Define the Load Case and Failure Limit
Map every static, cyclic, impact, assembly and fastener load, including direction, duration, temperature and frequency. Define allowable deflection, creep, permanent set, fatigue life, impact condition and failure location. Also record humidity, chemicals, electrical or flame requirements, appearance, weight, wall thickness, critical dimensions and the intended validation method.
A request for higher stiffness is incomplete unless the part-level target is measurable. Increasing reinforcement may improve one load direction while creating a new weld-line, warpage, surface, toughness, flow or equipment risk. The preferred candidate is the lowest-complexity grade direction that can plausibly meet the full acceptance criteria.
Understand What the Glass Fiber Level Does and Does Not Define
Within a related grade series, increasing glass fiber commonly raises stiffness and load response. The actual result also depends on fiber length distribution after compounding and molding, fiber-matrix adhesion, polymer viscosity, modifiers, specimen orientation, moisture state and test temperature. Two compounds with the same nominal fiber percentage are therefore not automatically equivalent.
Higher reinforcement can change melt flow, surface texture, fiber visibility, weld-line response, notched sensitivity, ejection, dimensional directionality and wear on screws, barrels, hot runners and tools. It can also change contact behavior against mating parts. Use the percentage to narrow the catalogue, then compare complete grade data and the intended production system.
- Fiber content and test method, not only the grade name
- Dry and conditioned mechanical values at relevant temperatures
- Flow family, heat stabilization, impact or flame modification and color
- Surface, wear, weld-line, equipment and document requirements
Choose PA6 or PA66 Before Finalizing the Fiber Level
Compare PA6 and PA66 at equal glass content to separate thermal and moisture differences. Prioritize PA66 grades for heat-deformation screening; for assembly toughness or complex filling, check impact and flow data in the same conditioning state.
Use matched reinforcement levels for the first comparison, then adjust the percentage only when the part requirement justifies it. For example, compare PA6 GF30 with PA66 GF30 before comparing PA6 GF15 with PA66 GF50. This separates polymer-matrix effects from reinforcement-level effects and produces a clearer trial plan.
Design Around Fiber Orientation and Weld Lines
Short glass fibers align through the injection-molding flow field. Stiffness, strength and shrinkage can therefore differ along and across local flow directions. The relationship between gate, flow, weld lines and the load path is part of the material decision, not a detail to address after the grade is chosen.
Review gate position and size, wall transitions, ribs, bosses, inserts, fasteners, corners, end-of-fill zones and critical dimensions. Avoid placing a governing load across an uncontrolled weld line. Use molding simulation or a short-shot study where useful, then confirm orientation-sensitive behavior through molded specimens or the finished part.
- Primary load direction compared with expected local fiber orientation
- Weld lines, notches, inserts, screw bosses and sharp section changes
- Longitudinal and transverse shrinkage, flatness and cavity variation
- Surface acceptance zones, exposed fiber and mating-part contact
Use the Catalogue Ladder as a Screening Tool
The grades below connect glass content with tensile, flexural modulus, water absorption and HDT. Exclude grades below the stiffness target, then rank trials by impact, warpage and filling behavior.
Catalog typical values. Glass: ISO 1172; tensile: ISO 527; flexural modulus: ISO 178; water absorption: ISO 62, 23 °C/50% RH; HDT: ISO 75, 1.8 MPa. See the grade TDS for conditioning and current values.
Selected Taiyi glass-fiber grade ladder
Confirm Molding Feasibility and Equipment Readiness
Review drying and material transfer, machine capacity, screw and barrel condition, residence control, runner and gate restrictions, venting, fill balance, packing, cooling, ejection and surface requirements for the exact grade. Higher-fiber compounds may require a different feasibility review from the lower-fiber baseline and can increase wear on material-contact and tooling surfaces.
During trials, record material condition, lot, fill time, transfer, pressure, cushion, part weight, mold-surface temperatures, cavity balance, cycle, appearance and visible fiber or weld-line effects. Establish a stable process window for each candidate instead of forcing all grades through one inherited setting sheet.
Release the Molded Part at the Required Conditioning State
Measure cavity-marked parts after agreed conditioning intervals using fixed datums and methods. Check dimensions, warpage, surface, assembly, fastener retention, weld-line performance and any load-direction dependence. Compare dry, conditioned and service-relevant results where the application requires them.
Complete sustained-load, fatigue, impact, temperature, humidity, chemical, electrical, flame or other project tests on the intended geometry. Release the exact grade, color and process only after the original failure limit, production capability and document requirements are closed.