Views: 0 Author: Site Editor Publish Time: 2026-02-05 Origin: Site
The mold trial (T1) is the most critical phase between tooling completion and mass production. A well-executed trial doesn't just test the mold—it lays the foundation for stable, profitable manufacturing. A failed trial, however, leads to costly delays, endless engineering changes, and frustrated teams.
This guide provides a comprehensive, stage-gated checklist used by leading manufacturers to transform trial runs from chaotic guesswork into a predictable, scientific process.
70% of trial success is determined before the mold ever touches the machine.
Technical Files Verified:
Latest 3D & 2D Part Drawings (With critical dimensions, tolerances, and inspection points clearly marked)
Complete Mold Drawings (Assembly, core/cavity, cooling circuit, and electrical diagrams)
Bill of Materials (BOM) (Steel grades, hot runner brand, standard component details)
Mold Flow Analysis Report (Key recommendations for gate location, cooling, and processing window)
Production Standards Locked:
Material Data Sheet (MDS) Confirmed (Resin grade, correct drying temp/time, MFI)
Color Standard Available (Signed-off physical color chip or approved Pantone number)
Golden Sample Identified (A pre-approved sample for visual and dimensional reference)
Acceptance Criteria Defined (Agreed limits for sinks, weld lines, voids, etc., with boundary samples)
Incoming Mold Inspection:
Visual & Physical Check: Mold number, lifting holes, rust prevention, parting line protection.
Critical Fit Checks: Mold thickness, locating ring diameter, sprue bushing radius, ejector rod hole position.
Peripherals Present: Hot runner junction box, temperature controllers, spare parts (springs, ejector pins).
Pre-Mount Procedures:
Deep Cleaning: Remove all rust preventive and machining debris from cavities, pins, and sliders.
Circuit Testing: Pressure test cooling lines for leaks and flow rate. Record inlet/outlet ∆T.
Function Test (On Bench): Manually cycle all sliders, lifters, and hydraulic cores for smooth operation.
Pre-Heating (If required): For high-temperature materials (e.g., PEEK, some PC), bring mold to near operating temperature off the press.
Injection Molding Machine Readiness:
Capacity Match: Shot size (part + runner weight) is 20-80% of machine barrel capacity.
Clamp Force Verified: Theoretical tonnage calculation < 80% of machine's rated clamp force.
Machine Condition: Clean barrel, verified thermocouple accuracy, smooth mechanical movements.
Auxiliary Equipment Check:
Dryer: Correctly set, material dried for sufficient time (verify with dew point test if possible).
Mold Temperature Controller: Fluid quality/level checked, flow and temperature stability confirmed. Start heating early.
Robot/End-of-Arm-Tooling (EOAT): Program loaded, grippers fit part safely, all safety signals tested.
Granulator: Clean and ready for uncontaminated sprue/runner regrind.
Trial Kick-off Meeting:
Roles Defined: Mold Tech, Process Engineer, Quality Inspector, Project Lead are present.
Goal Clarity: Is this trial for "Mold Function" or "Process Locking"?
Decision Authority Clear: Who adjusts parameters? Who inspects? Who makes the final go/no-go call?
Contingency Plan: Defined steps for a critical issue (e.g., core crash, major flash).
Goal: Safely inject the first shot and establish a baseline process.
All safety gates functional and closed.
Tool area clear of debris and tools.
Personnel positioned safely, away from potential parting line spray.
Establish Conservative Start-Up Parameters:
Reference MDS & Mold Flow: Start at mid-range temperatures, low-to-mid speeds and pressures.
Shot Size Setting: Set screw recovery to 1.5-2x the total shot (part + runner) weight.
Injection Profile: Use at least a 3-stage profile (Slow start -> Fast fill -> Slow pack/hold transition).
Temperatures: Bring barrel and mold to the material supplier's recommended mid-range.
Perform a Purge Shot:
Without the mold, purge material to check for uniform melt, contamination, or degradation.
First Molded Shot & Inspection:
Fill Balance (for multi-cavity molds)
Severe Flash?
Ejection System Functional? (Did the part eject?)
Record Transfer Position (V/P switchover point).
NO HOLDING PRESSURE. Use slow speed just to fill the mold.
Primary Purpose: Verify mold fills, basic functions work.
Critical Checks:
Goal: Use a scientific method to refine the process toward target part quality.
Establish the Fill Phase:
Using the first-shot V/P point as a baseline, gradually increase injection speed until you see slight flash or a sharp pressure spike, then back off by 5-10%.
Target: A stable, fast, and balanced fill that is repeatable.
Optimize Pack/Hold & Cooling:
Pack/Hold Pressure: Use the "Decaying Hold Pressure" method. Start with a long hold time and high pressure. Gradually reduce pressure until part weight decreases, then set pressure slightly above that threshold.
Cooling Time: Start long. Gradually reduce until parts show slight distortion or ejector pin marks, then add 1-2 seconds.
Dimensional & Cosmetic Fine-Tuning:
Sink Marks: Increase pack/hold; enhance cooling near thick sections/gates.
Weld Lines: Increase mold/melt temp; adjust injection speed or gate sequencing.
Jetting/Jet Stream: Decrease first-stage injection speed; increase mold temp.
Part UNDER size: Increase pack/hold pressure/time; increase mold temperature.
Part OVER size: Decrease pack/hold; decrease mold temperature.
Warpage: Check cooling line ∆T; balance pack pressure; adjust mold temperature zones.
Measure Critical Dimensions: Use calipers, CMM. Compare to drawing.
Adjustment Logic:
Cosmetic Defect Elimination:
Short-Run Stability Test:
Run a consecutive 30-50 cycle run at the "optimized" settings.
Sample every 5 cycles for visual check and key dimension measurement.
Calculate Short-Term Process Capability (CPK): For critical dimensions, assess stability. Target: CPK ≥ 1.33.
Goal: Create definitive documentation to guide the next steps.
The Report MUST Include:
Mold Status: Approved for Production / Requires Modification (List Items) / Requires Redesign.
Process Window Assessment: Wide / Moderate / Narrow. Notes for production control.
Estimated Scrap Rate (Runner/Regrind percentage).
Recommended Standard Cycle Time.
Summary of dimensional measurement data.
Photos of acceptable/unacceptable cosmetic defects.
Physical samples: First/Last shots, typical defects, and good parts for reference.
List ALL mold issues found (e.g., insufficient venting, uneven cooling, sticky ejection).
Include photos/videos as evidence for each issue.
Provide clear corrective action recommendations for the toolroom.
Trial Header: Date, Machine ID, Mold Number, Material Lot, Attendees.
Final Process Sheet: Screenshot of machine settings or detailed parameter log.
Mold Condition Report:
Part Qualification Data:
Conclusions & Recommendations:
Production Readiness Handover:
Save final parameters to machine controller or MES system. Create a backup.
Conduct a face-to-face meeting with production shift leaders and technicians. Highlight critical control points.
Deliver a physical trial sample kit and the signed trial report.
Before you conclude, validate your trial against these five markers of true success:
Safe: Zero safety incidents or equipment/mold damage.
Objectives Met: The predefined trial goals were accomplished.
Problems Documented: All issues were captured, analyzed, and have assigned next steps.
Data Captured: All process parameters and inspection results are recorded and traceable.
Path Forward Clear: The decision is unambiguous—"Release to Production" or "Mold Modification" with a defined plan.
