Pad Printing Machine Product

Overview

Pad printing is the standard way to put graphics on objects that are not flat: golf balls, syringe barrels, bottle caps, keyboard keycaps, automotive switchgear. The machine is an indirect gravure press. Artwork is etched a few tens of microns deep into a Cliché Plate, the etch is filled with ink, and a soft Silicone Pad picks the ink film up and lays it down on the part — wrapping around curves, into recesses, and over textured surfaces that no direct printing process could follow.

A single-colour benchtop machine has four working groups: the Sealed Ink Cup System that inks and doctors the plate, the Pad Assembly and its two-axis Pad Drive, the Part Fixturing that holds the workpiece, and the Control System that sequence them. All motion is pneumatic from a 6 bar shop-air supply conditioned by the FRL Unit.

How it works

Each cycle begins with the Ink Cup parked over the image. The cup is an inverted reservoir of ink pressed rim-down against the plate; as the Cup Slide strokes it back, ink floods the etched artwork and the lapped Ceramic Doctor Ring doctors the plate surface clean in the same pass. A Cup Magnet pulls the ring against the steel cliché with constant force, so doctoring pressure does not depend on operator adjustment. Only the etch — 20 to 28 µm deep — retains ink.

A short pause follows, and it matters: solvent flashes off the exposed ink surface, making it tacky. The Vertical Cylinder then presses the pad onto the plate. Because silicone has very low surface energy, the tacky upper face of the ink prefers the pad to the plate, and roughly half the film lifts off. The pad's convex profile is deliberate — it rolls into contact from the centre outward, squeezing air aside so no bubbles are trapped under the image.

The Horizontal Cylinder carries the Drive Carriage over the part while more solvent evaporates from the now-exposed underside of the film, reversing the tack gradient. The pad descends onto the workpiece held in its Part Nest, deforms to follow the surface, and releases the ink almost completely — transfer efficiency on the second face exceeds 95 %. Compression depth on plate and part is set independently by the Stroke Stops, and Hall Sensor end-of-stroke switches confirm each motion to the PLC Board before the next begins.

The pad and the plate

Pad selection is most of the craft. Pads are cast RTV silicone between Shore A 2 and 12; harder pads roll cleaner and resolve finer detail, softer pads conform to deeper 3D geometry. Shape is chosen so that contact always rolls rather than stamps — round pads for circular images, long bars for linear text, custom forms for parts like syringes. Pads wear by losing surface gloss and typically print 50,000–100,000 impressions before replacement via the Pad Quick Clamp.

Clichés come in two families. Photopolymer plates are exposed and washed in minutes and suit short runs of about 10,000–50,000 impressions. Hardened steel plates are laser- or acid-etched and run into the millions. Etch depth meters the ink: too shallow prints weak, too deep and the doctoring ring leaves a wet centre that the pad picks up unevenly.

Fixturing and registration

The print lands wherever the part sits, so registration lives in the tooling. The XY Registration Table gives micrometer adjustment of nest position under the pad during setup, the Cliché Holder registers the plate against ground stops, and the Guide Rails keep pad placement repeatable to about ±0.02 mm. In production the Part Shuttle moves the nest between an operator load position outside the Safety Light Curtain and the print position; the Part Presence Sensor vetoes the stroke on an empty nest so the pad never prints onto the fixture.

Sealed cup versus open inkwell

Older machines flooded the plate from an open trough with a separate doctor blade. The sealed cup, standard since the 1990s, closed the ink against air: solvent loss drops by an order of magnitude, viscosity stays stable across a shift instead of needing thinner every 20 minutes, and operator solvent exposure largely disappears. A 90 mm cup holds enough ink for tens of thousands of impressions; topping up means lifting the cup lid sealed by an O-Ring Set and adding ink and thinner by weight.

Cycle sequencing, delay timers for the two tack pauses, batch counters, and fault states are programmed at the LCD Panel; in manual mode the operator loads a part and triggers each cycle with the Foot Switch. Multi-colour work uses the same mechanism repeated — carousel machines index the part under two to six cup-and-pad stations, printing wet-on-wet with only the inter-station transfer time as flash-off.