Repeatability and reliability in 3D printers are like the proverbial box of chocolates

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Repeatability and reliability are sorely lacking in modern 3D printers. Like the proverbial box of chocolates, you never know what you’re going to get – and that can leave a bitter aftertaste, writes our regular columnist SJ

Life is like a box of chocolates – you never know what you’re gonna get. A bittersweet analogy that can also be applied to the most common box-shaped things in my life: 3D printers.

Printers are inconsistent, even those bearing the same brand name. In fact, printers from the same original equipment manufacturer, or OEM, are famous for being like children from the same family. Each one has its own unique personality and temperament.

Like chocolates from the same box, each one has its own flavour profile – but since everyone in this industry is still focused on protecting their own interests, rather than the interests of the industry as a whole, no one is sharing the flavours they’re getting. As a result, it’s easy to assume, naively, that all boxes of chocolate are the same.

Flavour profiles

If you’re an experienced chocolatier like myself, by contrast, you already know that there are typically two things lacking with the chocolate boxes that we call 3D printers: repeatability and reliability.

No two ‘chocolates’ from these ‘boxes’ give you the same flavour. Even if they come with the same wrapper, the same shape, the same logo – they all taste different.

No two ‘chocolates’ from these ‘boxes’ give you the exact same flavour. Even if they come with the same coloured wrapper, have the same shape and the same logo pressed into the top of that fragile little chocolate shell, they all taste different. I experienced this early on in my career when I helped run a fleet of small-sized metal printers. Starting my rotation on the factory floor, I quickly found each printer had its own special type of filling.


Some fillings were easy and smooth and could purge down more consistently than others. Those were my milk chocolate. Some machines had excellent gas flow – white chocolate. One particular machine kept getting its elevator jammed – that one was my raspberry-filled afternoon delight.

Those machines that produced deceptive, difficult-to-place false errors from bad sensor readings? Definitely hazelnut. But however you choose to look at it, these were machines costing upwards of a million dollars. So I can hardly be blamed for expressing dismay that they couldn’t even match my $20,000 Toyota for consistency.

A bitter aftertaste

Many advocates for 3D printing technology will vehemently disagree with me, insisting that these machines are reliable and repeatable – to a certain degree.

From their perspective, I can see their claim as being technically true. If you only need a machine to be utilised 50% of the year, it’s fine if it’s down for regular maintenance the other 50%.

With that knowledge and realistic expectations, you can factor this into your cost structure and your business model.

The risk mitigation strategy for a machine being serviced so frequently is generally to have higher costs per part, to make up for potential losses while it’s not running.

At the end of the year, you can cook the books, so that it all balances out. But why do all of that peanut-butter accounting, when you could instead create a process that’s more scalable?

Imagine that your million-dollar machine is repeatable and reliable. Let’s say it’s down 5% every quarter for regular maintenance and calibration, which leaves us with a whopping annual utilisation rate of 80%.

Your machine costs a million dollars, it’s running 80% of the time, your production is up and cost per part is down significantly. And year over year, you can count on that. It becomes so reliable that you can count on future growth, on future business, on delivering on time more consistently.

You can grow your business with significant margins and all you need are those two things: repeatability and reliability.

Decision time

As an industry, we must decide if we are going to build our house on rock or if we will build it on sand. Instead, I regularly find myself watching with scepticism and frustration as parts of the industry get distracted from these issues, preferring instead to go chasing off in pursuit of other goals.

For example, we focus on in-process monitoring, when we don’t even have an industry-wide accepted standard for every process or every material.

OEMs pump money into speed and accuracy of lasers, or improving material offerings, or ways to automate our post processing.

Industry leaders spend hours in meetings debating standards or designing the next frontier of digital infrastructure.

I’m not saying this as an attack on any of these discussions. They involve new and innovative topics that will increase AM’s acceptance in mainstream manufacturing.

But what I am asking, sincerely, is that we all work harder to reach the milestones of repeatability and reliability. Fortune, after all, flavours the brave.

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SJ is a metal additive engineer aka THEE Hot Girl of Metal Printing. She currently works as a metal additive applications engineer providing AM solutions and #3dprinting of metal parts to help create a decarbonised world. Get in touch on Twitter: @inconelle

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