Print takes on a whole new dimension
Simon Eccles visits ArtSystems to see Z Corporation's full-colour 3D inkjet printer in action.
 Imagine using an inkjet to print solid objects in full colour. A few years ago this would have been the stuff of blue-sky articles in ‘Popular Mechanics.’ Today it’s not only technically possible, but fully available: you can slap down £25,000 on ArtSystems’ counter today and they’ll wrap it up a Z Corporation ZPrinter 450 and deliver it. Well, actually they won’t because ArtSystems is a distributor and not a reseller, but they’ll put you in touch with the right people.
3D ‘printers’ called rapid prototyping machines are not new. There are several ways of building up solid three-dimensional objects from digital data on CAD or similar 3D modelling files, usually either by building them up from a series of digitally-controlled slices (originally by stereolithography, ie shining UV lasers onto liquid polymer, solidifying it into a photopolymer), or by carving out a shape in a solid material by using a computer-controlled milling or routing machine.
However Z Corp’s system is particularly interesting because it’s the probably the first commercially available product to print objects in full colour, and because it is so closely related to conventional digital print. Its technology incorporates standard HP inkjet heads and desktop colour ink cartridges.
The process involves printing the object in a series of slices that are built up on top of each other to form the 3D shape. To do this a glue-like binder fluid is printed onto a layer of dry powder that has been automatically applied onto a metal support platen. The binder and powder mix and set to form a solid layer in the printed areas. The platen is then dropped slightly, a layer of fresh dry powder applied on top of the first layer, and the printing process is repeated to create the next layer. The area of the platen and its vertical drop provide a more or less cubic printing volume.
Varying the 2D printed pattern for each layer means that the 3D shape cam be smoothly or sharply variable as it builds up. Objects can be hollow or can enclose objects within objects, or they can contain hollows in the shapes to represent, for instance, windows. Support struts can be added for strength or so that unbalanced objects don’t fall over as they are being built up.
The colour is added by printing standard HP aqueous ink in the same pass as the binder, though you can switch off the colour to give white objects. The colour can just be added to the outer edges of the object rather than all the way through, which saves ink.
Z Corporation is a US company based in Burlington, Massachusetts, owned by Contex Holdings, which also owns scanner makers Contex Scanning Technology and Vidar Systems. ArtSystems, which already distributes HP large format printers and Contex scanners in the UK, took on the Z Corp distributorship about six months ago.
 Conscious that 3D print is a brand new concept for many people, ArtSystems has installed a pair of demonstrators at its Nottingham showroom: an office-friendly ZPrinter 450 SP and a larger industrial Spectrum Z510. Last October it held a 3D day where it not only demonstrated the ZPrinter but also a whole range of related systems including the SolidWorks 3D software, a Z Corp SP 3D scanner, an Objet 3D polymer rapid prototyping inkjet (Objet is a spin-off from the old Scitex group), and a Cybaman six-axis cutter. There was also a case study description of Dendy, a commercial user of 3D systems.
So far about ten Z Corp machines have been sold in the UK, says Andrew Hand, ArtSystems’ marketing manager. They’ve gone to a fairly wide range of users, including architectural model makers, medical scanning companies, Bentley Cars, and the Royal College of Art (for its existing Rapidform rapid prototyping bureau). Worldwide, Z Corp says it’s shipped about 3,000 3D printers, to a customer list including Sony, Fisher-Price, Adidas, Canon, Kodak, Clorox, NASA, Lockheed Martin, Northrop Grumman, BMW, Porsche, United Technologies, Ford, Daimler Chrysler, Harvard, MIT and Yale. However not all operators are ‘end user’ manufacturers: there are also 3D bureaux in the same way that there are conventional printing companies.
There are three models in the Z Corp range at present. The full colour printers are the ZPrinter 450, priced at £25,495, and the Spectrum Z510, at £36,495. The 450 has a smaller ‘build’ volume of 203 x 254 x 204 mm, but more highly automated and is completely enclosed against powder escape so it’s described as ‘office friendly.’ Its resolution is 300 x 450 dpi and layer thicknesses can be selected between 0.089 and 0.102 mm (ie 35 to 40 thou in imperial). It can create two to four layers per minute.
The Z510 has a larger build volume of 254 x 356 x 203 mm, a higher resolution of 600 x 540 dpi and a wider range of thicknesses (0.089 to 0.203 mm), but it’s not fully enclosed so powder gets out, and it really needs a room to itself. Speed is around two layers per minute.
There’s also a monochrome model, the ZPrinter 310 Plus, at £17,250. It’s similar in speed and volume to the 450 but can print objects in a single colour, such as red or yellow, or leave them as uncoloured plain white.
The ZPrint Windows front end software acceps most 3D file formats including colour information. It offers a 3D preview of the object in the ZPrinter’s build ‘box,’ for visualisation and deciding if support struts are needed. You can move objects in the box and scale them to fit.
ZEdit lets you add colours to object files, apply image maps and create highlights or annotations.
Mimics Z is developed by Materialise, a medical 3D software specialist. It allows image slices from medical MRI or CT scanners to be assembled into 3D objects and output on the ZPrinters. It includes the ability to output specific elements, for example just the bones from a scan of a complete body part.
 Z Corp makes a pair of 3D laser scanners to read real-world objects. Andrew Hand says that ArtSystems is considering distributing these, but is also looking at scanners from other sources.
In practical terms, Art Systems output a model Nintendo games controller as a test. It took three hours to build up on the ZPrinter 450 demonstrator. A mobile phone sized object takes about an hour. Although the materials are cheap, at around £10 to £20 for these sizes, throughput may seem very slow if you’re used to the square metres-per-hour of conventional 2D printers.
“3D customers are used to waiting weeks and paying a small fortune for conventionally built models,” says Hand. “So from their point of view the Z Corp method is really fast.” In any case, this is a good speed in rapid prototyping terms. Remember too that the objects are self-coloured, while rival systems’ models have to be painted if colouring is necessary.
There are several types of powder available, with appropriate binder fluid to accompany them. The standard material is zp131, a general purpose powder that gives tough parts with good resolution and colour. This needs to be sprayed with the binder material to finish it and gain final strength after dusting-off.
A ‘greener’ and cheaper alternative, zp140, can be finished off with a misting spray of tap water instead of binder. This is also a whiter material than the slightly cream zp130.
There’s an elastomeric material and binder that combine to create flexible rubbery objects.
ZCast 501 is basically a mould material that allows you to cast metal parts inside it after printing. On similar lines, zp14 is a cellulose-based investment casting material. You dip it in wax after printing, and then use it as the core of a ‘lost wax’ casting, where the core is burned out after the metal sets.
Once cleaned off, the appearance of the Z Corp objects is slightly rough and very matt. This is reduced somewhat by the finishing stage where you over-spray the surface with the binder (or water for the zp141 material), which smooths out the roughness and gives a glossier appearance – this also increases the colour contrast, the same way that printing a photograph on gloss paper does. As the objects are self-coloured to a reasonable thickness, it should be possible to sand or polish them smooth without losing the image quality.
While the Z Corp’s ability to produce one-piece objects is very impressive, it does mean that you can’t get at some inner areas to clean them up or add to them – say to put plastic sheet glazing inside the windows of an architectural model. So in some cases it would be better to split the object into components that can be printed and worked on individually and then glued together, in the way that some of us remember from our days of assembling Airfix plastic models. Another ArtSystems demo is a model of Old Trafford football stadium that was output in pieces and then assembled.
The only drawback of the Z-Corp materials is that you can’t eat them. So we’ll have to wait a few more years for that e-mailable pizza.
Contact: www.artsystems.co.uk
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