pad print technical, pad print process

Printing Test

The elements of monochrome pad printing machine to complete printing include pad printing plate, pad printing ink, pad printing rubber head, and pad printing fixture. The pad printing fixture is actually a positioning device, which fixes the product on the workbench according to the printing requirements to ensure that it does not move during the printing process; the pad printing ink should be suitable for the material of the product, such as plastic, glass, metal, The color of pad printing ink should also be the same as the color of the printing design; the pad printing plate is to etch the printed graphics on the steel plate or resin plate; the pad printing rubber head is an important carrier to complete the ink transfer, it is made of silicone rubber vulcanization, different pictures The printing plate of the text needs pad printing pads of different shapes and hardness. Monochrome pad printing machines generally only need one fixture, one printing plate, one color ink and one pad printing head.

Monochrome rotary pad printing machine is the most popular pad printing machine in the market at present. Its degree of automation is greatly improved compared with monochrome pad printing machine. Compared with monochrome pad printing machine, its notable feature is that the Instead of a rotating turntable, it can clamp 4-10 products for continuous pad printing. Therefore, it needs more fixtures to fix each product. The elements to complete printing include pad printing plates, pad printing inks, and pad printing pads. , pad printing fixture. The pad printing fixture is actually a positioning device, which fixes the product on the workbench according to the printing requirements to ensure that it does not move during the printing process; the pad printing ink should be suitable for the material of the product, such as plastic, glass, metal, and pad printing ink. The color should also be the same as the color of the printing design; the pad printing plate is to etch the printed graphics on the steel plate or resin plate; the pad printing rubber head is an important carrier to complete the ink transfer, it is made of silicone rubber vulcanization, different pictures The printing plate of the text needs pad printing pads of different shapes and hardness. A monochrome rotary pad printer generally needs 4 to 10 fixtures, a printing plate, a color ink and a pad printing head.

Pad Printer Printing Test Trouble-shooting 1-2

1 Graphic fuzzy, poor edge definition

Possible causes	Trouble shooting
Rubber pad too soft	Replace more harder rubber pad.
The shapeof pad is unsuited	Replace Matched rubber pad
Depth of Forme too deep	Remake pad plate with shallow depth
Incorrect Film screening	Output film with another screening parameter
Ink film too thick.	Adding some thiner to ink
Drying speed of ink too slow	Adding fast-drying thiner.
Printing stock is polluted.	Clean the surface..
Corase ourside of products.	Replace harder rubber pad
Rubber pad slide	Replace fixture and aviod pad sliding
Fixture stabilty not well	Remake fixture, reduce printing speed.

2 Poor ink Adhesion

Possible causes	Trouble shooting
Silicon oil remains of rubber pad	Clean the rubber pad with Solvent
Pad forme Depth too deep	Remake pad forme
Ink is not matched	Replace another type ink
Use bi-Component ink	Replace Bi-component ink
Incorrect Hardner percent	Please Precision addng hardner
Dirty surface of product	Clean the surface with Solvent
Need surface Treatment	Take flame treatment or Chemical treatment
Processing time is unsuited	Printing after treating soon
Insufficiency Post-curing	With IR dying or UV curing.

Pad Printer Printing Test Trouble-shooting 3-4

3. Pinhole

Possible causes	Trouble shooting
Impairment surface of rubber pad	Replace rubber pad
Too Flat of rubber pad	Install more sharper rubber pad
Rubber pad too soft	Replace Harder rubber pad
Defect of pad forme	Remake pad plate
Ink too dense	Adding much more thinner.
Product surface too coarse	Choose more harder rubber pad
Dust on product	Clean the surface of object
Silicon Oil enter into ink	Replace new ink

4 Colour cross when miti-printing
Is a high-speed multi-color pad printing after printing the ink will stick before starting a phenomenon, this situation occurred in the substrate surface difficult to ink and solvent in case of infiltration of a large area printing. When the ink drying fast enough, and the shuttle table and the wheel table between the two stations to match the speed of change often occurs, usually rely on two sticky ink imprint of a pattern to solve this problem

Possible causes	Trouble shooting
Occur Pore and Ageing of rubber pad	Replace new rubber pad
The depth of pad forme too deep	Remake pad forme
Halftone percent and screen density incorrect	Renew output film with new halftome percent and screen density.
Excessive thinner	Adding ink
Drying speed too slow	Adding fast-drying thinner. Drying ink with Blowing-air.
Product Too smooth	Drying with cool wind and hot air between two times printing.
Dust on surface of product.	Clean surface with cloth

Pad samples show

5 Uneven ink thickness

It often occurs on large area ink coverage printing. This is one of the defects that pad printing process cannot fundamentally eliminate. Customers who have the conditions can purchase a large-area roller pad printing machine to obtain a balanced ink layer thickness

Possible causes	Trouble shooting
Wrong shape selection of pad printing head.	Replace the glue head with a more suitable shape. The effective cross-sectional area of the glue head should be at least 30% larger than the printing area.
Plate selection error.	Use resin plates with caution in solid printing to prevent ink from shrinking due to surface tension
There is a problem with the corrosion depth of the steel plate	Control the depth of the steel plate to re-plate, and use the steel plate depth gauge to detect the steel plate
There is a problem with the screening angle of film production	Choose a new screen angle to recreate the film
There is a problem with the direction of the graphics and text on the steel plate	Graphics and texts with longer lines should have a certain angle relationship with the steel plate
ink is too thin	Reduce the thinner in the ink or add the original ink for stirring
ink too thick	Add more diluent
Uneven ink mixing	Put the ink into the oil pan or oil cup and be sure to stir evenly
The identity of the substrate itself is poor	Choose the most suitable rubber head, and the required cross-sectional area can reach 150% of the printing area
Squeegee rigidity is too poor	Replace the rigid scraper or use the oil cup pad printing machine

6 Printed Image Distortion

This problem occurs most often when printing on complex and heavily curved product surfaces.

Possible Causes	Trouble shooting
There is a problem with the shape of the pad printing head	Replace the appropriate shape of the rubber head. The bottom of the rubber head should be as flat as possible.
Pad printing rubber head is too soft or too hard	Test and choose the most suitable hardness rubber head
Graphics are too close to the edge of the rubber head	Choose a rubber head with a larger cross-sectional area
Plate corrosion depth is too deep	If the depth is too deep and the ink is too thin, image distortion often occurs
ink is too thin	If the ink is too thin and the depth is too deep, image distortion often occurs
The substrate is loose or collapsed	Adjust the printing pressure and check the rigidity of the substrate.
Workpiece fixtures are not suitable	Modify the fixture to ensure that it can hold the substrate well
Fixture slippage.	Check the fastening of the clamp
Angle deformation of printed graphics	Change the clamping angle of the fixture.

7 The hiding power of the ink is very poor

This is a direct result of one pad printing on a dark substrate. A two pad printing process on such substrates will give a satisfactory level of hiding power. In addition, the process of printing a white background on the surface of the substrate or using a silver plating process to generate a bright printed image is also often adopted.

Possible causes	Trouble shooting
There are fine holes on the surface of pad printing head, too rough	Replace with a new rubber head
The bottom of the pad printing pad is too flat, the pad is too soft	Use a sharper tip
Corrosion depth is too shallow	Corroded steel plate
There is a problem with the screening angle	Use additional screen angles to make films and prints
Plate type selection error	Choose a suitable steel plate, such as a high-quality pad printing steel plate
ink is too thin	Add appropriate original ink and stir well
incomplete ink transfer	Printing with ink embossing delay lift mode
Poor hiding power caused by the original is not bright	Pattern printing with two ink sticks and one pad printing

8. Dirty image

Usually the reason is that the ink layer is too thin and the pad printing pad slips. When the pad is too hard, the imprint center of the pad is offset from the center line of the pad, the jig is loose, the angle of the jig to place the substrate is incorrect, and the pad printing pressure If it is too large, the level of the pad printing machine itself is not enough and the stability is poor, which will lead to the slippage of the rubber head. Image smudges can be caused by static electricity and environmental influences.

Possible causes	Trouble shooting
Pad printing head hardness is too hard	Replace with a softer rubber head
The cross-sectional area of the pad printing head is too small	Replace the rubber head with a larger cross-sectional area
Text too close to the edge	Adjust the imprint position of the rubber head to support a larger area with a fixture
Plate depth is too deep	Replacement of shallower depth plates
There is a problem with the printing version itself, maybe screen printing is required	Printing plates with dots, or printing plates with different screen rulings
ink is too thin	Add appropriate original ink, it is best to use special pad printing ink
Ink drying is too slow	Add quick-drying thinner to control the temperature and humidity of the environment
The surface of the substrate is more curved	Select a special shape of the rubber head or adjust the embossing position of the rubber head
Poor Fixture Stability	Re-make the fixture, and the force center of the fixture should be controlled at the approximate geometric center of the printed graphics.

9 Inaccurate overprinting

Inaccurate overprinting refers to the phenomenon of positional deviation in multi-color pad printing and color misalignment in the superimposed and copied images of dots. This is the most important factor in measuring accurate pad printing.

one of the important indicators. In terms of the overprinting accuracy of the printing machine itself, the overprinting angle of the shuttle type pad printing machine is higher than that of the rotary pad printing machine, and the overprinting accuracy of the combined printing of multiple monochrome machines is the worst. And the disc type multi-color pad printing machine with an independent plate control system controlled by a precision angle divider has the highest overprint accuracy. In addition, the depth control of the four-color printing plate, especially the four-color pad printing plate, involved in dot replication has a great influence on the overprint angle.

Possible causes	Trouble shooting
There is a problem with the pad printing head installation	Adjust the glue head to transfer the image and text at the most precise position to ensure that the four glue heads have the same pressure center
The shape of pad printing head is not uniform	The shape of the rubber head is identical. Make sure that the four glue heads have the same shape
Pad printing rubber head hardness is not the same	Use a rubber hardness tester to determine the identity of the hardness of the rubber head, and the deviation of the hardness of the rubber head is less than 2%.
There is a problem with the overprinting of the image itself	When remaking the film and re-drying the steel plate, it is necessary to fully consider the problem of printing deformation compensation.
Ink spreads in one color more than other colors	Use high-quality pad printing inks to add accurate diluents
Partial collapse of substrates (such as hard plastic bottles).	Choose a better fixture, or a blower with a higher air pressure
Work-holding is not stable enough	Make a fixture with good support and stability
Conveyor belts, shuttle tables and turntable tables are less accurate	Workbench with high precision installation
The fixture is not precise enough and the support is not good	Precise adjustment to make more precise fixtures

10 trachoma

Most of them are dry cracks and dot-like blank defects in the printing area caused by ink drying in the graphic area of the printing plate.

Possible causes	Trouble shooting
The pad bottom is too flat	Replace the rubber tip with a sharper bottom
The surface of the pad printing head is rough and aging, with pores	Replace with a new rubber pad
Plate corrosion depth is too shallow	Etching the steel plate with a deeper depth
Steel plate manufacturing process problems	Replace the screened film to remake the steel plate
ink too thick	Add thinner to dilute ink
The ink dries deep in the steel plate graphic	Clean the graphic area of the steel plate with a thinner, and add an appropriate amount of slow-drying thinner
The surface of the substrate is polluted by oil	Clean the substrate surface with alcohol
printing speed is too slow	Improve the printing speed of the printing press

Among multi-color pad printers, shuttle type pad printers and turntable pad printers are more common, while shuttle type pad printers have the highest precision. The workbench of the shuttle pad printing machine has an accessory similar to a shuttle block, which will drive the product and the fixture to move back and forth in different printing positions, and complete multi-color pad printing in sequence. The important feature of the multi-color pad printing machine is that it has multiple sets of colors and pad printing systems: Fixtures: The shuttle-type pad printing machine has only one fixture just like the single-color pad printing machine, but the fixture of the multi-color pad printing machine will move back and forth; The four-color shuttle pad printing machine has four sets of ink supply systems, which add four different colors of ink respectively. The four ink supply systems are respectively equipped with four pad printing plates, and each pad printing plate is supplied with ink by a separate oil cup or oil pan. , and the etching sequence of the four pad printing plates should be made according to the original manuscript provided by the user; the four-color shuttle pad printing machine has four pad printing pads installed on the front ends of different steel plates respectively, and the shapes of the pad printing pads can be the same or can be different.

11.Ink sticks to the surface of pad printing head

If the ink is picked up by the pad but not fully transferred to the surface of the substrate, there will be a blank area in the middle of the image. Ideally, the ink can only transfer 90%, and 10% will remain on the surface of the pad printing pad. Switching to a pad printing pad with better release properties will only increase the transfer rate by 2%. Ink sticking to the surface of the pad printing head will also cause layer loss during the dot reproduction process, so the idea of designing a pad cleaning device for the pad printing machine is the fundamental way to solve the problem.

Possible causes	Trouble shooting
Pad printing pad is too soft	Replace with a harder rubber pad
The shape of pad printing head is not suitable	Replace the rubber tip with a sharper bottom
The surface of the pad printing head is rough and aging, with pores	Replace the rubber pad with a new one, and the cost of silicone oil in the formula should not be too much
The depth of the steel plate is too shallow	Corrosion of steel plate with deepened depth
The depth of the steel plate is too deep	Reduce the depth of the steel plate, or use the method of empty stroke to adjust the ink to prevent the ink from drying in the depth of the printing plate
The ink dries on the surface of the rubber head	Add slow drying thinner or add necessary thinner
Adhesive tip too wet - unable to form ink film	Add quick-drying thinner, which should not be mixed with water.
The substrate is stained by oil stains and sweat stains	Clean with alcohol and use gloves if necessary.
Workshop temperature is too high	Shop temperature is best controlled at 64-68 °F.
printing pad is too low	Increased printing speed when ink dries on the pad surface
printing speed is too high	Dry with hot air and cold air to prevent the glue head from being too wet and give the glue head more drying time.

12 There are stringing defects on the edge of the image.

This is usually a problem caused by static electricity, but it can also be caused by other factors such as the shape of the pad printing pad and improper ink viscosity.

Possible causes	Trouble shooting
The pad bottom is too flat	Choose a rubber pad with a sharper bottom
Plate corrosion depth is too deep	Reduce depth, re-plate
Screening film is not selected or the number of screen lines is wrong.	Change different screen lines to make film and print
ink too thick	Add appropriate amount of diluent and mix well
Ink drying is too slow	Use quick-drying thinner to dilute the ink
Electrostatic influence	Increase the humidity in the workshop and use an electrostatic processor for treatment.
air humidity is too low	Control workshop humidity at 60-80%.
Too much pressure on the rubber head forces the ink to squeeze out	Adjust pad printing head pressure

13 Fine lines close to each other

This problem usually occurs when inscribed lines and text are used as the main picture.

Possible causes	Trouble shooting
Rubber pad too hard .	Replace with a softer rubber pad
The surface of pad printing pad aging and too rough.	Replace with a new rubber pad
Plate etching depth is too deep	Replace with a new printing plate, or print in the mode of two ink sticking and one imprinting
The first exposure time of the plate making process is too long	Reduce the first exposure time and re-plate (for resin plates)
There is a problem with the print itself	Use screened film to re-plate
ink is too thin	Reduce the amount of thinner used in the ink
The ink dries too slowly and the ink spreads	Choose quick-drying diluent, or choose the mode that the rubber pad is on the printing plate to delay the pressing down
The surface is too smooth (such as glass)	Thorough cleaning treatment, improved ink affinity, adding fillers to inks
The position of the rubber pad too high, causing the ink to overflow in the graphic	Reduce the height of the rubber pad or use the mode of printing that the rubber pad is delayed on the surface of the substrate