View Full Version : optimum diameter???

01-04-2010, 04:07 PM
On a 500mm axis run what would be the optimum diameter for running it with NEMA 23 motor of between 1.4 to 2.5Nm ratings? currently have a 12mm and looking at the following possibilities:

1) Increasing diameter for more rigidity.

2) Going over to a Ball Screw (Currently running Trapezoidal)

3) Doing both 1 and 2 together for improvement in transfer of force and less flex.

Thanks and good to see the board active. Been away awhile dealing with health and work.


01-04-2010, 06:39 PM
On 500mm there is little to be gained to going to bigger than 12mm for rigidity reasons, the main reason to do so would be to get a higher lead and faster traverses, but you could equally achieve this with a multi-start screw. The leadscrew should not be considered a bracing element in your machine. A ballscrew will improve efficiency therefore reducing potential for stalling out under a heavy cut and increasing acceleration (but a larger diameter screw works against higher acceleration) but won't increase rigidity (but will improve backlash).

Assuming you are currently running TR12x3 what do you see as your biggest problem?

01-04-2010, 09:35 PM
Backlash is the biggest problem in doing maintenance changed out the nut for the trapezoidal screw using now and was able to get up to 1500mm/min speed at 1/8 step. So main issue is trying to get Backlash down and keep things as precise as possible.

Good to see you still here Irving, been a bit busy but glad to see you folks still around.


01-04-2010, 09:45 PM
then change to ballscrews - it will reduce backlash but not eliiminate it unless you put some effort into an anti-backlash nut.. but it will maintain that backlash for a long time unlike a delrin nut which will wear and backlash changes as it warms up...

but you wont (easily) find 12mm ballscrews, they usually start at 16x5mm (although MD currently have 16x2.5 (http://cgi.ebay.co.uk/Retrofit-16x2-5-spindle-Ball-Screw-Ballscrew-CNC-XYZ_W0QQitemZ220518093872))

02-04-2010, 12:44 AM
Thanks for the info and will look at options as may have the space to fit the 16mm ballscrew. Also working on a design for a vacuum for my mill to pick up the wood chips from the cutting surface as the current configuration is just not working well.


Thank you Irving for your input and info.