Knowledge Bank

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Fillets, Ribs, And Corners

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FILLETS

Intersecting surfaces forming junctions of metal thickness are properly joined with fillets in order to avoid high stress concentrations in the die castings and to control and facilitate maintenance of otherwise squared edges in the casting die. Fillets projected in a direction normal to the parting plane require draft, but the amount is always governed by the draft of the intersecting surfaces. Draft in corners or fillets projecting in a direction normal to the parting plane have approximately 1.5 the amount of draft of the intersecting walls.

In the sketches above, consideration has been given to the stresses of use and to the stress induced in the die castings of moderate depth. Shallow die castings may have much smaller fillets, while deep pockets and other inside corners may have larger fillets. Sharply squared corners of much length projecting in a direction normal to the parting plane may cause spalled edges in withdrawing the die castings from the die.

RIBS

Ribs are used to increase the stiffness of, or add strength to, a die casting and to aid in making sound die castings. Ribs are something misused and can be a detriment if working stresses are concentrated by their use or if stresses at the edges of the ribs are high.

EXTERNAL CORNERS

Sharply squared corners may be used in many locations if die construction permits. This type of corner is often mandatory at parting line locations and die block intersections. Other than this, corners of die castings should have radii in order to prevent early die failure, to reduce the probability of nicking the edge of the die casting in handling, and to minimize material handling hazards for personnel.