2018 International Forest Industries IFI Feb March 2018 Digital | Page 30

Why Delta motion controllers?
Figure 1
The Prologic+ log scanner and optimizer (right) provides direction for the Delta RMC that operates the PHL log turner
Poetry in motion
T
The installation
of a coordinated
motion-control
system has enabled
big productivity
gains for a
Quebec sawmill
Author: Bruce Coons,
Application Specialist,
Delta Computer Systems
he typical sawline is an
inline factory with a flow of
material: raw logs in and
finished lumber out. The smoother
the flow the higher the mill’s
productivity.
And, when imperfect logs are
being processed, precision saw
and chipping head control in
response to optimizing inputs is
critical to maximizing the recovery
of valuable lumber. Cutting curved
logs along the curve will not only
allow them to dry straight, it will
also result in maximizing the
usable length of the boards that
are produced.
For the new curve-sawing
line at the Scierie Lapointe &
Roy softwood mill in Courcelles,
Quebec, optimizing mill output
requires the coordination of more
than 30 motion axes. A bank of five
electrohydraulic motion controllers
by Delta Computer Systems of
Battle Ground, Washington does
the job.
The mill managers
commissioned the development of
the new sawline following the fire
that destroyed the previous mill.
The old mill was manually operated
and the company’s objective was
to automate the milling process as
much as possible while increasing
the productivity of the line.
The new Sciere Lapointe & Roy
sawline (Figures 1 and 2) contains
hardware provided by PHL of
Saint-Éphrem de Beauce, Quebec,
integrated with scanner/optimizers
by Prologic+ of Saint-Georges
28 International Forest Industries | FEBRUARY / MARCH 2018
Québec, who also performed the
control system integration.
At the beginning of the line,
a Prologic+ optimizer scans the
raw log and plans out how the log
should be rotated to align it so that
the following stages of the line
can achieve the maximum lumber
recovery. The optimizer provides
this data to a PLC that tells the
motion controller operating the log
rotator how much to rotate the log,
and then how to move the chipper
heads to chip two sides of the log.
Then the two-sided cant is
rotated 90° and scanned by
another Prologic+ optimizer that
gives the curves to a second PLC.
This PLC tells the Delta motion
controller to position profiler heads
to profile the left and right boards
of the cant and finally prepare it for
the gang saws that will saw it into
individual boards.
“We selected the eight-axis
RMC150 motion controllers from
Delta (one controller is shown in
Figure 3) because of the flexibility
they provide and because they
are well-known controllers in the
wood industry,” said Francois
Giguere, Prologic+ Wood Process
& Optimization Specialist.
“We’ve been using Delta motion
controllers for years and have
found their software to be very
user-friendly.”
The RMCs’ closed-loop
control algorithms process axis
position information from linear
magnetostrictive displacement
transducers (LMDTs) mounted in
the hydraulic cylinder rods and
drive the cylinders via proportional
servo valves. Each Delta controller
has a built-in Ethernet port over
which it receives motion target info
from the Windows-based scanner/
optimizers and sequencing control
info from one of the two PLCs
controlling the sawline.
The Prologic+ team developed
and proved out the motion control
program for each machine in
sequence. For this purpose, Delta
Computer Systems provides a free
software package called RMCTools
to support its motion controllers.
After a motion program for each
axis is developed, the motion
must be tuned so that the physical
system functions as desired.
“We tune each axis
independently,” said Giguere.
“The first step is usually to do
the automatic tuning using
Delta’s Tuning Wizard tool (part of
RMCTools). After that we adjust the
control loop gains if necessary to
perfect the motion.”
Care was required in speed-
matching the process steps
because the line is compact in
Figure 3
The RMC150 motion controller can control and synchronize the operation of
up to eight motion axes simultaneously