Post on 08-Aug-2018
BAG FORMING
Stefano Rizzato
TNA
Contents
1. What’s difficult about bagging savoury snacks?
2. Types of bag makers on the market
3. Reel loading
4. Film carriage
5. Code printing
6. Forming shoulder
7. Film drive and back seal
8. Film sealing
9. Film cutting – types of knife
10.Bag types available
11.What type of machine should I choose?
What’s difficult? – the product
Loose product
Irregular shapes
Loose particles
and seasoning
Oily or sticky
products
Variable piece
size
High volume,
low mass
What’s difficult? – the film
• Flexible film is difficult to control
• Large range of film types – although mainly OPP
and OPP/OPP laminates used for snacks
• Large range of different bag widths, lengths and
film thicknesses
• Many different pack formats which can require
special films
How does the film affect performance?
Thickness/stiffness – Use lighter laminates for high speed and small bag
weights, heavy films for premium products, larger
and slower packing speeds.
Slip or friction - Some stiffer films will be difficult to pull through the
machine and will benefit from a slip layer added to
the film.
Hot tack strength - Ensure that the hot seal can resist the weight of
the product and the stripping action during the
bagmaking cycle.
Sealing properties - The sealing layer is added to the OPP laminate
during the converting process. Ensure that this is a
high quality to prevent pinhole leaks where the film
folds over.
How does the film affect performance?
Reel consistency - Ensure that the reel quality is consistent
from reel to reel so that reel changes don’t
result in downtime.
Reel tension - Each reel should be wound with equal
tension across the reel and through the
reel.
Print consistency - Ensure the print position is in the same
position through the reel and from reel to
reel.
Artwork design - Design the Artwork to be as machine
friendly as possible
Elements of a bagmaker
Film spindles.
Two required
for quick
change-over
Film dancer
controls film
unwind
Film drive.
Feeds the
film at the
required rate
Code printer Forming
shoulder and
product infeed
Film pull down
and vertical
seal
Horizontal seal
and product
stripping
mechanism
Control system
and HMI
What’s on the market
Types of bag maker
Systems available
All vertical form fill and seal (VFFS) machines for packaging snacks must
incorporate some form of product stripping action to ensure maximum
efficiency.
What is product stripping?
Systems available
Intermittent machines
• Mechanical or pull down machine (mostly obsolete)
• Single axis jaw motion – not generally suitable for snacks
Continuous machines
• Rotary flat jaw or D motion – longer sealing time for some heavier
films and speciality packs
• Rotary machine – one, two or three sets of jaws for high speeds
• Box motion machine – highly versatile for speciality packs
Types of machine – mechanical
Mechanical draw down action
An example of an intermittent machine
• Vertical seal made when the film is
stationary
• Stationary tubeclosers catch next
dump well above the jaws
• 75mm of stripping is possible
• Long seal time possible
• Moving jaw assembly pulls film
through the machine
• Speed restricted by mechanical
mass and the time lost when
the film is stopped.
Box motion principle
Strip zone
Seal zone
Film cut
Servo control of:
• Strip length
• Seal time Open/Close speed
• Film speed and position
Box motion principle
Bag forming – rotary flat jaw principle
Bag forming – typical rotary flat jaw principle
Typical rotary jaw principle
Rotary triple jaw principle
Reel loading – cantilevered mandrel
Cantilevered
film spindle
Film unwind
rate controlled
by dancer
Film carriage
Controls the
entire film path
Mounting for:
• Reel holders
• Dancer
• code printer
• film drive
• Other ancillary
equipment
Tracks entire
film path
Film carriage
• Manual or automatic tracking
• Machines with side mounted pull belts tend to require
automatic tracking due to unbalanced belt/film slippage
• Automatic tracking can be an unnecessary complication
• Simple film paths enable quick bag size changeovers
• Most machines incorporate some form of film splicing table to
facilitate reel changes.
• A few machines manufacturers also provide the option to
include an automatic film splicing attachment that can save
significant production time.
Auto splice assembly
Date code printing
Types of coders
• Continuous coding
• Rotary coders, ink rolls
• Thermal Transfer
• Intermittent coding
• Hot stamp, wet ink pads
Forming shoulder
Forming shoulder – important points
• Product infeed
• Product path
• Cross section of tube
• Back seal bar
• 80/80 rule
• For maximum efficiency the
largest product length must
be no more than 80% of the
internal tubeformer diameter
and the product volume
should be no greater than
80% of the internal volume
of the bag.
• Weight of former
• Ease of change
• Film path
• Gas flushing
Forming shoulder
FILM/BAG DETAILS (Circle figure below to select required backseal type.)
Standard Formers are FLOFIN Design. FLOFIN formers can produce Lap or Fin backseals depending on film reel width.
Please contact engineering if lap is required and film width > FBW X 2 + 1
For dimensions refer below:
QUANTITY REQUIRED: TWO
TNA RECOMMENDED FILM REEL WIDTHS:
FLAT BAG WIDTH: 130 mm Inches LAP SEAL: FILM WIDTH = (FBW x 2) + 12
FIN SEAL FBW < 120mm: FILM WIDTH = (FBW + 12) x 2
FILM REEL WIDTH: mm Inches FIN SEAL FBW => 120mm: FILM WIDTH = (FBW + 15) x 2
USED ON INTEGRATED SYSTEMS
TYPE OF FILM: OPP USE OF ABRASIVE FILM TYPES WILL CAUSEB=DIA 100 IF FBW <= 100mm
RAPID WEAR ON FORMER SHOULDERS. B=DIA 150 IF FBW >= 101 UP TO <= 220mm
FILM THICKNESS: 50 microns B=DIA 200 IF FBW > 220mm
GAS FLUSH FLOW RATE REQUIRED
A=380mm (STANDARD HEIGHT) YES <150 FBW FLOW RATE 250l/m @ 1 BAR
=>150 FBW FLOW RATE 350l/m @ 1 BAR
AVAILABLE ON REQUEST
IS WASH DOWN APPLICATION FORMER REQUIRED? NO SPECIAL COMMENTS - JUSTIFICATION REQUIRED
FOR NON STANDARD FORMER
IS GAS FLUSHING REQUIRED? YES
IS PLUNGER REQUIRED? NO
PROJECT MANAGER TO ENSURE EACH ROBAG INCLUDES:
- PNEUMATIC CONNECTION KIT (Integration Leg) TNA-0041655
- PNEUMATIC CONNECTION KIT (Non- Integration Leg) TNA-0041656 SALES AUTHORISATION:
Signature……….. Andre Tombült Date 13-Jun-14
DOES FILM HAVE HORIZONTAL PREAPPLIED ZIPPER NO
- PROJECT MANAGER TO ENSURE EACH ROBAG INCLUDES TNA-0055001 SPECIAL PEC BRACKET ENGINEERING AUTHORISATION: M GRUS
Signature……….. Date
IS BAG AGITATOR USED? NO
NOTE: SPECIAL FULL TUBE FORMER REQUIRED MANUFACTURING AUTHORISATION: M HERZOG
Signature……….. Date
Circle figure below to define unwind and print surface arrangement.CUSTOMER FILM REEL DETAILS
Film drive
• Mechanical pull down
• Belt pull down
• Wheel pull-down
• Vacuum belt pull down
• Side mounted
• Front/back mounted
Vacuum drives
Drives mounted in front of and behind
the film tube
• Promotes self tracking
• Provides easy access for
maintenance
• Allows easy removal and
replacement of the tubeformer
• Requires minimal internal
tube so maximising internal
space for product flow
• Not ideal for speciality packs
Vacuum drives
Drives mounted either
side of the film tube
• Requires internal
tube greater than
50% circumference
• Ideal for speciality
packs such as
block bottom
Back seal
Heat seal
Intermittent seal – Film is sealed while stationary. Stationary film
sandwiched between heated sealing bar and fixed
back bar. Heated sealing bar moves in and out -
usually by pneumatic actuator
Continuous seal – Film is moving as it is sealed. Film is
sandwiched between either a stationary heated
sealing bar and a fixed back bar – drag seal – or a
moving sealing band (heated) and a fixed back bar
Back seal
Whatever to configuration of the
machine the vertical seal there will
be a heated bar that provides a
combination of heat and pressure
to seal the tube of film
Film sealing
• Heat seal – accounts for 99% of all snack food packaging
• Purpose – presentation, seal through product, bag
hanger
• Size – narrow to maximise internal bag volume, wide
for presentation
• Tooth profile – stretch film and increase sealing pressure
• Material – must incorporate a heat sealable layer
• Temperature – must be accurately controlled. Too hot will burn,
too cold will not seal
• Pressure – requirement will depend on quality of the sealing
layer and the thickness of the film
• Time – time can be used for thicker films to enable the
temperature to be reduced.
• Special effects – Seals can incorporate holes and slots for hanging
the bag or promotional banners
Film sealing
Alternative sealing methods:
• Cold seal – Requires and adhesive layer to be incorporated into
the film laminate. Pressure alone is required to
make the seal
• Ultrasonic – Requires special films. Produces a narrow but
strong seal. An expensive option and not widely
available
Film cutting
• Cutting knives – used where the film is stationary between the jaws during the
sealing process
• Relies on a series of sharp points to pierce the film before slicing
between the initial penetration
• Usually pneumatically operated although can be operated by cam and
lever
• Can produce a zig zag cut
• Perforated cut and string bags are possible
• Modern materials can provide long life
• Crush cut knives – used on all rotary sealing machines
• Uses high pressure between a fixed knife and a fixed anvil to cut
the film
• Point contact between knife and anvil created by a helix knife
design
• Modern hard materials can give very long life. Ceramics can last
over a year but are very prone to breakage
• System not very flexible due to fixed nature. Zig zag cuts are
possible.
Available bag formats
Pack format Required bag maker configuration
BM
BM
BM
BM
BM RJ
Available bag formats
Pack Format Required bag maker configuration
BM
BM
BM
BM
BM
RJ
RJ
RJ
RJ
RJ
Available bag formats
Pack Format Required bagmaker configuration
BM RJ
BM
BM
BM
BM
RJ
RJ
RJ
RJ
Premium bag formats
How to maximise profit
• Choose the right bag maker for your requirements to ensure that you
optimize your output
• Keep your machines running
• Quick product change overs
• Automate as much as possible both on machine, upstream and
downstream
• Minimize waste
So, which bag maker?
• Depends on your primary packaging requirements:
• High speed pillow – rotary double or triple jaw for simplicity
• Premium film quad pack or block bottom bags – Box motion or D-
motion for maximum film control
Which bag maker?
Twins or single tube machines?
• Single tube machines generally offer the highest level of performance
due to scale and product transfer arrangements.
• Duplex machines can provide and advantage on very small bags –
not generally applicable to snacks
• Twins take up less space than two singles but don’t generally offer
twice the performance
Bag forming – the future
Speed - packaging small bags of snacks at speeds of
over 200bpm coupled with downstream
automation to match
Productivity - a reduction in the need for operator
intervention and downtime to increase output
per head
Efficiency - an increase in the percentage of good bags
produced to maximize machine output
Premium bag formats – as more companies look to differentiate their
product, premium bag formats will become
more common
THANK YOU