On Wednesday 25 May 2016 02:38:57 Gregg Eshelman wrote: > If I was that hard up for a vacuum nozzle reducer... lathe + random > bits of PVC pipe and other stuff laying about the place. ;) We know > you have a lathe... > Nah, the darned thing is busted again. Stripped the teeth off the drive belt. Probably more than 10 belts its done that to now. I was so PO'd that I haven't even looked to see if I had another spare, I just walked away because if I had pulled it out to start disassembly #21, I may have just taken a 4 lb hammer & made scrap iron out of it.
I don't care how much lipstick you put on it, that thing is still a pig that should be been sold as a 1x12 as the drive system, even when replaced with all metal parts as that one now has, that cogged belt simply cannot transmit the torque needed to take a cut of steel off big enough to cool the insert once the diameter of the workpiece exceeds 3/4". And the cogged belt in it now is a different, newer profile with 3x the horsepower rateing compared to the more rounded tooth profile of the OEM belt. I even put a jackscrew in to block the shaft and mounting flex from ever flexing enough to give it some slack, and it was tensioned to the no slack condition on both sides of the pulley. That setup can be had on flea bay, advertised as speed reducer fotr the 7x10-12-14's, which I do not need since the jackshaft is already a 3/1 reduction from the OEM motor, and this motor is a 1 HP treadmill, running on one of Jons PWM Servo amps with nominally 107 volts dc & at least 10 amps CCW available. 1400 rpms at the spindle sound like 10 grand at the motor. With the backgear in high. About 800 revs in low. If I fix it again, the lower pulley will be replaced by one with at least 10 more cogs in order to distribute the load over 5 more belt cogs. This belt is available in 5 cog increments, so I'd be in adjustment range if I order a belt 10 cogs longer, and a pulley with 10 more teeth. Let the motor slow down to about 60% and grunt some more, Jon's amplifier can certainly do it. How does that math work when you intend to stay within say 2mm of the same center to center distance? 10 more teeth on the lower, smaller pulley would bring it up to a much better match to the upper pulleys size, which is IIRC currently a 28 tooth. OTOH, I am about to go get a bigger lathe, which means I start the cnc conversion all over again, possibly even using some of the motors on this one. This one was a nice, VERY educational conversion but I've beat this horse to death too often asking it to do what it was advertised to do, swing and cut a 3" OD part when it was sold as a 7". And I have one of those 8mm ball screws with the teeny flangeless nut, for the crossfeed conversion, left yet. The problem with it is designing a swarf free environment as the nut has no felt wipers. I did make some for the toy mill, but that needs a redesign as the felt crush translates to backlash and its a cast iron b---h to tighten the nuts to take that back out. BTDT, 2x already. I'll need a longer Z screw of course, if I even change it. The half nut is all new and very tight. The question is how big a motor will it take to run it w/o the reduced friction ball nut. More learning curve for sure. Like how can LCNC track the carriages position when the ball nut has been disengaged? That will probably cost a few $heckels for something to measure it and report to LCNC, the cost of which have to be balanced against the cost of a ball screw permanently engaged as then the stepper's track it for you. Eventually the ball screw is the better deal in my mind. But we'll see. One thing is for sure, that pricey new line powered driver and the 910 oz motor on the mill's Z drive is amazing, it throws that head around at 70 IPM without a complaint, or counterweight springs, with ridiculous accel ratio settings. It can follow a rigid tap peck that drives it at 30 IPM, backlash and all, without a following error. Lots of questions yet to be asked. And I ramble, trying to think 90 days on down the log. :) 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) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Mobile security can be enabling, not merely restricting. Employees who bring their own devices (BYOD) to work are irked by the imposition of MDM restrictions. Mobile Device Manager Plus allows you to control only the apps on BYO-devices by containerizing them, leaving personal data untouched! https://ad.doubleclick.net/ddm/clk/304595813;131938128;j _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
