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Powder Coating

TROUBLESHOOTING GUIDE


FLUIDIZED BED
Trouble Causes Solutions
1 Dusting - Powder blowing out of hopper. 1 Air pressure too high 1 Adjust air regulator to lower pressure to fluid bed
2 Powder too fine 2 Reduce amount of reclaim added to vergin powder.
2 Rat holing-air blowing large jet holes through powder surface. 1 Powder level too low 1 Add powder until hopper is 2/3 full when fluidized.
2 Packed or moist powder. 2a Manually loosen powder and fluidize well with clean dry air.
2b Check compressed air booth air for high humidity.
3 Obstructed membrane. 3 Check bottom of bed for plastic, cardboard or other large obstructions.
4 Blocked or broken membrane. 4 Check membrane for blocked pores from dirty air supply, cracks or holes. 
HOSES AND PUMP VENTURI TUBES
Trouble Causes Solutions
1 Blocked from Fusion-Hard Buildup 1 Normal buildup 1 Clean or Replace parts
2 Air pressure too high 2 Turn down air settings on pumps and guns.
3 Moisture in air supply 3 Check air supply for clean, dry air
4 Composing of  powder feed hoses 4 Check hoses.
5 Worn venturi tubes and wear parts 5 Replace worn parts.
6 Powder too fine 6a Reduce amount of reclaim added to virgin powder.
6b Check particle size of virgin powder.
7 Powder type or formula. 7 Some resin types tend to have more impact fusion. Check with your powder supplier.

RECLAIM EQUIPMENT
Trouble Causes Solutions
1 Contamination in reclaim  powder 1 Reclaim in-line sieve torn, missing or inoperable. 1 Repair sieve or replace if necessary
2 Powder or dirt falling in spray booth from convey or hangers 2 Clean conveyor  regularly (or continuously) before it enters powder spray booth, strip hangers as needed.
3 Contamination of parts entering spray. 3 Check cleaning and pretreatment equipment and ensure proper part drainage before part enters spray booth.
4 Contamination from plant air circulated through spray booth. 4 Isolate spray booth area. Preferably, enclose in a room with filtered, humidity controlled air.  
Cured Finish Appearance Problems
Trouble Causes Solutions
1 Poor surface flow-too much orange peel. 1 Film thickness too low. 1 Increase film thickness by adjusting application equipment
2 Heat-up rate too slow. 2a Turn-up oven temperature
2b Modify oven baffling to increase heat rate
3 Powder resin type or formula. 3 Check with powder manufacturer.
2 Gloss too low for high type powder. 1 Incompatible powder contamination. 1 Clean application equipment before changing powders.
2 Micropinholing from gassing. 2a Check substrate for porosity.
2b Check substrate for moisture.
2c Check powder for moisture from reclaim or compressed air.
2d Check film thickness. (coating too thick)
3 Powder resin type or formula. 3 Check with powder manufacturer.
3 Gloss too high for a low gloss type powder. 1 Under curved. 1a Increase temperature of oven.
1b Increase dwell time in oven.
2 Powder formula. 2 Check with powder manufacturer.
4 Inconsistent film thickness. 1 Guns positioned wrong. 1 Check and reposition guns so spray patterns overlap slightly
2 Reciprocators not matched to line speed. 2a Adjust line speed.
2b Adjust reciprocator stroke.
3 Air flow in booth disturbing spray patterns. 3 Consult your equipment supplier.
4 Defective spray equipment. 4 Consult your equipment supplier.
5 Off color 1 Incorrect oven exhaust. 1 Check exhaust ven fan(s).
2 Bake time too long. 2 Adjust line speed.
3 Oven temperature too high. 3 Lower oven temperature.
4 Variation in film thickness. 4 See cured finish Appearance section, Inconsistent Film Thickness, causes 1 through 4. 
5 Powder formulation 5 Check with powder manufacturer.
6 Pull away or tearing coating film shrinks leaving bare substrate. 1 Uncharged powder 1 See Powder Application  Problems Section Poor Charging, causes 1 through 7.
2 Poor cleaning metal preparation or dry-off 2 Check pretreatment equipment dry-off oven and part drainage.
Powder Application Problems
Trouble Causes Solutions
1 poor charging-inadequate powder buildup or wrap-round 1 High voltage source not providing enough KV at charging electrode or grid. 1a Check if high voltage source is on. Systematically  check electrical continuity from voltage source to electrode (grid), including cable, resistors and fuses.
1b Replace missing or broken electrode (grid).
1c Clean electrode (grid) insulated by powder buildup or impact fusion.
2 Poor earth. 2 Check earth from conveyor rail (or rub bar when used) through hanger to part. All contact areas must be free of powder buildup, heavy grease and other insulating material.
3 Powder delivery (feed) is too high. 3 Turn down powder feed until all material passing through charging corona (field) is adequately charged.
4 Excessive moisture in powder both air. 4 Moisture in humid air will tend to dissipate the charge on the powder particles. Control the humidity in the powder spray area.
5 Powder too fine. 5 Reduce amount of reclaim added to virgin powder.
Check particle size of virgin powder.
6 Powder type or formula. 6 Some resin type charge better than others and some formulas are designed for low film application. Check with you powder supplier.
7 Powder delivery air too high. 7 Turn down air setting or move gun position further away from part.
2 Poor penetration powder will not coat Faraday cage area (holes, groves, channels, inside corners and recesses). 1 Powder delivery too low. 1a Turn up powder delivery air setting.
1b Use gun barrel extension.
2 Poor earth 2 Check earth. See powder application problems, poor charging section , cause 2.
3 Powder spray pattern too wide. 3 Selected smaller deflector or use suitable slotted barrel end cover. Consult your equipment supplier.
4 Voltage too high. 4 Turn voltage setting down so powder builds on part edges and leading surfaces do not repel powder from corners. 
5 Powder velocity too high 5 Turn air settings down so powder/air stream does not blow powder out of corners.
6 Poor gun placement. 6 Adjust gun position so powder cloud has a direct path to recess.
3 Back ionization Powder layers are repelled from part in spots. 1 Voltage too high. 1 Turn down voltage setting.
2 Gun positioned too close to part. 2 Charge gun placement further way from part.
3 Poor earth. 3 Check earth. see powder application problems, poor charging section, cause 2
4 Powder feed surging or spitting-interrupted powder feed. 1 Insufficient  air pressure or volume. 1 Check air supply piping to equipment is large enough. Enough air volume must be provided so that when other equipment such as reverse air cleaning in reclaim housing pulses. Air pressure to powder feed does not drop.
2 Hoses kinked, flattened or too long. 2 Check powder feed hoses. See powder supply problems, insufficient feed, cause 2.
3 Hose pump venture tubes or guns clogged with powder. 3a Clean hose, venturi tubes and guns.
3b Check air supply for moisture that causes powder compaction.
3c Check powder flow properties.
3d Check spray booth air humidity.
5 Poor spray pattern. Not a symmetrical powder cloud (not applicable using a special deflectors for desired effect). 1 Worn E/S Gun parts 1 Replace worn feed tubes, on surfaces, deflectors and covers.
2 Impact fusion build. 2 Check gun parts as needed.
3 Delivery (feed) too low. 3 Check air supply, increase air for powder feed.
4 Hoses, venturi tubes or gun blocked with powder. 4 Clean hoses, venturi tubes and guns.
Cured Finish Physical Problems
Trouble Causes Solutions
1 Poor impact resistance poor flexibility. 1 Undercured 1a Increase oven temperature.
1b Increase dwell time in oven.
2 Poor cleaning or pretreatment 2 Check pretreatment equipments and chemicals.
3 Film thickness too high 3 Reduce film thickness by adjusting application equipment
4 Change in substrate thickness or type. 4 Check substrate with supplier.
5 Powder resin type or formula 5 Check with powder manufacturer
2 Poor adhesion 1 Poor cleaning or pretreatment 1 Check pretreatment equipment and chemicals
2 Change in substrate 2 Check substrate with supplier.
3 Undercured 3a Increase oven temperature.
3b Increase dwell time in oven.
4 Powder resin type 4 Check with powder manufacturer
3 Poor corrosion resistance 1 Poor cleaning or  pretreatment 1 Check pretreatment equipment and chemicals
2 Undercured 2a Increase oven temperature.
2b Increase dwell time in oven.
4 Poor chemical resistance 1 Undercured 1a Increase oven temperature.
1b Increase dwell time in oven.
2 Powder resin type or formula 2 Check with powder manufacturer
5 Poor pencil hardness / poor abrasion resistance 1 Undercured 1a Increase oven temperature.
1b Increase dwell time in oven.
2 Powder resin type or formula 2 Check with powder manufacturer


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