Hi Robert,
I set acceleration (in Slic3r’s speed settings) to 120 - 150 mm/s². Default (i.e. the reset value) is 500 mm/s², which corresponds to my firmware; 1000 would be as provided by Velleman - see Configuration.h, line 228 here.
Speeds are generally set to 50 - 60 mm/s, exceptions being perimeters, top solid infill (for surface quality), and gap infill, all slower. And travel, which is of course set higher, at 200 mm/s.
With default settings some of my prints had problems. One example: in a print, upper layers, there was a short, ca. 20 mm long zig-zag infill. The same infill had already been present in some lower layers without problems, but for some reason at that point the carriage would built up vibration, locking the x-bearings and thus loosing steps. Reproducible, each time same point of failure. Otherwise, the x-axis is running smoothly, just the increased weight and high center of mass in my heatbed config seem to cause trouble in the drivechain.
Apart from such critical failures, setting the acceleration also had the nice effect of producing better infill. E.g. for rectlinear infill: when the nozzle started infilling, the first few lines were often broken, as if the material did not immediately flow at the right rate. With acceleration, those (mostly very short) first lines are slowed down enough to prevent gaps, while allowing the printer to operate at the set infill speed when long lines are printed.
There are some quality issues you can get rid of by setting a reduced acceleration, others will appear. So this stuff is not without tradeoffs, unfortunately. In my case, I’d rather use it than frequently face lost steps and skew.
Above values may of course be far away from the optimum, for your configuration and also for mine. I started low and increased the values until the printer was fast enough for my taste (at least at the moment). All those tests were done using PLA, in case it matters.
Happy experimenting!
Cheers,
kuraasu
