Although the finished product might look simple, and no doubt the experts make it look easy, the deep drawn process is actually one of the most complicated methods of manufacturing available. The act of forcing metal into a given shape introduces a host of possible problems and concerns. To the trained eye, the finished product can tell a very clear story about the quality of the process.
Most deep draw problems stem from a combination of design and tooling. Listed here are five of the most common, along with a short summary of possible causes.
This is one of the most common deep draw problems. Fracturing of the metal during the draw process can be caused by several issues although the most common is the clearance between the punch and the die. If this is too small, too large, or uneven, the material can be cracked during drawing.
Wrinkles on the Top Edge
This problem is typically due to issues with the blank holder. If the holder is too tight, unbalanced, or if the blank has a burr on the holding edge the metal will not flow correctly and create tell-tale wrinkles along the upper edge.
Uneven Top Rim
The upper rim of the part should be even and concentric. If not, the issue is most often attributed to poor punch die alignment. This condition can cause too much material to be drawn into the die and preventing the formation of an even top rim.
Fractures at the Bottom of the Cup
This deep drawn problem is also attributed to the condition of the blank and blank holder. If the surface is nicked or galled it can reduce the flow of material into the die, causing cracks to form in the bottom of the cup.
Excess Material at the top of the Drawn Shell
This issue develops when the material is too thick, or the die clearance is too small. Both conditions prevent the metal from flowing properly during process, resulting in a thicker region at the top.
Understanding the deep draw method in detail, along with the knowledge of how to inspect a finished part, is very important in the decision making process. This information can prove invaluable during both the concept and design phase of the project, and can ensure the right outcome the first time.