Automotive Hemming

Hemming (Automotive) Hemming is a technology used by the automotive industry to join inner and outer closure panels together (hoods, doors, tailgates, etc.). It is the process of bending/folding the flange of the outer panel over the inner one. The accuracy of the operation affects significantly the appearance of the car’s outer surfaces and is therefore a critical factor in the final quality of a finished vehicle.

Hemming Processes

Press Hemming

Hemming presses are widely used in automotive manufacturing for hemming of sheet-metal body components. The process uses traditional hydraulically operated ‘stamping presses’ to hem closure parts and being the last forming process in stamping, it determines the external quality of automotive outer parts such as doors, hood and trunk-lid.

Hemming press features and benefits

• Die storage systems
• Fully automatic die-changing systems with parameters that change with each die
• Pressing capacity typically 60 to 180 tons
• Large panel size capacity
• More than one part can be produced on same line
• Electric hemmers do not need hydraulic oil, are quiet and eco-friendly

Hemming Press Limitations

• Restricted to flat un-complicated panel profiles
• High Cost

Table Top Hemming

Tabletop hemming machines are utilised for the manufacture of medium to high production volumes, with the ability to achieve cycle times as low as 15 seconds.

Table Top features and benefits

• Optimum panel quality guaranteed through the hemming principle of the closed ring.

Table Top Limitations

• Dedicated to one panel
• Relatively high cost.
• Cost lower than Press Hem, but higher than Robot roller hem

Robot (Roller Hemming)

Robot hemming is utilized for the manufacture of Low to medium production volumes, with the ability to achieve cycle times as low as 39 seconds.It uses a standard Industrial Robot integrated with a roller hemming head to provide a flexible solution to closure manufacture. The flange of the outer panel is bent over the inner panel in progressive steps by means of the roller hemming head. The process allows the advantage of using the robot controlled hemming head to hem several different components in a single cell. Minor changes and modifications to panel hemming conditions can also be accommodated allowing a quick and cost-effective reaction.

The robot can also be used for other tasks for example, by equipping it with a tool changing system. This will allow it to also operate dispensing equipment for adhesives and sealants, or a gripper which will enable it to carry out panel manipulation within the assembly cell.

Robot Hemming features and benefits

• The ideal solution for all volume production demands, via multiple robots and split operations
• Overall quality better than press or tabletop with MBE hemming technologies implemented
• Flexibility:

a)robot can hem various panel shapes that press and tabletop can't achieve due to flange attack angles and physical accessibility
b)can perform panel shape changes via quick program changes, while saving the original programs for future recall
c)can perform other tasks by changing the hemming tool with another tool such as a dispensing nozzle 

• Low cost, simple and quiet in operation when used with standard industrial robot
• Reduced mechanical effort for tryout

References