Mold Base Terminology - L

Laminar Flow

The movement of one layer of fluid past or over another layer without the transfer of material from one to the other. Laminar flow is achieved by solidifying the layer in contact with the mold surface. This acts as an insulating tube through which material can flow to fill the remainder of the cavity.This process is essential to mold surface duplication.

Leader Bushing

A leader bushing is what the leader pins enter into that aligns the mold base halves. Leader bushings are easily replaced when they wear. The life of a leader bushing can be extended withthe proper amount of lubricant applied during the production run.

Leader Pins

These are pins that go through the top clamp plate into every plate with one pin offset to keep the plate from being assembled incorrectly. The pins are also used to guide the mold back together after the mold opening during the cycle. The pins serve two purposes. One is to guide the mold back together without misalignment. Without them there could be a possibility that the core and cavity would hit upon closing and cause damage the steel. Leader pins also prevent the mold halves form being assembled 180 degrees. This is why the offset pin is used on what mold makers call the zero corner.

Lifters

Lifters are sometimes used as an alternative to cam actions. Usually the lifter concept is used where it is not feasible to have a cam. They are primarily used to allow the steel to be removed by the use of a cam action that slides the steel away from the plastic. There are few things that the designer must be aware of when using lifters: The top of the lifter surface cannot protrude into the wall section. It is a good practice to have the top of the lifter at least .003 below the wall section to insure there is no hang up when it is activated. The lifter should not pull the part over with its action and result in the part sticking. A protrusion in the non lifter area will usually help keep it for sliding the part over with it. There are many standard lifter designs that are that are available from mold component manufacturers Because lifters have a tendency to wear it is good practice to design a mold operation including standard components. These designs are mass produced and take into account the proper tolerances and steel selections to provide the mold with the maximum life.

Lift Holes

These are not just for lifting the mold into the press. The toolmaker needs to have lift holes in every plate so the mold plates can be handled safely when disassembled. Holes need to be located in such a manner that the mold will be as level as possible when it is being lifted into the press. It is wise to use the safety hoist style eyehooks rather than the eyebolt. The eye bolts will bend and the tensile strength is much higher.

Location Ring

This ring is used to locate the front half of the mold into the press plate. This ring protrudes from out of the top clamp plate and actually guides the mold base into the press platen during setup.

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