3D Printing Spare Parts Is Cool But Not A Silver Bullet

Last year my Baratza coffee grinder broke, and I was left to slum it with my ceramic-burr hand grinder with a bearing-mounted crank. It took a few days until a replacement part arrived, but what if I could have printed the broken part instead?

3D printers, specifically the filament/FDM printers popular for home and hobby use, are great for making widgets: cable winders, custom boxes and cases, accessible handles for home appliances, and on and on. But they’re also great for making spare parts. In theory, any part that can be replaced by a 3D-printed version is a candidate for DIY fixing. In practice, printing spare parts can plunge you into a rabbit hole of tolerances, material strength, and design.

Spares and Repairs

3D printing spares is extremely convenient. You can have a replacement part in hand in under an hour, and quickly iterate on it if you find the design wanting. You don’t have to store spares (which is what I do now for my Baratza), and you can download files for parts which would be otherwise unavailable for purchase, officially or even unofficially.

But there’s a downside. Depending on the materials you use, and even the direction you choose to print something, your spare part might be too weak or brittle, or too flexible, for its purpose. Let’s take a look at a real-world example to illustrate some of the problems you might encounter.

First, let’s take a look at my broken Baratza Encore coffee grinder. Baratza is an iFixit fave because it sells spares and upgrade parts, and shows you how to fix and clean your grinders via a series of videos on its YouTube channel.

The Encore’s burr assembly contains some consumable parts. The ring burr holder is a plastic cylinder which locates and retains the upper burr. It has three plastic tabs which align the burr, and they are designed to break away if the burr assembly is subject to too much force. This could be a stone in the coffee, or just bad luck, but the idea is that the tab will sacrifice itself to save the more valuable burr mechanism.

I’ve had my grinder for years, and it has gone for long stretches with no broken tabs, but I have also had three ring burr holders break in the space of a year. My regular supplier no longer ships to Spain, so I thought I’d ask my friend to print a replacement on his Prusa printer.

Grinding Gears

The first part was easy. We found an STL file on Thingiverse, loaded it up, and printed it. This isn’t an official Baratza STL file, to be clear; offering files that way is still an unfortunately rare practice. But the 3D printing community is full of people who are skilled at reverse-engineering and modeling, and luckily an engineer named Michał Barczewski had already done that hard work for us.

Then things started to get more complicated. Our printed part looked like this:

Actually, it looked worse. To get the part into shape, I had to heat two of the tabs with a hot knife, and press them into the correct position. I think the sections were too thin to survive the heat of the printing process itself.

Other than that, the printed part snaps onto the burr quite nicely, and the assembly fits into the grinder just fine. But that’s when I started worrying about the tolerances, and the strength of the material. Would it be up to the stress of the job? Had we chosen the right print filament? Might the piece itself break, and end up damaging my grinder? Could it (horror) ruin a cup of coffee?

I decided to ask Baratza. Such a repair-forward company must know about that, right?

I asked if they could comment on using 3D-printed parts for repair. Specifically, whether the company had considered making STL files available for appropriate parts, and also about difficulties of supporting 3D-printed parts, including materials, user knowledge, and so on.

I got one reply from Baratza’s training and content expert Elliott Spencer, telling me they didn’t have the STL files available (which I didn’t ask for) but could sell me the parts. I replied to say I just wanted to talk to somebody about the pros and cons of 3D printing for repair, and got another reply, this time from the head of support and service, Jordan Markezich. They told me they’d passed my email on to the marketing team, but the marketing team never got back to us by the time of publishing.

Without any official help, I did what any good researcher would do: I took one for the team.

There are two questions here. One is whether the printed replacement will actually last, and not fall apart. The other is, will it affect the quality of the coffee? The whole point of using a good burr grinder is to get as consistent a size as possible. Ideally, all the little ground coffee particles should be the same size and shape. The burr collar aligns the burr and also interacts with the grind size adjustment mechanism to hold the top, stationary burr accurately in place.

If the burr collar is inaccurate, it will need to be dialed in to compensate. That’s a one-off job though. Worse would be if it degrades over time, slowly changing either the grind size, or grind consistency. And this will be affected not only by the part’s design but the material you use, and how you print it. I was starting to see why the Baratza folks avoided the question entirely.

The result of my printing? A retaining tab broke off as soon as I tried to push the burr into the holder. There are two of these tabs, and they secure the burr tight in the collar. With one missing, the burr rattles loose inside the collar, and is useless.

We’re waiting on some nylon filament to see if we can get a better result, but the takeaway is that I do not trust 3D parts for this particular repair. My coffee is just too important to compromise (which is why I have a fancy-ish grinder in the first place). However, there are plenty of other repairs that aren’t so sensitive, or that have more obvious, easy-to-spot failure modes.

Printing Keys

Here’s another example of a real-world repair. I needed to repair a scissor switch under the spacebar of a very old MacBook Air for my sister-in-law’s computer lab project in Senegal. The cheapest and quickest way was to print the part, but we ran into problems right away. One was that I could not track down an STL file for the part. But worse was that I did not know whether the part would last.

Printing a scissor mechanism for myself would be pretty low stakes. If it broke, we could reconsider the design and material choice, and try again. And in the absence of any actual manufacturer-approved spares, making your own is the only option.

But we were sending the computer off to be used in the Senegalese savannah, where it could not easily be replaced. The spare needed to be as good or better as the original part, and in the end we decided against sending the MacBook, and used the suitcase space for other more useful stuff.

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Good News

It’s not all bad news. Far from it, in fact. 3D printing is perfect for many repairs, especially those where parts need fairly fine tolerances to work, are too complex to make by hand, but won’t be under too much stress. iFixit’s lead teardown technician Shahram Mokhtari bought a broken 2017 Logitech Meetup V-R0007 conference room camera, which is supposed to move up-and-down, left-and-right, to automatically center the person speaking in the frame.

“I bought this camera off eBay sometime in 2024,” Shahram told me. “The listing said the camera couldn’t move left/right. I opened it up to find the white gear attached to one of the motors had broken in half. That’s a piece of plastic Logitech doesn’t sell, and certainly wouldn’t now nine years after the device was released.”

Shahram thinks that the gear cog is probably a standard piece that could be bought/salvaged, but he had no luck with either. So instead he decided to print one. He counted the number of teeth, learned a bit about gear design (nerd alert: clicking that link may lead to several hours of lost time) and printed the part. He also shared it with the world, and his file already has had 25 downloads and one confirmed make.

This is a perfect example of how 3D printing can facilitate an otherwise almost-impossible repair, and also shows the importance of sharing.

And sometimes a dead simple repair is all you need. A few years ago, iFixit’s e-waste expert Chayton Ritter printed a replacement for a broken tape wiper on his tape gun. “I’ve heavily used the tape gun and the original repair still works great,” he told me in Slack. “I also printed a few extras for our kitting and shipping teams just in case. It’s up on printables too!”

Tracking Down Files, and Materials

To print a spare, you’ll need a file to do it. Start with a web search, and you’ll quickly see the same sites popping up in the results: Thingiverse, Printables, Cults3D, and lots more. Some of the provided printer files are free, others are paid.

You can also design your own parts from scratch, or by modifying an existing file. That’s beyond the scope of this article, but we do have some advice for anyone getting started. Find somebody experienced to do it for you.

If you have a friend with a 3D printer, a friend who has experience using that printer, then use them. They will be able to navigate the printer’s software, advise on materials, and they’ll understand some important parts of the process, like which orientation to use, and how to print the part with minimal filament waste.

Plus, if they own a 3D printer, they’re probably a big nerd who loves using it, but has already filled up their home and office with printed parts and projects, and will be happy to have something new to make. That’s definitely the case with my friend.

The other option is to find a local 3D print shop or knowledgeable maker space. A good one will offer the same experience and advice. It’s possible to get stuff printed online, but unless you already know a bit about the process, you’ll get put off as soon as you come to materials selection. I think that these services can be good, but only if you already know enough to specify exactly what you need.

If you do end up designing or modifying your own parts, make sure you share them. At the very least you’ll be saving somebody else a bit of work, which is no small thing. I’m sure there are folks like me who have access to printers but cannot, or don’t want to, start designing their own parts. Sharing your successful print files pays it forward and makes 3D printed repair more viable for everyone.

This is especially useful when gadgets are thoughtfully designed to use standard parts. It happens: Swedish designers Teenage Engineering used almost exclusively off-the-shelf parts for its EP-133 sampler, even if that was in response to pandemic supply shortages. The amusing thing here is that if more standard parts were used, it would be easier to buy replacements, and 3D printing would be less necessary.

So, is 3D printing a good option for repair? Sure, but with many caveats. Printing good parts is about more than just buying a printer and downloading patterns. You need materials knowledge, the ability to fine-tune the design over several iterations, and to understand the limits of 3D prints vs parts made via casting, milling, and other manufacturing techniques.

If you already own and use a 3D printer, then you’ll already know the ups and downs. But you also have the means and skills to experiment with spares until you get them right. 3D printers can be amazing, and can give old broken gear a new life; you just have to know their limitations.