Pressfit Assembly Process Simulation

Intro

A novel approach of the assembly process of a pressfit is shortly presented.

A pressfit is a method of fastening between two mating parts. The parts are pushed together and are hold in position with friction. Usually the parts are pressed together using a hydraulic machine. When the assembly process and its parameters are close to optimum the fatigue life of the mating parts is strongly improved.

Interference fit is almost found everywhere, from lego bricks to e-motors and aerospace applications.

Assembly Process

Generally there are two basic methods for the assembly of an interference fit

  • Assembly with the use of the temperature for shrinking or expanding
  • Assembly with Force

In this example we will speak about the 2nd case, i.e. Interference fit which is created via force. In this case, presses are used which can create significant forces, e.g 30KN and more depending on the application. These large forces can cause severe damage on the pressfitted parts. In some occasions, microcracks can be developed which can be very difficult to spot. Thus, later on during duty operation a breakdown can occur on the interfitted parts causing also abnormalities on system level.

Pressfit Simulations

There are two types for the pressfit simulations:

  • Simulation using offset parameter
    • The pressfitted parts are modeled in their final position and an offset parameter for the intereference fit value is applied
  • Assembly process simulation
    • This is closer to the real case scenario, e.g a force or an enforced displacement is applied on the one part and the other is fixed. This scenario simulates the force of the pressing machine which is used for the fastening of the two interference fitted parts. More accurate results are observed with this method since the level of detail is increased

 

Importance of Assembly Process Simulations:

  • More realistic results in comparison with the offset simulation
  • Prediction of force required for assembly
  • Virtual assembly process can be used to optimize real assembly configuration and procedure
    • Minimizing abnormalities on pressfitted parts
    • Proper selection of press machines
    • Enhancing quality and connection of parts