- September 27, 2013
“What impact do you think 3-D printing will have on the converting industry—if at all?” PFFC Editorial Director Yolanda Simonsis asked this question on her blog recently.
As a 3-D printing enthusiast, I have pondered this question often. It opens new possibilities because:
- It allows us to do things we couldn’t do before, especially shapes. For instance, in the medical field, parts, like hip and knee replacements, can be made specifically for each patient.
- It can slash prototype assembly from weeks to hours.
- The total cost for a few parts can be much less than the set-ups for conventional methods.
The current developments with 3-D printing remind me of the early days of wide format digital printing, except 3-D printing is moving faster. Yet I don’t think it will change our industry much: It won’t change our product mix, nor will it generate new cash streams. The reason? As of now, we work in an essentially two-dimensional world. Let me explain.
The term 3-D printing often covers all layer-by-layer, computer-controlled additive manufacturing methods within a fixed volume defined by the width and length of the base and the height the supporting table or the depositing unit can move. By contrast, converting seldom adds more than three comparatively thin layers on any one machine.
As the list in Table I shows, there are many additive technologies, but only two of them (direct deposition inkjet and inkjet liquid powder binding) use ink and fit our normal definition of printing. Both are versions of inkjet.
Table I. Additive Digital Fabrication Technologies
|Technology||Some Build Materials|
|Material extrusion||Hot melt polymers|
|Laminated object manufacturing||Paper|
|Selective laser sintering||Polymers and metals|
|Electron beam melting||Polymers and metals|
|Shaped deposition manufacturing (deposit and shape)||Polymers|
|Ultrasonic consolidation||Metal sheet|
|Direct deposition inkjet||UV-cured polymers, hot melt polymers|
|Inkjet liquid powder binding||Gypsum, sand, acrylic powder, ceramics, metal|
The main question—one I’m often asked—is, “How can you use inkjet to build the third dimension when its ink has such low viscosity?”
The two methods handle this problem differently.
Direct deposit 3-D inkjet printing uses either ultraviolet (UV)-cured or meltable polymer (wax-like) inks. During the process, both the ink and the printheads are heated to get jettable viscosities. Obviously molten ink will set immediately as it hits a cooler substrate. On the other hand, UV inks see a rapid viscosity rise upon cooling and are cured very soon thereafter.
Direct deposit 3-D inkjet printing needs at least two inks—a build ink to make the actual structure and a fill ink for the spaces that are empty in the finished part. (Without the fill ink part, geometry is very limited—ink can, of course, only be laid on a firm surface.) The fill ink is removed when the printing is complete. Usually the ink is a low temperature wax (hot melt build inks are higher temperature polymers) and a warm oven is sufficient for the process.
For UV-cured, there are many monomer families, to which a useful range of standard thermoforming and casting polymers have been matched. With multihead printers, several plastics can be used in one item to obtain color or tactile effects.
The resolution is quite good as the printheads are typically 300–600 dpi, while layers for different printers range from 0.3–4 mil (7–100 µm) in thickness. The down side to high resolution is slow build speed. A 2-in. (50-mm) tall item needs many hundreds of passes, which makes the technology painfully slow for traditional printers. Therefore, it works best from a business point of view for making high value items, such as prototypes, or highly customized, detailed objects with a special purpose.
The second technology, liquid powder binding inkjet, forms 3-D structures by fixing select areas of sequential layers of spread powder with aqueous polymer solutions, and it does not print the fill volume. The printer has two separate functional activities: powder spreading and powder binding. The final object can be the bound powder, or it may be a mold formed from the cavity left when the unbound powder is removed. Useful powders include gypsum, fine silica sand, PMMA, ceramics, and metal. The last two may be sintered into very strong structures. The devices range in size from small desktops with letter-size footprints to the giant Voxeljet’s VX4000, which has a 4x2x1-m build volume, and 600 dpi printing!
Going back to the question that started our discussion, for 3-D printing to become meaningful in the converting industry, it must allow us to develop new businesses or meet our own material requirements. In our interviews, buyers have stated that, for prototypes, they want to stay with vendors that are already skilled in 3-D design, and for production, with those who know all the performance requirements of the items. They need to trust part vendors at the same level we want them to trust us. As of today, we don’t have the capability that would add value to 3-D parts—if we did, we would be doing it with cast or extrusion molded items already. Furthermore our whole industry’s own needs for customized polymer parts will scarcely keep a handful of printers operating.
The lack of expertise and related capability also means that most of us lack an asset base to establish a new business segment with sales that would complement existing activities. Anyone seriously interested would be advised to set up a totally separate business. So in conclusion, there are good opportunities here, but they are extremely different from the ones we are used to.
There is a variant of 3-D inkjet printing that could work: some conventional wide format UV-cure films and paper inkjet printers can build 3-D patterns up to a millimeter deep. They are useful for embossing prototypes, mold masters, and decorating short run packaging. But none of these consume even modest quantities of substrate or coating fluids and so have no business interest outside of our own consumption, if indeed we use it at all.
Where we should start to see items made by 3-D technologies is in new equipment. Indeed, we might already have parts cast from digital masters. I expect that, as our machine design engineers—following the lead of their colleagues in the aerospace and automotive industries—get more adept, they will begin to use additive technologies with metals to make parts of greater functionality and complexity than the ones they’re making now by traditional molding and milling.
Please contact me for additional reading on this subject.
On Print columnist and printing expert Dene Taylor, PhD, founded Specialty Papers & Films Inc. (SPF-Inc.), New Hope, PA, in 2000 for clients seeking consultation for technical management, new product design, development, commercialization, and distribution, as well as locating/managing outsourced manufacturing. Contact him at 215-862-9434; firstname.lastname@example.org; www.spf-inc.com.