Speed Benchys were a trend that took off with the #speedboatrace challenge announcement by Annex Engineering in December 2020:
While anyone can try to print a fast Benchy any way they like, most people who've taken up the hobby use the "regulation" settings from the above: 10% infill, 3 top and bottom layers, 0.25 mm layer height, and 0.4-0.5 mm line width/nozzle size. There is a list of "official" entries maintained on the Annex Engineering Discord server, also accessible by this direct link to the Google doc.
At least as of this writing, almost all speed Benchys are printed at a nominal print speed under 400 mm/s, most probably even under 300 mm/s. The "speed" you see when watching videos is not actually the absolute velocity the printer's toolhead (and/or bed) is zipping around at, but the velocity relative to the size of the space it's moving in, and the speed at which it changes direction. Benchy is an acceleration-bound print.
When a 3D printer (or any kind of machine positioning a tool) performs a move, it doesn't simply go from a stop to motion at the requested speed instantaneously. It doesn't go from moving in the X direction to moving in the Y direction instantaneously. Because the toolhead (and possibly bed), and all the individual parts of the motion system moving it have momentum (some linear, some angular, some even electromagnetic), it takes time to change their velocities. As this acceleration/deceleration is taking place, the various parts of the motion system will resist changes in velocity, causing one or another to deflect from the intended path. The faster you try to accelerate, the more severe this deflection can be. In a worst case, this happens in the mesh of belt teeth with a pulley, or the alignment of the magnets in the motor with the field generated by the coils, and you get a layer shift. More commonly, you just get severe vibrations at resonant frequencies, showing up as ripples (ringing) in the surface of the print.
When I say Benchy is acceleration-bound, I mean it's very difficult to get a 3D printer toolhead to accelerate fast enough, without compromising quality, to make use of the full requested print speed the printer is capable of. This is because its layers are made up mostly of small segments, many of them on the order of (offhand guess looking at a boat on my desk) 1-8 mm.
To understand the relationship between attainable speeds and acceleration, you can use the formula velocity²/2 = accel*distance, or use the classic RepRap calculator (now hosted by Prusa). If you play around with it, you can see how, at the 500 mm/s² acceleration common on profiles for bed slingers like the Ender 3, you'll basically never reach speeds above 60 mm/s, and average much lower than that, on the majority of the Benchy. "Competitive" (or rather, perhaps "exciting" is a better word, since there's no actual ranking or rewards) speedboat entries generally run accelerations in the range 7000-50000 mm/s².
To achieve this kind of acceleration without compromising on quality, you need either a printer with an extremely rigid frame and motion system, or firmware with input shaper (aka resonance compensation) - preferably, both. Up until recently, input shaping was only available with Klipper firmware, but RepRap Firmware and now Marlin also have it, if you're using sufficiently new versions (note: as of Spring 2023 I'm not aware of any printers shipping Marlin with input shaping enabled, but this will eventually change). Bambu Labs' proprietary firmware also has this functionality.
Most people doing high-speed speedboats choose to use 0.25 mm layer height and 0.5 mm line width, rather than the more standard 0.2 by 0.4, and to combine every 2 layers of infill. All of these choices help alleviate the degree to which Benchy is "acceleration-bound", by making use of the flow the extruder and hotend can deliver without reaching high kinematic speeds. At 0.25 by 0.5, 300 mm/s takes 37.5 mm³/s of flow. This is considerably more than what most standard hotends can delivery (typically, 12-20 mm³/s with a normal nozzle, 25-30 mm³/s with a CHT) but very doable for high-flow ones.
At speedboat speeds, most layers of the Benchy take less than 5 seconds to print, and half or more take less than 3 seconds. If you have a minimum layer time configured in your slicer, it will override that, and you'll end up with a slow boat, no matter what speed and acceleration you request. Fast layers like this, however, require some extreme cooling, so that the previous layer isn't still soft when the printer goes to lay down the next one. Speedboat entries have a lot of different approaches to this, ranging from whole-layer fans mounted on the sides of the print to CPAP hoses to the toolhead to high power 40mm x 28 mm axial server fans or more standard 5015 or 5020 radial blower fans mounted on the toolhead. Many of the fastest entries use combinations of different types of cooling.
For anyone attempting to get started in speedboating, a checklist of things your printer needs would include:
- Firmware with input shaper, properly calibrated.
- Upgraded cooling. You can't have too much cooling.
- A decent extruder that can push at least 15 mm³/s or so without skipping.
Beyond that, things you should ideally have:
- Low moving mass.
- A CHT or other high-flow nozzle, and/or high-flow hotend.
- Decent stepper drivers with ability to control max current and put them in modes that won't compromise torque for quietness (so, TMCs you can put in Spreadcycle mode).
- Firmware with pressure advance/linear advance, properly calibrated, if you want your high speed prints not to look ugly.
- More cooling.
And to go really extreme:
- Multiple motors per axis.
- Wider/premium belts, etc. to deal with extreme forces on motion system.
- 48V stepper drivers and high current motors.
- High temperature hotend so you can run at higher temperature to get more flow.
- Further increasing flow with extruder and hotend upgrades.
- Still more cooling.
Really, though, you do not need a ridiculously expensive printer to do this. An Ender 3 with less than $150 of upgrades can do a high quality Benchy in under 20 minutes and and ugly (maybe even decent) one in 10. Looking at the official entry list is a really good way to get an idea what kinds of printers have been able to achieve what times.
