Re: Extending the length of ball screw

Hi Hannu,

The screw is going to be used for a mill. The original lead screw is
32mm in diameter, so will be my ballscrew. In my country there is a
ballscrew company called HIWIN, I haven't contacted them yet because
I still think eBay is my first choice. The cost will be high for a
new one I know.

Your recommendation of mounting design sounds excellent for me,
thank you.

Horace.

--- In CAD_CAM_EDM_DRO@yahoogroups.com, hannu venermo <hvenermo@...>
wrote:

>
> I will help if you can indicate a bit ...
>
> diameter in mm ?
> screw speed in rpm ?
> tolerances required ?
>
> Any general info ... what are you going to use this for ?
>
> What kind of ballnut ?
> 1-start, 2-start or more ?
> Rise, or How many turns per inch or mm per turn ?
>
> I think someone commented on this about 1-1.5 years ago ... and

they

> did it.
> If you anneal the ends, and weld, and can machine the grooves at

the

> joint it may work ... but difficult IMHO.
>
> Better is to drill/(maybe tap) the ends and join two identical

pieces of

> screw, either with screwed or pressed fitting.
>
> You could use drill rod or precision ground rod, about 1-1.5 times

screw

> diameter hole,
> and have an interference fit about 0.02 mm smaller hole than the

rod,

> then head the ballscrew to about 120 C, slide the rod in, and let

it set.

> It would hold fairly large forces, but the things to watch out for

may be

> your max screw rpm ?
> whipping of the screw if its a fast rotation (over 200-400 rpm),

will

> bend it and create *very* large tension/compression forces on the

joint.

> This depends on screw rigidity, material, and diameter.
>
> How do you mount the screw ? On bearing or two on fixed end ? Is

it

> rotating screw or nut ?
>
> My recommendation for this, as its fairly comples/advanced anyway,

is to

> a. rotate nut
> b. have screw use a dual-suppreted fixed end.
> c.have the screw under tension (slight tension pre-load), with

moving

> end having the ability to move away from the fixed end.
>
> Is this for plasma cutter, router, mill, or table positioner ?

What are

> the loads ?
>
> One example; rotating screw.
> Use about 25 mm screw (20 mm is normally enough, but the joint
> definitely weakens it)
> Rotate max 300 rpm
> Fixed end: use 2 dual-row angular contact bearings, separated by

100 mm,

> on one end. This is the fixed end.
> Use one bearing at the other end. Have the lead (=rise) mach your

needed

> speed at 300 rpm.
>
> i.e. if you need 2000 mm /min speeds (about 80 inches/min) , at

300 rpm,

> its 2000/300 = 6.6 mm rise per turn.
> Use nearest rise in 25 mm screw you can get, probably about 5 mm.

This

> would give you 300 rpm * 5 mm/turn or 1500 mm/min, or about 60
> inches/minute.
>
> For a rotating nut, use timing belt to rotate the nut, and tension

the

> screw maybe about 80 kg, for 100 cm working length,
> you would need a screw of about 120 cm.
> e.g. 15.9 mm NSK bearing + 100 mm space + 15.9 mm NSK bearing +

100 mm

> working are,
> plus ballnut (maybe approx 80 mm) + 4-bolt flange bearing about 33

mm,

> total 1164 mm == 120 cm.
>
> [ ref: 490-0776 in RS-components
> NSK bearing codes:
> 3202BTNG
> YRLN5
> 508 ]
> >
> > Hi,
> >
> > I need a ball screw of total length around 1000mm, but best I

can get

> > is about 500mm only, so I need to add some length at both ends

for

> > mounting the screw on the table. Have anyone done this before

any helps

> > would be much appreciated.
> >
> > Regards,
> >
> > Horace.
> >
>