Understanding 600mm/s Print Speed and 20000mm/s2 Acceleration

Two numbers get quoted together so often that people naturally assume they mean much the same thing. 600mm/s 3D printing speed is a ceiling; 20000mm/s2 acceleration is how often a printer actually reaches it, and on most real models it barely does.

Quick Answer

Top speed only matters on long, uninterrupted moves, which are rare on anything but a plain box. Acceleration decides how fast the toolhead gets there and slows back down again, and that happens dozens of times per layer on any model with corners or small features. The Creality K1C carries both figures at R12,599, and the acceleration number is the one that actually shortens a print with real geometry in it.

🚀 Why top speed rarely gets used

A printer needs real distance to accelerate before it ever reaches its rated speed, and the shorter the move is, the less of that rated speed ever actually gets used. A 40mm bracket wall covers so little ground that the toolhead is still speeding up when it needs to start slowing down for the next corner, so 600mm/s might never actually appear in that print despite being on the spec sheet.

Long infill lines and big travel moves across an open bed are the exception, and those are exactly the moves nobody is measuring with callipers afterwards.

📈 What acceleration actually buys you

20000mm/s2 is the rate of change in speed, and it is what determines how quickly the printer recovers from every corner, hole and small feature. A model covered in short segments, gears, brackets, anything mechanical, spends nearly its entire print accelerating and decelerating rather than cruising at top speed.

That is why doubling acceleration tends to cut real print time far more than doubling top speed does on a typical model. A tray of forty small brackets sees almost all of its time saving from acceleration, because none of the individual moves are long enough to reach a high top speed in the first place.

🧮 Reading the two numbers together

Treat the two numbers as a pair rather than picking a favourite. A machine with a high top speed and weak acceleration will look fast on paper and disappoint on small parts, while strong acceleration with a modest top speed still performs well on most real prints because it recovers from corners quickly.

Check the filament you intend to run too, since flow rate rather than motion speed becomes the limiting factor on wide lines regardless of how fast the gantry can move. A resin-based alternative sidesteps this comparison entirely, since resin machines are limited by curing time per layer rather than toolhead motion.

🧮 Doing the maths on your own typical model

Take any model you print regularly and count roughly how many direction changes it has per layer. A simple bracket with 4 corners per layer accelerates and decelerates a full 8 times just tracing its own outer outline, before infill or any internal detail is even considered at all, and each of those 8 separate events is exactly where acceleration, not top speed, decides how long that single layer actually takes to fully complete.

Multiply that by however many layers the part actually has, often 100 or more layers on a part standing several centimetres tall, and the cumulative effect of acceleration on total print time becomes genuinely obvious in a way a single top-speed number never reveals on its own. This is also exactly why two machines with genuinely identical top speeds but a 5000mm/s2 difference in acceleration rating can finish the exact same detailed model with a real, noticeable, measurable time difference sitting between them at the end.

📊 What manufacturers actually advertise, and why

Top speed is simply the easier number to make sound impressive and the easier one for a shopper to compare quickly at a glance, which is exactly why it dominates marketing copy over acceleration figures that genuinely require more explanation to properly appreciate. Treat a listing that leads with speed alone, with no acceleration figure given anywhere on the page, as an incomplete picture rather than a red flag on its own, and look specifically for the acceleration rating in the detailed specifications before ranking machines purely by their headline number.

Check the 3D printer range for both figures listed clearly side by side before deciding anything, since a printer publishing both numbers openly and confidently is usually more assured of its own real-world performance than one leading purely with speed and leaving acceleration to a small footnote further down the page.

Frequently Asked Questions

Which number matters more for a small, detailed model?

Acceleration, because short features never reach top speed and spend most of their time speeding up and slowing down instead.

Can a printer be fast on paper but slow in practice?

Yes, if it pairs a high top speed with weak acceleration, since most real prints are made of short moves that never reach that top speed.

Does a taller print always finish faster on a high-speed machine?

Not automatically; height alone says nothing about the shape of each layer, and a tall print made of small, fiddly layers still spends most of its time accelerating rather than cruising.

Is there a downside to very high acceleration?

Yes, it demands a stiff frame and light toolhead to avoid shaking the model; that is why CoreXY motion and acceleration ratings are usually quoted together.

How many direction changes does a typical printed part actually have?

Often well into the hundreds across a single whole print, since even a simple 4-cornered outline repeats a full 8 direction changes on every single layer, multiplied by however many layers the finished part is tall from base to top.

Why do manufacturers advertise top speed more than acceleration?

Top speed is a single, easy-to-compare number that looks impressive at a glance, while acceleration needs more explanation to appreciate, which makes it a harder figure to market even though it usually matters more.

Should I avoid a printer that only lists a top speed figure?

Not automatically, but treat it as an incomplete picture and look specifically in the detailed specifications for an acceleration rating before ranking it against machines that publish both numbers openly and clearly side by side.