T1 trial molding first article inspection LSR mold: what buyers should check

Approving a custom liquid silicone rubber (LSR) mold requires clear evidence that the tool will produce parts meeting design intent, regulatory standards, and volume expectations. The T1 trial molding run and first article inspection (FAI) serve as the critical gate before full production release. Buyers and engineers must verify dimensional accuracy, flash control, cure consistency, and documentation completeness during this phase. This guide outlines the key parameters, inspection methods, and documentation checks that ensure a smooth transition from mold qualification to reliable manufacturing, helping you avoid costly rework and delays.

T1 trial molding: shot parameters and evaluation criteria

The T1 trial is the first full‑scale molding run using the qualified LSR material and process settings intended for production. It validates that the mold can fill, pack, and cure parts within specification while revealing any design‑related issues such as venting imbalances or uneven cooling. Engineers should monitor injection pressure, clamp force, melt temperature, and cycle time, then evaluate the resulting parts for flash, shorts, sinks, and dimensional stability.

Parameter	Target Range / Acceptance Criteria	Measurement Tool / Method
Injection pressure (peak)	800–1200 bar (material dependent)	Machine hydraulic transducer
Clamp force	≥ 1.5 × projected cavity area × melt pressure	Machine read‑out
Melt temperature	20–25 °C (LSR typical)	Thermocouple in barrel
Mold temperature (core/cavity)	40–60 °C (uniform ±5 °C)	Inline IR sensors / thermocouples
Cycle time (injection + cure)	Consistent within ±5 % over 10 shots	Machine timer
Flash thickness	≤ 0.02 mm on all parting lines	Calipers / vision system
Short shot / sink mark	None visible	Visual inspection (10× magnification)

A typical T1 trial produces 10–20 shots; the first 5 shots are discarded for purge, and the next 5–10 shots are retained for FAI. Consistent shot‑to‑shot variation indicates a stable process, which is essential before moving to formal inspection.

First article inspection: sample size, tolerances, and reporting

FAI verifies that the first parts from the qualified mold meet all drawing requirements, including geometric dimensioning and tolerancing (GD&T), surface finish, and material properties. Buyers should define the sample size based on part complexity and risk, then ensure that measurements are traceable to national standards.

Inspection Item	Typical Specification	Tool / Method	Acceptance Quantity
Critical dimensions (holes, shafts, mating features)	±0.05 mm (or per drawing)	CMM (probe size ≤2 mm)	All samples
Overall length / width / height	±0.10 mm	CMM or handheld micrometer	All samples
Wall thickness (uniform sections)	±0.08 mm	Micrometer / optical comparator	All samples
Surface roughness (Ra)	0.4–0.8 µm (mold finish dependent)	Portable roughness tester	3 samples
Hardness (Shore A)	30–80 A (per material grade)	Durometer	3 samples
Visual defects (flash, bubbles, contamination)	None allowed	10× magnified visual inspection	All samples

FAI sample sizes typically range from 5 to 30 pieces, depending on part criticality and customer PPAP requirements. For medical or automotive applications, a Level 3 PPAP (including full dimensional report, material certification, and process capability) is often mandatory. Documentation must include measurement records, material lot traceability, and a signed FAI report referencing ISO 13485 or ISO 10993‑1 where biocompatibility is relevant.

Comparison: T1 trial vs. production run expectations

Understanding how the T1 trial differs from steady‑state production helps buyers set realistic acceptance criteria and anticipate necessary adjustments. The table below contrasts key variables between the trial phase and the first production shift.

Aspect	T1 Trial (Qualification)	Steady‑State Production
Number of shots	10–20 (5 purge, 5–10 FAI)	Continuous (thousands per shift)
Process stability	Must show <5 % variation in key parameters over trial shots	<2 % variation; SPC charts in place
Flash allowance	≤0.02 mm (tight to detect tool issues)	≤0.03 mm (allowing for minor wear)
Dimensional sampling	100 % of FAI samples measured	Statistical sampling (e.g., 5 pcs/hour)
Documentation level	Full FAI report, material cert, mold setup sheet	Production log, periodic QA checks
Adjustments permitted	Process tweaks (temperature, pressure, time) allowed	Only approved engineering changes; no uncontrolled tweaks

If the T1 trial shows excessive variation or out‑of‑tolerance features, the mold may require modifications such as additional venting, gate resizing, or cooling channel adjustments before final approval.

Frequently Asked Questions

What is the difference between T1 trial and PPAP submission?

The T1 trial is the initial manufacturing run that validates the mold can produce parts within specification. PPAP (Production Part Approval Process) is a formal customer-specific documentation package that includes the T1 trial results, dimensional reports, material certifications, process capability studies, and sometimes a production run at rate. Approving the T1 trial is a prerequisite for submitting a complete PPAP.

Frequently Asked Questions

How many FAI samples should I request for a complex LSR medical component?

For high‑risk or complex medical parts, a minimum of 10–15 FAI samples is recommended. This provides enough data to assess variation across cavities and to perform capability studies (Cp, Cpk) if required. Critical features should be measured on every sample, while less critical attributes can be checked on a subset.

Can I use the same LSR material lot for T1 trial and production?

Yes, and it is strongly recommended. Using the same material lot eliminates variability between trial and production, ensuring that any observed differences are due to the mold or process rather than material changes. Always retain the material certificate of analysis for traceability.

Conclusion

The T1 trial molding and first article inspection are decisive steps that protect your investment in a custom LSR mold. By rigorously checking injection parameters, dimensional tolerances, flash control, and documentation completeness, you gain confidence that the tool will deliver consistent, compliant parts at volume. Pay close attention to sample sizes, measurement methods, and PPAP requirements specific to your industry, and never hesitate to request data or clarification from your mold supplier.

If you are ready to validate your next LSR mold or need expert support with mold making services and LSR injection molding, contact World Strong Rubber today. Our engineering team works closely with buyers to ensure every T1 trial meets the highest quality benchmarks before moving to full production.