Over all, it is possible to print with less than 80mm/s with good results, maybe a bit more.
This is possible with looong straight lines with a pretty good filament and a perfectly calibrated machine. Not suggested!
If you have calibrated your machine well, your settings will be good for big models/surfaces.
Attention, the magnetic sheet could be easily rocked off the heated bed, you have to fix it with clamps or so!
Search for minimum layer time (I Googled, not sure about the correct name).
This post is so helpful. I’m trying to calibrate my A250, but I don’t get a response to M92 or M503 in the console. I can home it with G28, but is it Luban - it won’t return data? or is there a setting I am missing. I’m hoping not to have to install Octoprint or some other program if I can help it. I figure learning Luban and LightBurn and Prusaslicer is enough for now! Thank you!
Are you trying to use wifi?
It will only return commands over usb.
-S
That would be it. Thank you. I’ll try w/ the USB.
Wow, @brent113 — What version firmware came with those settings?
These are my out of the box defaults with v1.11.4:
M204 P300.00 R1000.00 T1000.00
M205 B20000.00 S0.00 T0.00 J0.18
If I’m reading that right, my junction deviation is 0.18mm, and my acceleration is 300mm/s^s.
I did a first run with the accelerator calibration test from Teaching Tech and indeed 0.02mm seems to be the better setting. I’m waiting to see what this run tells me about acceleration, and will report back if 750 matches your experience.
Interesting. Yea, very old firmware, don’t remember. I agree with you, I’m not sure the new default is an improvement.
@brent113 Yup. Confirmed by subsequent testing. Should be M204 P750 and M205 J0.02, just like you set. I’m just surprised it was changed so dramatically.
I am having a whale of a time trying to get my A350 to produce anything remotely nice after slicing with Cura. I am using the John Aldred profiles which I have slightly changed in terms of reducing print speed, reducing flow to 88.1% (I also follow Teaching Tech Flow Calibration), I added g-code to set my K-factor to 0.06 after some linear advancement tests, I tested and set my E-Steps to I think it was about 233.2 after some tests and to be fair I still have some ridiculous stringing and the occasional poor layering as a whole.
I found last night that Luban on high quality produced something far more better than I have done with Cura so not really sure how or why considering I set most of the settings in Cura to the same as Luban. I am also finding that any overhang looks like t1ts on a fish once printed so I am also looking at using applying Brent’s 5015 Cooling mod, I am just looking at an alternative way to power it as I am not too keen on driving the fan from the tool head itself. Yes it means I will have to power it on and off manually along with controlling the speed but that’s no biggy as I tend to sit in the room on my PC whilst the prints running
Would it be possible to share screenshots of the slicing settings in cura as well as the failed prints?
Sorry bud I wish I could, I deleted the profiles and started fresh with another import of the John Aldred profiles. I am now printing all the items which Brent has listed in aid of making the printing process more enjoyable like the filament guide, holders etc etc. Also ordered my 5015 fan and JT connectors will just do the mod as been done and documented by Brent’s post. It is probably the easiest thing to do. Once its all done I will try the failed prints again to see if there is any improvement. I will be sure to screen grab the settings so I can share them. Might be something obvious which I as a noob don’t yet know of 
Sounds good. I hope that just redoing the profiles fixes your issues. Also, sometimes problems can just be something we overlooked due to being tired of troubleshooting, I’ve definitely had that happen a few times 
@brent113 Is there a way to reinstall the default settings (without a full factory reset) once I have uploaded your fff file?
The FFF file is unique to simplify3D and is not applicable to machine calibration.
@brent113, one general question about your S3D profile:
How did you go about selecting the various speed settings?
Did you run some tests with various speeds to find “optimal values”?
Or are these rather “best-practice values” based on Snapmaker and/or other sources?
I feel I’ve managed to understand most of the important machine calibration and slicer parameters.
However, the speed settings remain somewhat foreign; beyond the obvious fact that going too slow or too fast will cause problems.
So I don’t feel I understand speed vs. quality trade-offs very well…
Too slow and you may get curling/ other heat issues if the filament stays hot for longer than it needs, too fast and machine vibrations start to impact the surface quality, you might clog the nozzle, or the extruder gear might skip
(at least, is as far as my understandings go)
Everything buzzplop said, plus some more:
I got a lot of speed testing out back in the day on my delta printer, trying to print at 300mm/s+. It doesn’t work lol.
50mm/s seems to have good layer adhesion without too much heat soak. It somewhat depends on the size of the part, nozzle size, nozzle temp, enclosure temp, cooling, required strength / accuracy dimensionally, other considerations.
Sometimes you can push the speed and get good results. Sometimes you can’t.
50mm/s is a common starting point used by many many printers.
Many thanks for clarifying this.
I was thinking of something in the range of 40/50/60 mm/s as a base speed.
But I don’t quite understand the trade-offs; assuming there are marked trade-offs in this range.
Personally, I would rather go “slow but steady”, so perhaps 40 mm/s is a reasonable base value… 
One more question:
Do you optimize the other various speeds (say for infill or for external contours) separately or do you make them depend on the base value?
I saw how you defined the speeds in S3D and also saw some PrusaSlicer profiles from other members, so perhaps a mix between these two options works OK?
I don’t have opinions that at the moment, both seem fine as long as there’s no issues
I’d like to measure the wall of a cube printed with Spiralize and confirm my wall thickness is correct… for my flow calibration. Using Luban, there’s obviously no way to set the line width, so what width should we be expecting? .4mm nozzle diameter? .4mm * 1.2 = .48mm?
Where did the 1.2 come from?