On Tuesday 02 June 2020 16:37:08 Chris Albertson wrote: > I just printed a set of 3mm pitch GT3 timing pulleys with my 0.4 mm > nozzle. They came out just fine. > > The final profile of the pulley tooth is not determined by the > nozzle diameter it is limited by the step size on the printer. My > pulley fit the belt well enough that tooth shape is not the limiting > factor. On my case it is runout, not tooth shape that will cause > the greatest error. > > Think of an end mill cutter. I can make sharp corners with a 12mm > diameter end mill. What I can't do is make less then a 6mm inside > radius. Same with the nozzle but backwards. A 0.4mm roud nozzle can > make at best a 0.2 radiu corner while the 0.2 nozzle can print a 0.1mm > radius. But the printer steps are that size and introduce a larger > error than the nozzle. In any case what you really care about is error > in motion transfer between the pulleys. Runout matters but a tiny > radius error on an outside corner does not change how the belt sits in > the pulley. > > There is a big disadvantage to 0.2 nozzles (1) they clog up and need > cleaning and (2) printing is about a lot slower. > > Your first step before printing pulleys is to print a cube. Use CAD > software so you know the exact dimension you specified, run it trough > the slicer, print and measure all sides and angles. Get those > measurements good enough. > > When designing with plastic, you have to make stuff bigger. Use the > largest pulleys that will physically fit and this keeps the percent > error down. > > I any case my A6 primer is the same as your Ender except mine uses > ground steel rods for track and yours uses extrusions, But everything > else is the same all down to the Merlin firmware. My 3mm pitch by > 9mm wide GT3 profile pulleys came out pretty good. I had to make > the flanges wider as the aluminum pulley design has tapered flanges > that came to a point. I made them thicker and blunter and used a 20mm > center bore. Odd that I could print the tooth profile just fine > but not the flanges. > I'm about 90% done with a 10 tooth XL, and not at all impressed by the actual tooth profile as it has lots of voids. Supposed to have a top flange, but its not gotten there yet. The bottom was supposed to be about 10mm thick so the captured nut would have lots of meat around it, but its not sitting flat on the bed, came loose in the first mm and the hub section is way thin, guessing 6mm is all. Cuda had a profile for an ender 3 pro, but this isn't showing me its optimum. Done. Looks like an XL belt will fit, the flange looks usable. Had to dig out the nut pocket as it had the first layer laydown across it, but I've no clue where I might find a nut that small. Even the base hub is semi transparent like the PLA feed was too slow to fill 100%, I can hold it up in front of the monitor, shade it from the overhead lights and see flashes of light coming thru between the strings in the nominally 6mm thick base hub. I wouldn't call that more than 25% filled. And the teeth are edgy enough to affect the service life of the belt.
So, redo it for a 10mm thick hub, and turn up the extruder feed to get better fill? Or reduce the xy feed rate, giving the pla a better chance to fill? Which stands the best chance to getting something usable on the next pass? Then I need to make a bigger one, 28 or 32 teeth. To serve as the Z drive on the Sheldon, first match the current tooth count just to see if a 3NM motor is froggy enough.. Mainly because I have spare belts for the existing rig. What I have obtained is a nema 34 to nema 23 adapter, and that won't change the belts tooth count since the motor shaft won't move laterally. Stay safe and well & thanks Chris. Gene _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
