On Saturday 13 February 2021 15:40:22 Chris Albertson wrote: > It is very unlikely that your printer is making (say) 99.9% scale > models of yor parts. It is using stepper motors and toothed belts, > steppers always do the commanded number of steps and timing belts > don't slip and always do the integer ratio of teeth, even if the size > is off.
I've been scaling it up, about .1% or less per run, differing amounts for X & Y to get a mre perfect circle yadda yadda, and have it doiin fairly well, but then the hot end froze up and I had to replace the teflon tube from the top of th heat sink to the rear face of the nozzle, allowing around 10 thou of compression between a washer on the bottom of the shark fitting and the rear of the nozzle, plugging off that src of leaks. So generally, its back amoung the living and I jst nowam finishing the top surface of a ETG pulley about 12 mm thick with a belt track 7mm wide for a 6mm belt, and a 41.6mm hub hole so it can be pressed oer the existing alu pulley used on the axle of the A drive that came with a 4 axis 6040. Then I made in openscad, motor pulleys with the same tooth profile as the 85 toother, in 13,15,17 & 19 teeth. But they have not yet been transfered to the U-SD card driving the ender-3. I am very disappointed that files can't be moved to the ender over a USB cable, and thats one reason I bought the best dremel off amazon. Supposed to be here last night, but the roads scared off UPS. and we got a new 6" of snow turning to freezing rain this morning. Roads are black now but likely icy, so I've no idea if it will arrive today yet. > Now back to the pulley you are printing. Why care about a slight size > issue? As long as the belt never slips a tooth the pulley ratio > holds. Only with plain pulleys does a tiny size error cause a tiny > error in speed reduction. Timing belts are like gears, it is the > ratio of the teeth that matter. True, but I started as you'll recall, with a printer that was not well calibrated OOTB, and I've been piddling the the scales ever since. Ejector feed is a huge puzzle as it was set so the waving cat was virtually weightless and see thru. OOTB scale was 35 or there abouts, when it should have been around 375. Then I found the advice from MicroSwiss about tension of the ejector, was full of it when he wrote the end of the screw was to be about 3mm into the thumb but, that was so loose it just sat there and ground the filament into dust on top of the head fan. With a corresponding very obvious click. And bringing that tension up to under a mm inside the thumb nuts face stopped that slippage so I can now make a feed adjustment that actually worked, and have played with the feed rate too, so a good part of this last pulley was made at a 200% feed rate, but it went to hell when it switched to infill so I slowed it down to improve the looks of the missing infill and its finish up the best pulley I've made yet. Very well shaped 3mm teeth. So my question, for a cura default 30% infill, is what is a good infill pattern that isn't subject to being torn out by the moving head, and eventually thrown clear of the workpiece? I tried 40% but the tear out demolition was even worse. I did find a better nozzle clearance gage than a sheet of paper, 2 layers of non-stick coated Reynolds wrap, a sheet of 22lb put it so high from the glass there is virtually no adhesion even with a good haze of matterhackers glue. 2 layers is about right, but one sticks so well you damage the part & feel like its gonna take glass with it when it finally comes loose. I've actually done that, had to ice cube the glass and lifted a piece about the size on a little fingers nail out when I did come loose after I'd put it in the freezer for half an hour. The dremel has a 9 point auto-zero bed leveler. And its build plate is not square, the Y is about 30mm less than the endder-3 X. And X is close to 50mm longer. > On Sat, Feb 13, 2021 at 2:06 AM Gene Heskett <[email protected]> wrote: > > Greeting all; > > > > Messing around with the parametric pulley designer, I have made a > > larger 86 tooth pulley for the big pulley on the A axis supplied > > with the 6040 mill. I'll also change the belt pitch as its presently > > a huge XL. > > > > But the chosen belt, a GT2_3mm, is not a good fit, throwing a just > > detectable slack in the center of the wrap, inicating the pulley is > > about half a red one too small. > > > > Is this a good excuse to add a couple counts to the xy scales in the > > printer, or to play with the variable > > > > additional_tooth_width = 0.2; //mm > > > > in the openscad recipe? > > > > Doing this in PETG, so the ender-3 is at the top of its heater > > range, with a 250 degree nozzle and a 70 degree bed. And around 7 > > rendering hours to try a new fit. > > > > Thanks for any advice. > > > > 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 > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
