Pad Printing Technology Introduction

Pad Printing Process

       1.Coating: Coating ink onto the pad plate by an ink roller or sealed cup

        Opened-inktray pad printer stores ink in the end of the tray, when the roller slide into the ink and out will bring ink to the pad plate; sealed cup pad printer stores ink in the sealed cup. Sealed cup moves from back to forth and brings ink into the cave of pad plate. 

    2.Removing ink: Removing ink on the pad plate with steel blade or sealed cup

        The ink in the cave of pad plate will remain. Removing the ink on the surface of pad plate completely is very important. when the ink remain on the surface of pad plate, pad will pick up them with the ink in the cave of pad plate, printing picture will be not same as standard document. 

       3.Picking up ink

       Pad above the pad plate press down and pick up the ink from the cave on the pad plate, then rise up. The ink will be transfered onto the pad surface because of pressure.

      4.Moving

       Pad move to the position above the working table and substrate. There are two kinds of moving way: one is parallel moving, the other is turning moving.

       5.Printing

       Pad press down to contact the substrate and print inks onto substrate. Substrate is installed on the fixture and the fixture is installed on the working table of pad printer.

Marabu Pad Printing Inks

        Although screen printing ink is able to be used by the pad printer. Appropriative pad ink is recommended by the pad printing expert because of steady surface tension and nice ink transfer result. There are three kinds of pad inks in Chinese pad printing market.

     1.TPR

     This glossy pad printing ink is distinguished by particularly high resistance. Being an one-component ink, it is very quick-drying and easy to be processed. To raise surface stability or other stabilities, hardener can be added. This pad printing ink can be widely used. On rigid PVC, polystyrene, ABS, acrylic glass, polyester, thermosetting plastics and varnished surfaces. Because of its high resistance, it can also be utilized for products subject to high mechanical stress, the effects of hand perspiration or cleaning agents, such as control knobs, camera housings etc. Under certain circumstances, this ink is also suitable for poly-acetal materials.

      2.TPU

       High-gloss, quick-curing two-component ink for high-demand adhesion, scratch resistance, mechanical and chemical resistance. By using a matte paste, the degree of gloss can be varied. Materials that are difficult to print on, such as pre-treated polyethylene and polypropylene, thermosetting plastics, metals and varnished surfaces, but also polyurethane, polyamide, melamine resins, powder-coated surfaces and suchlike are easily printed. It can also be used for polyacetal under certain circumstances.    

3.TPY

     Glossy, quick-drying pad printing ink with good resistance to many chemicals such as oils, greases, alcohol. Hardener can be added to further raise surface stability and other properties. Tampapol TPY is primarily used for printing on packaging made of pre-treated polyethylene and polypropylene, ABS as well as rigid PVC. It is also widely used for thermosetting plastics, metals and varnished surfaces.

Fixture

Different products require different fixture which orientation support and overprint function in the process of pad printing, screen printing or hot stamping.

1.For Regular Products

      Cylinder, cuboids objects need the fixture that is produced by mechnical process.This fixture can achieve the accurate position tolerance.

          2.For Irregular Products

          Most of mold-plastics products have complex surface. It is easy to make fixture by no-saturation polyester resin. When adding hardener and activator to the resin, infusibility solid will be build for chemicals reaction. Put the product into resin before it become solid, one fixture finish.

           3.For Standard Cylinder Products

           Cylinder products are usually used in screen printing, hot stamping and heat transferring. The fixture will keep the product runming around the axis freely. When screen plate, stamping plate or silicon roller press down and contact with products, the fixture brings product moving around.

         Regard anchor point

         It is important to look for commonness anchor point on product. High-quality fixture will ensure high quality printing .   

Hot Stamping & Heat-transfer Technology

      There are four types of hot stamping presses according to the stamping methods and substrate's shapes.

      1.Roller-to-Flat Hot Stamping

       Roller-to-flat hot stamping,is actually based on the principle of flat heat-transfer press,which is primarily used to decorate the planar objects and curved objects.Typically,a object that is completely required to be decorated,appliance panel,some facet of cosmetic packaging,top of the plastic box or wooden jewelry box,toys,PVC sheet,ski,and plastic posts are suitable to be decorated by a roller-to-flat hot stamping press .If a floating device is installed on the working station,roller-to-flat hot stamping press is also used to decorate the complex objects.

      2.Rotary Hot Stamping

      Rotary hot stamping is based on the principle of rotary heat-transfer press.

      (1)For Empty Platic Bottle

      For the rigid bottle,is able to endure the pressure of roller.so,such bottle is directly decorated plus an axis position system;For the pliable bottle,is decorated after the bottle full of air to support the roller.

     (2)Plastic Pliable Tube

   Toothpaste,shampoo,bodycare,gel's container,or tubes are dcorated by this press if a supporting axis is installed.

     3.Flat-to-flat Fot Stamping

    Flat-to-flat hot stamping press is suitable to decorate texts or logo onto some part of a planar object,such as VCD panel.

     4.Flat-to-roller Hot Stamping

     The flat-to-roller hot stamping press,is suitable to decorate the round objects,such as plastic cap, ball-point pen,soft tube,round dial,golf cue,cosmetic box and food plastic packaging.

Hot Stamping Foil & Heat-transfer Material

For the flat-to-roller and flat-to-flat processes,only hot stamping foil is employed.but,for roller-to-flat and rotary processes,hot stamping foil is not only used,but also heat-transfer material is consumed.Foil and heat-transfer material's structure is described as below.

1.Backing Film

Foil and heat-transfer material  built on the backing film,PET,are both the multi-layer structure.As for PET backing film,it characterizes as stable size,even surface tension and good resistance to high temperature,ect.

2.Release Agent

Release agent is in a solid state under some temperature,with some adhesion ability,and up to some temperature,release agent,oiled substance,becomes melt.It,actually,functions as the adhesion buffer between PET layer and transfer layer/printing layer.Usually,it's the silicon resin with low viscosity and is coated on the PET film by a gravure press or coaters.

3.Aluminum Layer/Graphic  Layer

Usually,the film,printed by a gravure press,is the graphic layer of  heat-transfer material,and the layer,created by the process of vacuum aluminum vaporized,is the aluminum layer of the foil.The difference between foil and heat-transfer material is how to produce this layer.No matter foil or heat-transfer material,they are both sensitive to the high temperature.

Heat-transfer is usually used to decorate the plastic objects and produce a vivid graphic.For the foil,is primarily used to create the metal luster and provide the objects with a value-added effect.

4.Adhesive Layer

The top layer of foil and heat-transfer material,is a layer of adhesive.According to the different substrates,the different adhesive is coated on the aluminum layer/graphic layer.If adhesive matchs the substrate,the good adhesion is achieved after decorated.

Silicon Rubber Plate & Silicon Rubber Roller

Silicon rubber rubber is used in the processes of flat-to flat hot stamping and flat-to-roller technology,and silicon rubber roller in the rotary hot stamping and roller-to-flat process.They function as heat transferring and pressure offset.

1.Heat Transferring

In the processes of hot stamping and heat-transfer technology,the adhesive on the top layer of the foil or heat-transfer material is melt by the heat transfered over a silicon rubber plate/silicon rubber roller and the graphic is achieved on the objects.

2.Pressure Offset

In the processes of hot stamping and heat-transfer technology,silicon rubber plate or silicon rubber roller can provide the plastic objects with the pressure offset during the process.Therefore,they are usually used to decorate the more rigid objects rather than paper and films.

3.Color

There are a few colors for these silicon rubber plate and silicon rubber roller,eg.red,white,yellow,black,etc.,among which,red silicon rubber is the most popular in the hot stamping process.

4.Rigidity

Rigidity,is a key factor for the elastic substance,such as rubber.So is silicon rubber plate or silicon rubber roller.Rigidity,indicates the elastic substance's ability to resist to the physical force.More rigid,less distorting under the same physical force.Therefore,under the same physical force,a more rigid silicon rubber plate or silicon rubber roller can produce the more sharp and accurate texts or graphics.You can utilize a Shawn sclerometer to test  the rigidity of silicon rubber plate or silicon rubber roller.

5.Thickness

Usually,silicon rubber plate consists of aluminum backing and silicon rubber layer,which are fixed together through a layer of metal-nonmetal adhesive.Thicker the aluminum backing,more even the rigidity of the silicon rubber plate/roller.The less thicker aluminum backing means flexibility,which means to readily setup the silicon rubber plate/roller's position for the operator.