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FAQ

FAQ.

FAQ

Advantages and Unique Features of Pad Printing?

The following list demonstrates the strengths and unique features of pad printing in comparison with other printing processes:

Advantages of pad printing in comparison with other printing technologies:
– Variety of substrates
– Printing of firm, hollow objects
– As indirect intaglio process, capacity to print fine subjects
– High resistance properties of inks
– Easy handling with little maintenance
– Multi color wet-on-wet prints
– Short change-over times, especially suited to small jobs
– Low up-front costs for printing run
– Relatively small space requirement
– Low drying costs
– High speed in rotational systems
– Integration into complex systems: online in assembly and production lines
– Less attention required for ink in sealed systems, e.g., consistency of viscosity
– Use of variety of printing media, e.g., lacquers, adhesives, pastes, inks
– Precise adjustment of tones

Unique features of pad printing in comparison with other printing technologies:
– Printing with almost no dependency on shape, e.g., concave, convex, curved objects
– Printing of varied surface types, e.g., grained or structured areas
– Possibility to print into depressions
– Physically sensitive products can be printed

What Factors influence obtaining Quality Print?

From the facts mentioned so far, it becomes evident that the result of printing is influenced by a multitude of factors. Experience shows that the root cause of a faulty print is virtually never to be found in the mechanics of the printing press.

Defects in the Pad Printing Machine itself are nearly always obvious, clearly definable and can be remedied by the technicians of the manufacturer. Hence, this issue can be ignored. To eliminate problems connected with printing, it is of greatest importance to describe deficiencies in as detailed a way as possible.

Any Pad Printing technician has difficulties on the telephone when a customer makes statements which are only general in nature. Not even the best technician can be of assistance when simply told “the press won’t print” or “the quality of the print is poor.”

factors_affecting_print

Sources of Deficiency in getting Optimal Printing Results

Deficiencies most commonly found in printed material:
– no opacity
– misregister
– motif distorted
– blurring
– poor leveling of ink
– problematic overprintability in multi color prints
– color does not correspond with artwork
– spiderweb effect on contours
– screen dots are visible/are not visible
– fine lines run together
– large areas not completely covered
– small bubbles (pinholes) visible
– motif smudged
– ink does not adhere to substrate
– desired grade of gloss cannot be achieved

During printing operation:
– pad does not pick up ink
– no deposit or only partial deposit of ink by pad

A number of additional problems arise, which are, however, very particular to the individual areas:

Pre-operational deficiencies, e.g.:
– inadequate pre-treatment
– no or only partial deposit of ink on substrate

Post-operational deficiencies, e.g.:
– ink/color turns after some time
– ink cannot be lacquered
– ink does not adhere to substrate

Containment of Deficiencies

In order for any problems which arise to be contained quickly, the individual components (e.g., substrate, pad, cliche and ink) should be systematically changed or replaced.

The settings of the Pad Printing Machine and the ambient conditions (humidity!) should be checked. Making individual sample prints at a higher or lower printing speed or blowing on the pad can also be helpful.

Potential Problems in Printing – Description of Problems and Proposed Solutions

Spots of poor ink pickup by pad in Pad Printing Machine?

Spots of poor ink pickup by pad in Pad Printing Machine?

Problem Solution
1. Too thick. 1. Add thinner.
2. Dried out. 2. Clean cliche with thinner.
3. Wrong thinner. 3. Use slower thinner or one suited to ink system.
Problem Solution
1. Insufficient etching depth. 1. Produce new cliche with greater etching depth.
2. Wrong screen ruling. 2. Test new cliche with different fineness of halftone screen.
3. Surface physically damaged. 3. Use new cliche.
Problem Solution
1. Too flat. 1. Use more tapered pad shape.
2. Surface roughened. 2. Replace pad.
3. Pad swollen. 3. Blow air on pad.
4. Surface too oily 4. Clean pad (several times) or replace.
Problem Solution
Problem Solution
1. Pad is pushed onto cliche too strongly. 1. Decrease head stroke of pad.
Poor or spotty release of ink by pad in Pad Printing Machine?

Poor or spotty release of ink by pad in Pad Printing Machine?

Incomplete or spotty deposit of ink by pad is referred to as “splitting.” It plays a minor role in a continuously
running process. The problem only arises when cycle times fluctuate or after short breaks. The pad deposits
the dried ink all at one time, producing an inconsistent image. Using fast thinners will decrease ink build-up
and improve ink deposition.

Problem Solution
1. Dried out on pad. 1. Use slower thinner.
2. Too wet on pad, not tacky. 2. Use faster thinner.
Problem Solution
1. Insufficient etching depth. 1. Produce new cliche with greater etching depth.
2. Etched too deeply. 2. Produce new cliche with shallower etching depth.
3. Wrong screen ruling. 3. Use new cliche with different fineness of halftone screen.
Problem Solution
1. Wrong shape pad. 1. Use more tapered pad shape.
2. Surface roughened. 2. Replace pad.
Problem Solution
1. Soiled surface (grease, oil, perspiration, mold release agents..). 1. Pre-clean objects.
2. Surface insufficiently pre-treated (polyolefines). 2. Check pre-treatment, repeat as required.
Problem Solution
1. Print speed setting too slow. 1. Maintain uniform cycle time.
2. High ambient (room) temperature. 2. Optimal room temperature is 18 °C to 20 °C
Insufficient opacity of Ink on substrate after Pad Printing?

Insufficient opacity of Ink on substrate after Pad Printing?

This problem very often occurs in pad printing, and cannot always be solved satisfactorily. Due to the low degree of ink transfer in pad printing, 100 % opacity cannot be achieved on many objects with only a single printing, especially in the case of dark substrates. Increased hiding power can be attained by double or triple printing or pre-printing with white.

Problem Solution
1. Too thin. 1. Reduce amount of thinner.
2. Transparent ink. 2. Use opaque color shade.
3. Wrong ink system. 3. Use pad printing ink .
4. Scanty ink transfer. 4. Locate defect in cliche or pad.
Problem Solution
1. Insufficient etching depth. 1. Use new cliche with greater etching depth.
2. Areas not screened. 2. Screen area.
3. Areas not slanted. 3. Slant areas.
4. Wrong cliche type. 4. Use cliche which allows screen to be etched with it.
5. Wrong screen ruling. 5. Test new cliche with different fineness of halftone screen.
Problem Solution
1. Too flat. 1. Use more tapered pad shape.
2. Porous surface. 2. Replace pad.
3. Too soft. 3. Use harder pad.
Problem Solution
1. Soiled surface. 1. Clean surface with alcohol.
2. Dark substrate color. 2. Double print.
3. Surface too rough. 3. Use harder, more tapered pad.
4. Stress cracks (esp. on injection molded parts). 4. Use milder ink/thinner system or quick drying ink/thinner to avoid any dissolution of substrate.
Problem Solution
1. Soiling from greasy residues on accessories (auxiliaries). 1. Clean cliche, doctor blade, etc. before installing.
2. Doctor blade sags. 2. Use harder or thicker doctor blade (or see cliche points 2 and 3).
Misregister in multi color prints while Pad Printing?

Misregister in multi color prints while Pad Printing?

The simplest way to contain these deficiencies is to produce a new cliche with precisely registered film.

Problem Solution
Problem Solution
1. Individual motifs not correctly aligned. 1. If motifs are all on one cliche, film must be corrected and new cliche must be produced.
Problem Solution
1. Pads mounted off center. 1. Readjust pad.
2. Pads not same shape. 2. Replace pads with ones of correct shape.
3. Pads not of same hardness. 3. All pads should be of same Shore hardness.
4. Head stroke not same over cliche and substrate material. 4. Adjust head stroke.
Problem Solution
1. Material is pliable. 1. Switch to different material.
Problem Solution
1. Jig not perfect. 1. Check for play in jig, refabricate as needed.
2. Carre, adjustable, or rotary indexing table inaccurate. 2. Check indexing.
3. Mounting screws not tight. 3. Screws not properly tightened during initial setup; they become loose during printing operation. Tighten screws.
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