Custom molded parts, built around material performance and part requirements.
GPT Precision supports custom thermoplastic injection-molded components, from housings and transparent covers to mechanical and electrical parts.
We review resin selection, part geometry, operating conditions and production requirements together. The goal is to establish a practical material and molding approach, with clear expectations for dimensional performance, appearance and sample approval.
PART APPLICATIONS
The right material depends on what the finished component needs to do—not simply the resin's general properties.
Equipment housings, instrument covers, viewing windows and cosmetic enclosures.
Engineering focus: Balance impact resistance, optical clarity, chemical exposure, surface finish and dimensional fit. Identify visible surfaces, joining features and assembly requirements before tooling decisions are finalized.
Gears, guides, sliding elements, clips and other functional components.
Engineering focus: Evaluate load, friction, wear, moisture and sustained deformation. Define mating surfaces and acceptable clearances under the expected service conditions.
Connector housings, insulating components, mounting parts and functional supports.
Engineering focus: Review electrical performance, operating temperature, flame-retardance requirements and dimensional stability. Specify applicable test methods and required material documentation.
These examples illustrate possible applications. Material grades, part geometry and molding feasibility are reviewed against each project.
RESIN SELECTION
Thermoplastic injection molding involves heating a suitable resin until it flows, injecting it into a mold and allowing it to solidify before the part is removed.
The resin affects how the mold fills, how the component shrinks and cools, and how it performs in service. Material selection and mold design therefore need to be considered together.
The following material families provide a starting point for comparison.
| Material | Aplicaciones típicas | Key Selection Considerations |
|---|---|---|
| ABS | Carcasas, covers and cosmetic components | Impact resistance, finish, color and exposure conditions |
| PP (Polypropylene) | Lightweight parts, clips and living hinges | Chemical resistance, flexibility, hinge design and dimensional behavior |
| PMMA (Acrylic) | Transparent covers and display components | Clarity, weathering, surface finish and impact sensitivity |
For visible parts, define color, texture, gloss, transparency and acceptable surface marks early. Living-hinge performance depends on the selected PP grade, hinge geometry and processing conditions.
| Material | Aplicaciones típicas | Key Selection Considerations |
|---|---|---|
| PA66 (Nylon) | Gears, guides and mechanical parts | Load, wear, moisture conditioning and dimensional change |
| POM (Acetal) | Sliding mechanisms and precision-fit components | Friction, wear, clearance and service environment |
| PBT | Electrical housings and connectors | Electrical properties, dimensional behavior and processing requirements |
| PC (Polycarbonate) | Impact-resistant covers and transparent components | Impact resistance, clarity, chemical exposure and stress cracking |
| PET (Polyester) | Selected structural and engineering components | Injection-molding grade, crystallization, drying and dimensional requirements |
For mechanical components, compare operating load, mating materials, temperature and acceptable dimensional variation. A resin family name alone does not define the performance of the molded part.
PPS, PEI and PEEK may be considered for applications involving demanding thermal, chemical or mechanical conditions.
Selection requires more than comparing published temperature ratings. Consider continuous operating conditions, exposure duration, mechanical load, chemical contact and expected service life.
These materials can also require specialized processing conditions and tooling arrangements. Grade availability and manufacturing feasibility must be confirmed before the project scope is accepted.
ENGINEERING REVIEW
Choosing a material is only the beginning. Its behavior during molding and in service influences the finished component's dimensions, appearance and function.
Different resins respond differently to filling, packing and cooling.
Shrinkage depends on the grade, reinforcement, geometry and processing conditions. Uneven shrinkage or cooling can contribute to warpage, while fiber orientation can make dimensional behavior direction-dependent.
Identify critical dimensions, datums, wall sections and mating interfaces early. Tolerance feasibility should be evaluated against the selected material, part design and agreed measurement conditions.
Some thermoplastics require controlled drying before molding. Excess moisture during processing can cause material degradation or surface defects.
After molding, certain materials—particularly nylons—can absorb moisture from the environment. This may affect dimensions, stiffness and other mechanical properties.
Drying resin before processing and conditioning finished parts address different requirements. Where moisture influences fit, agree on the material condition and inspection environment used for sample approval.
A component may experience continuous loads, intermittent temperature peaks or extended exposure to chemicals.
Consider temperature and load together, including creep, stress relaxation and changes in properties over time.
A published heat-deflection temperature is not, by itself, a continuous-use temperature rating. Use grade-specific data and application-relevant testing to assess suitability.
Wall thickness, flow paths, gate placement and cooling influence the final appearance and condition of the part.
Identify transparent areas, cosmetic surfaces and locations where gate marks or weld lines would be unacceptable.
For mechanically loaded components, review potential weld-line locations and their effect on critical features. Reinforcement and molding conditions may also influence surface appearance.
These considerations help connect material selection with the mold design and sample-approval requirements.
SPECIFIC REQUIREMENTS
Base resins can be modified to meet particular performance needs. The formulation must be evaluated as a whole because improving one property may change others.
Glass-fiber, mineral-filled and other reinforced grades may provide additional stiffness, dimensional control or mechanical performance.
Review strength, impact behavior, directional shrinkage, surface finish and potential tool-wear implications together.
Specify the required flame classification, relevant material thickness and applicable product requirements.
A published material flammability rating does not automatically establish compliance of the finished product.
Define the electrical property required, whether insulation, antistatic behavior, ESD control or conductivity.
Where EMI shielding is required, review the complete component design and the applicable shielding-performance criteria rather than relying on resin conductivity alone.
Consider sunlight exposure, weathering, temperature cycling and color retention.
Define the expected outdoor conditions and any required appearance or mechanical-performance testing.
For applications involving food contact, medical equipment or other regulated uses, identify the relevant market, intended contact conditions and required supporting documentation.
Suitability must be established for the exact grade and finished application. Material certifications, inspection records and traceability requirements should be agreed as part of the project scope.
MATERIAL TO PART
A successful material decision must carry through into the finished component, not stop at the resin data sheet.
Share the part's function, operating conditions, critical dimensions, appearance requirements and expected production demand.
Identify the requirements that cannot change and those where alternatives may be considered.
Review candidate materials against the operating environment, required properties, sourcing availability and processing needs.
If a specific grade has been designated, identify the approval process for any proposed substitution.
Review wall thickness, critical interfaces, part geometry and molding behavior alongside the selected resin.
Address shrinkage, warpage, gate locations and relevant tooling requirements before approving mold manufacture.
Define the checks required before production approval.
These may include dimensional inspection, visual standards, fit or assembly tests and specified functional checks.
Where environmental testing, durability evaluation or formal material verification is required, agree on the applicable methods, documentation and responsible parties.
The approved material grade, drawing revision and sample criteria should provide a clear reference for subsequent production.
ADDITIONAL OPERATIONS
Regrind may be suitable for certain thermoplastic applications, depending on the resin, processing history and customer specification.
Any permitted recycled or reprocessed content should be agreed in advance, including source, proportion, traceability and performance requirements.
If virgin-only material is required, identify this during quotation.
Painting, printing, laser marking and plating depend on compatibility with the selected resin and the required surface preparation.
Texture and molded surface appearance are also influenced by the tooling finish and part-release requirements.
Define the desired finish early so material selection, tooling and secondary operations can be considered together.
Metal threads, bushings or contacts may be incorporated through an insert-molding approach, subject to design and process review.
Where a second material is required for grip, cushioning or sealing, assess the appropriate overmolding process and material compatibility.
Thermoplastic elastomers, including suitable TPE or TPU grades, can be processed through thermoplastic molding routes. Liquid Silicone Rubber (LSR), however, follows a separate curing process and requires its own material and manufacturing review.
COMMON QUESTIONS
Compare the operating load, friction, wear, temperature, mating surfaces and dimensional requirements.
PA66 may be considered for mechanical components requiring suitable strength and toughness, but moisture conditioning can affect fit and performance. POM is commonly considered for applications requiring good sliding behavior and relatively low moisture absorption.
The final choice depends on the specific grades and operating conditions.
PC is often considered where impact resistance is important. PMMA is frequently considered where optical clarity and weathering performance are priorities.
Also review chemical exposure, mounting stresses, coatings, surface finish and the actual optical requirements before selecting a grade.
PPS, PEI and PEEK are possible candidates for demanding environments, depending on the application.
Start with continuous temperature, short-term peaks, exposure time, mechanical loads and chemical conditions.
Evaluate the complete service requirements against the specific material data and required validation tests.
Moisture can influence both processing and long-term component behavior.
Some grades require drying before molding to avoid degradation or defects. Certain finished parts, especially those made from nylon, may later absorb moisture and experience dimensional or property changes.
Define the operating humidity and any measurement or conditioning requirements for critical fits.
A proposed alternative should be reviewed against the required mechanical, thermal, chemical, electrical and appearance properties.
Processing behavior, material documentation and availability must also be considered.
Any substitution should follow the customer's specified approval requirements before use in tooling trials or production.
Potentially, where the selected resin, application and customer specification allow it.
Agree on the source, permitted content, material control and acceptance requirements before production. Virgin-only requirements should be clearly identified in the inquiry.
START A PROJECT
Share your drawings and the conditions your component needs to withstand.
GPT Precision can review the material requirements alongside the part geometry, proposed tooling scope and sample-acceptance expectations.
For a useful initial assessment, provide:
We review the submitted information to establish the appropriate manufacturing scope and expected quotation timeline. Specific material grades, production arrangements and verification requirements are confirmed according to the project.
Discuss Your Thermoplastic Part
Need a broader overview of mold manufacturing and finished-part supply? Explore our Custom Plastic Injection Molding services.
