Digital printing technology is highly varied, and depends greatly on the formats and applications one wishes to achieve. That said, the technology most widely used today is inkjet printing.
Within this segment there are printers that use different inks, different ways of moving the print heads across materials or the materials under the heads, different ink drying methods, and different material sizes that can be fed into the various machines.
For now we will set aside explanations of the various ink types available — a topic that will better define this subject in a future newsletter — and instead focus on the types of machines, their names, and how they differ in their suitability for different materials.
Roll-to-Roll Printers: as the name suggests, this type of printer can print roll media and output printed rolls. These printers range from minimum print widths of 137cm or even less, up to 5 metres for machines currently on the market. They are used to print roll-based materials such as self-adhesive films, "PVC" banners (we will see in the materials chapter that this term is used loosely), synthetic or natural fabrics, and almost anything that comes in roll form. They typically feature a media feeding system — we will call it media for convenience — similar to a wringer, over which a print head carriage travels, covering the unprinted area with each pass while potentially overlapping previously printed sections. These printers range from near-photographic image resolution, to the point that some are used for certified photographic reproductions, to machines capable of producing 500–1000 m²/h, albeit at varying quality levels. Materials must be flat and must feed uniformly under the rollers without wrinkling or rippling in a way that could make contact with the print heads.
Flatbed Printers: these are printers typically built around a table similar to a CNC machine, but instead of a bridge with cutting tools, they have a bridge carrying a print head unit. Flatbeds come in two main types: moving-bed with fixed head bridge, or fixed-bed with moving head bridge. The former generally occupies twice the floor space of their fixed-bed counterparts but often achieves higher quality relative to their output, while the latter (slightly more commercial) take up less space but still maintain strong quality, albeit at a somewhat lower throughput. The materials typically printed on these machines — as their design implies — are sheet-based rather than roll-based, flexible to varying degrees, but not truly rollable and with a rigid feel. These materials must be uniformly calibrated and non-porous, both for printing purposes and for secure vacuum-pump anchoring to the bed. Some of these machines reach 200 m²/h, though machines capable of 2,000 m²/h have been produced, with quality suited to supermarket-style packaging.
Hybrid Printers: these are printers capable of printing both roll media and rigid sheet materials. These machines came about for commercial rather than technical reasons — to allow operators to cover both needs with a single investment. Naturally, this means their performance figures are nominally lower than specialised machines, though technology has advanced to the point where some genuinely capable hybrids are on the market. They come in two types: flatbed machines adapted for roll-to-roll printing, and roll-to-roll machines adapted to also print rigid materials. The former typically have a bed completed with unwinding and rewinding rollers for virgin and printed media respectively, sometimes also featuring a conveyor system to guide material through the transition; the latter mount flat support tables in front of and behind the rollers to guide rigid sheets through when not printing flexible roll media. The first type is clearly better suited to rigid applications while remaining capable of handling flexible when needed, while the second type is better suited to flexible media but can handle rigid when required. In the second case — and in most hybrids generally — the inability to firmly and precisely fix media to a flat surface can cause difficulties in repositioning multiple print passes or ink layers accurately, which matters for relief or textured effects; though here too, technology (and more often skilled operators) have found ways to work around these limitations.
Next time we will discuss inks and their "specialities", and how they are typically paired with different technologies and why.
I hope this has once again given you some food for thought.
Until next time.
