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MIG Welding - Gas Metal Arc Welding (GMAW)
TIG Welding - Gas Tungsten Arc Welding (GTAW)
Stick Welding - Shielded Metal Arc Welding (SMAW)
Metal hemming is a process that involves folding the edge of the sheet metal to 180° onto itself. Then, two newly formed layers are flush with each other. Many automotive parts are produced by metal hemming, such as trunk lids, deck lids, hoods, tailgates and doors. There are 4 types of metal hemming: teardrop hem, closed hem, open hem and rolled hem. The closed hem is the most popular one as the process is simple. It is totally flush. However, it has material limitations, including thickness and angle limitations to avoid fracture.
Generally, metal forming is used to connect parts together to achieve a better appearance and strengthen the edges of parts.
For some material such as aluminum, the closed hem is not an ideal choice, since the flexibility them are not enough and they are easy to break during the process. Instead, teardrop hem is the best choice for this material. It is a flange which is bent over more than 180° with only marginal inside radius change, and that is the reason why it can process that low-ductility without fracture.
Hemming and seaming are two very similar metalworking processing that both involve bending metal over onto itself. The difference is that seaming is to use a seam to join two layers of metal sheet together and two layers are not flush with each other while on the other hand two layers are flush with each other with hemming.
