WITH MACHINERY IN 59 COUNTRIES,
I finally got a chance to go to China in
20 17. As the chief electrical engineer
doing 9 0% of the PLC and HMI program-
ming, I didn’t always get to go overseas
because we had service technicians that
would do the installations. Occasionally
though, when we were loaded up with
jobs and someone had to go, I get the op-
portunity to travel. But, even though we
did jobs in China throughout 1993 and
19 94, I never had to go until now.
My equipment company has been sold
twice, and people have been cut for aus-
terity measures, so I am now traveling
more than ever. We build tobacco-pro-
cessing equipment. There are essen-
tially four areas in the art of processing
tobacco leaves supplied by the farmers,
already dried:- Conditioning—where the tobacco is
set to just the right temperature and
humidity for - Thrashing—where the paper parts
of the leaves are separated from the
stems, the woody fingers of the leaves - Redrying—where the humidity is set
for long-term storage - Packing and labeling—this is the part
our machines do. It takes a tobacco
press about 80 feet tall, pushing with
about 37 tons of force to make 200 ki-
lograms of tobacco fit into a cardboard
case (Figure 1 ). The usual production
rate is 60 cases per hour.
This job, for Qinhuangdao Tobacco
Machinery, was a typical 3 4-foot-stroke,twin-ram tobacco press (Figure 2 ). Two
rams are supplied, so that one can be
filling while the other is packing, thus
no interruptions to the flow of tobacco to
the press.
In this job, the Chinese wanted to do
all the support equipment. We did only
the press, and they did the conveyors
and accessories (Figure 3 ). The control
design was based on Rockwell Automa-
tion’s Allen-Bradley CompactLogix series
L3 5 processor with remote Flex I/O in
two operator cabinets and a pump-unit
remote-rack cabinet, all running on an
Ethernet network.
I used simple AutomationDirect un-
managed Ethernet switches. The system
also included five Allen-Bradley Power-
Flex 400 series variable-frequency drives
(VFDs) from Rockwell Automation for
the hydraulic pumps and two PowerFlex
40 VFDs for the feed system, all with
Ethernet adaptors.
The system should have also included
a network-address translator (NAT), but I
left that responsibility up to the Chinese
engineers, so I hope they included one.
Using a NAT device such as Rockwell
Automation’s Allen-Bradley 9 300-ENA
module keeps the area Ethernet traffic
out of the PLC and its I/O network, which
can be critical if you need good Ether-
net speed, such as for tension control
between motors in a web system.
Since our equipment must receive
empty cases from the Chinese input
conveyors and then hand off the full
cases to the Chinese output conveyors,the Chinese and I composed a set of
“produced” and “consumed” tags for our
processors. Each of us owned the pro-
duced tags, which became the consumed
tags for the other PLC.
To do this, you must actually add the
other processor to your I/O structure so
that, when you create the tags in your
controller tags table, you can point to the
other PLC as the communications device
for the produced and consumed tags.
The beauty of using tags of this type
is that the communications is intrinsicControlDesign.com / May 2019 / 27Tall order
Figure 1: The tobacco press is about 80 feet tall,
pushing with about 37 tons of force to make 200
kilograms of tobacco fit into a cardboard caseFull-court press
A machine builder’s path to build and install tobacco equipment
in ChinaBy Stephen H. Jones, SHJCoWorking for a living
Figure 2: The machine, a typical 34-foot-stroke,
twin-ram tobacco press, was built for Qinhuang-
dao Tobacco Machinery.CD1905_26_35_CoverStory.indd 27 4/29/19 12:22 PM