Yun Goo - the man behind the viral HelixCore spinner

For the past 16 years, Yun Goo has been designing things that are produced in millions of copies. Injection molds, mass production, identical parts stamped one after another. Work where success means that the thousandth part looks exactly the same as the first one.

Meanwhile, he became known for something that is exactly the opposite - toys made one at a time, on a desktop 3D printer, one copy at a time.

At first glance, it is a very simple thing. A ball that you press and that starts spinning. That's it.

Yun called it HelixCore:

On the day this article was published, it had already reached 22.3k downloads, 19.2k prints and more than 1,200 ratings on MakerWorld. In Malaysia, where he lives, nobody recognizes him for it. In China, where he is mainly known by his MakerWorld nickname - YY the panjang - people stop him at events and ask for his autograph.

Asked how it happens that his models keep breaking popularity records, he gives a disarmingly honest answer.

“If you ask me how I make those things go viral, honestly I have no idea at all. It just happens.”

But don't be fooled. There is no coincidence here… It is the result of many years of work and experience in manufacturing, which naturally evolved into creating fantastic things with 3D printers.

The factory that taught him everything

Before we get to the printed bananas, oranges and spinning balls, we need to go back to the factory floor, because that is where the whole story begins.

Yun works for a family-owned company founded by his uncle, who is still its director today. He ended up there partly by accident and partly out of necessity. He studied aircraft maintenance, only to never actually enter the aviation industry.

“My education background is kind of weird. I studied aircraft maintenance, and I never went into aviation.”

His father died when Yun was young. That changed his calculations. He didn't want to spend years studying; he wanted to start earning money, so he joined his uncle's factory and learned it from the inside out. He didn't start behind a designer's desk or in some ready-made role. He started at the bottom and went through everything.

“Basically I learned everything in this company. Every process, from polishing to machining to laser welding. Every skill you need to make a mold, I learned it.”

It is worth stopping here for a moment, because this is not an ordinary CV. Making an injection mold is one of the more demanding things in the entire manufacturing industry. A mold is a negative of a product machined into steel, with tolerances measured in hundredths of a millimeter, and it has to survive tens of thousands of cycles of injecting hot plastic under pressure.

You have to design not only the part itself, but also how the plastic will flow into the mold, how it will cool, how it will shrink and how the finished part will be ejected without being damaged. Yun did all of it, from product design through mold making and production, all the way to line automation and PLC programming. The full chain, from the first drawing to the machine that runs by itself.

That is why his perspective on 3D printing is different from that of most people who enter the field from this side.

Yun doesn't look at a printer like a hobbyist who has just discovered that layers stick together and that the first layer needs to stick to the bed.

He looks at it like someone who knows exactly how many steps, how much money and how much responsibility stand between a nice drawing and something you can actually hold in your hand. That perspective will come back several times in this story, because it explains almost every decision he makes.

Ten years, three home-built printers and one failure

Yun has been involved with 3D printing for much longer than his recent popularity would suggest - more than 10 years. He started the way many people from that generation did, with a DIY kit ordered from Taobao.

A body made from laser-cut polycarbonate sheets, a heated bed covered with ordinary masking tape. A machine that required patience and an acceptance that a good portion of the prints would come out looking strange or simply fail altogether.

That would have discouraged most people. Yun got hooked - so much so that he started building his own machines from scratch.

The second one was more serious: a full metal body, an Ultimaker-like frame, linear motion based on MakerBot profiles.

The third was the most ambitious and the craziest. His own four-head printer, sometime around 2018, back when multi-material printing was the domain of a handful of enthusiasts.

Two heads worked. The other two never worked properly.

The project stalled. Yun put it aside, and soon afterwards he put 3D printing aside altogether, for several years.

Life moved on. The machines sat there.

It is an important moment in this story, because it shows that his later success did not come from an easy start. It came from a long period of trial and error, when nothing spectacular was happening and a few things simply failed.

He only came back last year. He came back because he kept hearing a name that was on everyone's lips at the time.

“When I got back to 3D printing, I kept hearing this name, Bambu Lab. Everyone was saying it's a very good printer, an amazing machine. So I got curious and I bought one, the P1S.”

The difference compared with his home-built four-head machine was fundamental. A machine that simply prints instead of requiring you to fix it first. Yun started printing again, buying filament, making this and that. And then, almost naturally, he moved from printing other people's files to creating his own.

A few hours after the kids go to sleep

The reason he started designing rather than just printing was mundane, and quite serious. Money.

“At first it was just for fun. Then last year I got into some financial trouble, and I was struggling to find a side income.”

The situation didn't leave him much room. A full-time job at the factory, two children, a home that only goes quiet late in the evening. Free time appeared in a narrow window, after the kids had gone to sleep. A few hours, no more. Whatever he wanted to do on the side had to fit into that window and not interfere with everything else.

He tried different things before he found the one that worked.

“I tested a lot of things. I tried e-commerce, I even sold insurance. But it didn't work out for me. Then I found that this 3D printing design thing suited me.”

Design had one advantage those other ideas didn't. It adapted to his rhythm, rather than the other way around. It didn't require him to be constantly available at specific hours, didn't chase him with client-imposed deadlines, and didn't require him to serve anyone in real time.

On top of that, it could bring in some income. At first, that was all he needed to give it a serious try.

Why a banana has to open

Yun knows something about mass production that most makers don't need to know, and it changes everything: when it comes to quantity, 3D printing has no chance against injection molding.

At tens of thousands, hundreds of thousands, or a million units, injection molding wins on cost every time, and by a huge margin.

Printing the same thing on a 3D printer is slower and more expensive per unit, and that isn't going to change. For someone with his experience, this isn't an opinion. It's arithmetic. And from that arithmetic, he drew a conclusion that became his method.

“3D printing cannot fight injection molding. There's no way to compete on quantity. So when we want to create something for 3D printing, we have to make it unique. We can't do it the normal way.”

For Yun, the word “unique” has a very specific, engineering meaning. Movement. A mechanism hidden inside the object. Something that comes alive in your hand.

You can already see it in his first model. Banana Katana came about because his son asked for a toy, and Yun happened to have a newly purchased printer and a reason to use it.

“I wasn't the first one to make this banana katana. But I printed one and I thought, hey, I can add a little mechanism inside to make it different. So I added a mechanism, and when you twist it, the banana opens. The mechanical thing, that's my strength.”

This is where 16 years of working with molds becomes a real advantage. Designing moving parts requires exactly the same knowledge used to build a mold: how components fit together, how much clearance to leave so something rotates without rattling, how to choose tolerances so it works correctly the first time.

On the factory floor, that knowledge is used to make an injection molding machine spit out identical, flawless parts. At Yun's desk, he uses it for something completely different - to make a single print have a spark that mass-produced toys simply don't have.

An orange, some lamps and a ball that spins

After the banana came the orange. Or rather, a citrus fruit fidget designed just before Chinese New Year, with a very personal origin.

“During Chinese New Year we eat these mandarin oranges in Malaysia. So I thought, why not make a fidget that looks like a citrus? And honestly, when I peel an orange, I always want to peel it a certain way.”

There is a little bit of Yun in this tiny object. He takes an everyday gesture — peeling an orange in a particular, satisfying way- and turns it into a design.

The model collected over 12,000 downloads, roughly the same as the banana. And that was the moment he felt he had found his direction. Fidgets and fruit, moving, simple, friendly. It worked.

There were failures along the way, too, such as the lamps. Yun noticed that selling printed lamps could have very good margins, with a big gap between production cost and selling price, so he gave it a try. It didn't work out.

And then came HelixCore. And that changed the scale.

As usual with Yun, it started with existing designs. He printed several popular stress balls, the kind you squeeze that click and make a satisfying sound. He liked them, but felt the same sense of incompleteness as always. They were missing something he knew how to add better than anything else.

Movement.

He sat down and designed a ball with a bearing and a screw mechanism inside. You press it, and it spins. A simple idea, precise execution, exactly the kind of thing he had learned to do with molds.

And while working on the model, something happened that he himself can't quite explain, but that many creators will recognize.

“When I was working on that design, I had a feeling. It's hard to describe, but it was like something pushing me from behind, telling me this could be the way. Like something magical was about to happen.”

His intuition was right. Helix went further than anything he had made before. 22.3k downloads, 19.2k prints, more than 1,200 ratings on MakerWorld.

On Chinese TikTok, a video of the spinning ball racked up around 400,000 views - which in the 3D printing community means that the vast majority of people involved in the hobby in China probably saw it.

No one in Malaysia, everyone in China

That was when the part he had never expected began. Recognition. Except not where he lives his everyday life.

“In Malaysia I'm still nobody, just a normal guy. But when I go to China, people recognize me. They ask for a signature, for a photo together.”

It is worth clarifying this honestly - we are talking about the 3D printing community, not street-level fame. His video was watched by hundreds of thousands of people involved in the technology, so when he shows up at a Chinese industry exhibition, people recognize him.

Outside that industry, he remains anonymous, both in China and even more so in Malaysia, where he picks up his kids and goes grocery shopping like everyone else. But for someone who, just a year earlier, was designing at night purely for himself, the mere fact that anyone asks him for an autograph must feel surreal.

Publishing on MakerWorld wasn't a matter of chance or vanity for him. Yun explains it like an engineer who understands that a design without an audience practically doesn't exist.

“No matter how good a design is, if nobody sees it, it's still a failure. To get anywhere, you have to put your work where people can find it. Otherwise it just sits on your hard drive and goes nowhere.”

Today he works with three Bambu Lab printers, and the way he chose them once again gives away the engineer in him. He started with a P1S. Then he bought an A1, but for a very specific reason. Comments started appearing under his models saying that the print profiles didn't work properly on the A1. Instead of ignoring them or guessing, Yun bought the machine specifically so he could test them himself.

“Before I upload any print profile, I make sure it prints well and consistently on my own printer. Only then do I upload it to MakerWorld.”

It is exactly the same discipline that determines on the factory floor whether a mold is ready for production. Something that works once for you isn't enough. It has to work consistently, and it has to work for someone who has never seen it before and has no idea where its weak points are.

He got his third printer, the H2D, by exchanging points earned on MakerWorld itself, closing a certain loop in the process: the platform where he publishes his work effectively paid for the machine he uses to create his next models.

He designs in Fusion 360, and that was also a professional's decision based on cost. Yun knows much more powerful and expensive engineering software from his day job, but he chose Fusion for a simple reason. His license costs him around 2,500 ringgit, while professional software can cost several hundred thousand, while offering very similar capabilities for what he needs to do.

For someone who started with a financial problem, that isn't a trivial difference.

It is worth zooming out for a moment, because Yun is also a witness to how 3D printing is changing in his part of the world. Malaysia is only beginning to get comfortable with the technology.

“Ten years ago, when I started with 3D printing, I couldn't find anybody with the same hobby as me.”

Today, Malaysian 3D printing groups on Facebook have 20,000 to 30,000 members. Relatively few of them still own a printer at home, and the overall user base remains small, but the leap from the days when Yun was assembling a printer from polycarbonate sheets is enormous. He is part of that change himself, and one of its more visible faces.

The millions he didn't lose, and the door he wants to open

There is a part of this story that would be very easy to frame as an injustice. Yun tells it completely differently, and his attitude toward it is probably the most interesting thing in the entire conversation.

Helix started being manufactured commercially. Someone took his design and began making physical toys for sale. At the time, Yun didn't hold a patent on it.

“I keep hearing people from China say I lost millions.”

That framing doesn't sit right with him, and it's worth being precise about why, because it's easy to misread. Yun is not shrugging off people copying his work, and he is not saying it's fine to mass-produce it without permission. His point is narrower, and it's the point of someone who understands scale.

“Even if millions of them were sold, I couldn't have made and sold all those millions myself anyway.”

Behind a design come manufacturing, quality control, packaging, distribution, logistics and something creators think about least often - responsibility.

Including the heaviest kind, the kind you only start asking about when something goes wrong, for example when a child pulls off and swallows a piece of a poorly designed toy. It takes factories, e-commerce, distribution and a lot of other people to make something happen at that scale.

So he doesn't look at every copy sold as money taken out of his pocket. He does, however, still believe the original designer should be respected and properly rewarded.

And crucially, the story didn't end at that realization. Since everything happened with HelixCore, Yun has started filing for patent protection and building a more proper licensing system around the design. He also found someone willing to back him - an investor who believes in the project and supports the IP side. Together they have already put around RMB 100,000 into patent and IP protection.

“Honestly, something I never imagined doing when I first uploaded a little spinning ball to MakerWorld, haha.”

What's more interesting is how he now thinks about that patent. For most people, a patent is a wall, a way to stop others. Yun is drawn to the opposite idea.

“Instead of using the patent only to stop people from copying, I also want to see if I can use it to open a door for other designers.”

The vision is still forming, but the outline is clear. If it works, other designers could build their own ideas around the HelixCore mechanism with proper permission, and Yun could help connect the good ones with manufacturers and licensing partners.It comes straight out of what he learned the hard way.

There are plenty of talented designers who can make amazing things on a 3D printer, but getting from a printed model to something produced at real mass-production scale is a completely different world - a gap he crossed himself with Helix.

“So maybe one day I can make that path a little easier for other independent designers too.”

For someone who, a year earlier, was designing at night purely for himself, that is a striking place to arrive. MakerWorld gave him the income that fit into a life with two children and a full-time job - exactly the side income he was looking for, and couldn't find in either e-commerce or insurance.

It gave him an audience on the other side of the world, printing his designs in places he has never visited. It gave him an identity as a creator he hadn't even thought about a year earlier. In his balance sheet, this isn't a list of losses.

“It already changed my life.”

Creating has never been easy. When Yun's designs began circulating across the web through unauthorized resales, the MakerWorld team reached out to him almost immediately. The platform frames copyright protection as one of its core obligations to creators.

“The moment we discovered this exclusive model had been infringed upon, we contacted him directly and offered our full support,”

says Dora Ding, Creator Relations & Operations Expert at MakerWorld.

In practice, that has meant helping Yun file takedown requests against infringing listings, and a stated commitment to keep pursuing action against unauthorized websites, so that a creator's hard work receives the respect it deserves.

Day to day, Yun still goes to his uncle's factory, still wearing the company uniform, and he talks about it fondly, because it is precisely the flexibility of the family business that allows him to jump on a plane to another exhibition in China when invitations come in.

He's already designing more fruit: bananas, oranges, maybe a pineapple someday. He's also preparing a smaller version of Helix, this time without the bearing, because users started asking for it in the comments - and he listens to them.

And when he tries to sum up what has happened to him over the past year in a single sentence, he sounds as if he still doesn't quite believe it himself.

“It's an amazing experience. I would say very amazing. I never expected something like this to happen in my life.”

Yun Goo, known on MakerWorld as YY the panjang, started with a banana made for his son, on a printer bought partly out of curiosity and partly out of necessity.

He ended up as a man stopped for autographs at Chinese trade shows, whose single model of a spinning ball reached hundreds of thousands of people.

Between the two lies 16 years of injection molding and one simple principle he took away from it.

If you want someone to print your thing instead of buying a finished product from a store, make it do something that the finished product can't.