Family Molds Benefits

A family mold is a mold which combines different part numbers into the same mold base.  There can be multiple cavities of the different part numbers.  Family molds can often have a mold building cost advantage over molds dedicated to a single part number.

An common usage case is combining the two halves of a housing into family mold. Case halves are almost always purchased in sets which makes running them together a good option.  Often a battery door or cover may be included in the family mold.  They may not always be run when the case halves are run so a shut-off runner is almost always included which allows one or more cavities to be turned off during production.

Family molds are often recommend over dedicated molds for parts with moderate production volumes, where dedicated multi-cavity molds would not be cost effective.  They do have drawbacks and there are many cases where they just won't work.  Look over the decision factors below to get an idea if a family mold is for you.

APP will always advise and assist you on making these decisions and can easily supply quotes for all variations.

Factors Effecting Family Molds vs. Dedicated Molds
Factor Family Mold Dedicated Mold
Mold Cost Cost savings compared to molds dedicated to single parts. More expensive to build separate molds for each part number.
Part Quality Harder to balance and control mold filling especially when parts have large variation in wall thickness or volume. Can cause cosmetic as well as dimensional problems Typically easier to balance and control part filling and therefore better cosmetic and dimensional control
Production Rates & Part Costs

Parts are usually produced in sets so molding costs are combined for a lower part cost vs a single cavity dedicated mold.  Production rate compares to a two cavity dedicated mold.

If only one of the parts is required then part costs is the same as a single cavity, dedicated mold.

If a single cavity molded part price may be higher.  Multiple cavity molds can produce much cheaper parts depending on cavitation.
Mold Design Flexibility Can have more limited gating options as parts must be aligned with each other. More flexible gating options.
Run Size Best suited for smaller run sizes (<50,000 parts)  and when multi-cavity dedicated molds don't make sense. Works for all run sizes
Part Geometry Parts should be close in physical size, volume and general design features.  Complicated core pulls or cams may not physically fit or collide with one another. No limits beyond standard design practices for plastics