Basic knowledge of Draft Angle for a part design

Draft Angle is the gradient made on the cavity or the core to make removal of parts from the plastic injection mold smoother.

Draft angle normally requires 1 - 2 degrees, but it depends on the material and designed part shape,if the cavity side need a texture process later (the process to make the surface a little rough) ,the draft angle need be added according to the texture No. on the texture template which provide by texturing plant.

During injection molding, because molten plastics will shrink after cool down, it's necessary to make as small draft angle as possible on the cavity side, and a large angle on the core (insert) side.

Because crystalline plastics has high mold shrinkage, it shrinks into the inside of the plastic mold on the cavity side, which makes releasing smooth, whereas it adheres to the mold on the core (insert) side, which makes releasing difficult. Therefore, to make a draft angle, you will need to take the adhesion to the core (insert) side in consideration.

On the other hand, amorphous plastics has low mold shrinkage and hardly shrinks to the inside. Therefore, a draft angle on the cavity side is made as large as the one on the core (insert) side.

Insufficient draft angle design will cause scratch or cracking during ejection