Daughter came around to scrounge some camping chairs. I offered a lightweight table too – an aluminium rollup top with stiffeners and parallelogram legs. Lay the top inverted, fit the stiffeners, clip legs, revert it. Done. By now you’re thinking “I’ve got one of those!” Very common and excellent until a gust of wind blows them end over end down the beach... As the parts shook out a stiffener was short of a plastic tip that mates the top and legs. Where’s that, I wonder. She says “You’ll be able to 3D print one.” (I have access to a 3D printer). She was right. Easy job to run up a 3D solid model on my CAD (Computer Aided Design) system, save as a .stl file, send it to the 3DP. As I write, sweating out a 30°C day, 3DP is beavering away squirting wiggly lines of molten plastic. Sometimes 3DPs talk to us, like a budgie that repeats its party piece. 3DP has endless vocabulary. At the moment it sounds like Donald Duck talking with someone holding him by the throat. Next it’s sending a short Morse message, repeatedly. Then its “Wait here, go over there, wait here, go over there.” You’ll never be lonely with a 3D printer in the room!
I needed a bonnet-prop clip as the original was broken. The parts outlets said “We’d need a sample to match to.” If I had a sample I wouldn’t need one, would I? There’s only one per vehicle, they clip into the metalwork and cannot be removed without breaking the clips off. So I designed and printed one. It worked fine, too, until the engine bay temperature melted it. It was made of PLA plastic so I made another from ABS. It works fine – higher temp plastic. A musical instrument had a button missing, five minutes drawing it up, five minutes squirting plastic, make a felt washer with wad punches and it’s all fixed. A friend gave me a new LED strip-light that was missing an end cap. Modelled one up on the PC – quite a complex shape – took about an hour, then ran a print that fits perfectly. 3DP is a conundrum, there’s lots to it – many settings that must be right for a good print – but it can make things that are impossible to make with traditional methods. That said, there’s quite a long learning curve. The most common plastics used are PLA and ABS. The former is ‘easier’ and lower temp, somewhat brittle, supposedly somewhat biodegradable. ABS is higher temp, stronger, more flexible and robust. Both are available in a myriad of colours. There are many other plastic varieties available with different properties, appearance and uses, including wood, metals, flexible, clear, water soluble (for making ‘lost wax’ type moulds). Low-end printers may not work all of them.
Slowly does it
3DP is a slow process. My end cap took two hours, the bonnet clip half an hour. Larger or more complex items can take all day. Material costs about $40 for a one kg roll of filament. As it is squirted through a tiny (0.4mm) nozzle at a fairly constant speed cost and time is proportional to mass. 3DPs need a .stl or G-code file to tell it how to make the item. These are created by PC-based CAD programs – 3D Solid Modelling it’s called. I’ve been using it for years for engineering projects and prototyping. These images can be revolved, rotated, cut, drilled, added to and assembled to other objects. The programs convert them to files to run on CNC (Computer Numerical Control) machine tools.
It all adds up
A 3DP is a CNC machine tool. Most traditional CNC tools begin with a lump of material and machine bits off it to create the required shape. That’s called ‘subtractive engineering’. 3DP is ‘additive engineering’ where you begin with nothing and it builds the object in layers. Subtractive translates to telling the cutting tool where to cut, 3DP interprets it to tell the nozzle where to squirt. There are thousands of object files available off the ‘net to make a vast array of items, useful, imaginative, artistic, interesting. And lots of ‘how to do it’ info. If you are the inventive sort you’ll need to learn 3D modelling to turn your dreams into reality. A range of programs is available at prices ranging from free to tens of thousands. I’ll not attempt to recommend any as I’d have to test them all first, other than ‘Alibre’, that I have used and liked. You won’t need to spend lots, most lower-end will have enough features to get a grip on. I’m told ‘Sketch-up’ works.
Sky’s the limit
3D modelling begins with drawing a 2D shape, as you would on paper, then ‘extruding’ it upward to create a 3D object – draw a square, extrude to a cube, etc. You then modify it by adding or subtracting other bits to it. CAD is accurate to hundredths of a millimetre, you can dimension as you go (and you should, ‘cos if you don’t the printer won’t know how big the object is!). You could, in theory, design your own aeroplane – but you’ll need ‘top-end’ for that!
A powerbox and the bonnet prop clip Geoff designed and 3D printed.