Which Materials Work Best for Collapsible Core Injection Molding?
Compare plastics for internal threads, undercuts and complex internal geometry.
Material selection directly affects shrinkage, ejection force, dimensional stability, tooling wear and the performance of a collapsible core. Explore suitable materials from PP and ABS to Nylon, POM, PC and high-performance engineering plastics.
Quick Answer: What Materials Can Be Used?
PP, ABS, PC, Nylon, POM and PBT are among the most practical materials to evaluate for collapsible core injection molding. High-performance materials such as PEEK, PEI/Ultem and Torlon can also be considered for demanding applications, but require more careful tooling and processing engineering.
Best Materials to Evaluate for Collapsible Core Molding
The right resin depends on part geometry, shrinkage, friction, mechanical requirements, production volume and tooling design.
PP
Lightweight, economical and flexible. Shrinkage and cooling should be carefully considered for collapsible-core tooling.
Good Candidate →ABS
A practical option for rigid components requiring good moldability, dimensional performance and surface finish.
Good Candidate →Polycarbonate
Suitable for tough, impact-resistant components where ejection stress and processing conditions require attention.
EXPLORE PC MOLDING →Nylon PA6 / PA66
Strong and wear resistant. Moisture absorption, shrinkage and glass reinforcement must be considered.
EXPLORE NYLON →POM / Delrin
Low friction, good stiffness and dimensional performance make POM an attractive option for functional components.
EXPLORE POM / DELRIN →PBT
Useful for automotive, electrical and industrial components requiring good dimensional and chemical performance.
Good Candidate →Collapsible Core Molding Material Comparison
Material suitability depends on more than flowability. Shrinkage, friction, stiffness, reinforcement, processing temperature and tooling wear can all influence collapsible-core performance.
| Material | General Suitability | Shrinkage Consideration | Ejection / Core Release | Tooling Consideration |
|---|---|---|---|---|
| PP | Excellent | Moderate to High | Moderate | Control shrinkage and cooling |
| ABS | Excellent | Low to Moderate | Low to Moderate | Generally straightforward |
| PC | Very Good | Low to Moderate | Moderate | Manage stress and processing temperature |
| PA6 / PA66 | Very Good | High | Moderate to High | Moisture and shrinkage control |
| POM / Delrin | Excellent | Medium to High | Good | Good candidate for functional parts |
| PBT | Very Good | Medium to High | Moderate | Cooling and dimensional control |
| Glass-Filled Nylon | Conditional | High / Directional | High | Wear-resistant tooling recommended |
| PEEK | Conditional | Grade dependent | High | High-temperature tooling |
| PEI / Ultem | Conditional | Medium | High | High-temperature processing |
| Torlon / PAI | Special Application | Grade dependent | High | Specialized tooling and processing |
What Makes a Material Suitable for a Collapsible Core?
A resin should not be selected independently from the mold mechanism. The material and collapsible core need to be evaluated as one manufacturing system.
Shrinkage
Material shrinkage influences the final internal dimensions, core clearance and release force. Semi-crystalline plastics often require additional attention.
Friction & Release
Excessive friction between the molded component and core segments can increase ejection force and potentially damage the part or tooling.
Part Stiffness
The molded part must have enough structural integrity to withstand ejection while allowing the core to collapse.
Processing Temperature
High-temperature engineering plastics can require specialized tooling materials, thermal control and processing equipment.
Reinforcement
Glass-filled and mineral-filled materials can increase tooling wear and may require hardened or surface-treated components.
Dimensional Stability
Tight-tolerance components require material behavior, cooling, tooling and process control to be evaluated together.
For a broader engineering review, see our Design for Manufacturability (DFM) Guide and Manufacturing Tolerances Guide .
What About PEEK, Ultem and Torlon?
High-performance thermoplastics can be considered for specialized collapsible-core applications, but the tooling strategy becomes significantly more important.
PEEK
PEEK is used where high temperature resistance, chemical resistance and mechanical performance are required. Collapsible-core tooling requires careful evaluation of thermal behavior, clearance and core materials.
EXPLORE PEEK INJECTION MOLDING →PEI / Ultem
PEI is suitable for demanding applications requiring temperature resistance and dimensional performance. Tooling must be designed around the actual resin grade and processing conditions.
EXPLORE ULTEM INJECTION MOLDING →Torlon / PAI
Torlon is used in demanding engineering applications. Because processing is considerably more demanding than conventional resins, tooling feasibility should be evaluated before mold construction.
EXPLORE TORLON INJECTION MOLDING →Is a Collapsible Core Always the Best Solution?
Not necessarily. Internal undercuts can be produced using several tooling strategies. The right solution depends on geometry, production volume, cycle-time requirements and tooling cost.
Collapsible Core
Ideal for many cylindrical internal undercuts, internal threads and retaining features where straight ejection is not possible.
COLLAPSIBLE CORE MOLDING →Unscrewing Core
Useful for continuous or deep internal threads where controlled mechanical rotation is appropriate.
EXPLORE Unscrewing Molding →Split / Side Core
Side-action and split-core mechanisms can be useful when the geometry extends beyond a simple cylindrical internal undercut.
SEE COMPLEX UNDERCUT CASE STUDY →Lifter
Suitable for selected angled undercuts, hooks and smaller internal or external features.
Prototype Tooling
For low-volume programs, prototype tooling or soft tooling may provide a better economic solution.
PROTOTYPE TOOLING →Part Redesign
Sometimes removing or modifying an unnecessary undercut can eliminate a complex tooling mechanism altogether.
EXPLORE DFM →Where Is Collapsible Core Molding Used?
Collapsible cores are particularly useful for components where internal threads, grooves, retaining features or other undercuts are essential to product functionality.
Automotive
Housings, retainers, fluid components and functional threaded parts.
Medical
Precision components with internal interfaces and complex geometry.
Robotics
Functional housings, joints, retainers and protective components.
Electronics
Housings, connectors and components with internal locking features.
7 Things to Check Before Ordering the Mold
A material and tooling feasibility review before mold construction can prevent expensive design changes later.
Confirm the exact resin, grade, reinforcement and additives.
Identify threads, grooves, retaining lips and undercuts.
Confirm sufficient collapse distance and release clearance.
Account for resin-specific dimensional behavior.
Evaluate part stiffness, friction and release behavior.
Match tooling materials to production volume and resin wear.
Evaluate thermal behavior and production requirements.
You can also review our H13 Tool Steel Guide , 420 Stainless Mold Guide and Mold Manufacturing Process .
Have a Part With an Internal Undercut?
Don’t select the material and tooling independently. Send your CAD model or drawing to Manufyn and let our engineering team evaluate the material, collapsible-core feasibility and tooling approach before you invest in production tooling.
Frequently Asked Questions
Common engineering questions about materials and collapsible-core molding.
What is the best material for collapsible core injection molding?
Can Nylon be used with collapsible core tooling?
Can PEEK be used for collapsible core molding?
Can glass-filled Nylon be molded using a collapsible core?
Is POM suitable for internal threads?
Is collapsible core molding cheaper than an unscrewing core?
How do I know whether my part needs a collapsible core?
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