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Applying Variable Data with Digital Thermal Transfer Marking

by John Kaverman

Pad Print Pros, LLC

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What is "variable data marking"?

Variable data marking is marking each successive part, or series of parts, with a different image. Examples of variable data include images such as expiration dates, serial or other progressive numbers, bar codes, 2-dimensional matrix codes or QR (quick response) codes, people’s names or company logos.

What is the difference between "marking" and "decorating"?

The terms "marking" and "decorating" rarely are synonymous. I’ve learned that most processes are better suited to one or the other, not both. I consider a marking to be more functional and less aesthetic, and a decoration to be more aesthetic and less functional – the exception being for the purpose of branding, which must be both functional and decorative.

Which processes are suitable for variable data marking?

Digital thermal transfer, laser engraving and inkjet.

What aren’t screen printing, pad printing and hot stamping suited for applications requiring variable data?

Screen printing, pad printing and hot stamping are not typically cost effective methods for applying variable data because they require a unique stencil (screen), cliché plate or die in order to transfer an image to a product. To apply variable data and make a profit, you would need to amortize the cost of an image-specific screen, cliché plate or die into the cost of every part. While there are pad printing systems that are capable of laser engraving reel-to-reel cliché materials "on demand" and hot stamping dies that can accommodate simple progressive numbering, their cost effectiveness versus digital-based processes like digital thermal transfer, inkjet and laser engraving are negligible at best.

What is digital thermal transfer marking?

Digital thermal transfer is similar to, but not the same as, hot stamping. While the final application to the product is essentially the same, the method of generating the actual image is completely different.

The digital thermal transfer process is different in that it doesn’t require any image-specific dies or pre-printed transfers. The digital thermal transfer process uses heat energy in two ways: first to transfer a digitally generated image from a single colored "inked ribbon" to a receptor ribbon, and then again to transfer the image from the receptor ribbon directly to the object.

What are some popular applications for digital thermal transfer marking?

In Europe, digital thermal transfer marking widely is used for marking labels and tags such as those used for product safety, serializing, tamper-proof seals and tracking and anti-theft labels. Examples of products that utilize digital thermal transfer marking include disposable medical devices such as vials, syringes, pipettes, filters, I.D. bracelets, bandages and compression stockings; dental products such as tooth brushes and dental floss containers; food and beverage containers and electrical components such as relays, circuit breakers, small chargers and transformers.

Other product examples include wire and cable housings, hoses, pens, pencils, brushes. Many other extruded products can be marked using the digital thermal transfer process, as can the small cardboard boxes, blister packs, tubes and containers used in the short-run cosmetic and homeopathic product packaging.

What are some limitations of the digital thermal transfer marking process?

Digital thermal transfer marking normally is limited to a single color. Additionally, just as with foils in hot stamping, the inked and receptor ribbons used in digital thermal transfer need to be matched with corresponding substrates for best results. For example, there are specific ribbons for marking gloss or matte cardboard cartons, smooth wood, fabric or leather, soft rubber, vulcanized rubber, PVC, ABS, PC, painted surfaces, PE, PP and PA.

Marking speeds are adjustable up to 90mm per second, so the process isn’t screaming fast; but then again, for short-run applications, it probably doesn’t need to be.

It is important to understand that digital thermal transfer marking systems cannot utilize conventional hot stamping foils. Thermal ribbons are available exclusively from the manufacturer of the thermal transfer marking machines.

What colors are available?

While there are a wide variety of metallic and colored ribbons available for most substrates, some less frequently used ribbon types have a limited color range. Custom colors can be formulated upon request. Ribbons typically come in 500-meter-long rolls, in widths varying from 30mm to 95mm depending upon the application.

What kind of resolution is available?

Standard resolution is 300 dpi, which is adequate for most marking applications. Optionally, 600 dpi resolution is available.

How much do typical digital thermal transfer systems cost?

The thermal transfer marking systems that I researched in writing this article were Italian-made and varied in price from just under $20,000 to just under $30,000, depending upon the model, image size requirements and optional accessories.

The systems also interface with external PLC controllers, making integration into existing production lines/retrofitting of hot stamping heads relatively painless.

What type of operating environment does digital thermal transfer require?

Digital thermal transfer printing is designed for use in industrial production environments, with temperatures ranging from as low as 45F to as high as 105F and relative humidity between 10 and 75 percent. As such, it is not nearly as sensitive to fluctuations in temperature and relative humidity as wet ink film transfer processes like screen and/or pad printing.

How does digital thermal stack up versus other processes in the US?

While the use of two thermal ribbons leads to slightly higher operation costs as compared to conventional hot stamping, the cost largely is offset by the flexibility of the process and the fact that you don’t have to create and/or inventory any screens, cliché plates, pre-printed transfers or dies.

When I shared this technology with several hot stamping, heat transfer, laser and label equipment manufacturers at the SPE Decorating and Assembly Division TOPCON last year, attendees seemed to agree that this technology has a unique niche in the US market.

Summary

As a consultant specializing primarily in the pad printing process, clients frequently inquire as to how they can cost effectively apply unique names, logos, serial numbers, codes and other information to a single part – or to lots of less than a few dozen parts. Prior to my exposure to digital thermal transfer marking, I could only recommend inkjet, laser marking or adhesive labels. Now, I can recommend a new method that enables manufacturers to really differentiate their product from those of their competitors – digital thermal transfer marking.

John Kaverman is president of Pad Print Pros, an independent consulting firm. Kaverman, who holds a degree in Printing Technology from Ferris State University, has nearly 25 years of experience in the plastics decorating industry. He can be reached via email at padprintpro@gmail.com or online at www.padprintpros.com.