This 3D-Printed Four-Stroke Engine Actually Runs

3D printing is amazing and so incredibly versatile, but it isn’t exactly known for producing strong parts. If you need something really strong, you’re still probably going to turn to a material like steel. That’s especially true if your application involves heat — FFF 3D printers use thermoplastic, after all. So, internal combustion engines are completely out of the question, right? Wrong! Alexander is 3D printing is own working four-stroke engines that actually run.

Before we go further, I do need to be upfront about something that the naysayers are sure to latch on to: these engines do use some metal parts. For example, it has steel cylinder sleeves and not just bare plastic. But the bulk of the engine, including the block itself, is 3D-printed plastic.

This is a fairly simple single-cylinder, four-stroke 125cc engine design. It is similar to what you might find on a scooter. But though it isn’t a some crazy turbocharged W12 or something, is still a four-stroke engine and is therefore fairly complex, with lots of parts. There is a valve train, a fuel injector, a spark plug, and so on. The bulk of that is regular old PLA Plus, with some carbon fiber-reinforced nylon thrown in. Some key parts, like a plate for the head, are aluminum.

Alexander has a goal to make his 3D-printed engine run at 10,000rpm, which is quite ambitious. Even most “real” single-cylinder engines redline well below that. He previously reached 6,000rpm, but this new version couldn’t even reach that without destroying itself.

I am, however, confident that Alexander will eventually reach his 10,000rpm goal — at least for a few seconds.