If you're using belts, and racks, why not span the top of the gantry with a drive shaft so the drive shaft drives both pinions, via belts. And as Dave said, probably x 1kW would be enough? Put the X motor on the left, and the Y motor on the right of the gantry.
On Wed, 3 Oct 2018 at 16:10, Dave Cole <[email protected]> wrote: > You will probably need two reduction stages to get a 10:1 belt drive > reduction. > There are some fairly cheap servo motor gear boxes out there now being > made in China. > That may be the cheaper/easier way to go. > > FWIW, 1 KW servo motors x 2 is probably an overkill unless you want to > go really fast or if your gantry is > heavy steel. > > Dave > > On 10/3/2018 9:41 AM, Leonardo Marsaglia wrote: > > Sorry for the lack of detail, I wrote the message too fast this morning > > when I just got up. > > > > I'm planning to use 1 kw servos on each side with a max RPM of 3000. The > > idea is to gear down from the motor to the pinion 10 to 1 using the > timing > > belts. The pinion I'm planning to use is a MOD 2 with 20 teeth. That > would > > give a theoretical linear max speed of 37 meters/minute. > > > > I was thinking about making a custom component for offsetting the index > > pulse on the encoders but I don't know if this approach will be reliable > > enough. > > > > El mié., 3 oct. 2018 a las 10:17, Todd Zuercher (<[email protected] > >) > > escribió: > > > >> I haven't really looked at the documentation for Master lately, but the > >> means for setting up a multiple joint axis (like a gantry) was > documented > >> reasonably well last time I checked. > >> > >> My personal experience with rack and pinion driven wood routers is that > >> for stepper-motor drive you are going to want between 2.5-5 > >> revolutions/inch of travel. With a leaning towards the lower end of > that > >> scale. With a 2.5 rev/inch ratio and half stepping the machine should > be > >> capable of 600ipm rapids and about 0.001" resolution. If you are going > to > >> run servo motors I would suggest a ratio probably double what you'd want > >> for a step-motor, but that will depend on the max rpm of your servo and > >> what you want your max feeds to be. > >> > >> The 10:1 ratio you mention doesn't tell us much without the pinion size, > >> is that motor revs to pinion revs, or motor revs per unit length? > >> > >> Todd Zuercher > >> P. Graham Dunn Inc. > >> 630 Henry Street > >> Dalton, Ohio 44618 > >> Phone: (330)828-2105ext. 2031 > >> > >> -----Original Message----- > >> From: Leonardo Marsaglia <[email protected]> > >> Sent: Wednesday, October 03, 2018 6:01 AM > >> To: Enhanced Machine Controller (EMC) <[email protected]> > >> Subject: [Emc-users] Yet another topic about gantry homing > >> > >> Hello to all! > >> > >> I'm building a CNC router for wood machining for a friend of mine and > the > >> best way I found to drive the Y joint for this particular design, given > the > >> size of the machine, is the following: > >> > >> One rack and pinion on each side of the longitudinal axis of the machine > >> and each pinion conected to a servo motor using two steps of reduction > with > >> synchronous belts to achieve a 10 to 1 ratio. > >> > >> I've found several topics on the forum talking about the homing of an > axis > >> arranged like this. I guess to have screw regulated home switches for > each > >> Y joint is almost a must (in case you don't use linear scales). But I > was > >> wondering if it's possible to use ,in conjunction with that, the index > >> pulse of an encoder coupled to directly to the pinion. > >> > >> My idea is to offset the index pulse on each encoder via HAL to make > both > >> sides of the Y joint trip the index pulse together and stay squared > during > >> homing. Is this a good practice? > >> > >> About how to drive both Y joints as one axis: I've read that there's a > way > >> of simply adding two Y joints for the Y axis in the 2.8 master branch > but I > >> don't know if there's documentation available already. > >> > >> But I was thinking about slaving one of the motors (using them as pulse > >> and direction at the beginning to make things easier) and use the > encoder > >> on the pinion only for following error and homing. I don't like the open > >> loop approach a lot, but I don't know if it's that easy to use them as > >> servos in position mode without having too much trouble. > >> > >> Any thoughts? > >> > >> Thank you as always! > >> > >> Leonardo > >> > >> _______________________________________________ > >> 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 > >> > > _______________________________________________ > > 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 > _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
