Products » Ball screws

### Ball Screws

The ball screw is a motion transmitting element for machine tools and various machine components, which converts rotary motion into rectilinear motion with high efficiency, high accuracy, load capacity, rigidity and long life.

The selection, installation and operation of the right type, power and size variants requires great care.

Production drawings can be based on
• customer drawings
• Sketches and design data
• supplied samples

#### Manufactured ball screw types

The size charts show our standard types and sizes.

Ball screw user manual

## General characteristics of Szimikron ball screws

### Accuracy classes

3 / DIN 69051, ISO 3408

Left / Right

### Material quality

spindle: 100Cr6, induction hardened
nut: BC3, case hardened

hardened, ground
HRC 60 ± 2

wiper: polymer

## DESIGN GUIDE

If the characteristic load data and the dynamic base load „C” of the ball spindle are known, the calculation can be done using the following formulas:

Nominal life duration in number of rotations:
L=(\frac{C}{F_m})^3·10^6

[turnaround]   where:

Fm = average axial load [N]
C = dynamic base load [N]

Nominal life duration in hours:
L_h=\frac{L}{n_m·60}

[Nm]   where:

nm = average RPM [min-1]
(Note: L h lifetime refers to the ball screw. The machine life in hours = L h ∙ X , where: X is the ratio of the machine and ball spindle start-up times)
Average RPM and average axial load calculation

With the variable speed and variable axial load force that characterise the use of a ball screw, the operating cycle of the ball screw must be broken down into a few typical working phases. The values nm and Fm of the above formulas must be calculated from the speeds and axial forces characteristic of the typical working phases

Average RPM:
n_m= \frac{q_1}{100} · n_1 + \frac{q_2}{100} · n_2 + … + \frac{q_n}{100} · n_n
[min-1]

where:

ni = rpm of the i-th phase [min-1]
qi = time rate of the i-th phase [%]
F_m= \sqrt[3] {F^3_1 · \frac{n_1}{n_m} · \frac{q_1}{100} + F^3_2 · \frac{n_2}{n_m} · \frac{q_2}{100} + … + F^3_n · \frac{n_n}{n_m} · \frac{q_n}{100} }

[N]

where:

F i = axial load of the i-th phase [N]

n i = RPM of the i-th phase [min-1]

n m = average RPM [min-1]

q i = time rate of the i-th phase [%]

If the ball screw’s characteristic load datas ni … Fi … qi and the Lh planned lifetime in hours are known according to the formulas above, then the required dynamic base load is calculated with the formula below:
C=F_m · \sqrt[3] {\frac{L}{10^6}}

[N]   where:

L=Lh · nm · 60 lifetime [turnaround]
(Fm; n m values according to the formulas above)
Driving torque – for conversion of rotary motion into linear motion
M_ta=\frac{F·P}{2000 · \pi · η}

[Nm]   where:

P = pitch [mm]
η = efficiency (~0,9)
Drive performance
P_a=\frac{M_{ta} · n}{9550}

[kW]   where:

M ta =drive torque [Nm]
n = RPM [min -1]

## USER MANUAL

Ball screws require precise and rigid installation. Both the parallelism deviation between the spindle and the guide rail and the deviation of the nut mounting inclination must be kept within minimum tolerances.

The ball screw endings are designed according drawings provided by customers. The ISO 3408 EU standard shall be used as a guide for the specification of tolerances on shape and positioning corresponding to the accuracy class.

Ball screws can be lubricated with basically the same lubricants as rolling bearings, but the lubricant consumption is higher. The lubricant can be oil or grease. Oil lubrication allows higher speed because the it heats up less, than grease lubrication.

For grease lubrication, re-lubrication every 6 months or so after the running-in cycle is sufficient.

Following the parameters and sequence below:
• nominal diameter: 40 mm
• thread pitch: 20 mm, right
• ball size: 7,144 mm