Resin dripping | Intermediate technician reference | Plated zinc-alloy bag hardware
Resin Drip Viscosity Windows: Full Temperature Compensation Data
A dispensing program that fills a decorative recess correctly in the morning can overflow the same recess after lunch. Resin temperature, mixed-material age, and shot delivery interact. An intermediate technician needs to separate those effects before changing pressure, pulse time, or nozzle size.
This guide addresses two-component epoxy doming over finished hardware, not PVC plastisol or liquid silicone. No verified QLQ epoxy temperature curve or batch-test report was available in the reviewed knowledge base. The temperature grid below is explicitly calculated; the experimental comparison sheet contains pending measurements. Neither represents production evidence or a universal resin specification.
1. Establish the material boundary first
Identify the exact resin and hardener codes, their lot numbers, the approved mixing basis, and the finish under the dome. A label-grade resin is a candidate for evaluation, not proof of adhesion to nickel, lacquer, or a painted recess. Verify compatibility on the actual finish before releasing customer parts.
Published examples establish realistic scale. JINHUA lists 308AB-3S1 at 3:1 by weight, with component A viscosity of 550–750 mPa·s and component B at no more than 150 mPa·s at 25°C. Its stated hardness is Shore A 58–72. The page gives differing cure references: a specification range of 10–18 hours, but an FAQ test of 12–20 hours for a 2 g mixture at 25°C. Obtain the current signed technical sheet before setting a release time. These are component viscosities, not a measured mixed viscosity. Manufacturer reference.
Fong Yong lists E-1158-2/H-1158-2 at 3:1 by weight, component viscosities of 400–1,000 and 70–120 mPa·s at 25°C, and a 30–40 minute pot life for 60 g at 25°C. It reports Shore A 80–90, with rated performance reached at seven days. Those conditions cannot be transferred to another resin. Manufacturer reference.
2. Complete working formulation: preserve the approved ratio
The following is a complete clear, two-component working mixture for a supplier-approved 3:1 system. It is not a disclosure of either manufacturer's proprietary ingredients. Internal resin chemistry and additive percentages are unavailable and require supplier confirmation. A permissible batch-size range does not mean the mixing ratio may vary.
| Component | Range | Typical | Function | Replenishment |
|---|---|---|---|---|
| Approved formulated epoxy, Part A | 30–75 g per proposed small batch | 75.00 g | Film-forming resin package; 75% of total mass | Dispense fresh material into a clean, tared vessel |
| Matched hardener, Part B | 10–25 g, exactly one-third of A | 25.00 g | Crosslinking package; 25% of total mass | Add by measured mass; never correct aged mixture with extra hardener |
| Extra solvent or water | 0 g | 0 g | Excluded from this solvent-free working mixture | None; do not thin at the machine |
| Extra pigment, filler, defoamer, or catalyst | 0 g in the qualified clear baseline | 0 g | Excluded to preserve the baseline formulation | Any addition requires separate supplier-approved qualification |
Batch-sizing rule: total mass equals dispensing consumption per minute multiplied by the validated usable window, with mixing and transfer time deducted. For an illustrative consumption of 4 g/min and a validated 15-minute dispensing allowance, prepare no more than 60 g: 45 g A plus 15 g B. This is arithmetic, not a pot-life claim. Never top up a partly reacted cup with fresh resin; its age becomes unknowable.
3. Build a temperature curve without disguising cure drift
Measure freshly mixed material at a fixed elapsed time using the same viscometer geometry, speed, sample volume, and conditioning procedure. Use separate fresh mixes at each temperature rather than repeatedly heating one reacting sample. Record actual liquid temperature, not the room thermostat. Report viscosity in mPa·s; its numerical value equals cP.
A useful commissioning model is η(T) = η25 × exp[B × (1/TK − 1/298.15)]. Here η25 is viscosity at 25°C, TK is liquid temperature in kelvin, and B is a fitted temperature coefficient in kelvin. The model describes a fixed-age measurement, not the changing viscosity of a curing cup.
For the worked grid only, assume η25 = 600 mPa·s and B = 4,000 K. These are selected teaching inputs, not measured properties of the products above. The normalized factor η/η25 lets a technician see temperature sensitivity without treating component viscosity as mixed viscosity.
| Liquid temperature | Calculated η/η25 | Calculated viscosity | First-pass pulse factor | Workshop decision |
|---|---|---|---|---|
| 15°C | 1.593 | 956 mPa·s | 1.593 | Condition material; do not compensate blindly |
| 18°C | 1.381 | 829 mPa·s | 1.381 | Outside proposed thermal control band |
| 20°C | 1.257 | 754 mPa·s | 1.257 | Run weighed-shot trials if qualification covers this point |
| 22°C | 1.146 | 688 mPa·s | 1.146 | Check nozzle temperature and edge filling |
| 25°C | 1.000 | 600 mPa·s | 1.000 | Reference setting |
| 28°C | 0.875 | 525 mPa·s | 0.875 | Check overflow and usable material age |
| 30°C | 0.801 | 481 mPa·s | 0.801 | Outside proposed thermal control band |
| 35°C | 0.647 | 388 mPa·s | 0.647 | Stop unqualified operation; investigate heating |
For ideal laminar flow through unchanged geometry at constant pressure, flow varies inversely with viscosity, so equal shot mass suggests pulse time proportional to viscosity. A 200 ms reference pulse becomes approximately 229 ms at 22°C in this model. Real valves have opening delays, tubing compliance, and cutoff behavior; approve settings using weighed shots, never this equation alone.
Fit B from two same-age measurements: B = ln(η1/η2)/(1/T1 − 1/T2). Validate intermediate points and endpoint behavior. Keep a separate age curve at the operating temperature. A resin warming while curing can temporarily show stable viscosity even as its remaining dispensing window disappears.
4. Normal fluctuation bands versus stop thresholds
These are proposed commissioning controls, not manufacturer guarantees or established customer specifications. Obtain engineering approval after trials. A stop threshold means hold the process for review; it is not a claim that every part beyond it necessarily fails.
| Parameter | Proposed normal band | Danger or hold threshold | Required action |
|---|---|---|---|
| Mixed-liquid temperature | 24–26°C around a 25°C setpoint | Below 22°C or above 28°C without qualification | Condition supply and repeat shot approval |
| Same-age mixed viscosity | 0.90–1.10 × qualified reference | Below 0.80 or above 1.20 × reference | Check temperature, ratio, contamination, and age |
| Hardener mass relative to target | Within ±1% of the prescribed B mass | Outside supplier-approved tolerance; any unknown ratio | Hold mix; do not repair by guesswork |
| Mean shot mass, ten shots | Within ±3% of approved nominal | More than ±5% from nominal | Inspect dispensing system and requalify pulse |
| Shot-mass coefficient of variation | No more than 3% | Above 5% | Check air, valve repeatability, and nozzle blockage |
| Mixed-material age | Below 50% of locally validated usable time | At the validated limit, or first sustained flow drift | Discard according to the approved procedure |
| Dome center thickness | 0.90–1.10 × approved drawing target | Outside drawing limits or any overflow | Hold affected tray and inspect recess geometry |
Do not add pH to this control plan: bulk solvent-free epoxy is not an aqueous plating bath. Also avoid a universal hardness threshold. Shore A and Shore D values are different scales, and a thin dome on metal is unsuitable for direct comparison with a thick manufacturer test specimen.
5. Experimental comparison: create evidence before release
No authenticated batch comparison was supplied. The table below is a ready-to-use experimental record, with unmeasured results explicitly pending. Use one resin lot, one matched hardener lot, one plated-hardware lot, identical recess geometry, and three independently prepared mixes at each temperature. Evaluate ten parts per mix. Repeat with a second material lot before adopting the curve.
| Trial batch | Test condition | Mixed viscosity | Dome thickness | Hardness | Adhesion / exposure |
|---|---|---|---|---|---|
| C22 | 22°C liquid; measurement at 3 min; approved cure schedule | Pending, mPa·s | Pending, center and edge, mm | Pending, suitable companion plaque | Pending; actual finished hardware |
| C25 | 25°C liquid; measurement at 3 min; same cure schedule | Pending, mPa·s | Pending, center and edge, mm | Pending, same plaque method and age | Pending; baseline comparison |
| C28 | 28°C liquid; measurement at 3 min; same cure schedule | Pending, mPa·s | Pending, center and edge, mm | Pending, same plaque method and age | Pending; identical exposure protocol |
Document the instrument method and cure age for hardness. Measure dome thickness optically or by a validated cross-section method rather than assuming a magnetic coating gauge reads the resin correctly. If salt-spray testing is required, quality engineering must define the method, exposure duration, masking, and acceptance criteria first. A clear dome does not prove corrosion resistance of the entire plated assembly.
Two useful diagnostic exercises are a cold-start underfill and a late-batch overflow. For underfill, compare conditioned fresh resin against the cold batch at unchanged nozzle geometry. For overflow, compare fresh and aged mixtures at the same measured temperature before adjusting pressure. These are training scenarios, not verified customer cases; the controlled comparisons distinguish thermal flow changes from reaction-age effects.
6. Engineer Notes
- Log temperatures at the feed vessel, nozzle outlet sample, and workpiece. Resolve gradients before changing pulse duration.
- Tare the balance separately for both components. Record actual masses and verify the approved weight ratio before mixing.
- Start the age timer when A first contacts B. Label every cup and tray with that timestamp and both lot numbers.
- Mix with the supplier-approved method, scraping vessel walls and base. Include transfer and any approved degassing time in the usable window.
- After any adjustment, weigh ten individual shots into separate tared containers. Record the mean, standard deviation, and coefficient of variation.
- Inspect recesses for residual water, polishing compound, oil, and dust. Use only a finish-compatible, qualified cleaning procedure.
- Never use extra hardener, solvent, or uncontrolled heating to rescue aged material. Follow the SDS, use specified protection, and control exotherm and disposal.
7. Shift Checks
| Shift stage | Check item | Frequency | Acceptance standard | Record |
|---|---|---|---|---|
| Before shift | Lots, expiry, balance, temperature | Every startup | Approved matched materials; calibrated balance; qualified thermal band | Startup release sheet |
| Before shift | Ten-shot mass and first tray | Startup and nozzle replacement | Approved mean/CV; no overflow or edge gaps | Shot sheet and retained sample |
| During shift | Ratio and mix timestamp | Every fresh mix | Prescribed ratio; traceable age below validated limit | Mixing log |
| During shift | Liquid temperature and shot mass | Every 30 min and after interruptions | Commissioning bands confirmed by local qualification | Trend chart and adjustment history |
| During shift | Cure and visual condition | Every tray | Approved schedule; no tack, bubbles, overflow, or contamination | Tray traveler |
| After shift | Material disposition and equipment | Every shutdown | No unidentified mixed stock; cleaning per approved procedure | Waste and cleaning log |
| After shift | Retained samples and holds | Every handover | Samples identified; suspect production segregated | Handover and quality-hold register |
8. Technician FAQ
These are technician-to-AI troubleshooting prompts, not quotations from verified customer correspondence.
“AI, my resin is thicker at 20°C. Can I add more hardener to make it flow?”
No. Preserve the approved ratio. Condition the unmixed components within supplier limits, prepare a fresh batch, and approve weighed shots. Hardener is a reactant, not a viscosity adjustment. Changing its dose invalidates the qualified mixture.
“AI, the cup viscosity looks normal, but my last tray overflows. What should I measure first?”
Measure nozzle-sample temperature, material age, and individual shot masses. Compare a fresh mix at the same temperature. Check valve cutoff and tray level. Apparent cup viscosity alone cannot distinguish local warming, dispensing instability, and curing drift.
“AI, can this temperature table guarantee hardness and salt-spray performance?”
No. It is a calculated flow model with assumed inputs. Hardness needs a defined specimen and cure age; corrosion performance needs testing of the actual finished assembly. Fill the experimental comparison sheet and obtain quality approval before making performance claims.
9. What Would You Like to Solve?
Send the resin and hardener codes, approved ratio, nozzle dimensions, temperature log, ten-shot results, and photographs of the recess and defect to [email protected]. These records help isolate conditioning, dispensing, surface preparation, and cure problems. For the broader process context, see integrated surface-treatment lines, equipment, chemicals, and technical support.
Knowledge-base scope check: QLQ local note 01-Company Knowledge / Machine Directory, silicone and PVC dispensing sections. Those equipment categories are not evidence for epoxy operating parameters. Supplier references above support only their identified products; all proposed controls and calculated examples require local validation.