Stiff 1610 ballscrews, need help.... asap.

Hi to all,

i'm Marco, from Italy (near Milano) and this is my first effective post.

I'm an electronic designer / firmware developer and after many years (25) spent in industrial and defence sectors, due to the fact that i often deal with electrical motors, power drivers and control software, i progressively got the passion for CNC world.

But let's go toward the problem :

i bought several items from Zapp Automation, including a couple of chinese 1610 ballscrews/ballnut set.

As far as i received the package i tested ballscrews, as more critical parts, founding some problems :

following standard rules and precautions, i screwed the first ballnut on one of two ballscrew, finding immediately some important stiffness.

I gently unscrewed the nut, checked balls in recirculation circuits, repeated the screwing on operation without any improvement.

Then i stepped to the next ballnut, no more luck, even stiffer ...

So i wrote an email to Gary, but being in a hurry with the related CNC project, i started to study the problem.

First action, both ballnut went disassembled, deep cleaned, greased and balls refitted, of course only in recirculation circuits; for some strange reasons, i find this activity funny :lol:

Some improvements, but the movement of both ballnuts were still stiff, sometimes with a periodical law, and still one of two were worst.

I also noticed that along the ballscrew the stiffness ranged noticeably, always in the same way, with both nuts.

With the worst one i limited runs to minimum, to avoid mechanical damages.

Then i have fallen into a spiral of dozens of attempts, changing balls, number of balls, type of grease with mixed results.

Gary's first answer arrived, he informed me about a potential ballscrew brand exchange, with incompatible root diameter for my ballnuts.

I measured root diameter, around 13.15 mm, but if i well understood from Gary answer, the wrong ones do not fit at all, but this point it's still to be verified.

Gary kindly tried 1610 nuts & screws at its facility succesfully, sending me a video showing that, for reference; i replied with my "performance video" and root diameter measurements, but i'm still waiting for an answer.

Well, after a couple of semi-sleepless night (i have a time deadline incoming in few days and usually i do not like to give up at first) i had the idea to try smaller diameter balls placed in circuits :

datasheet reports balls of 2.778 mm (7/64 inch) diameter but it is wrong, as Gary and me verified, the one found inside were about 3.18 mm (1/8 inch), so i bought metrical 3 mm balls.

The obtained coupling play was awful, actually the total diameter drop is excessive, over 0.3 mm.

From my cellar emerged an ancient box containing about 40 used balls with a diameter ranging from 3.13 to 3.15 mm.

I inserted them in one of two ballnut and .... now it seems to work at least in a fair way.

So, for balls diameter, we are moving in a useful range of few tens of microns.

Guys, is that rigth ?
Is this solution durable or i have to expect future problems ?

Maybe these questions / consideartionscould sound dumb to mechanical experts but ... i'm an electronic expert :lol:

As i already told, i'm still awaiting a Gary answer, anyway i would have another problem :

the "special" balls are enough in number only for one ballnut (17 + 17) and the ones that i bought later, 1/8 inch, are all really precise, very far from the wanted value ... of course, as it should be.

It seems that only standard diameter 3mm or 3.175mm are commercially available, at standard prices ...

There is a DIY method to reduce balls diameter in a reliable way, starting from 3.175mm, ending to about 3.14mm ?

I fear to know the answer ....
It's also to be considered that the other nut works in a less uniform way.

Well guys, any help or similar experience comparison will be appreciated.

Marco.

For precision balls, i would try contacting a ballscrew repair business. There are a few in the UK, and probably some in your area.

Marco are the ballnuts two piece IE Double Ballnuts ?

Phil

Hi Phil,
the ballnuts are the following :

http://www.slidesandballscrews.com/s...ath=39_128_131

Marco.

Quote:

---

Originally Posted by ccmarco

Hi Phil,
the ballnuts are the following :

http://www.slidesandballscrews.com/s...ath=39_128_131

Marco.

---

Sorry my theory has gone out of the window now you show a single ballnut.

Phil

Anyway,

i would point out that Gary is still patiently supporting me in a very
good way.

Today he contacted me several times, offering a prompt swap solution.

With this discussion i'm trying to understand if i could fix the problem by
myself, saving time, because i'm near to a time deadline.

I'm still wondering if there is a way to reduce 1/8" steel balls diameter
for 40-50 micron with a DIY method.

Any suggestion will be appreciated.

Marco.

Quote:

---

Originally Posted by i2i

For precision balls, i would try contacting a ballscrew repair business. There are a few in the UK, and probably some in your area.

---

It sounds like a strange job :smile:
But i could imagine well paid ....

I found some advertisement of steel balls manufacturer that offers special diameters service, but i guess it would be quite expensive for 100 pieces ;-)

What if i treat balls between a rigid sandwich of sandpaper ?

I know, i'm starting to be laughable :lol:

But there is a thing that i'm seriously asking to myself :

does the lettering applied to plastic tap on ballnuts have some meanings ?

The couple of ballnuts in object have double recirculation circuits each one, with different taps lettering.

See attached photo showing what i mean for "a tap".

Marco.

here's a link to a ballscrew repair company

http://www.bidefordballscrews.co.uk/

These are normally chemically reduced in size in a spinning contraption until they fall through the appropriate size hole. What chemical they would use i don't know but you would need to keep them spinning as not to loose shape and neutralise them with something suitable afterwards? What dissolves steel?

This experience let me understand what microns counts in precision mechanics.

I'm used to deal with nanoseconds, nanoAmpere, picoFarad and so on, sure i did not expect that a so small balls size gap could change coupling friction so deeply.

Sure, i have a lot to learn here ...

Marco.

Hi to all,

the end of the story is the following:

i sent to Gary some videos showing ballscrews behaviour and following his suggestion, i will send back one ballnut.

Marco.