Z-axis probs on my BF-20vario

[ironDigit]

hi guys since i know some of you got the same machine i hope you can tell me whats goin on

my Z-axis seems to be jammed it's really Really REALLY hard to turn the wheel
and i havent got a clue what might be the prob

did anyone encounter this prob with his machine ?? and more importantly (how)did you solve it ??

i remember reading about someone tightening the nuts on the trapezoidalscrews on this machine, to reduce backlash. a picture of this would be very helpfull too guys.
does any1 have any pics of the disassembled Z-axis. and does taking it apart as well as putting it back together need any special tooling?
i have an extractor for handwheels and pully's but no dialmicrometers, so might i lose accuracy when reassembling after taking it apart??

any kind of info will be dearly appreciated and handled with care
pls dont hessitate now

[ironDigit]

oke this is the situation right now

after taking the hole Z-axis apart i was happy to notice that all the castings were in good condition and no damage what so ever

but after sunshine comes rain
so that left me with the question of what it was causing the 'jamming'of the Z-axis
so i starterd testing all the parts manually on movement jamming and binding and can't come to another prob but the trapezoidalscrew has ??warped,bended,wear out??or something alike since when i manually move the trapezoidal nut along the screw it runs nice and smooth in the end of the screw and as i pass the half the nut all at the sudden it jams and is harder to turn not as hard as turning the handwheels is but none the less there is huge difference in friction and it sometimes almost binds wich i think is quite abnormal cause wear shouldn't cause any binding for as far as i can tell

could any1 else come up with a logical explanation for a leadscrew and a nut to suddenly start jamming and binding after a year of functioning without hessitation?

the leadscrew is nice and shiny i dont know what metal it is but the nut looks like grayiron/castiron though

since there isn't any visible damage photoos seem useless too me let me know if it would help answering my question i just hope no1 replied yet cause my problem was too vaguely described in the startpost but that was all the info i had at that time

[LongRat]

Take the nut right off the screw and inspect for pieces of metal swarf or debris in there. A small piece of metal would be enough to really bind up the screw.

[phil burman]

Just my thoughts:

If it was previously running OK then one of three things must be wrong.

1) The leadscrew has picked-up some material or it is gauled (spelling?). Carefully examine the offending area with an "eye piece type" magnifying glass. Cost you a couple of dollars. Its important to ge up real close.
2) The leadscrew is bent. This might explain why it is tighter with the handle wheel, in the assembled condition, with the leadscrew restrained. For it to be this one the point of binding would most probable be close to the center of the leadscrew length. Possibly you could check it on a flat surface with feeler gauges or between centers in a lathe with a DTI or a dummy cutting tool and feeler gauges. If you don't have a DTI then shame on you because you should . They are not that expensive and extremely useful.
3) A thread or threads on the leadscrew are deformed. not sure how to check this but if it is not 1) or 2) then maybe it must be 3). You might be able see it in a magnifying class.

Does the nut have backlash adjustment, what is the measured backlash in the free running area.

Based on the above it would be reasonable to ask if you have had a bad crash recently.

Methods for correcting any of the above would depend on the equipment you have and your ability.

Regards
Phil

[ironDigit]

oke debris and pieces of metal is the first thing i ruled out though i dont have a clue what gauled means

how can a leadscrew all at the sudden just bend while contained and assembled
ánd again i haven't got a clue what a DTI is though i'm sure its pretty usefull

phil i did move the machine to the other side of the room by meself a few weeks ago by just putting it on its side and pulling it over to the new bench ofcourse there is a possibility something went wrong but then again the nut and screw are contained in a quite massive pilar so...

p.s. when i took it apart at first the nut was full of VERY very fine metal powder that looked all grey like the nut itself so i'm sure the nut had wore quite a bit

i'll get started on a magnifying glass right away

thx alot guys any other tips still welcome and what do gauled and DTI mean exactly ??

its situations like this that make me wonder what should be on top of my christmaspresents list a lathe or a retrofit for me mill? any thaughts on that guys ?

[LongRat]

A lathe would help you set up your retrofit - I'd get one before a CNC mill conversion personally. By the way a DTI is a dial test indicator, essential equipment.