Abstract
Car manufacturing needs to be operated with maximum efficiency at optimum capacity of manufacturing facilities.
For this purpose, divided press method was adopted for pressing outer side panel of Legacy. For medium-scale production, relatively small machines can be used instead of supersized press machine by dividing the total press process. However, the issues of this method are how to reduce the cost for the divided panel welding and how to secure the quality of completed panels.
Facility cost of the vehicle body press method;discussed in this paper, also needs to be cut down. In addition, a full operation of the facility is essential.
Response to high-mix low volume production is conducted from a wide range of areas, such as pressing setup, reduction of running stock, minimization of production lot, reduction of facility cost, reduction of lead time, and quality of pressing setup. With regard to vehicle models of medium scale production, there is a potential risk for expensive facilities with exclusively supersized press machines to sit idle.
Even if possession of such expensive equipment is possible, the burden of maintaining a large size press die is high. The method of dividing a large sized press die into small ones contributes to cost reduction, by allowing the adaptation to small number of modified models, matching with high-mix low volume production, and fully operating an optimum facility.
The major concern we have for this method is to reduce the general cost of welding. Regarding the conventional MIG welding, we can no longer ignore the burden of the cost of thermal deformation measures and finishing, after welding. The braze method of powder plasma was developed by focusing on this point. In addition to the basic policy of reducing man-hour for finishing by cutting down heat deformation, which can be realized by minimization of heat affected zone with plasma, and by modifying to spatter-less method, we were particular about braze finish with copper powder. Molten metal deposited from iron powder penetration through the steel plate and the amount of deformation caused reaches the point that cannot be ignored. For this reason, we utilized copper powder for finishing portion as brazed, though there were several issues that needed to be solved, such as welding strength of braze.
Powder plasma welding was developed and applied to SUBARU B9 TRIBECA, in addition to the conventional MIG welding. Powder plasma welding reduces thermal(heat) deformation and simplifies the finishing work by the operator. Besides the development of a vehicle model with brazing on welded portions, we have also completed deployment of this brazing method to conventional vehicle models. As a result we were able to obtain the effect as it was expected.