To determine the necessary screw type and its service life for a machine drive with the following working conditions:
Max. load F1 = 38.000 N
Speed n1 = 30 min-1
Time q1 = 20%
Normal load F2 = 15.000 N
Speed n2 = 80 min -1
Time q2 = 50%
Min. load F3 = 8.000 N
Speed n3 = 300 min -1
Time q3 = 30%
Life desired for the machine = 20.000 working hours.
Screw operation = 75% of machine time.
Screw selection = d0 50 ÷ 63; Pitch 10
Calculation sequence:
a- Mean speed
b- Mean load
c- Utilisation factor
d- Necessary load capacity
On the data table we select a ballscrew od d0=50,Pfo=10 and 5 circuits which has a dynamic load capacity Cam of 80000 N, higher than necesay.
e- Service life in revolutions
f- Service life in hours
Resulting a service life superior to the service life required.
Critical speed and column load should be verified according to the select diameter, with the graphics and corresponding supports.
