You really CAN print pulley teeth. You might argue "plastic is not strong enough". If so then you will have a bigger problem with the rubber belt teeth not being strong enough. All the stress is in the hub. So make that from good quality steel. I've tested these for hours. They work and you can make a pulley on about an hour using low-tech equipment. The shear force on pulley teeth is low, if not the tech would quickly shear off from the inside of the rubber belts.
Yes the pulleys you buy are nicer but you do have to machine them to fit your shaft and the cost is high. The problem with 4:1 ratio is that there is a minimum number of teeth that need to be engaged and with a larger 4X size pully the smaller one has less than half of its teeth in contact with the belt. Again, think about changing to a better tooth profile and/or belth width You then have more options to play around with. A finer tooth pitch is not weaker if more teeth can be engaged. You just have to do the engineering calculations On Sun, Dec 27, 2020 at 12:39 PM John Dammeyer <[email protected]> wrote: > There's only one issue with buying timing pulleys. It appears most of the > stock sizes are limited to 60T. So I'd need a 15T pulley on the drive side > to get my 4:1. > > And it's really all about size. To get a decent hold on the 19mm motor > shaft (no threaded end hole) and to stay within my max 160mm driven pulley > size I'm stuck with a max of 40mm. Take away 19mm shaft plus 3mm key above > the shaft and I have 18mm/2 or 9mm worth of pulley body to work with. > > A 40mm pulley has a circumference of 125.6mm. Let's set it at 125 and use > a 5mm pitch belt. That's a 25T pulley. That means I need 100 teeth on the > driven. Again not a stock value. > > So I think like Andy I'll have to make myself a cutter for the tooth > profile I end up using. I could buy a 25T and bore it to 19mm and broach > the keyway. I have the tools on hand for that since the Mill Spindle drive > shaft is 19mm. > > But even 60T pulleys start pushing $100 so really it's time to make my > own. And since I want to change to toothed pulley for the spindle drive > it's a good excuse. Just need the size that can handle 2HP and 3000 RPM. > > So many choices... > > John > > > > > -----Original Message----- > > From: Chris Albertson [mailto:[email protected]] > > Sent: December-26-20 12:13 PM > > To: Enhanced Machine Controller (EMC) > > Subject: Re: [Emc-users] Making L Type Timing pulleys. > > > > I must have missed the designed size. Yes there is a minimum size. You > > need to have a minimum number of teeth engaged. So even if you have a > 13T > > pulley, if it is very close to a larger pully it would not have enough > > teeth on the belt. > > > > You CAN design a system that works if you move to different tooth size > and > > shape. The specs on modern belts are better then the older L and MXL > > belts so you might be able to fit hat you want into the same space as the > > original. You do a recalculation from scratch. > > > > As to how to make the pulleys. Just buy them. But for testing you can > 3D > > print timing gear pulleys. I make mine by printing a plastic ring with > > the teeth and then epoxying the ring to a steel pulley hub. Fully > printed > > pulleys don't work well but the hybrids are nearly perfect and really > easy > > to make > > > > To make a plastic ring, download the CAD file for the pulley from the > > vendors web site. I use SPD/SI and get the .step file. Then use yu CAD > > system to bore a huge hole (like 20mm or 30mm) in the pulley model. > Print > > that. Then as the printer is working turn a 20mm or 30mm hub on your > > lathe and drill and tap for set screws. What makes this a quick job is > > that they provide CAD files or every pulley so you don't need to know how > > to layout the teeth. > > > > > > > > On Sat, Dec 26, 2020 at 11:57 AM andy pugh <[email protected]> wrote: > > > > > On Sat, 26 Dec 2020 at 19:34, John Dammeyer <[email protected]> > > > wrote: > > > > > > > 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. > > > > > > I seem to recall that it is recommended to not go below 12T anyway. > > > > > > I don't know much about L and XL belts, all my machines have used T5. > > > T5 is available in widths from 8mm to 25mm. > > > https://www.bearingboys.co.uk/T5-Section-5mm-Pitch-1224-c > > > > > > I also have the correct hob for making custom T5 pulleys, so that is > > > one reason for _me_ to use them. > > > > > > You could consider ignoring the keyway, especially if the motor shafts > > > have a threaded hole in the end. > > > > > > I have several times taken inspiration from the Trantorque bushings: > > > https://uk.rs-online.com/web/p/keyless-bushes/7542545/ > > > However they require a huge central bore, so what I have done is > > > machine the pulley bore with a taper and then pull or push in a > > > sleeve. > > > At various times I have used a bolt in the end of the shaft, a nut > > > pulling the wedge through, or a ring of bolts to push the wedge in. > > > > > > Here is variation on the theme, with two tapers: > > > https://bodgesoc.blogspot.com/2017/01/gears.html > > > > > > -- > > > atp > > > "A motorcycle is a bicycle with a pandemonium attachment and is > > > designed for the especial use of mechanical geniuses, daredevils and > > > lunatics." > > > � George Fitch, Atlanta Constitution Newspaper, 1912 > > > > > > > > > _______________________________________________ > > > 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 > > > > _______________________________________________ > 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
