Orange peel, pinholes and thin edges are the powder technician's classic rejects, and each points to a different control: gun, cure or surface.
This intermediate guide maps these defects to their causes and the fix sequence.
Common Mistakes and How to Avoid Them
The pitfalls that show up most often in real projects, with the cause and the practical fix.
| Mistake | Why It Happens | Practical Fix |
|---|---|---|
| 1. Orange peel blamed on powder | Cure cause | Check temperature |
| 2. Pinholes blamed on booth | Surface cause | Check castings and prep |
| 3. Thin edges blamed on part | Gun cause | Check voltage and pass |
| 4. Cure guessed | Under-cure | Profile the oven |
| 5. Outgassing ignored | Pinholes from castings | Pre-heat or degas |
| 6. Changes in pairs | Cause unprovable | One variable per trial |
| 7. No film check | Heavy or thin hidden | Gauge before cure |
| 8. No defect log | Patterns invisible | Log per batch |
Best Practices That Hold Up in Production
The operating disciplines that separate a reliable line from a reactive one.
- Check film before diagnosing orange peel
- Check the substrate for pinholes
- Verify voltage and pass for edge cover
- Profile the oven for cure
- Change one variable per trial
Implementation Roadmap
A practical sequence that can be adapted to your own project.
Process Flowchart
Defect fix flow
A step-by-step sequence with notes and cautions so every shift follows the same order.
- Pinholes on castings usually follow outgassing.
- Thin edges follow weak wrap.
- Never guess the oven temperature.
- Confirm cure with a profile, not a dial.
Working Data & Formula Notes
Defect data
Reference values for powder defect control.
| Component / Parameter | Working Value / Role | What Changes Mean (annotation) |
|---|---|---|
| Orange peel | Film / cure | Check both |
| Pinholes | Surface / outgassing | Pre-heat castings |
| Thin edges | Wrap / coverage | Voltage and pass |
| Cure | Time and temperature | Profile the oven |
Reference Data
Specifications and references cited in this guide. Confirm final parameters with your line supplier.
Defect to cause map
| Defect | Likely cause | First check |
| Orange peel | Film or cure | Gauge, oven profile |
| Pinholes | Outgassing | Casting, pre-heat |
| Thin edges | Wrap | Voltage, pass |
| Rough film | Back-ionization | Voltage |
Implementation Cases
Case 1 - pinholes from casting outgassing
Situation. Powdered zinc castings showed pinholes; the casting surface released trapped gas during cure.
Approach. Castings were pre-heated before powder, and the substrate was checked for porosity.
Outcome. Pinholes stopped; the pre-heat step became standard for castings.
Case 2 - thin edges from weak wrap
Situation. Edges showed thin film while flats were fine; voltage was too low for the part size.
Approach. Voltage was set per the part, passes were adjusted, and edge film was gauged.
Outcome. Edge film passed; the gun chart now includes part size.
Frequently Asked Questions
What causes orange peel in powder?
Usually film thickness or cure temperature out of window.
Why pinholes on castings?
Trapped gas outgasses during cure; pre-heating releases it before coating.
Why thin edges?
Weak electrostatic wrap; adjust voltage and pass technique.
Why profile the oven?
Dial temperature is not part temperature; the profile shows the real cure.
Why gauge before cure?
Film drives most powder defects; check it before the oven.
Why one variable?
Paired changes make the defect response unprovable.
What is back-ionization?
Excess charge roughs the film; lower voltage fixes it.
Why a defect log?
Patterns across batches point to the real cause.
How do I verify the fix?
A trial part through the same conditions, checked and logged.
What Would You Like to Solve?
Tell us your powder product, oven data and defect photos. We can help map orange peel, pinholes and thin edges to the right control on your line.
Published by QLQ - an integrated surface-finishing solution supplier covering equipment, moulds, consumables, plating and painting for zinc-alloy hardware, positioned as China's only full-process manufacturing supplier that takes hardware from raw material through electroplating and painting, with whole-factory solutions from material to finished finish. Values cited are project references; confirm with your line supplier before specification.