A Seminar on

Design of Rolling-Friction Power screw(Ballscrew)

Savitribai Phule Pune University

Department of TechnologyPune Presented by :

Shinde S. M. (MM15M09) Jadhav Nilesh (MM15M13)

EXPERIMENTAL STUDY ON BALL SCREWS“International Conference onDiagnosis and Prediction in MechanicalEngineering Systems, 2009 by Galati, Romania (XV), ISSN 1221-4590, Issue 1 TRIBOLOGY

Guided by :Dr. Rachaiya

HISTORY OF BALL SCREWS There have been attempts to replace sliding

friction screws with rolling friction screws since the 19 century.

The first practical application of ball screws was by General Motors, who used ball screws for their steering columns. Since then the technology surrounding ball screws has advanced rapidly.

Then used in CNC machines, automated manufacturing, and medical devices. With superior accuracy, repeatability, and high efficiencies ball screws are the best way to translate rotational motion into linear motion

INTRODUCTION The primary function is ball screw is convert

rotary motion to linear motion. The Surface of the screw and nut are

separated by Ball. The screw and nut have approximately semi

circular thread profile.

CLASSIFICATION OF BALL SCREW CIRCULATION

A) External recirculation 1.The balls are diverted from the ball tracks and carried back by the ball guide return tube from a loop.

2. The return tube are located outside the nut body.

B) Internal recirculation 1. The circuit is closed by a ball return cap in the nut allowing the balls to cross over adjacent ball track.

2. The ball return cap are located inside the nut body.

C) End-cap recirculation

1.The system is the same as the external recirculation type nut .

2. The return tube is made inside the nut body as through a hole.

CLASSIFICATION OF BALL’S

DESIGN Preload Calculation

Fig 4.20

Variable load and constant speed

A) Common transmission (rotary-linear)

B) Reverse transmission (linear-rotary)

Mechanical efficiency of ball screw

The formula for motor drive torque is

a)

b)

STIFFNESS An indication of the rigidity of a machine. Total stiffness of the machine feed system.

THE STIFFNESS OF BALL SCREW

The Stiffness Of The Nut calculated by,

SELECTION AND INSTALLATION1. A ball screw must be thoroughly cleaned.

2. The ball track free from dirt and damage.

3.To achieve the ball screws maximum life, recommend the use of antifriction Bering oils

ADVANTEGES Efficiency is as high as 90% The operation is smooth when compared to

other type of screw A ball screw is virtually wear free due to the

presence of lubricating film. Load carrying capacity is more light weight.

DISADVANTEGES Costly. Overhauling due to low friction. Separate brakes are used to hold the load. Bucking of screw and critical speed are serious

problems. Require high degree of cleanliness.

APPLICATION

Automobile steering gear. Power actuator. CNC machine. Aircraft landing gear retractor. Transport machinery.

CONCLUSION Based on the equilibrium of the forces and moments

acting on the ball, the sliding forces between ball and both screw and nut in a ball - screw system was determined without an integrating of the shear stress on contact ellipses.

A general analytical model for friction torques and efficiency in a ball screw system has been developed . The analytical model includes influence of the rotational speed, axial load, lubricant viscosity and geometry of the ball-screw system. The developed model leads to realistic values both for the friction torque and for the efficiency of a ball – screw system. A relation for the global friction coefficient has been proposed. So, it can be determined a global friction coefficient in a ball screw - system,

REFRANCE Journal on basic of AUGUST 2014 screw drive rod

less actuators –by- Igo glikin, senior Mechanical Engineer, tolomatic,inc -http;//goo.gl//TMEOzn www.rockwellautomation.com/go/tolomatic.

International Conference on Diagnosis and Prediction in Mechanical Engineering Systems (DIPRE’09)22 - 23 October 2009, Galati, Romania

Ball screw broacher by industrial motion control system www.hiwin.tw

Ball Screws. Technical Catalogue, Korta, available onlineat:http://www.kortasa.com/uploads/descargas/CASTELLANOINGLES.pdf

Thank you!