My source for buying belts and pulleys is SPD/SI. On their web site is some tables that will allow you to select the proper size belt. https://sdp-si.com/resources/ <https://sdp-si.com/resources/?__hstc=17737510.3e5772cd89fd8895ac0a28d5443e3d45.1608251035258.1608756820467.1609012093153.3&__hssc=17737510.2.1609012093153&__hsfp=4202248466>
Here is a good on-line length calculator. Length: https://www.bbman.com/belt-length-calculator/ One more thing: If you are going to replace the belts and one pulley why not replace BOTH pulleys and move to a more modern tooth profile? The newer GT2 profile will be stronger, have near zero-backlash, and is quieter. In general, the newer rounded profile is better than those square profiles. On Sat, Dec 26, 2020 at 11:34 AM John Dammeyer <[email protected]> wrote: > Hi everyone, > As I mentioned in a previous posting I'm expecting a Bergerda AC Servo to > replace the Stepper motor on the knee of my mill. > http://www.autoartisans.com/mill/KneeDrive.jpg > > The photo shows how the stepper is connected. The L type pulleys were a > gift from a friend who salvaged them from some equipment. The ratio is 3:1 > with the smaller pulley having an insert for the 1/2" shaft on the stepper > motor. With 3:1 the 7NM motor can work up to 300 RPM before the torque > falls below about 3.5NM and it stalls. That 3:1 reduction puts 100 RPM > works out to 25ipm. > > The 80SM-M0320MAL I've ordered will handle the 3.5NM all the way to the > 2000 RPM max speed will give 166 ipm which is probably way more than the > vertical ACME screw can handle on a regular basis but I'll be more likely > to do a quick move to a tool change position than right now where it > appears to take forever to get out of the way. > http://www.autoartisans.com/mill/80SeriesACServoMotor.pdf > > I'm right on the edge though. I'd like to change to 4:1. Currently the > upper pulley at 36T, as shown in the photo, is slid onto the 25mm shaft and > anchored onto the square handle drive part. The lower pulley at 12T has a > steel insert with a single set screw on the stepper motor 1/2" flat. > > Making a new lower pulley with 9 teeth is out of the question. It's too > small for only 9T and definitely won't fit on the 19mm motor shaft. And > that's the kicker. At almost 3/4" the pulley that goes onto it has to be > large enough to have a decent grip with set screws onto a 6mm key. > > And so here's the problem. A large enough pulley from say Misumi, in L > Type, makes for too many teeth to get 4:1 without a huge driven pulley. > I've been using the various pulley calculators and I can't seem to come up > with a different belt size that will work. > > My thinking is as follows: > 1. A 4:1 ratio implies driven pulley is 4x the diameter of driving pulley > 2. A driven pulley of 6" diameter means 1.5" max for the driving pulley or > a Pd of 38mm driving 152mm Pd. > 3. 38mm - 19mm shaft diameter leaves 19mm or a hub thickness of 9.5mm. > 4. Minus half the key width of 3mm I'm left with 6.5mm set screw length. > That's enough right? > 5. Circumference of 38mm Pd pulley is about 119mm. > 6. Using an XL size belt with a pitch of 5.08mm suggests about 24 Teeth > and a Pd of 38.8mm. > 7. So I need 96 teeth or circumference of 487.68 gives 155.23mm diameter > (6.11") which is just at the max size. > > Will an XL series 9.5mm wide belt be strong enough turning a 24T 39mm > pulley at 2000 RPM which drives a 96T 155mm pulley at 500 RPM? > > Do I have enough 'meat' on the driving pulley? > > Is there a better more appropriate belt style? > > Thanks > John Dammeyer > > > "ELS! Nothing else works as well for your Lathe" > Automation Artisans Inc. > www dot autoartisans dot com > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
