can be used without
problems in the harsh environment of a machine shop because the
cartridges of the recirculating ball-bearing guide are protected by
Floor space was another design consideration. Machine shop managers must
deal with inflexible floor plans and facility costs that increase by the
square foot. An advantage of a rodless linear actuator is that the same
stroke can be achieved in about half the distance of a standard
cylinder. Thatís because the piston drives the movement within the body
of the actuator, rather than through an attached rod. This space-savings
design philosophy matches the rest of the machineís design in which a
vertical tower attains the maximum part storage volume with minimal