so, as some of you know, i have a novakon nm200 (as well as a nm145).
i am not the first owner but if worked with it since it was nearly new. its a long and stupid story, but what it ends with is the nm200 is now mine.
the original owner used the machine often, but was not very skilled with it. at some point this year he seems to have damaged it, and it now has 0.002" backlash in the y ball screw, and 0.013" in the x ball screw. ive measured and checked thoroughly and the play is definitely in the ball nut. my assumption is that one of his many crashes with the machine damaged the ball nut leaving it with play. when the machine was newer, i had measured it, and it had near zero backlash. the Z still has no measureable play.
so, i decided this was an oportunity to upgrade and overhaul the beast.
first on the list is new X and Y ball screws. i decided to skip any attempt to repack and repair the old ones, as quality new screws from taiwan are not very expensive. so with the new screws will come the first 2 enhancements:
1 - ill be using 2510 screws this time. double the pitch of the stock ones. this will put the steppers into a better rpm/torque range, and should easily improve rapid speeds to 200-250IPM with solid reliability.
2 - i will be altering the X travel. right now i get up to 28" travel, overrunning the table on the non drive side about 7.5", and on the drive side about an inc and a half. this seems to let the table sag a little on the extreme end which i dont like. so ill be recentring the screw and offsetting the motor mount so that the table over travels the saddle 5" on each side. this will give me a comfortable 29" travel, and be more stable than it is now.
3 - im rigging the limit switches to estop the machine 1/8" from the hard stops. steppers seem so innocuous when they "bounce" off an obstical, but i have the strong feeling this causes real damage, especially with those huge nema42 motors. ill have a push button override to allow you to job back into the safe area.
george at xzero in toronto will be providing me with the screws, i just need to get the ends machined with good precision. ill be using standard grade 7203B angular contact bearings in custom steel blocks for supports. i think higher precision grades are overkill for this application. total cost should be under $500. ill post more as things progress.