DEFINITION
Pad printing also named tampo printing or tampography, is a kind of gravure printing in which a silicon pad transfers a 2-D image on laser etched printing plate to a 3-D object. Because of pad printing with modern pad printing supplies, now it’s practicable to print various products of difficult shapes, including concave, convex, spherical, texture, cylindrical, compound angles, and so on. While these are unavailable with traditional printing.
The necessary pad printing supplies are listed below:
- Pad print ink
- Pad print plate
- Pad print ink cup
- Pad printing machine
- Pad print pad
HOW TO PAD PRINT?
Step 1:Put the closed ink cup on the etched artwork area on pad print plate to cover the image and fill it with ink. It is called home position.
Step 2: Move the closed ink cup away from the etched artwork area and take all excessive pad printer ink and expose the etched image filled with ink. As soon as the top layer of pad printer ink is exposed to air, it becomes tacky. By this way, the pad printer ink adheres to the pad and then to the printed product.
Step 3:Press the pad down onto the plate immediately. The compressed pad pushed the air outward and lift the ink from the etched artwork area on the pad.
Step 4:Pick up the tacky film in the etched artwork area on the pad when the pad lifts away. A little ink stays in the pad print plate.
Step 5:The ink cup moves covering the etched artwork area of the plate when the pad moves forward. Preparing for the next cycle, the ink cup refill in the etched artwork image of the transfer plate.
Step 6: The pad compresses the product to transfer the ink layer from the print pad plate to the surface of products. Later, the pad lifts the substrate and goes back to the normal position.
TYPES OF PAD PRINTING MACHINE
Four types of pad printers for sale are listed, and pad printer machine price and feature are given below.
1. Manual Pad Printing Machine
Manual pad printing machine is available for 1-2 colors. Manual pad printer for sale is designed with experience and know-how in automatic models. Manual pad printing machine includes basic elements including close ink cup, ball guidance, XY pad adjustment, etc. Manual pad printer allows easy and reliable utilization of equipment in pad printing technology. The manual pad printing machine price ranges from 150$ to 300 $ per set.
one-color manual pad printer
- A 90mm ink cup
- Economical and convenient to use
- The same result as that of automatic pad printing machine
two-color manual pad printer
- Two 65mm ink cups with 2 color versions
- Manual operated shuttle
2.Automatic Pad Printing Machine 1000-4000
Automatic pad printing machine is available for 1-6 colors, applied in sectors including glass, electronics, plastics, etc. The price of a pad printing machine ranges form 1000$ to 4000$.
3.Semi-auto Pneumatic Pad Printing Machine
Semi-auto pneumatic pad printing machine needs minimum maintenance and is convenient to operate. Pneumatic pad printing equipment manufactures the offered range with durability and efficiency and its ink up is of longer serving life. The average price of the pad printing equipment is 1000$.
4. Rotary Pad Printing Machine
The pad of rotary pad printing equipment gives a full length of the band to the tooling. Then it spins the part below the pad automatically to transfer the band to a round part when it passes by the pad. The band wraps for 3 times for maximizing the ink opacity. The price of each set of rotary printing equipment is from 27,000$ to28,000$.
APPLICATION FOR PAD PRINTING
Pad printing machine is used to print difficult products in various industries. Printing International especially concentrates on certain product groups including:
- Manual pad printer for gel capsule and coated tablet in pharmacy
- Decorating lipstick holder, perfume bottle in cosmetics
- Manual pad printer for sportswear printing
- Beverage packaging
- Manual pad printing machine to print gum and coated sweets
- Printing component of medical device in medical industry
Also, manual pad printing machine and automatic pad printing machine also can be used for materials of tranfer function like adhesive, lubricant, flavor, conducive ink, nutritional additive and natural dye.
1. Adhesive
Lots of manufactures consider applying adhesive a labor-intensive and time-wasting process. Translucent or small part calls for precise application, often driving up profits. When taking clean-up nd waste into account, people started to seek for alternatives to adhesive application. One method as it is, adhesive film also produces waste materials. The ideal solution is the pad printing machine allowing for precise viscous liquid deposition. The closed ink cup stops the glue drying out, and the plate can be etched to the exact line thinness and desire depth.
The pad once adjusted, deposits adhesive of the same amount exactly in the same place each time. The finished part like a cell phone lens, as part of automative process, can be set in a customized machine shuttle fixture holding the part in home position as s the glue applied to its edge. Then the lens is transferred to a robot arm setting the cell phone onto the glued area. Further automation is able to transport the joined part onto another conveyor sending them through a dry tunnel or down the assembly line. Heat-cured or ultraviolet adhesive can be applied in the process, so can lots of solvent-based glues not too hydrophilic or aqueous.
2.Lubricant
Lubricant is another hands-off and exacting utilization for pad printing machine. Also, in the area, precision is challenging and waste is messy and costly. Without integrating different and new material like dry or powered film lubricant to re-invent the manufacturing process, pad printing machine offers a reliable and simple mechanical solution.
No matter it is grease, oil or other substances reducing firction, it can be printed with a pad printing machine as long as long as it is able to cling to a silicon pad and be altered to another substrate. For manual pad printing machine suits well for 3-D items like bearing, hinge, housing and threaded part, every production line manufacturing similar component is able to integrate the tech into the process. Especially when catastro[hic failure in adjacent mechanism caused by misapplication, a manual pad printing machine or automatic pad printing machine can realize precise lubricant application, such as fine line, squiggle, miniscule dot or angular confinement.
3.Flavor, natural dye and nutritional additive
Using a manual pad printing machine or automatic pad printing machine in flavor is another area with its potential beginning to be explored. It’s more than a way of high-tech to decorate with natural dye, pad printing machine can also apply nutritional additive or flavor to the surface of receptive food. The pad of manual or automatic pad printing machine is of different hardness, allowing end-users to select the pad “durometer ‘ depending on the substrate strength. For example, printing a flavor into an antacid hollow requires a softer pad in case of the tablet be crushed, while a gum needs a harder pad able to wrap 180° around.
4. Conductive ink
Progresses in the technology of conductive ink allow for a pad printing machine used in touch-key application, circuit board, etc. It reduces the material and process cost, like leaving out the soldered wire, gold plating or graved copper. For instance, replacing gold plating with carbon ink with better robustness than the expensive material and lower electrical resistance than copper. More and more economic sectors are utilizing conductive ink for REFID that is streamlining shipping and inventory rapidly in the marketplace around the world.
There are other applications of conductive ink like transistor, electrode, sensor, antenna and so on. Moreover, pad printing machine can print on recessed, curved or uneven surfaces, making it an advantage over traditional flatbed method of material position. But, like printing adhesive, conductive ink need be solvently based. Materials too hydrophilic or too aqueous cannot be transferred by pad printing effectively.
COMMON PROBLEMS IN PAD PRINTING
1.Ink Cannot Stick to the Part
The material’s surface energy is too low. The dyne level for ink to stick to a pert is 42 or better. It’s also helpful to add an adhesive modifier to the ink when the material surface is of minimum energy.
Another culprit is contamination. The residuary oil from mold-release, upstream or perspiration of handlers may become the barrier to efficient ink adhesion or transfer. Human handlers should keep away from agents of mold-release and the image area on parts.
Use the ink wrongly or test too early. Before initiating production, handlers must test adhesion additives, inks and chemical resistance. There is no ink can adhere to everything or satisfy all performance requirements. Printers need to seek help from their suppliers to evaluate with print test.
It’s a common issue to test too soon. Every ink is post-curing, that is, dry as it is, it hasn’t cured to the degree with maximum chemical and adhesion resistance. UV-cured ink can also post-cure for a day after being used, while two-component ink for 2-5 days. Before testing quality control, abide by curing and drying recommendation of ink manufacturers.
2. The Pad Printer Cannot Doctor the Cliches
The doctor ring of ink cup is damaged. Doctor rings are mostly porcelainous. If handled properly, they can keep several thousand cycles. It is time to change the doctor ring when tits sharp end wears to a 0.25mm flat edge and starts smearing the ink.
Poor maintenance of ink cup. A flexible O-ring is designed in most cups to provide an interference fit between the doctor ring and the cup. It allows the doctor ring to contact intimately with the cliché surface when it changes direction and traverses the cliché within the cycle. The doctor ring fails to flex or float and leaks out if the ink up not properly maintained or cleaned.
Skimp on ink. Ink is like the lubricant for ink cup in doctoring. A minimum amount of ink is designed in most ink cups to allow the cup to efficiently doctor the cliché. When run production is short, people usually skimp on ink, especially when using the two-component ink. That’s for two-component ink has to be abandoned after the pot life expires. The ink level of the ink cup must to be enough to wet the cliché over the inside diameter of the cup of every cycle.If not wetted sufficiently, the cup is unable to clean sufficiently the surface of the cliché.
Scooping. Scooping sometimes occurs in magnetic ink cups on laser etched clichés and thin photopolymer. The magnetic pull of the clichés may deflect the cliché for the design of ink cup, the doctor ring scooping ink out of the image area. The highest deflection degree is caused by magnet in the image area. Sometimes, this can be eliminated with a spacer on the cup to increase the distance between the cliché surface and the magnet.
3.Poor Print Quality
Manipulate solvent evaporation properly to make pad printing work well, otherwise, it won’t effectively transfer and pick up with wet ink. According to the capability of machines, workers should program short delay in the cycle allowing more time for ink to change physically for complete transfer.
When program delay is impossible, blow low-pressure air of low-volume to the pad between the transfer and image pick-up to quicken the solvent evaporation. It’s also helpful to do so if printing colors within the cycle. When neither air nor delay is possible, use a thinner with a faster evaporation rate. If the cycle is faster, faster thinner, air, and specific etch depth of cliche may be required.