On Monday 16 November 2020 04:12:02 andrew beck wrote: > Sweet. I have 8 big servo drives for all my machines turning up > tomorrow I think finally. Will be so good to get my cnc lathe and > second cnc mill working. > But Andrew, that will generate a lot of 4 letter words, called "work". At my age, I ration that to what I can do with a 30% pump.
Unless it was originally built with motors. adapting it for servo motors will be a lot of work. I think the most work I did was on the Sheldon lathe, it was in bad shape, compound broken, spindle bent, crossfeed in tatters. I had to strip it down to the bed and build it back up with new designs at every aspect. Finding the right ball screws was just a start. The only thing left of the original X drive today is the crank bearing screwed into the front of the carriage. And its been machined to be the new X anchor point complete with roller bearings in both directions. None of the taper attachment that was the original X anchor is still on the machine. I sealed up the trench in the cross feed where the screw lives so swarf can't get into the new ball screw, and I covered the new ball type Z screw with pleated bellows to keep swarf out of it. I used some motors I had on the shelf which weren't that well suited for the job, and just this summer replaced both of them with the new 2 and 3 newton, 3 phase steppers that think they are servo's, reducing the stepper rattle about 99%, its now Casper the ghost when moving at cutting speeds, those 3 phase motors are very low noise. The drivers are MUCH smaller. And alarmed. I can run z into a stopped chuck jaw with a chipped tool mounted at 5 ipm, it see's the stoppage, kills the motor enables which allows them to spring back to clear the chuck jaw about 10 thou, and cancels all homes. And does it w/o crushing the $15 chip in the tool. I made clamps for the rear of the faceplates that clamp the backing plate to the spindle flange, and put a retuned vfd on the spindle motor. I've made some hal code show how far it turns at overtravel, and If I do the gcode right, calculates the overtravel distance when motion issues a reverse when doing rigid tapping. With an 8" 4 jaw chuck mounted, a good 35 lbs, and turning 100 rpm, the overtravel is .245 turn. I made a new apron plate, and it has a pair of 100 ppr dials, that I can drive by hand since there are not any hand cranks left, at selectable speeds starting at .0002" per click. LinuxCNC lets me correct for bed wear, which is considerable right in front of the chuck, so I can run it from the chuck to the tail stock at a maximum uncorrected error in the .002" range. The great unknown is the error in the 1.5 meter long, grade C7 Z screw. The X screw is a bit better, but its history is unk. Backlash is in the range of 1 to 2 thou, both ways. Pretty good for a nearly 80 yo lathe That's good enough for the girls I go with these days. :) > So I'll be asking a lot of questions about linuxcnc again soon I > think. Bring `em on. I've not quite done it yet, but I'll learn about servo's since that is what I am hanging on the side of a Chinese BS-1 clone to run it. Using a brushed 100 watt sliding estate gate motor, which has an encoder in it and is a worm drive output. > Regards > > Andrew 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
