Rotary Screen Textile Printer

Overview

The Rotary Screen Textile Printer prints continuous lengths of woven or knitted fabric by pushing coloured dye paste through engraved nickel screens that rotate in time with the moving cloth. It is the dominant machine for high-volume textile printing because it runs continuously rather than step-and-repeat, so a single line can print 30,000 to 80,000 metres of fabric per shift. Each colour in the design gets its own Rotary Screen Cylinder, and a typical machine carries between six and twenty-four heads. The fabric is glued to a wide rubber belt, carried under every screen in turn, lifted off, and dried.

The machine is built around a long welded Machine Frame that supports the belt cradle and a precision rail for the print heads. Cloth enters at one end through the Fabric In-feed and Gumming Unit, travels the length of the Printing Blanket System, passes through the Hot-air Drying Tunnel, and exits to a batcher, steamer, or roll winder.

How it works

Incoming fabric is first squared and tensioned. The Dancer Tension Bar holds web tension steady while Edge Uncurler (Bow Roller) rollers flatten curled selvedges. The Gumming Roller lays a thin film of water-soluble or thermoplastic adhesive from the Gum Trough onto the blanket, and the Stick-on Pressure Roller presses the cloth down so it cannot shift while it is printed. Holding the fabric fixed to the belt is what keeps colour registration tight.

The glued fabric then moves under each Print Station (Colour Head). Inside every rotary screen sits a Internal Squeegee Assembly. Dye paste is pumped into the screen, and a Squeegee Rod held down by an external Magnet Bar forces the paste through the open cells of the engraved Nickel Screen Mesh onto the fabric below. Print pressure is set by the magnet current rather than by mechanical springs, so it can be tuned per colour from the control panel. For very fine lines a Doctor Blade is used instead of a rod.

Each screen is rotated by its own End-ring Drive, a servo coupled through the cylinder Screen End Ring. The screens do not share a mechanical shaft. Instead the Repeat and Registration Drive runs an electronic line shaft: a master controller broadcasts a virtual angle, and a Servo Axis Controller at each head keeps its Screen Encoder Ring locked to that angle. When a colour drifts, the operator nudges the Registration Micro-adjust stage, which moves the whole head lengthwise, sideways, and in skew on ball screws to bring the colours back into register, usually within 0.1 mm.

The rotary screen cylinder

The screen itself is the consumable heart of the machine. It is a seamless nickel tube about 0.1 mm thick, grown by electroforming and then laser-engraved with the image for one colour. Open cells let paste through; the Screen Lacquer Coating coating closes the rest. Mesh count, from roughly 60 to 215 holes per inch, sets how much paste is laid down: coarse meshes for heavy pigment coverage, fine meshes for sharp detail and pastels. Aluminium end rings are glued into both ends so the End-ring Drive can turn the cylinder and the Paste End Cap can seal it. Screens are mounted and removed in seconds with quick clamps, and a print shop keeps hundreds of them on racks, one set per design.

Paste supply and blanket wash

Dye paste is thick, so each head has a dedicated Colour Paste Supply. A Paste Feed Pump draws paste from a floor-level Paste Bucket through a Paste Hose, and a Paste Level Sensor keeps the paste level inside the screen constant so the print density does not wander. After the cloth is lifted off, the belt continues on its return run through the Blanket Wash Unit, where a Wash Spray Bar and rotating Rotary Wash Brush strip off gum and stray paste. A wiper blade pulls the water off so the Endless Printing Blanket is clean and dry by the time it reaches the gumming station again. The whole blanket is driven from the exit roller by the Blanket Main Drive, and the fabric speed it sets is the master that every print head follows.

Drying

Wet printed fabric cannot be touched, so it runs straight into the Hot-air Drying Tunnel. Air heated to 120-180 C by Heating Element banks is blown through slotted Air Nozzle Box plenums by Circulation Fan units, floating and drying the cloth as it passes over the Dryer Guide Roller guides. An Exhaust Fan bleeds off moisture to hold humidity down. Drying only fixes the paste enough to handle; final colour fixation happens later in a separate steamer or curing oven, depending on the dye class.

Materials and variants

Wetted parts that touch dye paste or wash water are stainless steel or rubber, since textile pastes are alkaline and abrasive. The blanket is neoprene for chemical resistance and dimensional stability. Frames and girders are welded steel; the print head frames are cast iron for vibration damping. Machines are sized by printing width and by screen repeat, the circumference of the screen, with 640, 819, 914, and 1,018 mm being the common repeats that match standard design sizes. Wider machines for home furnishings reach 3.2 m and beyond. Rotary screen printing competes with flatbed screen printing, which is slower but handles thicker pastes, and with digital inkjet printing, which needs no screens and suits short runs but cannot match rotary throughput or paste coverage on dark grounds.

Use

Rotary screen printers run in textile mills printing dress fabrics, bed linen, curtains, scarves, and technical textiles. A job change means hanging a new set of screens, loading the matching pastes, and registering the colours, after which the Control System recalls the stored speed, pressure, and registration settings for that design. Operators watch the first few metres for register and paste flow, then the line runs unattended at full speed for the length of the order.