Material Selection for Machined & Molded Parts
Engineering Plastics & Composite Materials
Engineering plastics can reduce weight, provide electrical insulation, improve sliding behavior or create transparent covers. Their behavior depends on the exact resin, additives, moisture, temperature and production route. Compare the eight families below; FR-4 is a thermoset glass-epoxy laminate, while the other listed families are thermoplastics. Stock availability and suitability for your drawing are reviewed per project.
Plan Your Plastic or Composite Part
Send the part drawing, quantity, operating conditions and preferred resin or laminate grade for a material and process review.
Send Drawing Files by Email
Share drawings and project requirements at rfq@junchumfg.com.
Discuss confidentiality and NDA requirements before sharing sensitive project files.
Start with the Operating Conditions
- Mechanical duty: impact, load, sliding, wear and long-term creep
- Temperature and humidity during storage and operation
- Chemical exposure, cleaners and outdoor UV conditions
- Optical appearance, electrical insulation and visible surfaces
- Machining, molding or laminate fabrication requirements
Specify the Grade & Process
- Exact resin or laminate grade and supplier datasheet
- Unfilled, glass-filled, lubricated or other modified formulation
- Color, transparency and any required performance classification
- Stock shape versus molding resin; conditioning before inspection
- Required documentation and application-specific validation
Eight Material Families Explained
Match the polymer to its job
01
ABS
ABS suits equipment covers, housings and appearance prototypes, combining toughness, rigidity and a surface that can be finished. It can be machined from stock or molded.
Selection: specify the grade for heat, UV, solvent or flame requirements. Machined and molded parts need separate validation.
02
POM (Acetal)
POM is a stiff, machinable choice for gears, bushings, locating pieces and sliding mechanisms. Low moisture uptake helps dimensional stability.
Selection: distinguish POM-C, POM-H and modified wear grades. Define load, running clearance, counterface, lubrication and operating temperature.
03
Nylon (PA)
PA6 and PA66 are common options for rollers, guides, bushings and loaded wear components. Filled grades change stiffness and wear behavior.
Selection: moisture absorption can change dimensions and fit. Specify grade, service humidity and inspection condition; distinguish cast or extruded stock from molding resin.
04
Polycarbonate (PC)
PC is often considered for tough transparent covers, viewing windows and equipment components where impact resistance matters. Clear and opaque grades serve different needs.
Selection: review cleaners, residual stress, scratching and UV exposure. Define optical finish and any protective coating; transparency alone does not establish a safety rating.
05
Acrylic (PMMA)
PMMA suits display windows, clear covers and visual prototypes where transparency and polished appearance are priorities. Cast and extruded stock can machine differently.
Selection: compare impact and notch sensitivity with PC. Review corner radii, screw loads, cleaner compatibility and whether machined or polished surfaces are required.
06
Polypropylene (PP)
PP is a low-density thermoplastic for compatible chemical-service parts, covers, spacers and molded components. Homopolymer and copolymer grades differ in stiffness and impact behavior.
Selection: check chemical concentration, temperature, creep and thermal expansion. Living-hinge behavior must be validated in the intended molded design.
07
PVC
Rigid PVC, often PVC-U, is used for machined or fabricated panels, fittings and compatible chemical-service components. Flexible PVC is a different formulation.
Selection: identify PVC-U, PVC-C or flexible material explicitly. Chemical concentration, service temperature, impact exposure and joining method determine suitability.
08
FR-4 Composite
FR-4 is a cured glass-fabric epoxy laminate for insulating plates, spacers, supports and machined electrical components. It is cut or machined from laminate rather than injection molded.
Selection: specify laminate grade, thickness, edge quality and electrical requirements. Review exposed glass edges and delamination risk.
From Polymer Family to a Production Specification
Use the material cards as an initial comparison. The production specification should identify the exact grade and conditions that matter to the part.
Service Conditions
Define load, sliding speed, temperature, humidity, chemical exposure, transparency and electrical requirements.
Grade & Additives
Identify resin or laminate grade, reinforcement, lubricants, color and any required UV or flame performance.
Process & Dimensions
Select machined stock, molding resin or laminate. Review shrinkage, moisture conditioning, stress and finished-part measurement.
Evidence & Validation
Check the exact grade datasheet and required records, then validate critical fit or performance with a suitable sample.
From Part Design to Process Planning
Custom Manufacturing Applications
Explore typical component designs, process combinations and quality considerations to help prepare your own manufacturing requirements.
- Enclosures & Housings
- Manufacturing Applications
- Sliding Assemblies
- Manufacturing Applications
- Appearance Parts
- Manufacturing Applications
Before You Start Your Project
Plastic & Composite Selection Questions
Understand moisture, processing and grade differences before selecting a polymer.
Can I choose a plastic using only its family name?
No. ABS, PA, PC and other families contain many grades with different fillers, stabilizers and processing characteristics. State the operating conditions and identify the exact grade when performance matters. Numerical values should come from the relevant grade datasheet and test conditions.
Can a machined prototype replace a molded sample?
A machined part is useful for checking geometry and assembly, but stock material, residual stress and processing history differ from molded parts. Molded shrinkage, fiber orientation, weld lines, texture and flexible features require validation through the intended production process.
Should I choose POM or nylon for a sliding part?
POM is often a starting point for dimensional stability and low-friction parts; nylon is widely used for loaded and wear-related components. Nylon’s moisture uptake can affect fit. Choose using actual load, motion, counterface, lubrication, temperature and humidity, then validate the critical interface.
Is FR-4 suitable for injection molding?
FR-4 is a cured glass-fabric epoxy laminate. Custom insulating shapes are generally cut, drilled or machined from sheet rather than melted and remolded like ABS or PP. Laminate grade, thickness, edge quality and electrical requirements should be specified.
Are clear, flame-rated or food-contact properties automatic?
No. These requirements belong to a specific grade, thickness, process and supporting evidence. A polymer family name does not establish a safety, flame or food-contact approval for the finished component. State the required classification or documentation before material selection.
Compare Plastic Families Without Assuming Grade Equivalence
| Family | Common discussion point | Specification to resolve |
|---|---|---|
| POM (acetal) | Sliding interfaces and dimensional control | Exact grade, load, wear conditions and chemical exposure. |
| Nylon (PA) | Wear-related and mechanical components | Grade, reinforcement, moisture conditioning and measurement state. |
| PC / PMMA | Impact resistance or optical appearance | Required optical finish, chemicals, stress and actual performance needs. |
| ABS / PP / PVC | Application-specific molded or machined components | Grade, temperature, additives, joining and any required evidence. |
| FR-4 | Machined insulating shapes from cured laminate | Laminate grade, thickness, direction, edge quality and insulation requirements. |
Specify performance at the grade level
A food-contact, flame, electrical or other application requirement must be supported for the actual grade, thickness and process where relevant. A machined stock prototype does not automatically validate a later molded component. Identify the intended production resin and agree the necessary evaluation.
Ready To Start Your Project?
Start With Your Drawings - or Tell Us What You Need
Share drawings, photos or sketches with your quantity, material, finish and target date. We review the available information, clarify technical requirements and confirm quotation timing. Complex or multi-process projects may require additional review.
Discuss confidentiality and NDA requirements before sharing sensitive project files.