Are Small Pad-printed Products Stuck by The Rubber Head? Don’t Panic, Here Is A Complete Solution

In the precision pad printing process, small products are "carried away" by the rubber head, which is one of the most common "stumbling blocks" on the production line. This not only directly leads to product scrapping and positioning deviation, but may also scratch the fixture, causing batch quality accidents. To cure this stubborn problem, we cannot just rely on "adjusting pressure", but should systematically investigate from the three dimensions of ink status, glue head parameters and fixture rigidity.

Keywords: pad printing adhesive products; glue head adsorption force; surface dryness of ink; pressing depth; positioning fixture

1. Ink "neither dry nor wet" is the primary culprit

Many operators mistakenly believe that the wetter the ink, the fuller the printing effect. In fact, they are completely wrong. When the rubber head dips in the ink and presses down, if the solvent content of the ink is too high (especially if too much slow-drying water is added), the initial tack of the ink is much greater than its adhesion to the product surface, and the product will naturally be "uprooted" when the rubber head rebounds.

Standard countermeasures: The ink should be adjusted to a state where the surface dryness is about 85% to 90% - that is, the surface of the ink is slightly sticky but not stringy when touched with a finger. At this time, the cohesion of the ink has been established and the rubber head can be released smoothly. At the same time, switch the diluent from slow-drying to medium-drying or fast-drying, and strictly control the ambient humidity between 50% and 65% to accelerate the evaporation of the solvent and allow the ink to "rush" to complete the initial solidification before the rubber head rebounds.

2. The depth of pressing of the rubber head - "too much is not enough"

Pressing the glue head too deep is another invisible killer. Excessive downward pressure will sharply increase the deformation of the rubber head, and its elastic retraction force will instantly amplify several times, forming a "suction cup effect". Especially for micro plastic or metal parts weighing less than 1 gram, this adsorption force is enough to separate the product from the vacuum fixture.

Standard countermeasures: To just cover the pattern transfer area, control the pressing depth within 1/3 of the total stroke of the rubber head, and give priority to the rubber head with higher hardness (Shore 40~45 degrees) to reduce the amount of deformation.

3. Fixture positioning - the ignored "last straw"

Even if the ink and glue head are perfect, if the product has micron-level shaking on the jig, the lateral friction force when the glue head is pressed down will lift the product. Please check: ① Whether the vacuum suction force of the fixture is ≥ -60kPa and the suction hole is not blocked; ② Whether the positioning insert is worn, resulting in a gap of more than 0.05mm between the product and the fixture; ③ Whether a non-slip rubber pad or lateral stop is added to the edge of the fixture to offset the vertical pulling force of the rubber head when it is demoulded.

4. Emergency fine-tuning and daily monitoring

In an emergency, 1% to 2% anti-adhesive additives can be temporarily added to the ink to reduce the surface energy of the rubber head. But the fundamental strategy is to establish standardized operations: use a dynamometer to check the demoulding force of the rubber head every 2 hours, and use a magnifying glass to check whether there are residual ink stains on the bottom of the product - if there is wet ink on the bottom of the product, it means that the pressure is too deep or the drying is insufficient.

In short, the essence of solving the problem of pad printing adhesive is to balance the relationship between the "cohesion of the ink, the resilience of the rubber head and the binding force of the fixture." By following the above steps to check item by item, your pad printing yield rate will surely return to above 99.5%. Remember: pressing 0.1mm less and waiting 5 seconds more is more effective than blindly changing the rubber head.