So what next, your milling machine gets to decide the cutting rate and how fast the spindle turns?
Curra does in fact know exactly how the printer moves because you told it the maximum acceleration and even that you are using "Merlin" firmware. Cura is controlling the speeds of all four axis and even the fan speeds and both heaters. Cura can assume the printer follows the g-code. That controller car in the printer is very impressive compared to Linux CNC. It is doing software stepper pulse generation at over 6,000 steps per second on four motors while also reading g-code and PID loops on the bed and nozzle temperature and running the user interface control All that runs on an 8-bit processor with a 16 MHz clock speed. On Tue, Jun 16, 2020 at 3:31 PM Gene Heskett <ghesk...@shentel.net> wrote: > On Tuesday 16 June 2020 17:07:30 Chris Albertson wrote: > > > On Tue, Jun 16, 2020 at 1:32 PM Gene Heskett <ghesk...@shentel.net> > wrote: > > > On Tuesday 16 June 2020 13:41:32 Bruce Layne wrote: > > > > On 6/16/20 10:23 AM, Gene Heskett wrote: > > > > > I've not been anyplace to get a glass plate yet. At my age & > > > > > health, I'm steering as clear of this damned virus as I can. > > > > > > > > Good plan. Stay healthy. > > > > > > > > https://www.amazon.com/Glass-Print-Borosilicate-Printer-235x235x3- > > > >7mm/ dp/B07JKGNB6W > > > > > > > > Plenty of options on eBay when searching for "Ender 3 glass". > > > > > > I see that, and all are quite pricy. > > > > So that's why some people buy mirror tiles. They cost only $1.70 each > > at Home Depot but you have to cut them down yourself. > > > > > This next half a sprocket is about 30% complete and I can already > > > see its at least 80% air, starving for plastic. > > > > 80% air is about correct if the infill is at 20%. The interior of > > most parts doesn't need to be solid. In fact you'd get large and > > uneven shrinkage it it was. 50% infill (or 50% air) is a good > > compromise for structural parts that need to be strong. > > > > What is the "correct" extruder speed? Let's lay the layer height > > is 0.1mm and the nozzle is 0.4 mm The the cross-section of a wall is > > 0.04 mm squared. Then if the extruder draws a 1mm long line 0.04 > > cubic mm of plastic is needed. But the filament is 1.75mm diameter > > and a 2.4 mm squared cross-section. > > But sq area is PI*(r*r). Not d*d. > So r is d/2 or 0.875*pi=2.75mm squared x section. > > > So the extruder needs to extrude 0.04/2.4 mm of filament per mm of > > travel or 0.0166 mm filament per mm of line. If moving at 100mm/sec > > that is 1.6mm/sec of filament. > > Its not moving anywhere near that fast > > > Ifthe layer thickness is 0.2 mm then the extruer rate is dubled over > > what is was for 0.1. Bu the print speed is always changing so the > > extruder speed has to constantly change too. > > > > There is another issue too. There is a volume of liquid plastic and so > > a lag between when the extruder motor pushing in new cold filiment and > > the hot liquid leaves the nozzle. The larger the volume the more the > > lag. > > And that will vary with both the temp and the speed. > > > Also some extruder place the rollers close are farther from the > > hot end. In the ectream case some use a teflon tube ad place the > > extruder stepper motor on the fixed frame. This makes the print > > head very light in weight and can move much faster. But huge "lag" > > time. > > > > So remember the quote from that famous hockey player "I don't skate to > > the puck. I skate to where to puck will be in a few seconds." The > > extruder has to anticipate the lag-time so it will not exactly follow > > the nozzle speed but looks at where the nozzle will be in a few > > milliseconds. > > > > These printers work because many people have invented hundreds of > > rules of thumb and encoded all this into the slicer software. > > That IMO is the wrong place for it, its the dynamics of the printer so > put that level of smarts into the driver sw. But whats done is done, so > we have to both outsmart it, but if cura hasn't a clue about the > printers ballistics, we are screwed. > > > OK, bottom line, if you say "110%" you are just adding a 10% bump to > > the rules the slicer uses. I would only do that if using undersize > > filament or if the printer has 10 undersized rollers in the extruder. > > But errors so large or unheard of. 2% or 3% maybe at most. > > > > > Whats the steps/mm for the > > > extruders default on your printer? cura is set to 110% flow, and > > > default extruder/mm is 94.50/mm at the printer. > > Which still doesn't answer the question. > > Thanks Chris. > > Cheers, Gene Heskett > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > Genes Web page <http://geneslinuxbox.net:6309/gene> > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
