6 Things on Pad Printing Introduction

Pad printing is a process that converts a 2-D image into a 3-D object.  It is an indirect photogravure process, which means the transfer of an image to a substrate or medium. It is referred to as an indirect process because the printing plate does not once come in contact with the medium. The ink for printing is indirectly transferred by the help of a silicon pad, using heat, and in a printing machine.

Pad printing has evolved greatly since the time it was first discovered and used. All the developments have led us to the present-day process and pad printing equipment that are highly efficient. The fact that silicon is one of the best mediums in printing methods, gives it such value in today’s market.

Pad printing is a popular technique in many industries. The first modern application included the printing of Swiss watch faces. Today industries such as cosmetics, medical and electronics, etc., use this technology and its development has not stopped, ever since.

 

1. Pad Printing Process

The process, as the name indicates, involves transferring toner(ink) from a silicon pad to any item of your choice. The printing machine grasps the item firmly and the pad is pressed onto the item. In simple terms, that’s pretty much it, but in details, the process involves the following steps:

Pad printing process

 

  • Home position

The first step is often known as the home position. In this step, the closed ink cup is placed on the engraved area of the plate. The printing plate covers the image and fills it with the ink.

 

  • Ink removal

The excess pad printing ink from the desired image is removed when the ink cup moves away from the printing plate. As soon as the ink on the image is exposed to the air, it becomes sticky.

 

  • Transfer pad

Due to the stickiness, the printing ink is shifted to the transfer pad (silicon pad) and later to the object. The transfer pad pushes into the printing plate to lift the ink from the image to the pad. When the plate and pad come in contact, air moves outward and the ink is moved to the transfer pad.

 

  • Printing

The print is made on the 3-D object when the transfer pad compresses down onto the object to be printed. The silicone pad transfers the ink layer picked up from the printing plate to the surface of the object. The ink layer is very thin (4-20 microns), so it is easy to apply the second film of ink without waiting for the first one to dry.

 

  • Completion of one cycle

The pad then moves up from the medium (object) and comes back in the home position, completing one pad print cycle. The leftover ink on the printing plate is used for the preparation of the next cycle where the ink cup fills the next image and the cycle is repeated.

 

2. Pad Printing Equipment and Supplies

Pad printing requires a lot of different supplies to complete one cycle. Each of them has its importance and need in the overall process. The most significant of all are transfer pads, plates, ink, and ink solvents.

 

Transfer pad

The pad printing uses silicon pads as they wrap around the item to be printed without damaging the item. That’s one of the reasons pad printing can be done on an object of any shape. The silicone pads used for the printing are made up by adding silicone oil and fillers. The shape, size, and durability of the pad matter a lot in the printing process.

 

Pad Printing plates

The plates have a vital role in the pad printing as they hold the images which are to be printed on the items. The quality of the print can be influenced by the type of plate used. Most commonly used types of  printing plates include:

  •         Steel plates: When the prints are needed at a larger scale, steel plates are a great choice. They are made up of first-class steel which makes them durable and long-lasting. Depending on their application, some of them are refined with chrome coating.

 

Pad printing with steel plates

 

  •         Plastic plates: They are made up of a photosensitive layer of plastic wrapped around a thin metal sheet. The plates are washed off with water after their exposure to the UV rays. There are many uses of plastic plates as they are easy to use and flexible. Due to their cheaper price, many small and medium printing setups use them.

 

Pad printing ink types

Pad printing ink is without any doubt, the most important component of the printing process. Printing inks are available in many colors, series, and types. The standard colors of inks are white and black, although many different colors are also used. Printing ink series are for particular mediums such as plastic, glass, and metals, etc. The inks contain a lot of binding substances like resins, polyester epoxy, and pigments. Based on the content, there are four major types of inks:

  • One component ink
  • Two-component inks
  • LED inks
  • Mixed inks

Ink solvents

A solvent is added to the ink to enhance the transfer and the drying process of the ink layer. Usually, the solvents with a faster evaporation rate are considered best for pad printing processes. At the same time, solvents maintain the right amount of ink cohesion to the pad, as well as to the medium to be printed.

3. Pad Printing Machines

Based on the operating systems, there are two types of pad printing machines. The two working principles used in those machines are:

  •         Open system: In the open system, the ink cup is not sealed and most of the outside layer of the printing plate is in use. The open ink pool draws the ink to the picture on the plate and the excess ink is wiped by a sharp blade. The ink solvents evaporate and the ink dries up in the air. The color modifications in the open system are a lot easier than in a closed system.

Open pad printing system

  •         Closed system: In this system, the ink cup is closed and has a sharp edge which is used for wiping away the excess ink from the image. There is limited exposure of ink to the air which changes its thickness. This helps the operators to manage the printing process more easily than a closed system.

 

Pad printing with closed ink cup

4. Pad Printing Vs Screen Printing

The difference between pad printing and screen printing is mainly based on the size of the items that will be printed. For instance, for smaller items (e.g. labels and barcodes)  it is more suitable. Pad printing can easily be done on any unusual three-dimensional object.  Alternatively, for items with greater surface area (e.g. boards, shirts), screen printing works best.

Pad printing is a modern printing method that works by transferring ink from a silicon pad to the item that is to be printed. The pad printing machine keeps in place both the object to be printed and the silicon pad. The ink is passed on to the product by compressing the silicone pad. The silicon takes the shape of any item which needs to be printed and the process is completed when the object dries.

Screen printing, on the other hand, is a method that has been in use for 100 years. It is commonly known for transferring a stencilled design onto fabrics such as t-shirts and silk. The process begins with creating a pattern on a transparent film. After that, the mesh screen is chosen, which plays the most important role in screen printing. The transparent film is then coated on the mesh and it is left to dry. After the creation of the stencil, the printer uses the ink to print out the design on the fabric.

Although the technique used for screen printing originates from the Chinese, it became well known in the 1960s. Because Andy Warhol used screen printing for creating many prints of Marilyn Moore and Elvis Presley. Today, the screen printing process is being used all around the world with highly automated equipment and tools. The most common application of this method is quick printing on t-shirts, on a commercial level.

5. Advantages of Pad Printed

There are numerous advantages of using pad printing, some of them include:

  •         Prints on irregular shapes

When compared to other printing methods (e.g. screen printing), it has the advantage of creating prints on items with irregular shapes and sizes. It can imprint images on objects with difficult geometries as well.

  •         Adaptability

The silicon pads adapt to any shape or structure without destroying them. It eliminates the size and shape restrictions faced by the manufacturers in other printing processes.

  •         Flexibility

The transfer pad is made up of silicon, which makes it especially flexible. This property of silicon allows the ink to be transferred to the medium smoothly.

  •         Less space and cost

The printing setup is fairly small and compact in terms of size. Many operators have their pad printing operations in just one room as they take very little space and are cheap to set up.

  •         Easy process

With simple and smaller machinery, the pad printing process is easy to work and delicate products are achieved. The elaborate detailing of the items is accomplished with fine quality prints.

  •         Better resolution

It provides greater resolution prints, even on those materials that are difficult to be printed. Not only we can see/ read the prints easily, but they are also resistant to chemicals and rust.

6. Applications of Pad Printed Parts

With its advanced printing benefits, pad printing has several applications in almost every sector.

Industries like, medical, branding, food, automobile, pharmaceutical, cosmetics, electronics, paper, sporting, and apparel, etc. use it for branding and logo printing.

Some of the common pad printing products include:

  •         In the pharmaceutical industry, it is used for printing on medicines, such as gel capsules and various tablets.

Medical pad printing

  •         In the food sector, it is used for the prints on the candy wrappers, and chewing gum papers. The packaging designs on the beverage bottles and their caps are also created with pad printing.
  •         The cosmetic sector uses it for labeling their perfumes and makeup products. All the colorful labels and designs on the lipstick holders and different makeup palettes etc. are done with this method.
  •         The Pad printing method is used for printing face masks as well. It offers a great solution for managing a large number of mask production with ink prints that have been tested and approved.
  •         For any kind of promotional items, the pad printing method is preferred. It delivers more than a hundred different designs, in multiple colors at reasonable costs.
  •         For sign printing and decoration of the silicon products, it always stands out commercially. Many promotional products, pet supplies, and kitchenware made up of silicon are printed by this technique.

Sign prints with pad printing process

  •         It is perfect for custom prints on pens, notebooks, canvas, rulers, clipboards, and many other things. From logo printing to bar codes, it provides everything.
  •         The pad printing method is safe with all kinds of electronic items. Electronic gadgets like battery banks, flash drives, and smartwatches are perfect to be printed by this method. Mostly because they are small and do not require any pre-treatment.

Printing of watch dials.

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