On Saturday 26 December 2020 14:32:16 John Dammeyer 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 > One of the things I will do if and when I put the bigger motor and 3 phase driver on the A axis of my 6040, is to add a couple idler pulleys to improve the wrap on the smaller pulley in addition to giving me a better way to tension the belt. I've acquired several 5 pack bags of B01H3FNZ4M pulleys for that use. Then run on 3mm axles and look to be around 7mm wide but are made in most any size you might need. Meaning I should make a carrier that supports both ends of the 3mm bolt. With those mounted near the smaller pulley, I can wrap well over 190 degrees of that pulley while spanning a larger pulley at 5/1 ratio.
This should cancel any underwrap concerns re the smaller motor pulley. And it looks like you'd have buckets of room to do that to the knee drive by mounting idlers of suitable widths an inch above the motor pulleys there. With the adjuster slots I see at the top of your plates, you might not need a longer belt unless the bigger pulley gets a lot bigger. > 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. If that is the only Z feed, its a bit slow. > 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? A GT2 is probably better as it would engage more teeth, but a kevlar backed XL should get the job done. And you already have that if the adjuster slots are lengthened a bit and any clearance problems that might cause are alleviated. Oh, and show us what you make when its done and working. :-) > 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 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
