is a commonplace enough process in any manufacturing or distribution business
using palletised loading, but the task of automating the wrapping procedure
relies on sophisticated control. Which is why shrink and stretch wrapping
specialist Nissen Packaging selected Hitachi drives and PLCs from HID
Limited for its latest automated wrapping machines.
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Nissen's latest Easywrapper machine has two axis drives with 0.55kW AC
induction motors controlled by Hitachi's latest L100 inverters. One motor
controls a rotary turntable on which the pallet to be wrapped is placed.
The second controls the rise and fall of the roll of stretch film material
on its vertical linear axis using a chain drive.
A Seeka photocell is employed to detect whether a pallet is loaded on
the machine and then to identify when the film roll has reached the top
of the pallet. Once the top of the pallet is detected, a routine enables
the film carrier to lower slightly to allow a top sheet to be placed on
the pallet before completing the wrapping. Alternatively, where no top
sheet is required, the roll continues to rise a discrete amount to give
a finishing overlap wrap to the top edge of the loaded pallet. The logic
functions of the programs are controlled by a Hitachi EC28HRP PLC with
28I/O. Surprisingly, for what appears to be a relatively simple process,
all 14 outputs are employed in the Nissen machine.
The two L100 drives are pre-programmed by Nissen to each give seven speeds
and there are five recipes also pre-programmed to provide for just about
any wrapping sequence. The recipes include different speeds for single
and double wrapping, different film overlaps and so forth. Programs are
selected via a simple MMI from Horner, which has a plain English menu
operation. Clearly, if the recipes provided are insufficient for an application,
the machine can be reprogrammed by a supervisory engineer or by Nissen
if required. A further level of control is provided by fitting an electromagnetic
clutch to the film roll holder that enables film tension to be adjusted
via a simple potentiometer knob adjacent to the operator panel.
The L100 drives and the Hitachi EC28 PLC are interfaced with the MMI.
The L100 drives have an RS422 communications port and there are seven
inputs, of which five are programmable, and two programmable outputs as
well as an alarm output. Access to the terminal rails is by opening the
hinged front case.
Nissen Packaging commented, "HID has been extremely helpful and supportive
both during the design stages of the machine and afterwards. The company
has also assisted in automating the machine through its PLC programming
and work carried out to identify and then interface with the Horner MMI."
Unusually, the Easywrapper is made largely from standard off-the-shelf
components from UK sources.
Hitachi L100 drives are used on Nissen's semi-automatic machines and there
is also a larger Easywrapper machine that uses 0.75kW L100 inverters.
In conjunction with the drives, Nissen are using Hitachi's latest Windows-based
programming software for the L100s, making multiple programme storage
for various machines possible.
Nissen began in the UK as a sales subsidiary of a Swedish film packaging
company in 1971. Six years ago, the company was established as an independent
British company as the result of a management buyout. About three years
later Nissen designed and manufactured its first semi-automatic stretch
film wrapping machines at its Leighton Buzzard premises.