3D printing in the home: Reality Check

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There’s nothing like spending evenings and weekend doing carpentry to focus the mind. There’s something about the whir of a chop saw or clack of a torque ratchet to get your mind wandering while you carry out a task that’s more physically than mentally demanding. I found myself sharpening up a chisel this weekend and realised that I’d broken my jig some time ago. Of course, my first thought is, I’ll wing it.

Then I got to thinking about how nice it would be to have a 3D printer again so I could model a jig up, print it and do the job properly. I also thought about how there’s been so much talk of 3D printing revolutionising the world these days.
Only this month, it has been in the Guardian and the Economist – and something bothers me deeply. So here’s how I think it’s going it might pan out.

THE PREMISE & ASSUMPTIONS

Let’s start with the assumption that people have access to a 3D printer. Let’s also assume that the printer in question uses one of the current, commercially available build processes that’s safe for the home environment. That means plastics – no-one wants lasers and near melt temp metals powder in the home.

So. You’re at home. You break something in the home. A knob off your cooker, perhaps a component from your vacuum cleaner. A part that a simple gorilla glue and duct tape job won’t fix. Most people either ignore it, jerry rig a solution or order a new one.

But you’ve got your 3D printer sat in the basement not doing a lot. You fire it up, but what next? If you’re lucky, you have the remnants of the part. Let’s do a roll call. Busted Part: Check. 3D Printer: Check. See what’s missing? Yeah, the data to print out.

MYTH #1: DOWNLOAD 3D DATA

This is one of the most commonly used analogies whenever the 3D printing revolution is talked about and for the most part, it’s a nonsense.

Most manufacturers would rather give you their first born child rather than post the 3D geometry of their products online. Spares and servicing are a revenue stream and they’re not going to disrupt that.

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So you head to whatever sources are available. Google Warehouse, Thingiverse, GrabCAD, whatever and hope that there’s a match to your part.

The cooker is seven years old. Your vacuum cleaner went out of production a while back. Chances are you don’t get a match. You think “I’ll model it up myself.”

MYTH #2: MODELLING IS EASY

No. It’s not. If you’re modelling a cooker knob, you’re in safe territory. It’s a few simple features. If it’s something more complex, these days the chances are that it’s a single part, but one that serves several purposes – part casing, part aesthetic surface, part structural or functional support. And guess what – it’s broken into five pieces.

Two of which you can’t find.

Good luck with that. But you’re smart, you’ve got a design or engineering background. Most people haven’t.

MYTH #3: ABS IS ABS IS ABS

So, time for another check. 3D printer is warmed up, 3D data is ready. Let’s load it up and get it building. You’re typically building with ABS, right? Let’s deal with this one right here.

3D Printing isn’t injection moulding. ABS, melted, fed through a nozzle and layered up, partial hardened, then more ABS added on top isn’t the same as an injection moulding. It’s nowhere close.

Injection moulded parts are created in tool-steel moulds, the material is almost liquid at the point injection and they’re shot into that mould under high pressure. That gives you a wonderfully happy mix of surface quality and a very strong, homogenous part.

3D printing parts are vague approximations of the real thing. The build process introduces weaknesses between the layers and the layers themselves aren’t typically 100% solid. But the part you have is intended for injection moulding.

Even if it is built using ABS in the real world, just replicating that form in 3D printed ABS isn’t going to give you the same part. It’ll look the same, but that’s about it.

And there are many more exoctic materials in production used, before you even get onto filled polymers and such.

END RESULT: THE PART

If it’s a non critical part, then you’re likely to be in luck. It’ll function nicely assuming the parts don’t delaminate, that it’s not exposed to too much UV light or temperature variation. If the part is in a more harsh environment, such as a handle, perhaps a casing or a fixture, then it’s not going to withstand the pressures and forces acting on it in day-to-day life in the home. Why? Because you’ve not redesigned it to account for dramatically reduced material strength.

END RESULT: THE CONSUMER

So, what’s the end result. Some parts will be fine, but if you’re doing anything vaguely complex, vaguely interesting, then chances are you’ll end up with either another part that doesn’t fit properly, doesn’t perform it’s function properly or will fail sooner rather than later. What you’ve essentially printed is another broken part – it’s just not broken yet. Designers and engineers will know all of this – it’s our job after all. The average consumer, even those tech-aware enough to have a 3D printer, won’t.

A TOUCH OF THE CURMUDGEON?

Don’t get me wrong, I love the idea of 3D printing getting into the hands of more people. I love the idea that these machines allow the “so inclined” to be able to build parts and to experiment without the costs of traditional manufacturing processes. And yes, I’m missing a crystal ball to see a time when you can 3d print parts with production intent material or at least a variant that has the same mechanical, thermal and UV properties. But at the moment, you don’t. So, ultimately, I’m a bit down on the whole thing and I’d like to see a little more realism and fewer flights of fancy.

There’s also a question of safety. You build the new handle for your vacuum cleaner. The part builds nicely and it fits to the existing parts. Then you carry it up the stairs. Because of the weaknesses in the material and build process and the fact that these haven’t been accomodated for, it splits, shattered under impact, whatever. I just hope there’s no-one behind you when you do.

The mainstream media outlets talking about 3D printing is a good thing, but I do wish they’d look into what they’re espousing. If the Economist talks about 3D printed hammers, then something is deeply wrong. I’m sure they double check their financials. Why not this?

Al Dean challenges media assertion of a new industrial revolution
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