Wall draft angle

Mold drafts facilitate part removal from the mold.

The draft must be in an offset angle that is parallel to the mold opening and closing. The ideal draft angle for a given part depends on the depth of the part in the mold and its required end-use function.

Allowing for as much draft as possible will permit parts to release from the mold easily. Typically, one to two degrees of drafts with an additional 1.5 degrees per 0.25mm depth of texture is enough to do the trick.

The mold part line will need to be located in a way that splits the draft in order to minimize it. If no draft is acceptable due to design considerations, a side action mold may be required.

 

The reason for draft.

Drafts (or taper) in a mold, facilitates part removal from the mold. The amount of draft angle depends on the depth of the part in the mold, and its required end use function.

The draft is in the offset angle in a direction parallel to the mold opening and closing.

It is best to allow for as much draft as possible for easy release from the mold. As a nominal recommendation, it is best to allow 1 to 2 degrees of draft, with an additional 1.5° min. per 0.025 mm (0.001 inch) depth of texture. See below.

The mold parting line can be relocated to split the draft in order to minimize it. If no draft is acceptable due to design considerations, then a side-action mold (cam-actuated) may be required at a greater expense in tooling.

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 Draft and Knock-Out Pins
Draft is essential to the ejection of the parts from the
mold. Where minimum draft is desired, good draw
polishing will aid ejection of the parts from the mold.
Use the following table as a general guide.

When knockout pins are used in removing parts from
the mold, pin placement is important to prevent part
distortion during ejection. Also an adequate pin
surface area is needed to prevent puncturing, distorting
or marking the parts. In some cases stripper plates
or rings are necessary to supplement or replace pins.