Pad printing is the process of transferring a two-dimensional image onto a three-dimensional part. The offset printing process requires the use of an engraved plate (also known as a cliché) and a pad to transfer the image. Pad printing machines vary in style depending on the number of colours and the size of the image.
Pad printing operations are used in a wide variety of sectors, including industrial, promotional and apparel.
The digital printing or photographic printing does not allow the printing of these three-dimensional parts.
It doesn’t matter if your items are curved or have an uneven surface, using this printing method will still give you a quality print.
The inkwell accommodates the ink as it glides over the engraved plate and leaves a tiny amount of ink in the engraving.
The printing pad is the delivery system, where a somewhat soft silicone material is pressed onto the ink-filled engraving to pick up the image and moved onto the substrate where it is pressed again to transfer the image.
This process does not use any heat or any lasers although it may seem logical. It has nothing to do with thermal printing or 3d metal.
Advantages and disadvantages of pad printing
One of the main advantages of using pad printing is that you can use it to print on three-dimensional surfaces and products of all shapes and sizes. It doesn’t matter if your items are curved or have an uneven surface, using this printing method will still give you a quality print.
Pad printing is also suitable for delicate and mechanically sensitive products. If you need to print very fine motifs, you will find that the resolution of pad printing is much better than screen printing.
Many companies choose to carry out their own pad printing operations in-house, as the installation costs are quite low. In addition, the pad printing equipment does not take up much space and the process is fairly easy to learn.
Although pad printing is excellent for precise results, it is slightly limited in terms of speed. Usually several colours have to be applied separately, quatricolour printing cannot be used, so there is a slight risk of making mistakes. However, in terms of reliability and versatility, it doesn’t get any better than that.
What materials are needed for pad printing?
The pad
A pad is the ink transfer mechanism in a pad printing machine. The pad is compressed over the ink-filled engraving to “pick up” the image. The pad is then slid over the part and compressed again to apply the image.
The pads are made of a silicone material. The type of silicone and the hardness (durometer) of the pad depend on the application. Pads are available in a variety of shapes and sizes.
The size and shape of a pad depends on the application and the artwork. Common pads are round and rectangular. However, there are special pads with unique shapes made for specific applications.
Inkwell
An inkwell is the mechanism for holding the printed ink in a part. The inkwell slides across a plate over an engraving and back again, leaving only a small amount of ink in the engraving.
There are normally two main components of an inkwell: the ring and the cup. The ring is used for scraping the plate and to ensure that only ink remains on the etched part of the plate.
Depending on the manufacturer, rings are made of ceramic, metal and plastic. Ceramic is usually the best material, as it is soft enough not to scratch the plate and strong enough to withstand the constant movement of the pad printer.
The cliché or plate
A pad printing plate, also known as a cliché, contains the image to be printed. The plate is engraved with the image. There are two types of plate engraving processes: photopolymer and laser.
Photopolymer platemaking
Photopolymer platemaking requires the use of photosensitive plate material and a UV exposure unit. The plate is exposed to UV light numerous times, each time with a different component, such as a positive film or a line screen film. Exposing pad printing plates is the most cost-effective solution for platemaking, however, the photosensitive curing process is significantly longer than laser platemaking, taking more than 30 minutes to etch a plate.
Laser platemaking by computer
Laser platemaking is the process of engraving a plate with a Co2 or fibre laser. Computer-to-plate technology allows for complete repeatability without concern for variation in engraving depth, dot pattern and image quality. Laser platemaking is extremely fast, typically engraving a plate in 5-7 minutes.
The ink
Pad printing ink is possibly the most important component of the pad printing process. There is a wide variety of ink series and choosing the right one is critical to adhesion. Each pad printing ink series is developed for specific materials such as glass, metals, plastics and others.
Pad printing inks are available in a wide variety of colours. Standard colours such as black and white are always available, but are you looking for more than just the standard colours? Most inks are available as mixing series to allow custom colour matching. Pantone is also a possibility.
The solvent
Solvent is an additive to pad printing ink. The solvent is mixed with the ink to facilitate the transfer and drying of the ink from the pad to the part.
Solvent is available in various types. Some solvents only work with certain types of ink. Other solvents work with certain inks and vary the evaporation rate. Evaporation rate is an important factor because climate, print speed and application are all factors that influence the transfer of ink to the product.
Ink hardener
The pad printing ink hardener acts as a catalyst that aids in the curing process. The addition of hardener often makes prints more durable and resistant to abrasion. For example: adding hardener to ink for printing on glass will make it dishwasher resistant.
It is not always necessary to mix hardener with all types of inks. However, it is recommended to use it to increase the overall durability of the pad printing ink.
What is pad printing used for?
Pad printing is a very dynamic printing method that can be applied to a large number of products:
Pad printing is typically used for applications that require print quality, precision or a complex shape.
- Medical devices (syringes, surgical instruments, etc.)
- Implantable and body-worn medical devices (catheter tubes, contact lenses, etc.)
- Pharmaceuticals (pills)
- Candies
- Cosmetic packaging (eyeliner, perfume bottles, etc.)
- Caps and closures (beverage bottle caps, etc.)
- Golf ball logos/graphics
- Hockey pucks
- Decorative designs/graphics appearing on toys (Hot Wheels or Matchbox toy cars, balls, etc.)
- Automobile parts (turn signals, control panels, etc.)
- Computer keyboard letters and calculator keys
- Television and computer monitors
- Identification labels and serial numbers for many applications
- Garment industry for printing labels directly onto garments
- Promotional gifts and giveaways
- Shoe heels
Frequently Asked Questions about pad printing
What are the limitations of pad printing as a printing method
Pad printing equipment is limited in the number of colours a machine can print, machines with four to six colours can be challenging to register every colour on the part. Image sizes larger than 150mm in diameter pose a challenge for printing equipment. Graphics can be modified, but the process of making a new plate can be time-consuming, depending on the method used.
Which is better, pad printing or screen printing
When choosing between pad printing and screen printing, it is not a question of which method is better in general, but which method is better for the printing project you want to carry out.
When choosing between pad printing and screen printing, it is not a question of which method is better in general, but which method is better for the printing project you want to carry out.
Before determining which printing method to use, it is best to study your product and consider the results you hope to achieve.
If your product is small (e.g. barcodes and labels) and has intricate details, pad printing is the best option. The same is true if printing in 3D or on an irregular surface. Pad printing is fast, cost-effective and ideal for small, high-quality prints.
Pad printing is fast, cost-effective and ideal for small, high-quality prints.
If, on the other hand, the surface of your item is quite large and you need a large print (e.g. on a T-shirt), screen printing will make much more sense. If you are in doubt about which is the best option, check with your local print shop.