October '15

For the Business of Apparel Decorating

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86 || P R I N T W E A R O C T O B E R 2 0 1 5 Screen Printing Both drive systems use air cylinders to raise and lower the mechanical engagement of platens to screens. Air cylinders do a good job of accelerating during the index, but have difficulty in the deceleration phase. In fact, most systems use some form of external mechanism to assist in the deceleration of the inertial load created by the weight of the platen arms. How the drive handles the de- celeration is the biggest difference between a pneumatic and a servo. A pneumatic system uses less-expensive hardware than a servo system so it costs less, and it also is easier to repair. In fact, many printers can do the repairs themselves. A servo system is more expensive and general- ly requires a technician to repair it, so repair costs are higher. The advantage of the servo drive over the pneumatic is performance. A servo drive adjusts to changes in conditions. You can change out the platen from a sleeve size to a jumbo size with no mechanical adjustments. The servo automatically adjusts itself based on the platen size selection. With a pneu- matic drive, you would need to adjust the press to accommodate the different platen and/or job weights. Although pneumatic indexing has become more sophisticated over the years, it still requires the turning of a knob or a screw. TYLER DUMMETT, WORKHORSE PRODUCTS I have some unwanted wa- ter-based ink on my garment; can I remove this somehow? Fill your spot gun with water and blast the unwanted ink as you would plastisol. This should remove the water-based ink, even after it cures. JAKE FRANKS, RYONET I'm shopping for a dryer. What are the pros and cons of gas versus electric dryers for screen printing? Gas and electric dryers offer different advantages depending on budget, required capacity, available floor space, and the cost of gas versus electricity. Gas dryers have an open flame that heats air within a chamber and transfers the heat- ed air to the area the garments pass through. The heat is then transferred to the ink by air convection. This is the equivalent to heating food slowly in a gas oven. An electric dry- er, by contrast, uses infrared radiation that causes the ink molecules to vibrate, generat- ing heat that rapidly raises the temperature of the ink without heating the air around it, akin to heating food in a microwave. The primary advantage of a gas dryer is its ability to maintain a constant tempera- ture and avoid overheating of the ink. Pri- mary disadvantages are dwell times of two to three minutes to heat the ink, and long dryer lengths that increase capital cost and consume floor space. Addition- ally, thick insulation is needed to pre- vent the outer walls from attaining dan- gerous temperatures. As a result, gas dryers are generally recommended for large print shops, providing that natural gas or pro- pane is available and less expensive than electric is locally. By comparison, infrared conveyor dryers are smaller and less expensive because they do not require insulation, and are shorter in length due to reduced dwell times since infrared radiation attains ink curing tem- peratures more rapidly and efficiently than heated air—particularly when curing plas- tisol inks. However, if items are conveyed through an infrared dryer too slowly, the ink can overheat and break down chem- ically. Infrared conveyor dryers are also expandable, which can increase productiv- ity by adding one, two, or three heating chambers, in addition to lengthening the conveyor and increasing its belt speed. MARK VASILANTONE, VASTEX INTERNATIONAL Should I use a screen regis- tration system? The benefits of a registration system are immediate, significant, and indisputable. Screen printers only make money when presses are running. A good registration system in the hands of someone who knows how to use it can reduce on-press registration time from 50 to 95 percent. The benefits of a screen registration system are even more obvious for screen printers who own or are considering a direct-to- screen imaging or imaging/exposure sys- tem. Since those systems use digital images instead of film, most are capable of gener- About half of all automatic presses on the market are pneumatic drives while the hald are servo. (Image courtesy Workhorse products) Q & Q & Q A & A &

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