Rotating Ballnut - design ideas

[D-man]

I would like it to cut Ali is there a reason you think it's just a woodworking machine? What have I done wrong lol?

If you wanted to test the R2020 screw and nut I don't have a problem sending some over as long as you send them back when your done :-)

[JAZZCNC]

If you wanted to test the R2020 screw and nut I don't have a problem sending some over as long as you send them back when your done :-)

Sure he will but in 5yrs time then they'll be bent and worn out. . lol

[Jonathan]

I would like it to cut Ali is there a reason you think it's just a woodworking machine? What have I done wrong lol?

Er, not sure really... maybe the MDF bed. That wont stop it working, but my router bed is currently MDF and it is rather limiting.

If you wanted to test the R2020 screw and nut I don't have a problem sending some over as long as you send them back when your done :-)

Thanks for the offer, but it wouldn't really be practical/worth it .. I'll just wait and see how it goes on your machine.

Was the 3x figure a guestimate or based on based on "real world" experience? Your reply may help me determine if some unlabled steppers I have will work reliably in my first router.

I used 3x because that's what's in irving's motor calculation spreadsheet. In reality I got a lot better than that - if you include the inertia of the pulleys in the calculation it's quite a lot more accurate.

[boldford]

I used 3x because that's what's in irving's motor calculation spreadsheet. In reality I got a lot better than that - if you include the inertia of the pulleys in the calculation it's quite a lot more accurate.

Many thanks for the pointer. That's really useful information which may save me some grief.

[jcb121]

I'm just wondering, that timing pulley you used? was it around 26 teeth 5mm pitch?

[Jonathan]

I'm just wondering, that timing pulley you used? was it around 26 teeth 5mm pitch?

For the one in post #61 I used a 30T HTD 5m pulley. Clearly it depends on the ratio you require, but if you can keep the pulleys small that helps a lot with reducing the moment of inertia of the rotating assembly.

[jcb121]

yeh, i was thinking of using a 24 tooth one as that would give me a lot of factors to change the gearing.

but it has the same amount of factors as 30 so either will be good in my design :)

[Jonathan]

But factors aren't the only factor...
Ideally you don't want to be using less than a 15T pulley as that bends the belt a lot and gets lower tooth engagement, so if you need a 1:2 ratio then you've got to go with at least 30T. However if you're happy with ratios from 15:24 and you can fit the ballscrew shaft through the 24T, then use it as it's inertia will be about 60% less than the 30T pulley. That will help get high acceleration, although you need to consider the system as a whole not just the pulley.