You’ve heard about “high speed 3D printing”, but what are the things you need to know about it?
In recent months there has been a wave of “high speed” FFF 3D printers hit the market. These are generally a reaction to the introduction of Bambu Lab’s high speed equipment and a couple of high speed DIY open source projects, all of which provide equipment that can operate at incredibly fast speeds. In some cases the print speeds can be as much as 10X the speed of older 3D printers.
But is it as easy as just buying one of these machines? Are they really as fast as they say? What do you need to know? Here are seven things we’ve learned about high speed 3D printing.
You Don’t Actually Get That Speed
The most important thing to know is that you don’t actually get prints to run at “500mm/s” or whatever the specification says.
In truth the toolhead must slow down to go around corners, and so the effective print speed is always less than stated. Sure, the prints are indeed faster, but you cannot simply multiply by the print speed to determine print duration. Keep your expectations modest, and hope to be surprised.
This means that certain geometries that are complex tend to be slow because the printer simply doesn’t have any long, straight paths to crank up its speed.
We did an entire story about this, but the words “high speed” are basically meaningless for several reasons. The usual approach by manufacturers is to describe their device as “high speed”, but the truth is found by looking at the actual specifications.
We’ve seen some devices listed as “high speed” print at a whopping 120mm/s, whereas another company’s “high speed” is 650mm/s. That’s quite a difference, even accounting for the lowered expectations described above.
Tip: ignore the words “high speed” and instead look at the specifications.
The Ultimate Speed
How fast is fast? After performing quite a bit of testing of high speed equipment, I’ve seen a pattern among manufacturer specifications. There is usually a “maximum print speed” spec, which is actually a theoretical figure, achieved only if everything else is optimal. Then there is usually a more practical lower speed that prints should actually use.
For example, a machine that states the maximum print speed at 250mm/s might actually be practical at only 150mm/s. This is usually discovered when you realize that none of the stock print profiles seem to use the maximum speed; instead you find a slower, practical speed.
You can try running the machine at the maximum speed (or even more), but you’re likely on your own. Print quality will almost certainly be compromised.
One very important realization we had was that many of the manufacturers specify their maximum print speed when extruding 0.1mm layers instead of the more standard 0.2mm layers.
Why do they do this? It’s because the extrusion system has a maximum flow rate: it can only deliver so much material per second. Typical desktop slow machines might have a maximum flow rate of say, 20 cubic mm per second, while a true high speed machine might range from 30-35. Highly tuned specialized machines might even reach 60.
Regardless of everything else, that figure represents the most material that can be delivered by the equipment. When you’re printing 0.2mm layers there is a certain amount of material delivered.
But if you’re printing 0.1mm layers, there is a lot less material being delivered per second. Therefore you can move the toolhead faster.
That’s how many manufacturers develop their “high speed” specifications: they “cheat” by extruding thinner layers to compensate for a low maximum flow rate. Unfortunately most manufacturers don’t say this, and buyers assume the stated print speed applies to standard 0.2mm layers.
I’ve tried several machines that supposedly print at 300mm/s, but I could never achieve that. Until I switched to 0.1mm layers, that is.
But printing at 0.1mm layers means your print will take longer because there’s twice as many layers. In the end we want fast prints, not fast toolhead movement.
What Spec Should Be Used?
If that’s the case, then what is the correct specification to look for? Perhaps the most important would be the maximum flow rate. High speed machines should have something over 30 cubic mm/s. In order to achieve a high flow rate, the system’s hot end is likely enhanced or lengthened to heat filament more efficiently.
However, a great many machines don’t even list the flow rate. That’s a big problem, because then you have to rely on the more loose figures of toolhead speed. It is possible to perform a flow rate test to determine your machine’s capability. There is a web based tool to generate such a test, if you want to run one.
However, even if a machine has a good flow rate, it may still not be able to print at high speeds. Proper extrusion is actually a balance between several factors beyond flow rate. The machine must also be able to very quickly cool layers quickly so that subsequent layers can be built on top of them. Look for beefed up cooling, as well as advanced motion systems to handle the rapid movements.
What? Materials matter? They do — and they do not. You will start to see some filaments billed as “high speed”, which again has similar standardization issues as the machines themselves. Nevertheless, high speed filament is actually a thing. The chemical mix is tweaked to ensure the material absorbs heat just a bit faster than “normal” filament. This is very helpful for high speed machines, where the rapidly fed filament has a shorter time inside the hot end.
However, the truth is that many “normal” filaments work just fine in “high speed” 3D printers. That’s because the printers are not actually running at those high speeds as explained above. In the cases where the machine is actually engineered to be high speed, it can actually push the filament through the hot end faster than it can soften, resulting in a clicking extruder. In those situations it’s best to use true high speed filament.
Accelerometer or Not?
One of the features that allows high speed operation is vibration compensation firmware. This software depends on a calibration of the toolhead’s weight and behavior when moved at high frequencies.
Advanced high speed 3D printers will have an accelerometer on board, and use it to calibrate the toolhead with a brief test. Sometimes this is done before each and every print job.
However, many desktop 3D printers don’t have accelerometers yet, and so the calibration factors have been pre-calculated at the factory. This is possible because they know the weight and behavior of the stock hardware.
If you happen to change the weight scenario, however, by swapping nozzles, using very dense filament or other changes, the hard coded calibration will not work as well.
The bottom line here is that accelerometers are good, look for them.
And that’s our list of things you should know about high speed 3D printing.