The Solution
Industrial Techno Logic (ITS) of Israel has been supplying the machinery industry with precision long
travel systems, comprised of ITS’ heavy duty RHS steel beams, linear bearings and a drive system – linear
DC motor, lead screw or timing belt. Machine designer can now implement positioning systems up to 8
meter in length, achieving motion accuracy, high stiffness, long-term stability, structural simplicity and cost
effectiveness. Such systems have been successfully implemented in demanding applications as extra-wide
format industrial digital printers, where gantry axes float 200Kg print head over a 5.1 -meter wide billboard
print at speeds of 2.2 m/sec and accelerating at over 1.5 g, while maintaining total motion accuracy of
better than 70 μm and yaw, pitch and roll below 200 μRadian as a standard or below 50 μRadian as a
special design.
Design
Achieving the best performance in the end-equipment requires careful and knowledgeable optimization of
many design factors in several disciplines – materials, structures, drive and control. The required travel and
payload, together with the mounting constraints, determine the beam’s dimensions – length, height, width
and wall thickness. These also define the machining method and sequence. The desired motion precision,
payload, velocity and acceleration, as well as the environment, all affect the bearing type and dimensions.
Moving on to the drive mechanism: belt drives; low-backlash or no-backlash lead screw connected to DCservo
or stepper motors; linear DC brushless motor – each type has its own advantages to suit particular
needs. The forces acting on the payload during its operation and the required positioning accuracy and
resolution, unidirectional vs. bidirectional operation, tolerable velocity fluctuations, and minimal positioning
resolution all play a part in choosing the appropriate components.
The vast experience, accumulated at ITS over the years of pioneering and supporting the large format
digital print industry, position ITS as your partner-of-choice for supplying you with complete turnkey
solutions – from concept design to ready-to-use systems.
Technology
ITS has invested over six years of relentless efforts in developing its support beams. Working closely with
its raw material, forming, machining and tool suppliers, ITS was able to fine tune a unique beam fabrication
process that consistently delivers the required dimensional accuracy and stability. This process consists of
several steps – formation, stress relaxation and iterative machining cycles. Finally the linear bearings and
drive are installed
Machine Planning, Development and Production
Industrial Techno-logic Solutions Ltd.
Formation
It all starts with the raw material. High grade construction steel plates are heat-treated, rolled into a
rectangular hollow section (RHS) and welded along the seam. Seamless profiles are also available.
The resulting profile has the advantageous toughness and the uniform thickness of the rolled steel plate,
plus the strength and stiffness contributed by the high moment of inertia of the RHS.
Stress Relaxation
Several cycles of heating and gradually cooling the beam between controlled temperatures help relieve
residual stresses. Vibrating the beam mechanically completes the treatment to achieve a stress-free structure
that will not deform during machining and will retain its straightness throughout its service life. Aging on
the shelf for a few months (“shelf relaxation”) stabilizes the beam and prepares it for the following step.
Heat treatment furnace
Machining
All linear bearing guideways are only as straight as the surface they are attached to. To ensure that ITS
beams meet their precision tolerances, engineers from ITS and Iscar Metalworking, the world-renowned
cutting tool manufacturer, carefully defined the exact tools and milling parameters for each step of the
entire machining process. Multiple steps in a colossal machining center gradually planarize the surface
intended to support the guideway. Periods of shelf relaxation in-between milling passes relieve stresses and
allow the beam crystallographic structure to recover. In the last pass, which takes about 4 hours, a single
tool tip cuts the last few hundredths of a millimeter, while the beam lies unfastened on the table, supported
only by its own weight. The beams are mounted in the machining center in the same orientation and
support points as they are intended to be installed in the equipment. This way it achieves its accuracy at its
natural position, under almost the same deflection forces.
Guideway Installation and Fine Tuning
The beam, machined to tolerance, arrives at ITS’ assembly floor. Skilled technicians install the linear
bearing guideway and the drive mechanism – a direct drive linear motor, lead screw or belt drive.
The beam is supported the same way it will be mounted in the equipment. The guideways are installed
and a load similar to the designed payload is mounted on the carriage. The beam is ready for its final test
– motion linearity. Two digital instruments measure the three types of linearity deviations – yaw, pitch and
roll – in micro-radians precision. One instrument measures pitch and roll; the other pitch and yaw. Having
two independent instrument measure the same entity cross-verifies the readings. Both instruments are
computerized, and the readings are automatically analyzed and reported.
The straightness of the beam as-machined is sufficient for most applications. In more demanding cases,
ITS’ computerized instruments guide the technician in fine-tuning the guideway into tighter tolerances.
In critical applications, where a performance of a linear encoder depends on the exact parallelism of the
reading head to the scale, ITS installs a special router onto the carriage, and utilizes the guideway itself to
make a final machining pass to bring the encoder seat into perfect parallelism with the rail.
The result of this meticulous installation and fine tuning procedure is a precise, heavy-duty axis, built to
carry the burden of repetitious motions at high accelerations, many times in hostile environment, while
maintaining its accuracy over years of service.
As a part of its complete solution approach, ITS can support its customers in the design and control
aspects, from selecting the appropriate drive type and components to defining motion parameters and the
control interface between the machine and the axis controller.
Machine Planning, Development and Production
Industrial Techno-logic Solutions Ltd.
5 Atir Yeda Industrial Park, Kfar Saba 4464305 Tel:+972-9-7903000, Fax:+972-9-7903030 # www.its
