Printing on parts.

Pad, screen, and dry-offset printers now offer more colors, higher output, improved registration, easier operation, and greater versatility.

If you're shopping for equipment to print on plastic parts, expect to find higher speeds, quicker changeovers, and the capability to handle more colors than ever before. Today's pad-transfer, silk-screen, and dry-offset printers are loaded with microprocessor controls for all major machine functions. And more in-line automation - including autoloaders, pretreaters, vision inspection systems, assembly stations, and packaging equipment - is getting to be the rule.

Improvements aimed at safety and environmental compliance are also major trends. UV-curable inks are fast becoming the order of the day for screen and dry-offset printing. The case is different for pad printing, where uv-cured inks have yet to provide the crisp, clean images of their solvent-based counterparts.

Pad Printing

Sealed ink cups represent the most revolutionary change in pad printing equipment of the last five years. Together with covered inkwell systems, they make up about 90% of pad printers currently sold. Low maintenance is one major advantage: Sealed ink cups maintain ink viscosity with-out the need to stop operation in order to add solvents or thinners. Equally important is that VOC emissions are cut by at least 90%, suppliers say. The drawback is that sealed ink cups are limited in the size of image they can print under 4.5-5 in. diam., while conventional linear, open inkwells can print images up to 11-12 in. diam.

For this reason, several suppliers offer pad printers with linear inkwells that keep the ink covered except for the few seconds it takes the pad to pick up the ink from the cliche. These models typically have a metal shroud attached to the inking arm that carries the doctor blade and flood bar.

Some suppliers, such as Imtran Foilmark, Printflex, and Trans-Tech America, now offer convertible printers that allow in-plant changeover from a sealed ink cup to an open inkwell within minutes. Some suppliers also offer modular designs that permit converting a single-color machine to a multicolor Unit.

Today, a greater number of pad printers also have stepper-motor drives that provide more precise image-to-image registration than standard pneumatically driven machines. Higher speeds are also provided by the latest printers with sealed ink cups and covered inkwells: They're typically capable of 1800-3600 cycles/hr, although some models provide up to 7000 cycles/hr. Traditional open-inkwell systems run at up to 1400 cycles/hr.

Even more recent are microprocessor controls that bring full programmability to the printing operation, greatly simplifying troubleshooting and easing integration of in-line automation.

Yet semi-automatic, single-color machines are still big sellers for custom molders and decorators whose short runs don't justify full automation. These processors value simpler machines that allow quick changeover from one part to another.

Due to its ability to handle curved shapes and irregular surfaces, pad printing is also finding use in non-ink "functional printing" applications, such as applying lubricants, conductive agents, adhesives, or special coatings on electronic and biomedical parts.

Screen Printing

Six- to eight-color in-line screen printers capable of handling all types of bottles, tubes, and jars at higher speeds are representative of today's new equipment. Machines that use uv-curing inks now account for over 50% of all systems sold, particularly for CDs and debit or "smart" cards. UV ink curing is safer, faster, and generally a fraction of the cost of conventional hot-air drying tunnels. UV-curing speeds can be 6000-7000 cycles/hr versus 3000-4500/hr for hot-air curing. UV curing also does not require skilled operators and is a big space saver (i.e., 4-6 ft versus 25 ft for a hot-air tunnel with 10-ft drying chamber). UV reportedly also provides very high-resolution images, good chemical resistance, and a high-gloss finish.

Solvent-based inks continue to be used in applications such as cosmetic packaging, since the product ingredients tend to attack the imprint. Research is under way to develop a UV process and inks that will provide good adhesion to difficult substrates like polyolefins, acetal, and other engineering thermoplastics.

Dry-Offset Printing

Demand for sophisticated graphics and multicolored logos from the container and promotional cups markets have resulted in the advent of six-, eight, and even 10-color dry-off-set printers. Whereas it used to take four to five hours to set up five- or six-color jobs, new quick-plate-mounting processes reduce set-up time to an hour. Consequently, there is now interest in moving up to five and six colors (from the more typical three or four) for custom applications such as pen barrels decorated with cartoon characters.

Another key trend in dry-offset equipment for tapered containers and tubes is turnkey packages that include automatic handling, flame or corona pre-treatment, printing, drying, and packaging. Maximum speeds of today's dry-offset printers reach 550-600 parts/min as compared with 300-350/min for older units. Most new machines use on-mandrel uv curing and microprocessor controls that store registration parameters of each job, thereby allowing faster set-up and changeover. Demand is also increasing for uv clear overcoating in-line with printing to protect the imprint and give a high-gloss finish.

Special Processes

Although screen printing has largely taken over decoration of CDs since the late 1980s, two new approaches are emerging for both CDs and the new DVDs (digital video discs).

One alternative is systems that combine dry-offset with screen printing. Although costing $100,000-150,000 more than fully automatic CD screen printers, the new combination systems use waterless photopolymer plates that allow production of photographic images with much higher resolution (350 dots per in. versus 120-125 dpi in the past) and can print multiple colors at outputs of 60-90 discs/min. Screen-print heads are typically used for the white background, titles, and protective clear coat, while the offset heads are used for the process-color decoration. A combination machine can also be used as a full dry-offset or two- to three-color screen printer.

In addition to the two current suppliers - Dubuit and SM Graphics - Printex Div., Pemco Industries, San Diego, will soon launch a combination offset/screen printer for CDs.

A newer alternative is a rotary letterpress unit adapted to print on plastic discs. Introduced by Apex Machine Co., Ft. Lauderdale, Fla., it uses reverse-reading plates for dot-on-dot printing of photographic images with high resolution. The system is typically configured as a four-color, continuous-motion printer that applies basecoat and overcoating with uv curing at up to 100 parts/min. Two models utilize inexpensive water-wash photopolymer plates that are mounted with an off-line registration system, which reportedly allows four-color jobs to be changed in less than 5 min. Price ranges from $400,000 to $800,000, depending on number of colors and whether in-line overcoating is required.

RELATED ARTICLE: Gallery of New Printing Equipment

Pad Printers

Autoroll Machine Corp., Middleton, Mass. - Padflex 3000 sealed-ink-cup machine does multicolor printing on up to six cups at 40 cycles/min. Has microprocessor control with RS-232 serial port and touch-display operator interface.

Soon to be launched: pad printer for photographic images on CDs at 100 parts/min.

Diversified Printing Techniques, Charlotte, N.C. - Perfecta Series (PP-300 PFC and PP-350 PFC) printers have programmable up/down stroke and in/out positioning for printing on large parts. Max. print area per color: 280 mm diam. x 750 mm long for PP-300 and 800 x 800 mm for PP-350. Prints two to five colors at 900-1300 parts/hr. Enclosed ink trays reportedly reduce VOCs by 70%. Stepper motor drives pad in/out stroke and shuttle movement.

GS-125-2C will soon be launched as a two-color upgrade to the GS-100 model. Will be able to shuttle either pad or parts.

Imtran Foilmark, Inc., Newburyport, Mass. - GS-200S convertible vacuum/pressure, single-color printer has sealed ink cup or open inkwell. Programmable stepper-motor drive can stop in varying locations on the print plate; stroke is independent from station to station. With a programmable shuttle indexer, each station has independently adjustable length of stroke and x-y positioning of artwork. Registration to within [+ or -] 0.001 in. is adjustable from the touchscreen controller.

Markem Corp., Keene, N.H. - Model 596 multicolor and 590 single-color printers have sealed ink cups and programmable touchscreen controls. Up to 10 set-ups can be stored for instant recall. Closed-loop microprocessor control of ink cups with stepper motors provides repeatable print accuracy to [+ or -] 0.0005 in. Max. print areas: 4 x 6 in. for model 596 and 1.25 x 1.5 in. for model 590. Speeds: up to 30 cycles/min for model 596 and 100/min for model 590.

Printex Div., Pemco Industries, San Diego - Transverse Cup Printer has a sealed cup (4.5 to 6 in. diam.) and wide-format plate that prints up to 24-in.-wide images on rulers and medical tubes. Plate is 6 in. deep so two parts can be printed at once. Prints cups up to 6 in. diam. at up to 1000 cycles/hr.

COS-100/4S four-color sealed-ink-cup machine has programmable servo-shuttle. It is for short and medium runs and multicolor work at up to 600 parts/hr. Comes with four 4-in. cups and 9.4 x 18 in. plate format. Precision linear indexer has x-y/r table and index accuracy of [+ or -] 0.001 in. end to end.

Printflex, Inc., Germantown, Wis. - Colorsafe series with enclosed inkwells has four models with speeds of 1400-3000 cycles/hr. Prints up to four colors on round objects from 1.6 to 4.7 in. diam. and rectangular parts from 3.1 x 1.0 in. to 6.3 x 2.4 in.

Colorseal series with sealed ink cups has four models with speeds of 1200-3000 cycles/hr on rectangular, round, and oval parts. Sealed ink cups (including oval version) available up to 6 in. diam.

Both series have microprocessor controls and pneumo-mechanical drives with independently adjustable plate and printing stroke.

Trans-Tech America, Inc., Carol Stream, Ill. - Carousel 80 is a totally electromechanical, sealed-cup printer for one to five colors. Prints single colors at up to 3600 parts/hr and four colors at over 700/hr. Each color cliche can be individually micrometer adjusted in x-y-z axes for accurate registration, regardless of indexer used.

Ecoprint 90 is an automatic, pneumatically operated, bench-top, sealed-ink-cup machine for short to medium runs. Prints up to 1800 cycles/hr.

TampoPrint International Corp., Vero Beach, Fla. - Two modestly priced, pneumatically driven, sealed-ink-cup printers are Model 60 with a 60-mm-diam. cup ($6000) and Model 90 with 90-mm cup ($9000). Print up to 800 cycles/hr.

United Silicone, Inc., Lancaster, N.Y. - Model UP 450 semi-automatic machine has covered inkwell. It prints on flat or complex shapes and at least 90 [degrees] of circumference on cylindrical or spherical parts. Accommodates up to four colors through split-inkwell configuration. Prints up to 2000 parts/hr. Quick-lock cliche positioning reportedly allows fast changeovers.

Model UP 303 single-color, semi-automatic unit is smallest in company's sealed-cup line. Prints up to 2000 cycles/hr. Sealed ink cup includes spring-loaded holder to provide consistent cliche doctoring. It also has an assembly device that reportedly makes changeover easy.

Both models have DSP microprocessor controller with self-diagnostics and flexibility for expansion.

Screen Printers

Dependable Machine Co., Cedar Grove, N.J. - RP9 and RP12 are linear, automatic, walking-beam-transport systems for bottles and jars. RP9 prints full-wrap on gallon containers at 3200 cycles/hr. RP12 prints 4-in.-diam. containers at 4200-4500/hr. Both come in one or two color versions with in-line registration, which allows printing up to four colors via two passes on each machine.

RP3-MI is an indexing machine for jars, tubes, and bottles of less than 4-in. diam. Speed: 3600-3800 cycles/hr. A variant is model RP3-TO, a semi-automatic unit that prints a color on two sides of oval containers in one pass at 1000-1100 cycles/hr. Another variation is RP3-HS that converts the RP3 within 10-15 min to a banding hot stamper.

MS-1050 from M.O.S.S. of Italy is a fully automatic, two- to eight-color machine available with various loading systems and with on-mandrel lacquer coating plus conventional or uv on-mandrel lacquer drying. Prints on flat, round, or oval forms at up to 6000 cycles/hr.

Diversified Printing Techniques, Charlotte, N.C.- Kent multicolor series prints up to six colors in one cycle with uv inks. Fully automatic printing on cylindrical, rectangular, or flat parts. Model KSP-030 prints up to three colors at up to 350 parts/hr; KSP-040 prints up to four colors at 170/hr; and KSP-060 prints up to six colors at 140/hr.

Dubuit of America, Inc., Niles, Ill. - S.P.ACE universal automatic machine prints on oval and cylindrical containers at up to 4500 parts/hr. Features include quick changeover, bottle orientation, flame treating, uv curing. Modular design comes in one- to six-color in-line versions.

Screen Tech Inc., Oakville, Conn. - Proflex R25 fully automatic unit for small cylindrical parts (i.e, caps, jars) prints up to 6000 parts/hr at max. screen size of 26 x 12 in. Includes 12-station Camco rotary indexing turntable that's mechanically driven and timed to the screen stroke.

Proflex R15 automatic rotary unit is for 3-D printing on flat and cylindrical parts at up to 2700 parts/hr. Comes in horizontal or vertical dial configurations with one to three colors. Operates in standard or reverse registration.

Optima 8.0 semi-automatic, rotary-table machine has microprocessor control of all functions. Designed for shorter runs. Prints on flat and cylindrical parts at up to 2250 parts/hr.

SM Graphics International, Inc., Markham, Ont. - Novamax automatic high-speed printers from O.M.S.O. of Italy handle cylindrical, oval, and flat bottles of 20-120 mm diam. and 40-320 mm height. Units print and transport two containers simultaneously at outputs up to 10,000 parts/hr. Standard features include mechanical transport system, flame treatment, "no bottle/no print" safety function, mechanical pre-registration for up to five colors, and intermediate and final uv drying.

Systematic Automation, Bloomfield, Conn. - Model NCC rotary indexing unit with computer control prints one to 12 colors on 3-D shapes at up to 3500 parts/hr. Fully modular design allows easy customization with automated secondary operations. Changeover is performed quickly without tools.

RC series are entry-level, semi-automatic, rotary indexing units. They print one to 12 colors on 3-D shapes at 2500 parts/hr.

Model T-4 is a single-or dual-color, servo-driven machine for use in-line with injection molding. Speed: Up to 1800 parts/hr. Robot transfers part from molding machine to printer and then to a conveyor.

Dry-Offset Printers

Apex Machine Co., Fort Lauderdale, Fla. - Model C-500 six-color printer for industrial and cosmetic tubes automatically feeds, pretreats with flame or corona, prints the full length of tube, uv dries, applies full uv overcoating, assembles cap, and delivers tube to filling station.

Kase Equipment Corp., Willoughby, Ohio - Kase 908 sidewall printer for dairy cups and containers is a nine-color unit that can reproduce line, halftone, or process printing. Reportedly allows maximum flexibility in color separation for printing up to 500 parts/min. Automatic job memory provides quick set-up and repeatability. Electronic motion-control system is interfaced with the main PLC. Plate-cylinder and print-tower adjustments are computer controlled.

Polytype America Corp., Union City, N.J. - Model CP-250-12 for large cylindrical containers (i.e., 1.5-gal paint cans) prints in register with the container handle at up to 60 parts/min. Prints six to eight colors, including varnish coat with on-mandrel uv drying. Has automatic container infeed and quick discharge to a conveyor belt.

Model BDM-611 high-speed, eight-color, fully automatic sidewall printer for round dairy containers can decorate 8-oz (2-3 in. diam.) containers at 600/min. Handles cups up to 6 in. diam.

One of two new lid printers for ice-cream containers is Model DDM-150, which prints up to six colors on tops of deep-skirted lids. It automatically feeds Model SKP-S200, which prints lid sidewall in up to four colors. Combined output is 260 lids/min.

Van Dam Machine Corp., West Paterson, N.J. - Model 5610 Com III 10-color automatic cup printer offers on-mandrel uv curing and speeds up to 550 parts/min. Prints up to 8-in.-diam. cups.

For short runs, model S65 eight-color printer features off-line ink preparation and quick-change units for ink supply, as well as off-line plate registration. Changeover reportedly can be achieved in 20 min.

Offset/Screen Printer Combos

Dubuit of America, Inc., Niles, Ill. - Model 528 for process printing on CDs has three screen-print heads for the white background, titles, and clearcoat, as well as four offset heads for process printing and intermediary curing to keep colors from mixing. Flat instead of rounded cliche reportedly provides quick and easy changeover and resolution up to 350 dpi. Prints up 60-70 discs/min. Can also be used as independent three-color screen printer with speeds up to 3600 parts/hr.

SM Graphics International, Markham, Ont. - O.M.S.O. Novadisc series for audio CDs and CD-ROMs has speeds up to 90 parts/min. Off-line registration provides fast changeover. Registration error is claimed to be effectively zero between offset colors. Each screen-printing station has a mechanical cam that engages the disc holder prior to squeegee motion. This arrangement reportedly ensures registration between screen heads and between screen heads and the offset groups. Offset/screen combination permits using line-screen work together with halftone offset. Can be configured in up to six combinations for a max. of 10 colors - i.e., Model 1441 has one screen, four offset, four off-set, one screen. Also functions as two- to three-color screen printer by turning off the offset portion. Waterless or traditional photopolymer plates (or combinations) can be used.

By mid-year, the company will have a commercial dry-offset/screen printer for tubes that will use waterless plates.