Injection Molding Supplier Sample Evaluation: How to Review T1 and T2 Parts

When you commission a new литьевая форма, the first physical proof that your design works arrives as T1 samples. These first-shot parts, followed by T2 iterations, are the most critical checkpoint before volume production. At ZetarMold, catching dimensional drift or surface defects at the T1 stage has saved weeks of rework and thousands of dollars in tooling corrections. The evaluation process covers three pillars: dimensional verification against your drawings, surface quality inspection, and material identity testing. Each pillar catches different types of defects that the others would miss. This guide walks you through a structured approach so you can review литьё под давлением¹ samples with confidence and approve tooling before committing to production.

Understanding the full sample evaluation workflow helps frame why each checkpoint matters. The process begins when the mold maker completes fabrication and conducts initial test shots on a sampling press. These first shots, sometimes called T0 or pilot shots, let the mold maker verify basic fill, pack, and ejection. Only after the mold maker confirms that the tool functions mechanically do they produce the formal T1 samples shipped to you. Your evaluation should focus on whether T1 parts meet your design specifications, not on basic mold functionality. This distinction prevents confusion about which party is responsible for correcting specific issues.

What Are T1 and T2 Samples in Injection Molding?

T1 (Trial 1) samples are the first plastic parts produced from a newly fabricated injection mold. They represent the mold maker’s initial attempt to translate your 3D CAD model into a physical part. T2 (Trial 2) samples are produced after the mold has been modified based on T1 evaluation feedback. Modifications may include steel adjustments for dimensional deviations, surface polishing for cosmetic defects, or changes to the gate and runner system for filling issues. Some projects require T3 or T4 iterations, but a well-managed T1 review combined with precise tooling adjustments should resolve most issues by T2. At ZetarMold, roughly 40 percent of projects achieve approval at T1, while 60 percent require a T2 round.

Для более широкого обзора, наше injection molding complete guide охватывает основы процесса, поведение материалов и производственные решения.

Why Does Sample Evaluation Matter Before Mass Production?

Skipping or rushing sample evaluation is the fastest way to end up with defective parts in production. The sample phase is your last opportunity to verify that the mold produces parts matching your design intent before you invest in production scheduling, raw material sourcing, and logistics. A missed 0.15 mm wall-thickness deviation on T1 can lead to structural failures in the field. A thorough evaluation catches these issues when the fix is still a simple steel cut rather than a full mold rebuild. Beyond dimensional accuracy, the sample phase validates gate location, weld-line placement, and material flow behavior that directly affect part performance in service.

How Should You Prepare for a T1 Sample Review?

The essential preparation steps are gathering 2D drawings, material data, surface references, and inspection equipment before T1 arrives. Define tolerance expectations upfront. General tolerances following ISO 2768-mK are a common starting point, but critical dimensions may need tighter bands. Request at least 10 to 15 T1 samples for measurement and destructive testing.

TABLE:{“headers”:[“Preparation Item”,”Details”,”Priority”],”rows”:[[“2D Drawings with GD&T”,”All critical dimensions, datums, and tolerance callouts”,”Required”],[“Material Data Sheet”,”Confirm grade, color, and additives”,”Required”],[“Surface Finish Reference”,”Approved beauty board or Ra/Rz target values”,”Required”],[“Inspection Equipment”,”Calipers, micrometers, CMM, surface roughness tester”,”Required”],[“Sample Quantity”,”10 to 15 parts minimum”,”Recommended”]]}

What Dimensions and Tolerances Must You Check?

The dimensions to check first are bores, mounting-hole patterns, snap-fits, and sealing surfaces. These features directly affect assembly and structural performance. Use a CMM report from your supplier as baseline, but verify the top 5 to 10 critical dimensions independently with calibrated equipment.

After identifying critical dimensions, record all measurements in a structured format. Most suppliers provide a CMM inspection report with their T1 shipment. Compare this report against your own measurements for the most critical features. Any discrepancy between supplier-reported and independently verified dimensions warrants immediate discussion. At ZetarMold, we encourage buyers to compare our CMM data with their own measurements to build confidence in the tooling before T2.

General dimensions can follow ISO 2768² general tolerances with mK class (plus or minus 0.1 mm for sizes under 6 mm, plus or minus 0.2 mm for 6 to 30 mm, plus or minus 0.4 mm for 30 to 120 mm), but your drawing should explicitly call out tighter dimensions. Pay special attention to wall thickness uniformity. Variations greater than 10 percent often indicate uneven packing pressure or gate issues that worsen in production.

Surface finish evaluation is often rushed or treated as secondary to dimensional checking. However, for consumer-facing products, surface quality can be just as important as dimensional accuracy. A perfectly dimensioned part with visible sink marks or weld lines on the A-surface will still be rejected by your end customer. Invest the same rigor in surface evaluation as you do in dimensional measurement.

TABLE:{“headers”:[“Feature Type”,”Typical Tolerance”,”Notes”],”rows”:[[“Bore Diameter”,”plus or minus 0.05 mm”,”Critical for press-fit or alignment”],[“Mounting Hole CCD”,”plus or minus 0.10 mm”,”Affects assembly alignment”],[“Overall Length”,”plus or minus 0.20 mm”,”General tolerance”],[“Wall Thickness”,”plus or minus 0.10 mm”,”Must stay within 10 percent of nominal”],[“Flatness”,”0.05 to 0.10 mm”,”Critical for sealing surfaces”],[“Snap-fit Engagement”,”plus or minus 0.05 mm”,”Over-tolerance risks fracture”]]}

When recording tolerance measurements, note whether each dimension was measured at room temperature and standard humidity conditions. Plastic parts can exhibit dimensional changes of 0.1 to 0.3 percent depending on environmental conditions. This is especially true for hygroscopic materials like nylon or polycarbonate that absorb moisture from the surrounding air. Always measure under consistent ambient conditions and record the temperature and humidity.

How Do You Evaluate Surface Finish and Cosmetic Quality?

The correct method is evaluating under daylight-balanced lighting at 30 to 40 cm. Check all surfaces for sink marks, weld lines, flow marks, and gate blush. Compare against your beauty board or Ra/Rz values. Cosmetic surfaces should achieve Ra 0.4 to 0.8 um for polished or Ra 1.6 to 3.2 um for textured.

Document every defect with high-resolution macro photos including a scale reference. Classify each finding as critical (visible on customer-facing A-surface), major (affects function or sealing), or minor (cosmetic on non-visible surface). This classification helps your supplier prioritize mold corrections for T2. Pay particular attention to sink marks opposite thick-wall sections and rib intersections, as these are the most common surface quality issues found during T1 evaluations at our facility.

Surface quality defects on T1 samples often reveal underlying mold design issues that need correction before production. A weld line on a visible surface usually indicates that two flow fronts are meeting in an undesirable location. The mold designer may need to adjust the gate position, increase the number of gates, or add a flow leader to redirect the flow front. Similarly, persistent sink marks opposite thick sections indicate insufficient packing pressure or inadequate cooling time. These surface defects are not merely cosmetic problems; they signal potential structural weaknesses in the final part.

What Material Tests Should You Run on Injection Molded Samples?

The required tests are Индекс расплава³ (MFI), tensile, and color match verification on every T1 batch. MFI confirms material identity and reveals contamination. For engineering resins like PC, POM, or PA66, compare tensile strength and elongation against the datasheet. Color matching requires a spectrophotometer measuring Delta E less than 1.0.

Beyond the standard tests listed in the table below, consider your application requirements. Parts subject to UV exposure should undergo accelerated weathering testing. Components in electrical applications may require dielectric strength verification. Parts bearing mechanical loads benefit from creep testing, especially when using semi-crystalline materials like POM or PA66. Tailor your test plan to the end-use environment, not just the material datasheet.

Additional Testing Considerations

For parts in food-contact or medical applications, request certification that samples meet FDA or USP Class VI requirements. Consider running a drop test or impact test if parts will experience mechanical loading in service. Always document all material test results alongside dimensional data in your T1 evaluation report for complete traceability. These additional tests add cost but provide critical assurance that the molded parts will perform safely in their intended environment throughout the product lifecycle.

TABLE:{“headers”:[“Test Type”,”Equipment”,”Pass Criteria”,”When Required”],”rows”:[[“Melt Flow Index”,”MFI tester”,”Within 10 percent of datasheet”,”Every project”],[“Tensile Strength”,”Universal testing machine”,”Match datasheet minimums”,”Engineering resins”],[“Color Match Delta E”,”Spectrophotometer”,”Delta E less than 1.0″,”Colored parts”],[“Surface Roughness”,”Profilometer”,”Ra within 0.2 um of target”,”Cosmetic A-surfaces”],[“CMM Dimensions”,”CMM or height gauge”,”All dims within tolerance”,”Every project”]]}

When Should You Request T2 Samples After T1 Review?

T2 samples are required when critical dimensions fall outside tolerance or surface defects need mold changes. Not every deviation needs T2. Minor findings on non-visible surfaces can often be fixed through process adjustments alone.

A well-documented report also serves as a legal record in case disputes arise about whether the supplier met the agreed specifications. Keep copies of all CMM data, photos, and correspondence. Many professional procurement teams use a standardized T1 evaluation template that scores each dimension and surface defect on a pass, conditional, or fail basis. This scoring system removes ambiguity and provides a clear go or no-go decision framework that both parties can reference throughout the project lifecycle.

How Do You Document Feedback and Communicate with Your Supplier?

The best approach is to create a formal T1 evaluation report. Include a dimension summary table, categorized defect photos with location markings, material test results, and a disposition for each finding. Use a standard template. Suppliers who receive structured reports complete T2 corrections faster because requirements are unambiguous.

What Common Mistakes Do Buyers Make During Sample Evaluation?

The most common mistake is evaluating only appearance while skipping dimensional verification. A part can look perfect yet be non-functional if critical dimensions are off. Another error is approving T1 based on a single part instead of measuring a statistical sample. Injection molding has natural variation, so one conforming part does not guarantee the next batch will match. Buyers also frequently fail to specify whether T1 should run on the production press, leading to discrepancies when production starts.

Neglecting to define acceptance criteria before T1 is another common mistake. Without pre-agreed tolerances and surface quality standards, the evaluation becomes subjective and prone to disagreement. Establish a formal quality agreement with your supplier that specifies dimensional tolerances by feature type, acceptable surface finish ranges, and the required material test results. This agreement should be part of your initial purchase order. Buyers who define clear acceptance criteria upfront experience fewer disputes and faster approval cycles.

Frequently Asked Questions About Injection Molding Sample Evaluation

Часто задаваемые вопросы

What is the difference between T1 and T2 samples in injection molding?

T1 (Trial 1) samples are the first parts produced from a newly built mold, while T2 (Trial 2) samples are produced after mold modifications based on T1 feedback. T1 verifies the initial mold design and material flow behavior; T2 confirms that corrections resolved the identified issues. At ZetarMold, most well-managed projects achieve approval at T2, with roughly 40 percent passing at T1 when the mold design is well-optimized from the start. Understanding this two-stage process helps you set realistic project timelines and avoid rushed approvals.

How many T1 samples should I request from my supplier?

Request at least 10 to 15 T1 samples for a thorough evaluation. You need enough parts to perform dimensional measurements on multiple samples, conduct material testing such as MFI and tensile checks, and retain reference specimens for future comparison. For large or expensive parts, five to eight samples may be acceptable if your testing plan is simplified. Having sufficient samples lets you assess process consistency, since measuring only one or two parts cannot reveal the natural variation in your molding process.

What inspection equipment do I need to evaluate samples?

Basic evaluation requires digital calipers, micrometers, and a surface roughness tester as absolute minimum equipment for any sample review. For complex geometries with tight tolerances, a CMM is essential to verify GD&T callouts accurately across all critical features. A spectrophotometer handles color verification against your approved standard, and an MFI tester confirms material identity. Third-party inspection labs offer comprehensive sample evaluation services with certified measurement equipment if you lack in-house tools. Budget approximately 500 to 2000 USD for a complete third-party T1 evaluation.

Can T1 samples be approved without T2 if dimensions are within tolerance?

Yes, T1 approval without a T2 round is possible when all critical dimensions pass, surface quality meets requirements, and material testing confirms the correct resin grade was used consistently across all provided sample parts. At ZetarMold, roughly 40 percent of well-planned projects achieve T1 approval on the very first submission. Key success factors include a thorough mold design review before fabrication, properly dried and conditioned raw material, and optimized processing parameters that are established and validated before the first sample shot is fired.

What tolerances should I expect on T1 injection molded samples?

General tolerances following ISO 2768-mK are typical for injection molded parts: plus or minus 0.1 mm for sizes under 6 mm, plus or minus 0.2 mm for 6 to 30 mm, and plus or minus 0.4 mm for 30 to 120 mm. Critical functional features like bores, snap-fits, or sealing surfaces often require tighter plus or minus 0.05 mm tolerances that should be explicitly called out on your drawings. Always agree on tolerance standards with your supplier before mold fabrication begins to avoid disputes.

How do I know if a surface defect requires mold modification?

A surface defect requires mold modification if it appears on a customer-facing A-surface, affects a sealing or functional surface, or exceeds the agreed surface roughness specification in your quality agreement. Minor sink marks on non-visible rib intersections or small ejector-pin marks on B-surfaces can usually be addressed through process adjustments such as increased packing pressure or longer cooling time. For defects on critical surfaces, the mold maker will need to polish, re-texture, or modify steel to achieve the required finish quality before producing T2 samples.

1. литьё под давлением: injection molding refers to a manufacturing process in which molten plastic is injected into a mold cavity to produce parts. ↩

2. ISO 2768: ISO 2768 refers to an international standard specifying general tolerances for linear and angular dimensions. ↩

3. Индекс расплава: Melt Flow Index refers to a measure of thermoplastic melt flow ease, in grams per 10 minutes through a standard die. ↩