As appeared in May 2013 PBE
Copyright CSC Publishing
www.powderbulk.com
What should I consider when
selecting an automatic bagging
system that will handle both
paper and plastic bags?
P
aper and plastic open-mouth bags have very different properties. Paper bags offer a
more stable package, are easier to handle, don’t sweat (condensate), and are easily
discarded or recycled. Plastic bags can have a simpler, cheaper construction and offer a
clear view of the product, but are typically less stable to handle, may cause sweating, and
can hold static electricity, making them more difficult to separate from other bags and
open.
When it comes to automation, the different bag materials’ characteristics require different solutions. First, consider the closing method. Paper bags are typically sewn shut
using a heavy-duty industrial sewing machine, whereas plastic bags are most often heatsealed. Sewn bags can be folded over before stitching to create a better seal; a filler cord
can be applied to the bag to further improve the seal, or a tape can be applied to improve
both the seal and the bag appearance. For heat-sealing a stationary bag, an impulse, hot
bar, or ultrasonic sealer can be used. For heat-sealing a moving bag, the system can use
hot air, radiant, or band sealing. Then there are crossover types, like paper bags with a
poly liner. With these, the poly liner is sealed using a heat sealer and the outer paper is
sewn above the heat seal; this gives the combination of a hermetic seal in the poly liner
and extra protection of sewing the outer paper. Another option is the stepped-top paper
bag with preapplied, heat-activated glue; these are sealed while in motion, using a special
heat sealer that applies heat to activate the glue and then folds the top down and compresses it to make the seal. The bag type and sealing type required may depend on the
bagged product’s characteristics and value and the point-of-sale presentation required.
No matter which bag you’re using, be careful when choosing an automated system.
Make sure you talk to the manufacturer about all your requirements, current and future.
If you need to use both paper and plastic bags, then understand the constraints and requirements of each type. Machines to do both are available and work well, but they have
limitations and you should be sure the manufacturer understands these and has the experience to provide the right solution.
Ian Merchant, Pacepacker brand manager, Spiroflow Systems, 704-246-0900
S
pecial issues to consider when using
plastic bags:
without burning through the bag’s
center portion.
•Static can make it difficult to remove
only the top bag from an empty bag
pile.
•Consider deaeration methods to prevent excess air in the bags and palletizing problems after filling.
•Bags transported from the manufacturer often arrive deformed and misshapen.
•Because plastic film is slippery, a special surface treatment may be required to palletize filled bags.
•Plastic is softer than paper, requiring
control over the bag top during the
filling and closing process.
•Plastic and paper bags typically require different closing systems, so
make sure the closing units are easily
changed out. Closing systems with
quick-disconnect power connections
and electrical interlocks are desirable.
•Proper bag film thickness will prevent
bag stretching during filling.
•Side-gusseted bags require precise
sealing control so gussets are sealed
Greg Vander Vorste, sales manager,
Premier Tech Chronos, 866-571-7354
P
aper bags and plastic bags need to be
handled differently, and the automated equipment must have continuous
bag control. The equipment shouldn’t
drop or release the bag until the filling and
closing process is complete.
Equipment features to consider:
•System’s empty bag magazine
should hold a significant number of
bags and be refillable without equipment shutdown.
•System should gently move both
empty and filled bags, with no dropping, pushing, or bumping.
•System should integrate easily with
the scale and the bag closer, whether
the closer is heat-sealing poly bags or
sewing or gluing paper bags.
•System should be adjustable without
tools when switching the bag size or
type.
•System should automatically detect a
bag’s absence to prevent inadvertent
product dumping.
Tom McDonnell,
sales and marketing manager,
InPak Systems, 608-221-8180
Equipment suppliers are a valuable
source of information about equipment
and processes. In light of this, each
month we ask suppliers a question of
concern to our readers. Answers reflect
the suppliers’ general expertise and
don’t promote the suppliers’ equipment. If you have a question you’d like
suppliers to answer, send it to Kayla
Carrigan, Associate Editor, Powder
and Bulk Engineering, 1155 Northland
Drive, St. Paul, MN 55120; fax 651287-5650 ([email protected]).