Avoiding problems early on in your color separations will cascade down into gains at every step of the screen-printing process.FULL STORY
Screen Printing: Production
Textile Dryer Basics for Screen PrintingIs your screen-printing shop ailing from confusion when it comes to what to look for when buying a dryer? Follow these tips for the cure
A thermal probe has a long lead wire with a “donut” attachment that supports the conductive wire that runs to the heat sensor. Photo courtesy of International Coatings
Buying the right textile dryer in the decorated apparel industry comes down to three factors: choosing a reputable equipment manufacturer; basing your purchase on your shop’s realistic production capabilities; and buying a larger-than-needed dryer to allow for future production growth. The latter is important because the last thing you want to do is outgrow a newly purchased dryer in six months.
A colleague of mine once said the conveyor dryer is the most important piece of equipment in a screen-printing shop, and I agree. It doesn’t matter how many bells and whistles your screen-printing press has if the dryer can’t keep up with production. There are many ways to increase production speeds with an automatic or a manual press, but there’s only one way to cure the ink on the garment properly: Buy the appropriately sized dryer for the job.
To determine the optimal oven length needed for your shop, break things down into simple terms and do the math. If the ink manufacturer recommends a 60-second drying cycle, figure out how many printed garments fit into the oven section at one time. Next, multiply this number by the amount of cycle times that will fit into an hour.
For example, with a 6-foot oven section, if six shirts fit in the oven chamber at a time for a one-minute dry cycle, the dryer can produce 10 cycles, or 60 garments, per hour.
If production requires the need to cure 120 garments per hour, then consider upgrading to a dryer with a wider oven section that will hold 12 garments at a time, multiplied by 10 drying cycles, which means you can cure 120 garments per hour. Buying a dryer with a longer oven section is another option to increase production speeds, but I prefer a wider oven and belt because of the flexibility gained, especially when loading 2XL and 3XL garments.
Many screen printers make the common mistake of speeding up the dryer belt to keep up with production; this is a recipe for disaster because the ink will not properly cure. Furthermore, it likely will result in the customer returning the product and lost revenue for the shop.
Electric vs. Gas Dryers for Decorated Apparel
The two main types of textile dryers are electric and gas. Electric infrared (IR) heat is considered a “radiant” heat source and typically is used in small to mid-sized shops. Belt widths range from 24-36 inches, with 4-foot or 6-foot oven sections, depending on the model.
Generally, model numbers reflect an electric dryer’s size. For example, model 2408 indicates a 24-inch-wide belt and an 8-foot overall length from end to end. Model 3610 indicates a 36-inch-wide belt with an overall dryer footprint length of 10 feet.
Research a dryer’s oven-section length and electrical requirements on the manufacturer’s website before purchasing it to ensure your shop has the necessary space and electrical or gas requirements for this important piece of equipment. Also, check to see what size door opening the dryer requires. I’ve gone to shops to install dryers, only to discover they won’t fit through the shop’s door.
Gas dryers use convection heat or forced hot air and are available in 36-, 48- and 60-inch belt widths — up to 72 inches wide — with 8- or 12-foot oven sections. These types of dryers commonly are used in medium to large screen-printing shops.
In the 1970s and 1980s, there was an abundance of large 48- and 60-inch-wide electric dryers in the field, but the cost of utilities required to run these high-amperage dryers became excessive. Gas-dryer sales surged in the 1990s, and this still is recognized as the most economical dryer type to use in high-production environments.
Some manufacturers also offer electric IR/convection dryers because of the recent interest in printing with water-based ink. Several dryer manufacturers in the United States have upgraded their air-flow systems on electric dryers to accommodate this type of printing.
When drying water-based inks in a small electric dryer (with air), the belt speed needs to be slower and, in some cases, the garment will require a second pass. In this case, always conduct wash tests when curing water-based inks in a small electric dryer to ensure the ink is fully cured.
Types of Heat
Infrared waves are located on the electromagnetic spectrum scale that extends from the visible light region. A good example of infrared heat is burning charcoal; although it may not give off light, emits a glowing red cast of infrared radiation, which is felt as heat.
Infrared dryers are equipped with either IR ceramic heat panels, electrical rods or quartz infrared tubes, all of which are ideal for curing plastisol ink.
With gas dryers, air is heated with a gas burner, collected in the dryer’s air plenum, then forced onto the garment’s surface with blower motors, flowing though air knives or nozzles. Convection heat is efficient for curing both plastisol or water-based inks, since the forced hot air removes the moisture from the garment, making it easier to fully cure the ink on its surface.
Profiling a Dryer For Apparel Decorating
With the advent of screen printing on performancewear, tri-blends and 100% polyester garments came the need to precisely control oven temperatures to avoid scorching and dye migration when printing on these heat-sensitive fabrics.
Excessive dryer heat — temperatures higher than 300˚F — causes the polyester fabric to “gas out” and release dye from the garment through the sublimation process. This dye-bleeding issue has fueled the need for low-cure inks in our industry. Keeping polyester garments below the 300˚F melting point is the key to reducing dye sublimation.
The best way to profile or “map” a dryer is by using a thermal temperature probe to test its accuracy. The thermal probe has a long lead wire with a “donut” attachment that supports the conductive wire that runs to the heat sensor. When using this device, remember the following:
- The crosshair wires on the donut probe should be embedded in the ink on the garment and cycled through the dryer.
- The digital display will show the rise in temperature as the donut probe passes through the oven section.
- Write the temperature — after every 2 feet the probe travels on the dryer belt — on graph paper. The result will be a chart that indicates at which point in the oven the garment reached the necessary cure temperature. If the cure temperature isn’t reached, make adjustments by either raising the oven temperature or slowing down the conveyor belt.
Textile dryers have become more sophisticated since the days of the old percentage timer-type heat controllers that would cycle the heaters on and off, regardless of whether there were garments in the chamber. Today’s dryers can be purchased with many high-tech features, including internal heat sensors that monitor the garment’s temperature as it passes through the oven; split belts that allow two different ink types — with different cycle times — to run side by side; audible alarms when the oven temperature drops below the desired setting; and more.
Doing advance research and following these tips will point you in the right direction and help you make the right decision when you are ready to buy the most important piece of equipment in your screen-printing shop.
James Ortolani has more than 30 years of experience in the decorated-apparel industry, specializing in hands-on, direct screen printing and heat-transfer production. For more information or to comment on this article, email James at email@example.com.
Article updated Oct. 25, 2023
Dryer or Oven for Screen Sprinting
There’s an age-old debate in our industry regarding the correct terminology to use when referring to textile-curing equipment. Is it an oven or a dryer? Truthfully, it can be called both, depending on the ink type being cured.
To get a full cure with plastisol ink, a resin is melted during the heating process — no forced air is needed. In this case, the equipment is functioning as an oven. However, when curing water-based inks, the unit truly acts as a dryer because it evaporates the water from the ink.
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