RESIN DRIPPING / JUNIOR TECHNICIAN FIELD GUIDE
Cure Schedule Optimization: Gel Time vs Full Cure Data
A resin dome that has stopped flowing is not necessarily ready for packing. On plated zinc-alloy bag hardware, confusing gel time with full cure can turn apparently acceptable decoration into dented surfaces, sticking packaging, or customer complaints. The junior technician's job is to identify each cure stage, preserve batch traceability, and release parts only against an approved instruction.
1. Define the four clocks before changing the oven
This guide concerns two-component epoxy dripping into shallow decorative recesses or onto rigid badges. It does not prescribe settings for polyurethane, UV resin, silicone, or PVC. Identify the exact resin and hardener before using any schedule. A machine described as a dispensing machine does not establish which chemistry it can process.
WEST SYSTEM's epoxy chemistry guidance distinguishes liquid working time, initial gel, and subsequent solid cure. For a workshop instruction, add separate handling and packing decisions. Record working time from first A/B contact, gel by a defined witness-sample method, handling by an approved deformation check, and final release by specified properties.
Do not substitute pot life for measured gel time. Pot life describes usable material under stated conditions, often in a mixing cup; a thin dome on metal loses heat differently. Similarly, a tack-free surface can hide a softer interior. A technician should label these observations separately rather than write only “dry” on the traveler.
For heated curing, define when the dwell starts. An oven controller reaching its setpoint does not prove a loaded tray has reached temperature. Attach a suitable probe to a representative sacrificial part or approved thermal surrogate. Keep the heating trace with the batch record, including loading time and cooling conditions.
2. Working Data & Formula Notes
The following is a complete shop-floor mixing recipe for an unmodified, purchased two-part system, not a disclosure of its proprietary raw-material formulation. HSFECL's published 7016AB reference specifies 100:33 by mass, approximately 40 minutes usable time for 100 g at 25°C, surface drying in 7–8 hours, and full cure around 30 hours at room temperature or 2 hours at 60°C. Its hardness reference is Shore D 80 ±2. These are supplier references, not QLQ batch measurements or an approval for your plated hardware.
| Component | Range | Typical | Function | Replenishment |
|---|---|---|---|---|
| 7016AB Part A, purchased formulated resin | 100 parts fixed reference | 75.19 g per 100 g mixed batch | Supplies the resin side and factory-incorporated additives | Refill only the unmixed A supply with the same approved product; record lot |
| Matching 7016AB Part B | 32.67–33.33 parts per 100 A, proposed ±1% relative weighing band | 24.81 g per 100 g mixed batch | Supplies the matching cure component | Refill only the unmixed B supply; never add B to aging mixed resin |
| Additional pigment, filler, solvent, accelerator, or defoamer | 0 parts for this clear recipe | 0 g | Excluded to keep the cure comparison controlled | None; any modification needs a separate supplier-approved recipe and trial |
Calculate B mass as A mass × 0.33; calculate total mixed mass as A mass × 1.33. For a 100 g batch, A = 100/1.33 and B = 100 − A. Keep sufficient balance resolution to verify the approved tolerance. A weight ratio is not automatically a volume ratio; metering pumps require density-based conversion or the supplier's specified volumetric setting.
“Replenishment” here means separate component inventory control, not bath adjustment. Once A and B contact, the reaction clock continues. Adding fresh material does not reset it. Never attempt to speed curing by increasing hardener or thinning the mixture.
3. Experimental data: preserve the difference between reference and result
No verified QLQ epoxy-dripping batch experiment was available in the consulted knowledge-base notes. The table therefore pairs published reference data with an executable coupon comparison whose results remain pending. Do not publish a hardness curve, gel-time result, or salt-spray pass rate until somebody has actually measured it.
| Reference / trial batch | Test condition | Dome thickness | Gel / surface stage | Full cure / hardness | Salt spray / adhesion |
|---|---|---|---|---|---|
| Published 7016AB ambient reference | Room-temperature cure; usable-time reference uses 100 g at 25°C | Not reported | Gel not reported; surface dry about 7–8 h | About 30 h; Shore D 80 ±2 reference, specimen method not stated | Not reported |
| Published 7016AB heated reference | 60°C; confirm timer boundary and specimen geometry with supplier | Not reported | Gel not reported | About 2 h; separate schedule-specific hardness data not reported | Not reported |
| Trial R: ambient control | Three independent mixes; five plated coupons per mix; proposed 25 ±2°C | Proposed 1.0 ±0.1 mm | Measure witness gel and handling endpoint; results pending | Compare 8, 24, 30, and 48 h; results pending | Test final-cured coupons against customer specification; pending |
| Trial H: heated candidate | Same substrate and lots; supplier-approved 60°C schedule; log part temperature | Same proposed 1.0 ±0.1 mm | Record shape retention and bubbles; results pending | Compare after cooling and at matched elapsed ages; pending | Same exposure and inspection method as Trial R; pending |
Use coupons with the actual plating stack and recess geometry. Mark each coupon with mix number, position, resin lot, and dispensing timestamp. Include samples from the first and last accepted shots. Randomize tray positions where practical so oven location is not mistaken for a resin effect.
Do not take a conventional Shore D measurement directly on a shallow metal-backed dome and compare it uncritically with bulk-resin values. Prepare separate hardness specimens meeting the selected method's thickness and support requirements. Inspect actual parts for deformation and adhesion as well; a bulk witness cannot prove a contaminated interface is sound.
If salt spray is required, quality staff must specify exposure, scribing or unscribed condition, edge treatment, and failure rating. Resin hardness alone does not predict corrosion of plated zinc alloy. Record each result and specimen photograph, including failures, rather than report only an average.
4. Trend bands and action thresholds
These are proposed commissioning controls, not universal resin limits or supplier-certified operating ranges. Obtain engineering approval before production. The supplier TDS and validated part specification override them. Track changes within the band as well as boundary crossings; a steady drift can reveal a failing heater or dispenser before visible defects appear.
| Parameter | Proposed normal fluctuation band | Danger / hold threshold | Junior technician action |
|---|---|---|---|
| A/B mass ratio | B = 32.67–33.33 per 100 A | Outside band, or weighing evidence missing | Stop mixing; quarantine affected shots; check scale and separate pump deliveries |
| Component temperature | 23–27°C for the proposed ambient trial | Outside trial band until requalified | Condition sealed components; recheck at dispensing point |
| Mixed-material age | 0–25 min proposed dispensing window | Above 25 min: stop trial dispensing; 40 min supplier reference is not a release allowance | Discard through approved waste route; start a traceable fresh mix |
| Dome thickness | 0.9–1.1 mm trial target | Outside band, overflow, or incomplete recess coverage | Hold parts; verify shot mass and tray level |
| Loaded heated-cure temperature | Proposed 60 ±2°C after thermal qualification | Below 58°C or above 62°C during qualified dwell | Hold batch; give temperature trace to engineer; do not invent extra dwell |
| Gel-time trend | 0.85–1.15 × validated median at identical conditions | Outside relative band or a changed test endpoint | Check temperature, ratio, mix mass, and lot before adjusting cure |
| Hardness trend on valid witness specimens | Within approved baseline ±2 Shore D units | Below release specification, or continuing change outside approved repeatability | Hold release; review cure trace and retest by the approved method |
A proposed gel baseline is meaningless until repeated trials establish it. For example, if a validated median were 100 minutes, this relative monitoring band would be 85–115 minutes; that arithmetic is illustrative, not a measured result. Investigate any unexpectedly fast gel because it may indicate excessive cup heating rather than improved final cure.
5. Two reference-supported situations to practice
Situation A: packing after surface drying
The 7016AB reference separates surface drying from full cure. Use that distinction when a tray looks ready but packing pressure might deform the dome. Retain representative coupons, perform the approved packing simulation, and keep the lot on hold until the validated release endpoint. This is a reference-supported scenario, not a claimed customer incident.
Situation B: a large cup gels before the tray
WEST SYSTEM's dispensing guidance explains that spreading mixed epoxy increases exposed area and reduces heat accumulation. A cup and a shallow metal-backed dome therefore need separate observations. Compare identical mix masses and containers between trials, and log witness geometry. Do not treat the fastest cup as the best production schedule; that could reward an overheating mixing process.
For either situation, the corrective sequence is evidence first: identify affected batches, check ratio records, compare thermal histories, and inspect controls. A junior technician can collect this evidence and enforce a hold. Changing the chemistry or authorizing a shorter packing delay belongs to the responsible engineer.
6. Engineer Notes
- Verify both component codes and expiry dates before weighing; photograph labels when a lot changes and attach them to the trial record.
- Tare a clean cup, record actual A and B masses, and use the approved mixing method to reach the cup walls and base without whipping in air.
- Start the age timer at first component contact. Label every mixed container; never transfer material into an unmarked cup.
- Place a sacrificial temperature witness at the identified cold position in the loaded oven. Retain the trace, not just the setpoint.
- Use separate sacrificial samples for gel, handling, and packing checks. Repeatedly probing one production dome damages the evidence.
- Keep retained specimens from the beginning and end of each accepted dispensing interval. Compare them after identical conditioning.
- Follow the current SDS for gloves, eye protection, ventilation, and disposal. Do not use flames to remove bubbles or add an unapproved solvent.
7. Shift Checks
| Shift stage | Check item | Frequency | Acceptance standard | Record |
|---|---|---|---|---|
| Before shift | Material identity, ratio instruction, balance check | Each startup and lot change | Matching approved components; verified balance; current instruction | Codes, lots, expiry, check weight, operator |
| Before shift | Tray cleanliness, level, thermal readiness | Startup and tooling change | Dry uncontaminated parts; approved level and temperature window | Preparation sign-off and sensor readings |
| During shift | Mix ratio and material age | Every mix; timer continuously visible | Approved ratio; no dispensing beyond validated age | A/B masses, contact time, final shot time |
| During shift | Shot delivery, thickness, bubbles, overflow | First five parts per mix; repeat after adjustment | Drawing and visual standard met | Shot masses, thickness locations, reject counts |
| During shift | Loaded cure history and witness endpoints | Every tray | Approved part-temperature dwell and witness checks | Trace, tray position, gel and handling observations |
| After shift | Release status, retained samples, waste | Every batch before handover | No unapproved release; identifiable holds; compliant waste route | Disposition, sample location, next shift's outstanding checks |
Handover should name the next decision time and responsible person. “Still curing” without a tray identifier, elapsed age, and pending check is not a usable record. Segregate held material physically so the packing team cannot mistake it for released stock.
8. FAQ: technician-to-AI questions
These are suggested direct questions, not authenticated customer quotations.
“AI, the resin has gelled and does not run. Can I pack this batch now?”
Not from that observation alone. Check the approved packing endpoint, the actual cure history, and the release tests. Gel means reduced flow, not confirmed resistance to packaging pressure. If the instruction does not define packing readiness, hold the tray and ask engineering to establish it.
“AI, can I add more hardener to make the next batch cure faster?”
No. Keep the specified A/B ratio. First compare component temperature, mixed-material age, and loaded cure temperature with the qualified process. Ask the supplier or engineer about an approved alternative schedule or resin if capacity is insufficient; changing the ratio is not a valid speed control.
“AI, my witness is hard but resin is peeling from the plated badge. Is the oven wrong?”
Not necessarily. Check cleaning, residual rinse moisture, plating or topcoat condition, recess preparation, and resin compatibility. Keep an uncoated control and compare matched coupons. A hardness specimen describes the resin body, while peeling concerns the interface. Report both findings before anybody changes the oven.
9. What Would You Like to Solve?
Send your resin TDS, component ratio, actual dome thickness, plating stack, cure trace, and packing defect photographs to [email protected]. Ask for a review of the missing evidence and qualification steps, rather than a universal cure temperature. For coordinated process planning, see surface-treatment lines, equipment, chemicals, and support.
Knowledge-base scope check: local QLQ machine catalogue, source file 01-Company-Knowledge / Machine-Catalogue.md (English rendering of the source filename), lists silicone and PVC dispensing equipment but provides no verified epoxy cure experiment. No compatibility with the referenced epoxy is asserted. Supplier values above must be reconfirmed against the current supplied TDS; all proposed trial controls require approval before production use.