Multi-Cavity and Family Injection Molding

Maximize each shot with multiples of the same or different parts from a single mold

Certification
ISO 9001:2015

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What is Family and Multi-Cavity Molding?

Family molding and multi-cavity molding are injection molding techniques designed to increase production efficiency by manufacturing multiple parts in a single molding cycle.

Multi-cavity molding uses a mold containing multiple identical cavities, allowing several copies of the same part to be produced with each shot. This approach is ideal for high-volume production and helps reduce cost per part.

Family molding, on the other hand, utilizes a mold with different cavity designs to produce multiple related components simultaneously—such as matching left- and right-hand parts or components that are assembled together in the final product.

Both methods improve manufacturing efficiency, reduce cycle costs, and optimize production throughput for large-volume applications.

Family and Multi-Cavity Molding Capabilities

Our engineering guidelines for family and multi-cavity molds are designed to maximize manufacturability, improve part consistency and appearance, and streamline production for greater efficiency and lower overall costs.

General Design Guidelines
Maximum Part Size
Maximum Part Volume
Maximum Number of Cavities
Maximum Surface Area
Lead Times

General Design Guidelines

Maximum of 12,000 psi (82.74 MPa) for the entire assembled family tool
Maximum clamp tonnage of 500 tons (453,592 kg)
Brand model cavities must fill within 2,000 psi (13.79 MPa) of each other

Maximum Part Size

Maximum part size is a function of mold size and part complexity. The largest size we can support with plastic injection molding is 18.9 in. by 29.6 in. by 8 in. (480mm by 751mm by 203mm).

Maximum Part Volume

Maximum is 59 in. (1,499mm). Specs below exclude tiny parts less than 0.05 in. (1.27mm). Between two parts, if volume is:

If part size is:	Maximum Difference in Part Volume
< 2 in. (50.8mm)	20%
2 in. (50.8mm) to < 5 in. (127mm)	15%
5 in. (127mm) to < 10 in. (254mm)	10%
10 in. (254mm) to 59 in. (1499mm)	5%

Maximum Number of Cavities

The number of possible cavities can be 2, 4, or 8 per mold. This ultimately is dependent on part complexity and size.

Maximum Surface Area

Maximum is 175 in. (4,445mm), each cavity added together. Between two parts, if surface area is:

If part size is:	Maximum Difference in Part Surface Area
< 5 in. (127mm)	20%
5 in. (127mm) to < 10 in. (254mm)	15%
10 in. (254mm) to < 20 in. (508mm)	10%
20 in. (508mm) to < 59 in. (1499mm)	5%

Lead Times for Multi-Cavity and Family Tools

Fundamentally, lead times are based on the complexity and size of your mold and can vary from 1 to 20 days, based on those attributes. Below is a rough idea of what you can expect in terms of turnaround for your parts.

If maximum part size is:	Design Specs	Lead time is:
2.75 in. by 2.50 in. by 1 in. (69.85mm by 63.5mm by 25.4mm)	No side-pulls, hot-tip gates, contoured ejectors, steel core pins, family and multi-cavity molds	1 business day
15 in. by 9 in. by 4 in. (381mm by 229mm by 101.6mm); depending on gate type, maximum part size could be smaller	Does not contain more than two side-pulls; no pick-out cams; family and multi-cavity molds may include only two simple parts.	5 business days
15 in. by 9 in. by 4 in. (381mm by 229mm by 101.6mm); depending on gate type, maximum part size could be smaller	Does not contain more than two side-pulls; no pick-out cams; family and multi-cavity molds may include only two simple parts	7 business days

General Design Guidelines

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Maximum Part Size

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Maximum Part Volume

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Maximum Number of Cavities

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Maximum Surface Area

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Lead Times

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Tolerances: Typically, Protolabs can maintain a machining tolerance of +/- 0.003 in. (0.08mm) with an included resin tolerance that can be greater than but no less than +/- 0.002 in./in. (0.002mm/mm).

Injection Molding Materiales

ABS
Acetal Copolymer
Acetal Homopolymer/Delrin
ETPU
HDPE
LCP
LDPE
LLDPE

Nylon
PBT
PC/ABS
PC/PBT
PEEK
PEI
PET
PETG

PMMA (Acrylic, Plexiglas)
Polycarbonate
Polypropylene
PPA
PPE/PS
PS
PSU
TPU

Surface Finish Options

Finish	Description
PM-F0	non-cosmetic, finish to Protolabs' discretion
PM-F1	low-cosmetic, most toolmarks removed
PM-F2	non-cosmetic, EDM permissible
SPI-C1	600 grit stone
PM-T1	SPI-C1 + light bead blast
PM-T2	SPI-C1 + medium bead blast
SPI-B1	600 grit paper
SPI-A2	grade #2 diamond buff

How Does Multi-Cavity or Family Molding Work?

Multi-cavity molding uses a single mold containing multiple identical cavities to produce several copies of the same part in each cycle, improving throughput and lowering unit costs.

Family molding expands on this concept by combining multiple different but related components within one mold, enabling an entire set of mating or assembly parts to be produced in a single shot.

The molded parts remain connected by a runner system and are separated after molding, similar to the components found in plastic model kits.

This approach helps streamline production, reduce tooling investment, and improve manufacturing efficiency for higher-volume applications.

Benefits

Higher Production Output – Produce multiple parts in every molding cycle.
Greater Efficiency – Maximize machine utilization and manufacturing throughput.
Lower Unit Costs – Reduce cost per part through higher output and shorter effective cycle times.

Considerations

More Complex Tooling – Advanced mold design and manufacturing increase initial tooling investment.
Flow Balancing Requirements – Optimized runner systems are essential to ensure consistent filling and part quality across all cavities.

Applications for Multi-Cavity and Family Molding

Consumer Electronics

Standardized components used across multiple products, including housings, enclosures, and internal parts for a wide range of devices and equipment.

Automotive

High-volume production of fasteners, connectors, sub-assembly components, interior trim parts, and other standardized components.

Construction

Ideal for the production of commodity items such as fittings, fasteners, connectors, closures, and other repeatable high-volume components.

Medical Devices

Commonly used for disposable medical products, casings for handheld diagnostic tools, and portable testing kits.

Packaging

Ideal for high-volume packaging applications in the beverage, food, cosmetics, and pharmaceutical sectors.

Appliances

Commonly used for housings, covers, and internal components in small appliances and consumer products.

Types of Parts	Function
Electronic device housings	Front/back casings, battery doors, button sets for a specific remote control, phone, or gadget
Buttons and keys	Keyboards, control panels, remote controls
Caps and closures	Bottle caps, jar lids, flip-tops, spray nozzle components (huge volumes needed)
Connectors	Electrical connectors, terminal housings, fiber optic connectors (standardized, high quantity)
Fasteners	Plastic clips, rivets, screw anchors, cable ties (commodity, high volume)
Medical disposables and casings	Syringe barrels/plungers, pipette tips, test tubes, vial caps, parts for IV sets, sample cups. Two halves of a glucose meter casing, parts for a specific diagnostic test kit (high volume, consistency crucial)
Small ears, bushings, washers	Standardized mechanical components
Small pipe fittings	Elbows, T-connectors, caps for plumbing/irrigation