Driving floating end (ballscrew)

[irving2008]

coefficient of linear expansion of steel is about 13 - 17 x 10^-6 m per m per degC. i.e. a 600mm length will expand max 0.01mm per degC, so allowing for normal working environment say +20degC +/- 10degC you can expect a variation of 0.2mm.

Force = delta_L * E * A/L where E=Youngs modulus (207x 10^9 N/m^2), A = area in m (2e-4 for a 16mm screw), L = length, delta_L = change in length

=0.2 * 207e9 * 2e-4 / 600 = 13800N... not a force your stepper would be happy with!

[blackburn mark]

jesus irving!! dose your mind ever sleep?

i was starting to sweat over the figures... id have still been at it till the sun came up

0.2mm... thats a bit depressing... i was hoping the aluminium frame would off set some of it but at almost twice the exspansion of steel (with a bit of carbon in it) im still looking at about 0.2mm i think

back to the drawing board

cheers for doing the maths irving xxxxxx

[AdCNC]

coefficient of linear expansion of steel is about 13 - 17 x 10^-6 m per m per degC. i.e. a 600mm length will expand max 0.01mm per degC, so allowing for normal working environment say +20degC +/- 10degC you can expect a variation of 0.2mm.

Force = delta_L * E * A/L where E=Youngs modulus (207x 10^9 N/m^2), A = area in m (2e-4 for a 16mm screw), L = length, delta_L = change in length

=0.2 * 207e9 * 2e-4 / 600 = 13800N... not a force your stepper would be happy with!

Bloody ell irving, it makes me chuckle every time i read a post off you like this, it remind me of James May off top gear when i kicks in with his maths :lol: not thats theres anything wrong with that... i wish i could understand all that lot.:tup: