3D printing: Alternatives and accessories

3D printing isn't the only way to get 3D objects out of your computer. Here are some complementary tools for everything from crafting your own designs to serious structural engineering.
Written by Mary Branscombe, Contributor

Cricut Explore

Image: Cricut

One of the limitations of 3D printing is the materials. Consumer 3D printers usually stick to ABS plastic and while you can print anything from metal to ceramics, those machines are expensive. If you want to work with less specialised materials like leather, felt, fabric, board and vinyl, the £249.99 (inc. VAT) Cricut Explore can precision-cut shapes that you can assemble into objects. Basically this is a CNC cutter disguised as a craft system. Early models could only cut, score or draw shapes from custom (and pricey) cartridges, but the Explore connects to your computer over USB and you control it from the Cricut Design Space, a Flash-based website with both preset projects and design tools to create your own projects.

Cricut's crafting heritage shows in the many designs for customising clothes, bags and napkins, and for cutting fancy birthday cards and leather jewellery. Some of the more technical projects are supplied by Autodesk (and there's an iPad app on the way to help you make more 3D designs like this). You can create dinosaurs, rockets, sharks, bowls, 3D heads (handy for storing your headphones) or phone and tablet stands out of precision-cut poster board that you slot together like a 3D jigsaw. There are plenty of designs for decorating existing phone and tablet cases with fancy vinyl cutouts and decals. The tablet case designs tend not to cover the whole case, so they'll fit most tablet shells. Most of the phone case projects are for iPhones, but the design tools make it easy enough to resize the images for other phones. Once you've measured your case, you can also pick and choose from the range of predesigned images or write a phrase in your preferred font and position it on a template. There are also designs for slipcases that you can resize to fit a variety of tablets, although you'll have to do some sewing or gluing to assemble them.

A 3D Autodesk project to make a 3D bowl ready to send to the Cricut Explore. Image: Mary Branscombe/ZDNet

It's easiest to adapt the pre-made projects, but once you get the hang of the fairly simple design options you can create your own from scratch, uploading your own images (bitmap images give you a single layer cut, but you can use SVG and DXF files to generate multi-layer cut paths for each colour in your image) and adding text or picking images from the Cricut collection (think of it as clip art with sharp edges). There aren't any drawing tools in Cricut Design Space, but you can create the shapes you want to cut out or embellish in your favourite design software (which will probably be far more powerful than anything you could run in the browser).

Using colours to make it clear which objects will be cut from which material for this tablet case decal. Image: Mary Branscombe/ZDNet

You lay out your design on a background Cricut calls a 'canvas', which shows an example of the object you're decorating or the background it will be used on (so you can experiment with the angle for the witty saying you're putting on your phone, for example). You can colour your various shapes to help you create the design — but obviously the cutter doesn't change the colour of the material you're cutting. If you're using multiple materials, you create a layer for each of them and load them into the machine separately. You do have to create the entire pattern for what you want to make, and we'd like to see the option for adding your own canvas — if you had a canvas showing the Apple logo on a MacBook Air, say, or the back of a Surface Pro 3, it would be easier to design your own custom decal, which could be as intricate a pattern as you wanted.

Working through the projects isn't as clear as it could be — we found broken links to promised PDFs in some instructions, and the Cricut blog has a big problem with spam comments. Once you start a project it's not easy to get back to the overall instructions, which you often need for assembly. We found it easiest to open two copies of the project in different tabs. Actually cutting the project is straightforward: the equivalent of a print dialog tells you which material to load onto the sticky mat that guides it into the machine, which material to set the cutting dial to (so the Explore knows how heavily to press on the blade) and when to put the next material on the mat to be cut. Watching the sheet of material move in and out of the cutter as the blade glides over it has the same as-if-by-magic feel as watching a 3D printer in action.

The Cricut Explore system is fairly flexible, but the costs add up. If you don't want to design everything from scratch there are a number of free projects, but beyond that you pay to use predesigned projects and the shape library. A shape might cost 75p, and project design might cost £1.99 or £2.99, or you can subscribe to get nearly all the designs and projects. You also have to include the cost of the materials. The Explore can cut a range of materials, but they have to fit on the 12-inch-by-12-inch mat that comes in the box (or you can buy a 12in.-by-24in. mat), so you either have to buy materials sized for the Cricut system or cut your own to fit first.

You'll also need to iron on interfacing to fabric to make it rigid enough to cut smoothly. Otherwise it can detach from the slightly sticky coating on the mat and wrinkle as the cutting arm moves over it, whereupon the material is scored rather than cut out completely. Even a heavy canvas didn't stay flat enough to cut cleanly without backing. And it's the materials you use that make or break a project: we had most success cutting projects from leather, felt, paper and card, like the smartphone stand that assembled into a handy support. Trying to cut a dinosaur out of cardboard that we'd cut off the side of a shipping box wasn't nearly as successful, however. You should budget for buying more mats if you use the Explore a lot, too, as they attract dust and fluff that will stop your materials from sticking eventually. If you want to draw in different colours you'll need to buy more pens, and you'll need new blades from time to time.

Unlike a 3D printer, you don't get a finished object out of the Cricut Explore, but if you want to use materials that aren't available with a 3D printer and you're comfortable with the idea of some assembly being required, you get a powerful and flexible tool for precision cutting and drawing — as long as you don't mind paying for any designs you can't come up with yourself.


Make your own 3D images

The Occipital Structure Sensor for the iPad costs $379. Image: Stucture.io

CAD software isn't the only way of creating 3D objects, especially if you only want to view them and not print them. Getting an accurate 3D scan takes the most work, and needs a 3D scanner. For example to use the Itseez3D iPad scanning app, you need the $379 Occipital Structure Sensor. If you already have a Kinect, you can use the $299 KScan3D or $499 Stratovan Checkpoint software to create 3D mesh models you can then export to your preferred 3D modelling software. Faro's SCENECT 5.1 is a free app — the company calls it 'experimental', but it has useful features like removing spurious points created in your 3D scan and you can export to VRML or DXF.

Microsoft Research recently showed off a hack for 3D scanning using a modified phone, by removing the infrared filter in a phone camera, but if you don't want to sacrifice a phone or shell out for a sensor, you can also get a 3D point cloud out of a Photosynth image.

Photosynth is Microsoft's free software for stitching multiple images into a 3D image; you can create simple ones with the iOS, Android and Windows Phone apps that fit your images onto the inside of a virtual sphere so you can move around the space, but if you use the free Windows software or the free cloud service at photosynth.net to stitch together a synth from multiple photos, you can then use the free SynthExport tool to extract the mesh of points on the surface of the objects in your scene and save them as a 3D model you can then work with in tools like VRMesh Studio or the free MeshLab. You also get the metadata about the images (like how far away the camera was in each shot, which is helpful for getting the scale right) and even the image textures, which you can stretch over the 3D model to get a more realistic look. Because the Kinect is an infrared camera, the models you make with it look shiny and grey; using Photosynth exports doesn't give you a perfect 3D image, but it's a slightly faster way to get a reasonably real-world look.

Extract 3D structures from your Photosynth scenes with SynthExport. Image: SynthExport

If all you want is a rotating 3D view of an object, for example to put on your website to show off products you're selling, you can do that with the 3DBin iOS app (currently free, it will eventually cost 99c). Basically, you move your iPhone or iPad around the object you want to photograph (or turn the object if that's easier) and tap the shutter button until you've captured it from all sides. You can only shoot in portrait mode, but you can use the rear or front camera (if you want a 3D selfie, for example).

3DBin has a simple interface, because all you can do is capture images and upload them to the cloud service. Image: Mary Branscombe/ZDNet

When you're done, you can review the images to remove some or go back and add more, then choose Save and the app uploads the images to a cloud service that stitches them together into a view you can pan around like a 3D model. That's something the current smartphone Photosynth apps can't do well, because they're designed to stitch together images on the outside of a sphere not on the inside.

What you get with 3DBin is like a low-res video that you can control, but you can only pan side to side, not up and down. The quality of the image is limited not just by the device camera, but by how well you align your original shots. If you only take a couple, 3DBin doesn't do a great job of aligning the images and you get a bit of a jump each time you move to a new frame. If you take several images and line them up well, you get something reasonably smooth. Consider using a turntable and a tripod to get things lined up on every shot.

You can share your 3DBin 3D images, but often what you get is more like a still image. Image: Mary Branscombe/ZDNet

You can save an image to your camera roll or mail it to yourself, but that simply gives you a still photo. The only way we were able to look at the pannable 3D version was in the app or on the 3DBin site, where you can't control the pan — you just watch it like a video.

Again, if you're prepared to take the images separately (with a camera or on a phone with a good-quality camera) and use the Photosynth website to stitch them, you can get a much higher quality result using the Technical Preview of Photosynth 2014 (which you can sign up for at the site). This supports four different kinds of 3D, including the 'spin', where you take photos all around an object and make a 3D map of it. Unlike the simple projection that 3DBin gives you, Photosynth 2014 can detect both the object in the middle and 3D backgrounds like walls and buildings. You need to take a lot of photos — 20 or 30 — and will see some artefacts as you rotate (especially on complex objects like motorcycles where the background is visible between the saddle and the wheel, or where a curved edge isn't perfectly elided), but the quality is generally excellent — especially if you use a high-resolution camera.

You can look at the images on the Photosynth site, or embed them in a web page and you get full control of panning around the image.

You get high-quality images with a Photosynth spin, although sometimes there are artefacts. Image: Mary Branscombe/ZDNet
You can view 3D Photosynths on the Photosynth website or embed them in your own web page. Image: Mary Branscombe/ZDNet


Build a structure that works

CAD and 3D software lets you build 3D models, but doesn't give you much guidance on the engineering side. You might need a lot of experience or to go through a lot of 3D printouts to work out how to get your structure right. Inspire 2014 from solidThinking isn't typical CAD software (although you can use it alongside CAD tools). Instead, it's for designing the structural parts of a product by reducing them down to the essentials, specifying the loads they need to deal with and having the software generate the layout of materials that will cope with those loads. You then export them back to your CAD tool to use them, or create an STL file for 3D printing.

You can import parts that you've designed in a CAD package or sketch them out in the Inspire workspace by drawing 2D shapes like rectangles, circles, lines and arcs and then breaking or trimming the shapes. Once you have a 2D sketch, the push/pull tools let you extrude the sketch into a 3D shape in a very natural way; you can also edit which parts of your design are solid and choose whether to join two shapes or cut one out of the other to get a more complex shape you couldn't easily draw.

If you don't have a design to import, you can build it up from 2D shapes in Inspire 2014 that you push, pull, break and intersect. Image: Mary Branscombe/ZDNet

If you're importing an object, this new version of Inspire lets you simplify the design by taking out decoration (you don't need the logo when you're checking something won't break) and removing screw holes and other elements that don't affect the design but would slow down calculations. If there are strengthening bars on a component you want to test out, you can remove those to see if you need them, and you can do that by having them highlighted like search results into a document. Just being able to step through a design and see where the gaps, holes and pockets are gives you a clearer idea of how it's going to function, and how you might be able to simplify it without running into problems. You can configure parts of a design you don't want to work on, but don't want to delete, to be ignored. Or you can cut the important components out of a design so you can place them quickly in a new one.

Then you split the design up into separate parts and mark up what materials they're going to made from; the list is mostly metals like different grades of steel or magnesium alloy, but it includes ABS plastic (which is what most 3D printers use). You can also create your own materials, if you have the mechanical specs for them.

Next you specify the loads you need your part to cope with; where the stresses will fall and what support the part will have — is it standing on a floor, connecting to a rotating wheel or bolted onto a wall? Again, you do that by drawing on your product design with the Inspire tools, so it's like sketching out a diagram.

You can also take other parts of the product into account as you design. If you're mounting your part into a larger product — a part that fits into a motor, for example — you can mark where the mass of the motor will be, so Inspire can take it into account when you use the really unusual features for analysing and optimising your design. You can set different loads (details can be imported, if you have an engineer supplying them for you) and see visually what will happen to your design.

In the circular standing desk we designed, it quickly became obvious that the stress where the edge's curved back wall met the tabletop would be fine for normal use, but could break if the desk ever fell over — or the user slammed a heavy object into the wrong place as they were rearranging things on the desk. If you're designing something cosmetic rather than structural (a lot of 3D printing is still decorative objects rather than functional parts), those kinds of stress points are where wear and tear will show the most, so it's really useful to know how your design shapes up structurally.

Look at the stress points of your design in Inspire 2014 to see how it might fail. Image: Mary Branscombe/ZDNet

For structural design, you usually care less about the look and more about the function — do you have the most efficient design, given constraints like how thick your component can be? Inspire 2014's Optimize tool lets you set the thickness and specify how safe the design has to be, whether it has to cope with vibration stress, whether to take gravity into account, and whether you care most about getting rid of as much mass as possible or about keeping your object as rigid as possible in use. When you run the optimisation, it will tweak your design to cope with those factors. Often that results in the removal of large solid areas, giving you something more like a honeycomb with struts that match the load positions. This is a good reason for taking the time to remove any existing pockets and hollows, so you can see if the optimised result is more efficient.

Getting Inspire 2014 to optimise the design can deliver an approach you wouldn't have thought of yourself. It's also a good way to compare what you get if you optimise for different constraints. This is a professional-grade tool (with a matching price of around £4,500 unless you're a student) and you do need to understand structural engineering to get the most out of it. But if you want to 3D-print objects that work properly, getting the engineering design right is essential, and Inspire 2014 can speed up that process.

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