RESIN DRIPPING / SENIOR TECHNICIAN WORKING GUIDE
Post-Cure Machining: Sanding & Polishing Resin Edges Data
Control edge geometry, cure maturity and frictional heat together. On plated zinc-alloy bag hardware, a shiny resin dome is not a successful repair if sanding has exposed the metal finish or opened the resin-to-metal interface.
1. Define the material and the evidence boundary
This guide concerns hard, cured epoxy decorative infills and domes. It does not apply automatically to flexible polyurethane, silicone or PVC dispensing systems. Identify the resin family, hardener, plating stack and subsequent coating before selecting abrasives. Similar-looking dispensers do not establish equivalent chemistry.
Data status: No QLQ post-cure edge-machining batch report was located in the company knowledge base. The numerical specimen comparison below is published manufacturer reference data, not a QLQ production trial. The pilot matrix is an unexecuted test plan. Suggested operating bands are engineering trial limits requiring approval for the actual resin and drawing.
The local reference, 01-Company Knowledge / Machine Directory (English translation of the source path in the QLQ Obsidian Vault), identifies silicone and PVC dispensing equipment; it does not establish an epoxy sanding recipe. No equipment capability, customer outcome or resin formulation is inferred from those listings.
2. Establish a cure gate before touching an edge
Separate handling hardness from machining readiness. A surface can resist a finger mark while the interior still deforms under a polishing pad. Check a same-batch witness casting with the same cure history. If abrasive material smears, pills or immediately loads the paper, stop and investigate cure, contamination and heat rather than increasing pressure.
For orientation only, the manufacturer's 105/207 cure guidance gives a solid-state interval of 10–15 hours at 22°C and a 100 g cup pot life of 20–26 minutes. Neither number certifies a decorative infill as ready for polishing. Follow its supplier's complete cure and approved post-cure schedule; do not introduce an arbitrary oven cycle into assembled plated hardware.
Use a properly prepared witness specimen for durometer readings. A thin dome over metal can produce a substrate-influenced reading and should not be compared directly with a bulk resin specimen. Record specimen dimensions, support, temperature and measurement procedure. For a production cure gate, correlate witness hardness with actual edge-machining behavior and, where necessary, laboratory cure analysis.
3. Working Data & Formula Notes
A complete, commercially defined clear-epoxy mixture is more defensible than an invented universal doming formula. The example below contains two supplied components; their proprietary internal compositions are not disclosed. It is a reference blend, not a recommendation that this marine epoxy is qualified for every plated emblem.
| Component | Range | Typical | Function | Replenishment |
|---|---|---|---|---|
| WEST SYSTEM 105 resin | 100 parts; fixed basis | 35.00 g | Epoxy component for the cured network | Weigh into each fresh batch; never top up reacting material |
| Matching 207 hardener | 28.57 parts per 100 resin; fixed target, not an adjustable range | 10.00 g | Matched curing component | Add once at the prescribed ratio; discard suspect batches rather than correcting them late |
| Added solvent, pigment, filler or accelerator | 0 parts in this reference blend | 0 g | Excluded to preserve comparison with neat-resin data | None; any modified recipe requires separate qualification |
The manufacturer's mixing instructions specify 3.5:1 by mass or 3:1 by volume for this combination. Do not substitute the volume ratio on a balance. Thoroughly mix the sides and bottom, and keep trial batches small. Changing hardener proportion to accelerate cure invalidates the mixture.
For the mass recipe, hardener = resin / 3.5; total mix = resin × 1.2857. Therefore 35.00 g resin needs 10.00 g hardener, yielding 45.00 g mixed material. If pigment is later approved, define whether its percentage refers to resin or total mixture, and preserve the required resin-to-hardener relationship.
4. Specimen data and a controlled batch comparison
| Specimen system | Test condition | Hardness, Shore D | Resin thickness | Salt-spray result | Interpretation |
|---|---|---|---|---|---|
| 105/205 neat epoxy | Manufacturer laboratory specimens; room-temperature cure for two weeks unless noted | 83 | Not stated on comparison page | Not reported | Reference hardness only |
| 105/206 neat epoxy | Same published comparison conditions | 83 | Not stated | Not reported | Same hardness does not prove identical machining behavior |
| 105/207 neat epoxy | Same published comparison conditions | 84.4 | Not stated | Not reported | Relevant clear-resin reference, not a production acceptance limit |
Source: WEST SYSTEM physical-property comparison. Values are typical, not specifications. No sample count or dispersion is supplied, so the 1.4-point difference cannot establish statistical superiority. None of these data proves corrosion protection on zinc-alloy hardware.
| Batch / specimens | Test condition | Thickness before / after | Witness hardness | Edge / corrosion result |
|---|---|---|---|---|
| A: 10 matched parts, untouched controls | Same casting, plating and resin lots; supplier-approved full cure | Measure at registered positions | Measure on suitable same-batch witnesses | Record baseline photographs; exposure result pending |
| B: 10 matched parts, supported hand sanding | Same cure; selected starting grit; progressive finishing to P3000 | Measure at identical positions | Same method as A | Record chips, interface lift and final gloss; result pending |
| C: 10 matched parts, controlled machine polish | Same sanding as B; approved pad, speed and recorded temperature | Measure at identical positions | Same method as A | Compare edge damage and customer-specified corrosion exposure; result pending |
Randomize allocation and retain matched specimens for destructive examination. Measure resin thickness by validated sectioning or an optical height method; ordinary metal-coating gauges may not isolate a thick resin dome. For corrosion testing, record the contractual method, duration, edge masking, scribing and failure definition before exposure. Report interface lift separately from metal corrosion and never translate exposure hours directly into service life.
5. Trend ranges: trial bands versus stop limits
These are proposed internal controls for an initial pilot, not published universal thresholds. Establish a baseline before using them for release. The actual supplier specification, component drawing and customer agreement override every provisional value.
| Parameter | Provisional normal band | Danger / hold threshold | Action and rationale |
|---|---|---|---|
| 105/207 resin-to-hardener mass ratio | 3.50:1 target; proposed metering band ±1% | Outside approved metering band | Hold batch; this band controls weighing, not chemical tolerance |
| Witness conditioning temperature | 22 ±2°C for comparative checks | Outside this band at measurement | Recondition; temperature drift confounds hardness comparison |
| Hardness difference from qualified witness baseline | Within ±2 Shore D points | More than 3 points below baseline, or any smear | Hold; repeat valid measurement and review cure |
| Resin surface temperature during polishing | 20–30°C pilot target | At or above 35°C, or any softening | Stop and cool; verify contact measurement on glossy resin |
| Local thickness loss | 0–5% of initial thickness, with drawing minimum maintained | More than 10%, or below drawing minimum at any loss | Hold; inspect profile and exposed metal |
| Edge-chip size under calibrated magnification | No visible chips; proposed instrument screen ≤0.05 mm | Any chip ≥0.10 mm, interface opening or visible defect | Segregate and check cure, fixture support and grit |
Intermediate values between a normal band and hold limit are alerts: increase inspection and obtain engineering disposition, not automatic acceptance. Plot these variables against part order and abrasive age. Average thickness can conceal one destroyed corner, so track minimum local thickness as well as the batch mean.
6. Build the sanding route around the defect
Map the unwanted resin ridge under magnification. Support the metal without bending it, shield adjacent plating with a qualified protection method, and approach the resin from its supported side. Do not use sanding to repair an already detached interface.
Start with the finest abrasive that removes the identified ridge efficiently. A provisional small-edge sequence might be P600, P800, P1000, P1500, P2000 and P3000; deeper defects may require a different qualified starting point. The supplier's epoxy polishing guide supports progressive wet sanding, careful low-pressure edge work and finishing to fine grits. Its coarse tabletop starting grit should not be copied directly onto a thin hardware dome.
Change sanding direction between stages and inspect the dry surface before advancing. Water can temporarily hide scratches. Use dedicated clean pads, keep coarse debris away from finishing stations, and capture wet slurry without carrying it back into plating or resin dispensing.
Polish only after the scratch pattern is uniform. Select a compound compatible with the resin and any later coating; EPODEX's polish instructions describe a silicone- and solvent-free option and preparation to P3000. Compound is not a substitute for removing deep scratches. No universal spindle speed is specified here: pad diameter, machine motion and contact area change heat generation.
7. Two diagnostic scenarios for senior technicians
Scenario A—white border after sanding a plated puller: These are diagnostic exercises, not documented customer cases. Separate resin scratches from lifted resin and damaged plating using a cleaned, dry edge and magnified photographs. Compare an untouched same-batch part. If the border is below the resin, stop abrasion and examine adhesion, pretreatment and cure shrinkage. If confined to the resin surface, return to the last grit that can remove the scratch without violating minimum thickness.
Scenario B—gloss returns, then the edge rounds and smears: Compare identical parts with hand finishing and machine polishing. Record temperature immediately after contact, plus pad identity and dwell pattern. If only machine-finished parts deform, investigate heat and pressure. If both routes smear, investigate cure and mixing. Obtain evidence before changing the upstream chemistry; neither observation alone proves a faulty hardener.
8. Engineer Notes
- Photograph the same marked corner before sanding, after every grit and after polishing; include a calibrated scale.
- Verify balance performance using suitable check weights before mixing, and record resin and hardener masses separately.
- Where the resin system can blush, wash and dry before sanding. WEST SYSTEM surface-preparation guidance identifies water washing rather than solvent wiping for removing amine blush.
- Place a physical support beneath thin pullers; reject a fixture that flexes the part under normal hand pressure.
- Replace loaded abrasive immediately, retain it with the batch record, and distinguish soft resin from contaminated paper.
- Check a contact-temperature reference against the infrared instrument; shiny small surfaces can produce misleading readings.
- Segregate grinding dust and slurry from dispensing and plating. Follow the resin SDS and site exposure assessment; manufacturer safety guidance warns against contact with epoxy and partially cured sanding dust.
9. Shift Checks
| Shift stage | Check item | Frequency | Acceptance criterion | Record |
|---|---|---|---|---|
| Before shift | Material identity, cure log and witness | Every lot / startup | Correct resin family; approved cure completed; witness passes qualified gate | Lots, cure history, operator, hardness |
| Before shift | Fixture, abrasive sequence and extraction | Startup and changeover | Secure support, clean grit separation, functioning approved controls | Fixture ID, grit lots, control check |
| During shift | Temperature and dry scratch inspection | First five parts; then every 30 minutes | Within approved band; no smear or unresolved coarse scratches | Time, part, temperature, grit |
| During shift | Minimum thickness and edge condition | First part after each adjustment; five parts hourly | Drawing minimum maintained; no exposed plating or interface lift | Registered positions, readings, photographs |
| After shift | Final release and retained controls | Every lot | Approved appearance and geometry; required tests completed or lot held | Disposition, inspection, retained sample IDs |
| After shift | Cleaning and trend review | Every shift | No cross-contamination; alarms reviewed; waste handled under site procedure | Cleaning log, alarms, corrective actions |
10. FAQ: technician-to-AI troubleshooting prompts
These are suggested prompts, not quotations from customer correspondence.
“AI, my resin feels hard but clogs P800 immediately. Should I cure it hotter or use coarser paper?”
Do neither automatically. Check the same-batch witness, mixing record and actual cure temperature. Clean contamination using the supplier-approved method, then trial fresh paper with lighter contact. A harder oven cycle can damage plating, pigments or the interface; authorize it only through the resin supplier and a controlled trial.
“AI, why is the edge cloudy after P3000 even though the middle looks clear?”
Inspect the dry edge under magnification. Look for remaining coarse scratches, pad debris, microchips and subsurface separation. Supported low-pressure finishing may correct surface scratches. A lifted interface or exposed metal is not a polishing defect and must be held for engineering disposition.
“AI, can I release a polished batch if its Shore D matches the untouched control?”
No. Hardness checks cure-related behavior but does not prove retained thickness, edge integrity, plating condition or corrosion performance. Use the complete approved release plan. If required corrosion exposure is pending, identify the lot as held rather than replacing that test with a hardness reading.
11. What Would You Like to Solve?
Send the resin supplier's technical sheet, plating stack, drawing minimum, cure history and paired edge photographs to [email protected]. Identify whether the problem is scratching, chipping, smearing or interface whitening so the next trial changes one mechanism at a time. For wider process coordination, see surface-treatment lines, equipment, chemicals and support. Record measured results before turning any pilot band into a production specification.