The name “heat transfer” has become a generic term referring to a preprinted image applied to a product using heat and pressure to transfer the image off a carrier to a product. There are different ways to print a heat transfer, including gravure, flexo, screen or digitally printed transfers. Plastics Decorating recently sat down with CDigital’s director of sales and marketing, Eric Steinwachs, to discuss the applications for heat transfers, application challenges, new transfer processes and hot markets.
How do you determine which applications work best?
The common determining factors in choosing a method of printing the transfer include the quantity needed of each artwork, time to market, number of colors and end use of the product.
The general rule of thumb is gravure- and flexo-printed transfers are for the highest volume. Next would be screen printed and finally, digitally printed transfers. The startup cost for plates or screens also follows the same order from highest to lowest.
Another factor in choosing the best printing method to produce the transfers is by the number of colors. The gravure, flexo and screen printing methods of printing heat transfers require each color to be applied one at a time with a cylinder, plate or screen for each color and another for a topcoat and adhesive applied to the film or paper. For digitally printed heat transfers, the artwork is electronically sent to the press, thus eliminating the need for expensive startup tooling cost and allowing for variable data, barcodes or serialization.
The time to market has become a bigger issue of late, with supply chain problems causing even longer than normal lead-times. Again, listed from longest to shortest above, gravure would be the longest and the digital would be the shortest lead time. Without the need for any of the plates or screens for a digital print, lead times can be as short as two days rather than months with other printing methods.
Lastly, cost per image always is a consideration. Startup cost and number of transfers required per image all have a crossing point where one process becomes a lower cost than the other. In some cases, the cost may be overlooked depending on decision criteria, time to market or finished look of the product. It is common for a new product launch or startup quantities to be printed using one method and switched to another as the volume increases.
What are the advantages of heat transfers?
Because heat transfers are a “dry process,” meaning the decorator is not the one printing with inks and solvents, this takes the burden of printing out of a production facility. Facility personnel are applying a dry, pre-printed image, usually with no pre- or post-treatments required. Compare this to pad printing or direct screen printing to a plastic part, when each color is printed separately and adds to the possibility of a printing error. The process is automation-friendly and typically faster than direct printing of multi-color images. Colors are all applied at one time, and the image is dry to the touch right after the application has occurred, eliminating the need for stacking or racking a bunch of parts while waiting for full drying time to occur before moving on to the next step in the process.
What challenges occur when applying heat transfers?
When looking at the best decorating process to choose, many factors come into play. These include the design and shape of the part, texture of the surface, image size and location, production rate and the accuracy of the image location on the part. If the process is understood, issues can be eliminated up front when designing the part:
- A smooth or only slightly textured part is preferable when choosing heat transfer.
- Does the image need to be applied around a raised area, like a knob, or in a recessed area? Heat transfer may not be the best choice for a situation like this, but can be done if the transfer can be diecut.
- Is the part to be printed a ball-shaped or multi-angled part? If so, a quick test is to lay a piece of paper down flat in the area to be print. If the paper wrinkles, it may not be possible to apply the image using heat transfer.
Oftentimes, the decoration is not thought of ahead of the design. In cases like this, reaching out to a sales engineer or technical representative may be the best route.
Are there new processes or updated technologies to apply heat transfers?
Besides the traditional methods of applying a heat transfer, like vertical stamp, roll-on and peripheral, there is a new pad transfer process. The pad transfer has the motion and design of a pad printer with web-indexing capabilities. Instead of the silicone rubber pad going back to pick up ink, the pad goes back and picks up heat. Then the pad sits on a heated platen in the back position and, when it comes forward, the pad conforms to the shape of the part to apply heat to the surface, thus transferring the image to the plastic. This type of machine allows for different-shaped products to be decorated without the expensive cost of contoured dies and tooling. This is popular in the promotional product industry where a wide variety of product can be decorated on one machine.
What are current “hot markets” for heat transfers and where are growth potentials for the plastic industry?
Digitally printed transfers have seen growth in several areas. During the height of COVID-19, there was a dramatic increase in hand sanitizers and soap dispensers. In addition, there was an increase in medical tubes with uniquely printed barcodes and images applied simultaneously. The medical and recreational marijuana packaging business is another hot market, looking for eye-catching graphics with full-color branding as well as required warning information printed on the containers. With the number of smaller dispensaries and shops with unique logos that require lower volumes, it becomes a good fit for digitally printed transfers. And, I see increased activity in companies looking to move the supply chain for manufactured prodcuts and transfer supplies to North America. It’s all very encouraging and a trend we hope continues.
Eric Steinwachs has been in the plastics decorating industry for 28 years with a focus in heat transfer, pad printing and hot stamping. His current position is the sales and marketing director for CDigital, a leading global supplier of digitally printed heat transfer film. Steinwachs can be contacted at firstname.lastname@example.org, 630.817.5227 or www.cdigital.com.