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Pad printing bounces into life
Kaye Dee’s TPE100 has to be the ideal start-up machine.
As demand for second user pad printing machines outstrips supply, Peter Kiddell explores the process and looks at a range of manufacturers’ entry level options
Anybody who says screen printing and pad printing are dead processes should have visited Fespa Berlin which represented the largest screen and pad printing exhibition for many years, maybe ever. Although UK visitors were up on previous exhibitions the number was not a true representation of our industry’s size. In broad terms, less than 10 per cent of UK companies using screen and pad printing sent visitors. That was certainly not for lack of promotion, Fespa was in every publication for months. UK manufacturers were well represented as exhibitors and many did startling amounts of business. Sadly most printers stayed at home, increasingly relying on the internet for information. The more enlightened read this journal. If you are one of the 90 per cent of companies that failed to attend, you missed a tremendous opportunity for inspiration, innovation and encouragement. Don’t miss it next time!
Talking with the UK’s main pad printing suppliers it is clear the headlong dash to China is over as reality hits the UK market. It might be cheap, but if delivery is unreliable and quality inconsistent, your business plan starts looking like last night’s takeaway.
This resurgence in the UK market was first seen by sub-contract printers, with many working to capacity. Second hand machines are no longer freely available. Some that were in mothballs are being re-commissioned.
Machine price
In spite of the slowdown in Western European industry, manufacturers have not lain dormant. Clearly Chinese and Far Eastern machinery manufacturers are keen to penetrate Western markets, with some degree of success offering very low cost equipment. A downside is the cost of sale remains the same, irrespective of the machine’s price. Thus, companies working on reduced margins find it challenging to deliver the back-up that established suppliers can provide.
It is interesting to see how Far East competition has stimulated European manufacturers to produce low cost entry-level models. Kaye Dee Marking solutions is offering its single colour TPE100 from Teca Print for £1,950. This looks like the TC70 of old with more sophisticated electronics and a 100 by 100mm plate. With this price, plus the back up of an established company, it has to be the ideal start-up machine.
Tampographic Services addresses this market with their MiMicro range of fully electric machines starting at £3,000. They can be used as bench mounted machines and are often built into fully automated systems where the machine runs continuously. Speeds of 3,500 to 5,000 cycles per hour are attainable.
Even Tampoprint, for years the doyen of pad printing machinery manufacturers, offers its Sealed Ink Cup 60/90 machine, an evolution of the hermetic closed-cup machine that was the fastest pad printer available, capable of 5,400 cycles per hour. The Sealed Ink Cup 60/90 reaches 3,500 and provides a quality print within its 90mm closed cup.
Increasingly, pad printing is being incorporated into fully automatic systems. The only way to compete against low and virtually no wage economies is to minimise our labour levels. Naturally, we cannot match the all to often non-existent environmental and health/safety policies of third world economies. Is it me or is it not wrong to deliberately expose people to hazardous materials? What is the moral difference between buying products of slave labour in the 18th century and buying furniture sprayed by hand in a room without extraction or any protection for the employees in the 21st? We in the developed world who invest capital in such practices claim to care for our fellow man, really!
Where did that come from? Probably from the many conversations I have with businessmen trying to make a living in UK manufacturing. Don’t worry, our grand children will get jobs as guides and character merchandisers in the national theme park called the United Kingdom.
Complex shapes and materials
Back to special purpose systems and automation. Innovative adapting of the pad printing process allows printing on complex shapes and materials.
The first questions are the substrate and ink’s working conditions. With this information, drying and/or curing requirements can be established. In turn, this affects machine configuration. Compared with screen printing inks, pad printing inks are more expensive. This is a mixed blessing, the advantage being that ink manufacturers are more likely to have or formulate inks for special applications.
Pad inks differ from screen printing inks in two ways. Pad inks tend to have a higher percentage of pigment and the solvents evaporate faster. Evaporation speed is a key mechanism in pad printing. Higher pigment concentration is a characteristic of the process’ thin ink film.
Here again, the thin ink film can be an advantage when printing four-colour process but if an opaque colour is used a double print maybe required. This applies in stand-alone and automated systems.
It is possible to pick up thicker ink films using thermoplastic ceramic inks. With these inks the transfer mechanism of ink from the etched plate, to the pad, and from the pad to the substrate is caused by using ink that is solid (like candle wax) in ambient conditions and liquid when heated to 80°C. Heating takes place in the ink reservoir and printing plate. Unlike conventional pad printing inks, pad wetting does not occur due to solvent evaporation but by the pad’s cooling effect when it contacts the ink in the plate etching. Similarly, ink transfers from pad to substrate because the ink’s outer surface becomes tacky when exposed to air, making it tackier than the ink on the pad’s surface. The cooling effect of the glass or ceramic substrate completes the transfer.
Film thicknesses up to >50µm are possible. This is normally used with ceramic colour fired at approximately 580°C for glass and 1200°C for ceramic.
Automatic systems often accept and orientate mouldings or components in bulk and place them on a feed mechanism for pre-treatment such as corona discharge or flaming to increase the surface energy of certain plastics.
Cold plasma pre-treatment is increasingly popular as it can remove oils on the surface of metals. When printing onto plastics, cold plasma removes release agents, slip modifiers, plasticizers and other contaminants. It also makes the surface more attractive to ink by raising the surface energy to a level where virtually any ink system will adhere. Cold plasma also removes dust and the static that attracts it in the first place. Plasmatreat (UK) provides equipment.
Rotate and inflate
Once prepared for printing, objects are located and, if necessary, rotated/inflated at the print station. The machine may print many colours on the flat, curved or rotationally.
Then comes drying. Most conventional pad printing inks dry fairly quickly because of their fast evaporating solvents. Accelerated drying can be achieved with flaming, infrared emitters or hot air. Some inks have UV resins in the formulation so UV emitters can be used for curing. Some time drying is applied between colours to prevent ink pick up off the object by subsequent printing pads. In sophisticated systems image recognition is used to check print quality or read printed barcodes.
A point often ignored by component producers is that when you want to print on an object, dimensional tolerances, surface finish and cleanliness become critical factors. A client will be uncompromising about a logo colour or the fine tonal work demanded.
If the system is inadequate it is possible to create rejects faster than the original component can be produced. It is moments like these when you wish you were on a slow boat to China returning the equipment.
