Buying guide

VFFS machinery guide: how to compare vertical form fill seal systems

Choosing the correct form fill seal machinery means comparing the full route: product feed, film, forming, dosing, sealing, coding, discharge and support access.

Why VFFS projects need line-level thinking

A vertical form fill seal machine does not succeed on the forming collar alone. Product feed consistency, film specification, coding, gas flush requirements, sealing integrity and discharge handling all affect the finished pack and the true output rate.

Because the machine forms the bag, fills it and seals it in one process, small upstream or material issues can quickly become production problems. The best VFFS selections consider the packaging route rather than only the bag maker.

What changes the shortlist

Bag width and length range, product density, particle size, flow behaviour and sealing material are primary decision points. A machine suitable for free-flowing granules may not suit dusty powders or fragile products requiring careful drop control.

Published speeds should be treated as a guide. Real production may include coding, checkweighing, rejects, film changes and SKU changeovers.

Questions to confirm before quote

What is the bag style, width, length and target weight or volume?
What film material and seal pattern are required?
How will product be fed to the machine?
Is coding, gas flushing, checkweighing or metal detection needed?
What is the target output after changeovers and operator work are included?
What space is available for roll changes, maintenance and discharge?

Quick answers

What products are VFFS machines commonly used for?

Powders, granules, small solid products and liquids that can be consistently fed into a bag-forming and sealing process.

What affects seal quality?

Film material, sealing jaw temperature, dwell time, pressure, product contamination in the seal area and the consistency of film tracking.

When should Lancing review the application?

Once product details, pack dimensions, target output and available utilities are known, Lancing can help narrow the likely machine route.

Process control

The VFFS process from film unwind to finished pack

1. Unwind and control the film web

The film roll must unwind without telescoping or sudden tension changes. Roll alignment, brakes or driven unwind, dancer position and web guides influence tracking. Variability here can appear later as an uneven vertical seal, registration drift or changing bag length.

2. Form the tube over the forming shoulder

The web passes over the forming shoulder and around the forming tube. Film stiffness, friction, static and the relationship between film width and forming set affect whether the web lies flat. Creasing at this stage should be corrected before changing seal temperature, because a mechanical fold cannot be solved reliably by additional heat.

3. Create the vertical seal

The vertical sealing system closes the longitudinal overlap or fin. Temperature, pressure, dwell time, jaw condition and film construction work together. Product dust or liquid on the seal path, a wandering web or incompatible sealant layer can produce intermittent defects even when the temperature display is stable.

4. Dose and create the horizontal seals

The filler releases product through the forming tube while the horizontal jaws form the bottom of one bag and the top of the next. The timing must prevent product from entering the seal zone. Bag length, product fall time, settling and jaw motion therefore need to be assessed as one sequence.

5. Register, code, cut and discharge

For printed film, the photocell detects the registration mark and corrects the cut cycle. Coding should be checked after the pack is formed, not only on flat film. The finished bag then needs a controlled path to a takeaway conveyor or collection point without pulling on a hot seal.

Photocell registration Seal quality checks Film waste reduction Troubleshooting guide

Acceptance framework

Evidence to record during a VFFS acceptance run

The exact sampling plan and pass criteria should be agreed for the project. Do not infer a universal tolerance from a catalogue value without the related product and test conditions.

Evidence	Record	Why it matters
Product and environment	Sample batch, temperature, humidity where relevant, bulk density or viscosity and feed method	Allows the result to be related to a defined operating condition
Film	Supplier, construction, thickness, roll width, printed repeat and registration-mark detail	Connects tracking and seal results to the production-intent web
Machine settings	Dose recipe, bag length, temperatures, timing, tension and line speed	Creates a repeatable starting point for the agreed test
Pack checks	Dose, dimensions, registration, seals, cut and code at an agreed frequency	Separates accepted output from raw machine cycles
Stops and restarts	Reason for stop, waste generated, time to stable packs and operator action	Tests recovery rather than only a continuous demonstration run
Lane or head comparison	Results from every active lane, pump or dosing head	Prevents an average result from hiding one under-performing channel

Buyer questions

VFFS process and acceptance FAQs

What causes a vertical seal to move across the bag?

Check film-roll alignment, web tension, forming-set alignment, pull belts and contamination before treating the fault as a heat-setting problem.

Why does bag length change on printed film?

Possible causes include poor mark contrast, sensor position, web stretch, tension variation, incorrect repeat settings or a mechanical tracking problem that changes how the mark reaches the sensor.

How should seal temperature be adjusted?

Change one variable at a time and consider temperature together with pressure, dwell time, jaw condition, film construction and product contamination. Record the setting and inspect cooled seals.

What is the difference between cycles and accepted output?

Cycles describe machine motion. Accepted output counts packs that meet the agreed dose, dimension, registration, seal, cut and coding checks while the connected line is operating.

What should happen after an emergency or planned stop?

The line should restart using a defined procedure, with affected product and film identified, unsafe access prevented and the first packs checked before normal collection resumes.

Application review

Define the VFFS process, trial conditions and acceptance checks together.

Contact Lancing

Acceptance and handover

Build one traceable record from factory trial to site handover

Freeze the trial inputs before settings are compared

Identify the product batch, storage condition, target dose, production-intent film, reel orientation, bag drawing, coding requirement and inspection method. If any of those inputs changes, record the change rather than treating the result as directly comparable. This prevents a successful setting from being attributed to the machine when the product or film has also changed.

Test normal production events, not only a stable centre run

A useful acceptance sequence includes initial start-up, recovery of the first accepted pack, a stable run, hopper refill or product-feed change, planned stop and restart, roll change and normal discharge handling. Each event can expose different issues in dosing, registration, film tension, seal temperature recovery and downstream coordination.

Retain labelled samples and the recipe that produced them

Samples should identify time, lane where relevant, product batch and test phase. Record the settings needed to reproduce the result, including dose controls, bag length, registration correction, seal temperatures and any other application-specific recipe values. Keep rejected examples as well as accepted packs so the boundary is clear.

Repeat the agreed checks after installation

Factory evidence is only transferable when site utilities, product feed, film, environment and downstream equipment are equivalent. Site handover should repeat the agreed pack checks and record any approved change. The final acceptance record should describe saleable output and quality, not merely that the machine completed a cycle.

Open the specification checklist Printed-film evidence Seal evidence Waste baseline Discuss an acceptance plan

Test sequence

Minimum evidence for a repeatable VFFS acceptance record

Stage	Record	Decision
Input definition	Product batch, film construction and reel, dose, bag drawing, utilities and line interfaces.	Are the test inputs representative of intended production?
Start-up	Number and cause of rejected packs before the first accepted pack.	Is recovery controlled and repeatable?
Stable run	Labelled dose, bag, registration, seal, code and cut samples across the agreed period.	Does accepted output meet the defined quality checks?
Normal interruption	Results after refill, stop/restart, roll change and downstream pause.	Does the process recover without uncontrolled waste or drift?
Site handover	Utilities, installed interfaces, final recipes, change parts and operator checks.	Can the site reproduce the agreed result safely and consistently?

Acceptance questions

Questions buyers ask about factory and site trials

Why keep rejected packs from a trial?

They show the actual failure boundary and help distinguish dose, registration, film, seal and line-interface faults instead of relying only on a final accepted sample.

Can a factory result be accepted without a site repeat?

The site should repeat the agreed checks because utilities, product feed, environment and downstream equipment can change the result after installation.

What is the most useful output measure?

Use saleable packs produced under the agreed test conditions, with rejected packs and interruptions recorded, rather than an empty-cycle or peak counter value.

Process questions

Questions that connect film movement, product fall and sealing

What happens to the film between the reel and the finished bag?

The film is unwound, guided under controlled tension, presented to any printer or registration sensor, drawn over the forming shoulder and wrapped around the forming tube. Its edges are joined by the vertical seal, while the horizontal jaws make the end seals and separate the bag. Each stage can influence tracking, registration, wrinkles and seal quality.

Why is the product-clear window important before the horizontal jaws close?

The product-clear window is the available time for the complete dose to pass through the forming tube and leave the jaw area before sealing. If product is still falling, it can be trapped in the seal, damaged by the jaws or delay the cycle. Dose release timing, fall distance, product shape and bag settling all affect this window.

How should a VFFS recipe be verified after a long shutdown?

Confirm that the correct forming set, film, product-contact parts and recipe are installed, then inspect the first packs rather than relying on stored values alone. Verify dose, bag length, registration, vertical and horizontal seals, cut and code after temperatures and product feed have stabilised. Record any authorised adjustment so the recipe remains reproducible.

Which evidence separates a film problem from a machine-setting problem?

Record the reel reference, film construction, roll build, splice position, tension and where the fault begins. Compare the same film on stable settings and, where available, an approved reel under the same conditions. A fault tied to one reel, section or splice points in a different direction from a fault that follows a machine adjustment or forming-set change.

Understand the forming shoulder Build a trial evidence pack Review VFFS film requirements Browse buyer questions

Project sequence

Use one evidence chain from product sample to accepted finished pack

1. Characterise the product and select the dosing route

Record the product condition that controls filling: bulk density and aeration for powders, particle distribution and fragility for granules, or viscosity, temperature, particulates and foaming for liquids. Select the filler against those conditions and define the signal exchange and product-clear time needed by the bagger. The VFFS dosing systems guide provides a cross-product comparison.

2. Convert the finished-pack requirement into film and tooling inputs

Use a dimensioned bag drawing, approved sample and production-intent reel. Define finished dimensions, gusset or depth, seal widths, headspace, artwork repeat, registration mark, code area and opening features. The bag styles and pack formats guide explains why pack geometry changes the forming and sealing arrangement.

3. Define accepted output and quality checks

State how accepted packs are counted and how dose, bag dimensions, registration, seal integrity, cut position, coding, inspection and reject handling are assessed. Include normal events such as refill, stop/restart and reel change so the requirement describes production rather than a short stable demonstration.

4. Confirm utilities, layout and acceptance responsibilities

Freeze the product-feed height, machine and platform footprint, power, compressed air, extraction, drainage, maintenance access and control interfaces. Identify which checks belong at the factory acceptance test and which depend on the installed site. Use the utilities and installation guide and the FAT and SAT guide.