How Non-Woven Bags Are Made: The Complete Production Process

Key takeaways

Non-woven bag fabric is made by spunbonding: melted polypropylene is spun into filaments, laid in a web and bonded by heated rollers.
Every custom bag passes through nine stages, from designing and cylinder making to printing, lamination, slitting, bag forming, QC and dispatch.
Ultrasonic welding seals seams without thread; stitching gives the strongest seams and handles, up to 20 kg.
Extrusion lamination protects rotogravure print under a film and makes bags water-resistant.
Our lead time is 7 to 14 working days after proof approval, and stored tooling makes repeat orders faster.

Introduction

A printed non-woven bag looks simple. It is light, soft, colourful and folds flat. But behind every bag that leaves a shop counter is a surprising amount of engineering: a fabric made without weaving, artwork engraved onto metal cylinders, inks matched to brand colours, layers of film bonded together under heat, and machines that cut, fold and weld bags at high speed with ultrasonic vibrations instead of thread.

Understanding how non-woven bags are made helps you order better bags. When you know where strength comes from, why print methods differ and what quality checks matter, you can choose the right specification, avoid common problems and get bags that carry your brand for months rather than days.

We have been manufacturing bags for 18 years. This article walks through the full production process we have refined over that time, from polypropylene granules to finished, packed bags. It covers how non-woven fabric is made, how artwork is prepared, the printing methods we use, lamination, slitting, bag forming, quality control and dispatch. It ends with a look at timelines, an illustrative example and answers to common questions.

What "non-woven" means

Most fabrics are made by weaving or knitting threads together. Non-woven fabric is different: its fibres are bonded directly into a sheet, without any weaving. The fabric used for non-woven bags is almost always made from polypropylene (PP), a light, strong and water-resistant plastic.

The most common way to make bag fabric is called spunbonding:

Melting. Polypropylene granules, often mixed with a colour masterbatch, are melted.
Spinning. The molten plastic is pushed through fine nozzles called spinnerets to form continuous filaments.
Laying. The filaments are cooled, stretched by air and laid in a random web on a moving belt.
Bonding. The web passes between heated rollers (a calender) with a dotted pattern, which fuses the filaments at thousands of small points. Those dots are the fine pattern you can see on most non-woven bags.
Winding. The finished fabric is wound into large rolls.

The weight of the fabric is measured in grams per square metre (GSM). Our bag fabrics range from about 45 GSM for light D-cut and W-cut bags to 130 GSM for packaging bags. Blog Article 1 explains how to choose the right GSM.

How spunbond non-woven fabric is made

1MeltPP granules and colour
2Spinfilaments through spinnerets
3Layrandom web on a belt
4Bondheated dotted rollers
5Windfinished fabric rolls

Figure 1: From polypropylene granules to a roll of fabric.

Our production process at a glance

Every custom printed bag goes through nine stages:

From artwork to dispatch

1Designingartwork and specification
2Cylinder or plate makingprint tooling
3Printingrotogravure, flexo, screen or offset
4Inspectioncolour and registration
5Extrusion laminationfilm bonded to fabric
6Slittingrolls cut to bag width
7Bag formingcut, fold, weld or stitch
8Final inspection and QCsize, strength, print
9Dispatchcounted, packed, delivered

Figure 2: The nine stages of making a custom printed non-woven bag.

The sections below explain each stage.

Stage 1: Designing

Every bag starts with a brief: what the bag will carry, how it will be used, where it will be given out and how your brand should look. From that brief, we agree the specification:

Bag type: D-cut, loop handle, W-cut or U-cut, box, stitched, packaging or thermal;
Size: height, width, gusset and handle length;
Fabric: plain non-woven, PP woven, laminated non-woven or laminated metallic;
GSM: matched to the load;
Printing: method, number of colours and print area; and
Construction: ultrasonic welding or stitching.

Our design team then prepares the artwork to fit the bag’s print area, with your logo, colours, message and contact details. With 18 years of bag manufacturing behind us, and a creative agency within the group, design is where we add the most value: a bag is a moving advertisement, and good artwork makes it work harder. Insights Article 2 explains bag design in detail.

Stage 2: Cylinder and plate making

Before printing, the approved artwork must be turned into printing tools:

Rotogravure cylinders. For rotogravure printing, each colour in the design is engraved as millions of tiny cells into a copper-plated, chrome-finished steel cylinder. The cells hold ink, and their depth controls how much ink is transferred, which is why rotogravure can reproduce photographs and smooth gradients.
Flexographic plates. For flexo printing, each colour is made into a flexible photopolymer plate with raised image areas, mounted on a print cylinder.
Screens. For screen printing, each colour becomes a fine mesh screen with a stencil of the design.
Offset plates. For offset printing, used on some packaging bags, each colour becomes a metal plate.

Tooling is made once per design and can be stored for repeat orders. This is one reason the first order of a new design costs more per bag than repeat orders.

Stage 3: Printing

We use four printing methods, each with its own strengths:

Method	How it works	Best for
Rotogravure	Ink transferred from engraved cylinder cells, usually onto a film that is then laminated	Photographic, full-colour designs on laminated bags; long runs
Flexographic	Ink transferred from raised flexible plates	Crisp logos and text in a few colours; medium to long runs
Screen	Ink pushed through a mesh stencil; we use water-based inks on a roll-to-roll automatic screen printing machine	Bold, solid colours; simple logos; shorter runs
Offset	Ink transferred from a plate to a rubber blanket, then to the substrate	High-quality packaging bag artwork

Blog Article 2 compares the printing methods in more detail.

Stage 4: Inspection

After printing, the printed fabric or film is inspected before it moves on. Inspectors check:

colour accuracy against the approved proof and brand colours;
registration, meaning each colour lines up exactly with the others;
print defects, such as streaks, spots, missing ink or smudging; and
text accuracy, including phone numbers, addresses and spelling.

Catching a print problem at this stage costs far less than finding it after thousands of bags have been formed.

Stage 5: Extrusion lamination

Many of our bags are laminated. In extrusion lamination, a thin layer of molten polypropylene is extruded between the printed film and the non-woven fabric, bonding them together as they pass through rollers. When rotogravure is used, the artwork is usually printed on the reverse side of a clear film, so after lamination the ink sits safely between the film and the fabric, protected from scratches and moisture.

Lamination gives bags:

a smooth, glossy or matte surface that shows photographic artwork beautifully;
water resistance, so the bag keeps its contents dry in light rain;
extra stiffness and strength, helping box bags hold their shape; and
an easy-to-wipe surface.

Metallic and shimmer finishes are produced by laminating special films onto the fabric. Our ready-design laminated bags use two-layer (105 GSM) or three-layer (120 GSM) construction.

Stage 6: Slitting

Fabric and laminate come in wide rolls. Slitting machines cut these master rolls into narrower rolls of exactly the width needed for each bag, using sharp rotating blades. Accurate slitting keeps the print correctly positioned on each bag and reduces waste.

Stage 7: Bag forming

Bag forming turns rolls of fabric into finished bags. Depending on the bag type, forming may include:

Folding the fabric to create the bag body, base and gussets;
Cutting the bag to length, and punching D-cut handles or cutting W-cut and U-cut handle shapes;
Attaching handles for loop handle and box bags; and
Sealing seams by ultrasonic welding or stitching.

Ultrasonic welding

Ultrasonic welding uses high-frequency vibrations to generate heat exactly where two layers of polypropylene meet, melting them together into a firm seam in a fraction of a second, without needle holes or thread. It is fast, clean and consistent, which makes it ideal for high-volume bags such as D-cut, W-cut, loop handle and box bags.

Stitching

Stitched bags are sewn with industrial sewing machines. Stitching produces very strong seams and handle joints, which is why our stitched bags carry up to 20 kg. It also allows extras such as zips, woven handles and decorative stitching.

Construction	Strengths	Typical bags
Ultrasonic welding	Fast, clean, no thread or needle holes, consistent	D-cut, W-cut and U-cut, loop handle, box bags
Stitching	Strongest seams and handles; zips and woven handles possible	Stitched shopping bags, packaging bags, heavy-duty bags

Stage 8: Final inspection and quality control

Before bags are packed, they go through final inspection. Typical checks include:

Check	What is checked
Dimensions	Height, width, gusset and handle length against the specification
Fabric	GSM, colour and freedom from holes or weak spots
Print	Colour, registration and position on the bag
Seams and handles	Strength and neatness of welds or stitching; secure handle joints
Load	Sample bags loaded to check they carry the specified weight
Count	Correct number of bags per bundle and carton

Stage 9: Dispatch

Approved bags are counted, bundled, packed in cartons or bales, labelled with the order details and dispatched. Clear carton labelling makes it easy for customers to receive and store bags, and to identify the right design when they have several.

Fabric colour and printed colour

Non-woven bags get their colour in two ways, and it helps to understand the difference:

Fabric colour. For plain (unlaminated) bags, the colour comes from masterbatch added to the polypropylene when the fabric is made. Fabric is available in many standard colours, such as white, black, red, royal blue, green, yellow, orange, purple and navy. The printed design sits on top of this colour.
Printed colour. For laminated bags, the colour and design come mainly from the printed film, so almost any colour or photograph is possible, including full-bleed designs that cover the whole bag.

When printing onto coloured fabric, light inks on dark fabric may need an extra white base layer to look bright. Our design team advises on colour combinations that give the clearest result.

Common production problems and how we prevent them

Problem	What causes it	How we prevent it
Handles tearing off	Fabric too light for the load; weak weld or stitch at the handle joint	Match GSM to load; reinforce handle joints; load-test samples
Blurred or misaligned print	Poor registration between colours	Careful set-up and inspection after printing
Colour not matching the brand	Ink mixed without reference to brand colours	Match inks to approved proofs and Pantone references
Lamination peeling	Poor bonding temperature or contamination	Controlled extrusion lamination and bond checks
Bags of uneven size	Inaccurate slitting or cutting	Accurate slitting and dimension checks during forming
Split seams	Weak or uneven welding or stitching	Regular weld and stitch checks; sample load tests
Wrong count	Manual counting errors	Counted bundles and labelled cartons

Packing options

Bags are usually packed flat in bundles, then in cartons or compressed bales. Bundle sizes, such as 50 or 100 bags, make it easy for shops to count bags at the till. Cartons are labelled with the design name, size and quantity, so customers with several designs can find the right one quickly. Special packing, such as individually folded bags for gift use, can be arranged on request.

Reducing waste in production

Making bags efficiently also means reducing waste. Planning the bag size to fit the fabric roll width reduces offcuts. Polypropylene offcuts and trimmings from cutting and slitting can be collected for recycling into new plastic products, where recycling facilities are available. Water-based inks, which we use for screen printing, reduce solvent use. Accurate inspection at each stage also prevents waste, because faults are caught before large numbers of bags are made.

The machines behind a non-woven bag

A non-woven bag production line brings together several specialised machines:

Machine	What it does
Rotogravure printing machine	Prints film or fabric from engraved cylinders, one station per colour
Flexographic printing machine	Prints from flexible plates, often with water-based inks
Automatic screen printing machine	Prints roll to roll through mesh screens
Extrusion laminator	Bonds printed film to non-woven fabric with molten polypropylene
Slitter rewinder	Cuts wide rolls into narrower rolls at the exact bag width
Automatic bag making machine	Folds, cuts, punches handles, attaches loops and ultrasonically welds bags
Industrial sewing machines	Stitch heavy-duty bags, handles, zips and packaging bags

Modern automatic bag making machines can form bags continuously from a roll, which keeps size and seam quality consistent across large orders.

How long does production take?

Our lead time is 7 to 14 working days after you approve the proof. Where an order falls in that range depends on the bag type, quantity, printing method and whether tooling already exists:

Ready-design bags can be supplied fastest, because no artwork or tooling is needed.
Screen and flexo printed bags need screens or plates, which take less time to make than gravure cylinders.
Rotogravure laminated bags need engraved cylinders and lamination, so first orders take longest.
Repeat orders are quicker, because tooling and specifications already exist.

We confirm the delivery date for every order in the quotation. Allow extra time before festive seasons, when demand for bags is highest.

Why process control matters

Every stage affects the final bag. A slightly low GSM weakens handles. Poor registration blurs a logo. Weak lamination peels. Badly aligned welds split under load. By checking each stage, from fabric to final count, we make sure every bag in an order matches the sample you approved.

An example in practice

The following example is illustrative and does not describe a real customer.

A textile shop wants laminated box bags with a full-colour photograph of a model in a saree on the front. Our design team adapts the artwork to the bag’s 35 × 30 cm print area and sends a proof. Once approved, four rotogravure cylinders are engraved, one for each process colour.

The film is reverse printed, inspected for colour against the proof, then extrusion laminated to non-woven fabric. The laminate is slit to width, and the bag forming machine folds, cuts and ultrasonically welds the bags, attaching loop handles. Sample bags are load-tested, and the order is counted, packed and dispatched. When the shop reorders before the New Year season, the stored cylinders make the repeat order faster.

Frequently asked questions

What is non-woven fabric made from?

Non-woven bag fabric is usually made from polypropylene, a light, strong and water-resistant plastic. Its fibres are bonded together rather than woven.

What is ultrasonic welding?

A sealing method that uses high-frequency vibrations to melt and fuse polypropylene layers together, creating seams without thread.

Why do laminated bags look so bright?

Laminated bags are usually printed by rotogravure on a film, which reproduces photographs and smooth colours. The film is then bonded to the fabric, protecting the print.

Are stitched bags stronger than welded bags?

Generally, yes. Stitched seams and handle joints carry the heaviest loads. Our stitched bags carry up to 20 kg.

How long does an order take?

Our lead time is 7 to 14 working days after proof approval. Ready-design and repeat orders are usually at the shorter end of that range.

Why does a first order cost more than a repeat order?

The first order includes tooling, such as gravure cylinders, flexo plates or screens. These are reused for repeat orders.

Can you make bags in custom sizes?

Yes. Most of our bags are made to your size, within each style’s range.

Can I order a sample before full production?

Yes. For custom bags, we can provide a printed proof and, where needed, a sample bag so you can check size, colour, handles and load before full production.

Do you use water-based inks?

Our screen printing uses water-based inks on a roll-to-roll automatic screen printing machine. Ink types for other methods are confirmed with each quotation.

Conclusion

A non-woven bag is the result of careful steps: fabric made by spunbonding, artwork prepared and engraved, printing by rotogravure, flexo, screen or offset, inspection, lamination, slitting, bag forming by ultrasonic welding or stitching, and final quality control. Each step affects how the bag looks, how much it carries and how long it lasts.

By controlling every stage and checking quality throughout, we make bags that carry your brand well, order after order.

Ready to make bags for your brand? Ask us for a quotation.

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