For a typical square tube draw, large-scale cracking can occur near the center of the straight side wall.
Root Cause Analysis
Geometry
① Draw height too large:
Before reducing draw depth to prevent cracking, verify all other conditions first. If the issue persists after checking everything else, then reduce the draw height and add a separate draw-and-restrike operation to hit final dimensions.
② Die fillet radius too small:
In square tube deep drawing, the usual fix for springback sag on the straight side wall is to use draw beads, but that leaves bead marks on the part. So when running without draw beads, set the die gap slightly tighter than the material thickness and use a small corner radius. If cracks appear beyond the material's tensile limit, increase the radius slightly and run a trial draw.
Stamping Conditions
① Excessive blank holder force:
A fully polished flange surface indicates the blank holder force is too high. Reduce it until the material flows in freely without wrinkling.
② Poor lubrication on die surfaces:
To promote material flow, check both the lubricant type and the application rate.
Methanol Injection System Solenoid Valve Housing Body
Methanol Injection System Solenoid Valve Housing Body
Tooling Issues
① Poor die surface finish or fit:
If the product cracks and the flange shows scratches, polish the die surfaces with a grinding wheel to get a smooth finish that lets material flow easily.
② Die gap too tight:
②the gap is too small:
When the side wall shows a shiny, cracked surface, that's typically a sign the wall is too thin for the draw. You'll want to open up the die clearance to reduce the thinning and prevent fracture.
③ Poor draw bead location or geometry:
Excessive draw bead force is a common cause of rupture. Reduce the bead pressure or adjust the bead profile to let material flow more freely without tearing.
④ Poor die accuracy:
If the tooling isn't precise, the core can shift, and the punch-to-die alignment—parallelism and perpendicularity—will be off. A thorough pre-run die inspection will catch these issues before you ever pull a trial part.
⑤ Insufficient blank holder rigidity:
Quando o sujeitador flexiona sob carga, apenas alguns pinos de amortecimento acabam suportando a força, o que leva a estiramento localizado e trincas. Reforce o sujeitador ou redistribua o layout dos pinos para uniformizar a pressão.
⑥ Baixa precisão da prensa:
Uma prensa fora de tolerância produzirá os mesmos defeitos que ferramental desalinhado. Antes de qualquer estampagem de teste, verifique se a máquina está mantendo sua precisão especificada—cheque o paralelismo do martelo, a folga das guias e o desempenho do coxim—e então execute suas peças de teste.
Material
① Se o defeito remete a resistência à tração insuficiente ou estrutura de grão superdimensionada no blank, você precisa mudar para um material de grau superior que suporte a estampagem.
② Se a falha é devido à chapa ser muito fina para a aplicação, especifique uma espessura maior para fornecer material suficiente para a estampagem sem estrangulamento ou ruptura.