Max print speed?  

Speed is an illusion

Not to be dismissive, but speed is an illusion. Speed is only one of (at least) three factors that go into a successful print:

• Extrusion width
• Layer height
• Speed

 This is usually referred to as "maximum volumetric speed" or rate, measured in mm^3/s. This is the amount of plastic that your combination of extruder, hotend, and nozzle can melt and move to make a successful print. If you want to go really really fast, reduce your extrusion width and layer height and everything will work well (though slowly). Double the extrusion width and layer height and you're now trying to move 4X the amount of plastic through that same hardware. The characteristics of your filament also matter. In some casual testing, I found that PETG can be printed at more than twice the rate of PLA. YMMV.

To answer your question, I'd say that if you're using PLA with a 0.4mm nozzle on a standard Mk3 with an E3D V6 hotend, the answer is roughly "11.5mm^3/s". If whatever combination of layer height X extrusion width X speed <= MVS, you should be close. (In reality, I find that the maximum rate is usually around double what produces good prints.) On a Mk3 with a 0.4mm nozzle printing PLA, that's around 50-70mm/s using 0.48 X 0.32mm extrusions. At a 0.2mm layer height, around 120mm/s. Of course, your filament may not handle those speeds well, and things like cooling and print temps factor in.

Mini?

Hey Bob, I appreciate your explanation, however

If you want to go really really fast, reduce your extrusion width and layer height

Isn’t that incorrect? Reducing layer height and extrusion width causes prints to take longer if I’m not mistaken

Thanks for the MK3 calculations, however I’m specifically asking this for the Mini, hence my post being on the Mini subforum 😜

How to answer this

The way the question is phrased it's basically impossible to answer. What's missing is what the characteristics of the model are. Eg, a 0.6mm nozzle is okay to speed things up but would I want to print objects with high detail with it? No. On the other end of the spectrum, I've been printing large objects with little detail, and a 0.8 mm nozzle at 0.6 mm layer height is perfectly fine for that, and super fast. Other factors are number of perimeters and infill percentage, which can dramatically affect the time it takes to print a model but depend on the final characteristics of the model you expect. 

RE: Thinking in 3D

Yes, the print will take longer to complete, but the nozzle will move around faster. I wanted to emphasize the point that the speed the nozzle zips around is only one factor in actual print completion times.

Early on, I got wrapped up in a "how fast" discussion before I was educated in MVS and did a bit more research. Always remember this is a 3D process. That's why I like the quote in my signature.

The same rules apply to the Mini. I've yet to see a hotend with infinite capacity. You can test for yourself to be sure. 

Accelerarion

One more thing to add to Bob's wise words is that depending on your model you may never achieve maximum speed anyway if the nozzle doesn't have time to accelerate. In the models I mentioned before, it's basically all long lines from one end of the print bed to the other, and setting the slicer to be driven purely by MVS led to a significant decrease in print time.

RE: Fuchsr

Posted by: @fuchsr

One more thing to add to Bob's wise words is that depending on your model you may never achieve maximum speed anyway if the nozzle doesn't have time to accelerate. In the models I mentioned before, it's basically all long lines from one end of the print bed to the other, and setting the slicer to be driven purely by MVS led to a significant decrease in print time.

Interesting! I have poked around in the advanced settings of PrusaSlicer for a bit, and did find two MVS settings. However, adjusting these did not seem to affect the print time at all. How do you set the slicer to be purely driven by MVS?

MVS keeps out of the way if it's not needed

Posted by: @superdennis 

Interesting! I have poked around in the advanced settings of PrusaSlicer for a bit, and did find two MVS settings. However, adjusting these did not seem to affect the print time at all. How do you set the slicer to be purely driven by MVS?

Depending on the size of your print, that is a good example of why MVS is such a powerful setting. The MVS throttle -- it always uses the more restrictive of the 2 settings -- only kicks in if and when your combination of settings will exceed your set MVS limit. Otherwise, the slicer uses your specified speeds. It lets you make a change in 1 place without having to slow everything down, and only slows down when needed.

Try slicing some larger parts and using the various View settings in preview mode after slicing with PrusaSlicer. You can view the Volumetric flow rate and see the impact (if any) on speeds.

After realizing how this worked, I've made a point of using PrusaSlicer whenever possible. It's a very powerful feature.

Speed

It's been a while since I set up that profile and I honestly can't recall the details but when I just checked I saw that I set all the speeds (except first layer speed) to 0. I think this may be necessary to make MVS the driver.