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!

Clip joint

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.

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