In practice, repair technicians often face a common challenge: even after pulling a vehicle frame back to the exact factory specifications according to the data, the frame partially springs back once the tension is released. This is not a failure of the auto frame machine; it is caused by the physical properties of the material itself.
Metal has a "memory effect." After plastic deformation, residual stresses remain within its structure. Simply using brute force to pull it back into position only overcomes the yield strength but does not eliminate these internal stresses, leading to spring-back. This not only negates all the precise measurement work but, more critically, allows the vehicle to return to the road with unresolved internal stresses. Long-term, this can lead to fatigue cracks at connection points, posing a serious safety hazard.
To solve this pain point, the repair process must move beyond simple "brute force pulling." The correct technique involves combining the stretching process with methods to "release stress." This is achieved by using specialized body hammers to carefully work the damaged area (a process known as "hot" or "cold" working), or by applying localized, controlled heat (strictly adhering to manufacturer guidelines). These techniques help realign the metal's crystalline structure and relieve the internal stresses. Only when the frame remains stable and holds the corrected position can the repair be considered truly complete and safe. This demands that the operator not only knows how to use the auto frame machine but also understands the principles of materials science.
