Possible Causes | Solution and suggestions | |
1 | Feed air pressure too low |
a.Check the pressure of compressed air b.Clean the air filter equipment |
2 | Clogging of fluidizing plate |
Check whether the fluidizing plate is blocked by ultrafine powder or grease dirt and impurities
of compressed air |
3 |
Overfill of powder in the fluidization barrels |
Reduce the filling amount of powder in fluidized bed, generally two-thirds of the volume |
4 |
Blockage of gas path of atomization or fluidization |
Check whether the gas path is smooth and regulating valve adjusts well |
5 |
Blockage of powder
conveying pipe because of scaling |
a.Keep periodic cleaning and replacement of powder conveying pipe after long-time use b.Reduce the length of powder conveying pipe to the greatest extent c.The airspeed blow of air is too high, thus heat is generated. So lower the airspeed blow or add more guns
|
6 |
Wear and poor absorption of Vuncheri powder pump |
Check and exchange Vuncheri powder pump regularl |
7 | Powder moist | Get the plastic bags sealed in dry and ventilated conditions |
8 | Powder clot |
a.select powder with #80 mesh before spraying b.store in dry and cool places at temperature below 35℃ |
Possible Causes | Solution and suggestions | |
1 | Low-voltage of electrostatic |
a.Check and adjust voltage b.Clean spear electrode and test electrode contact |
2 |
High-voltage of electrostatic gun leading to insufficient spray of recesses |
Reduce voltage and spray recesses first |
3 |
Powder does not adhere to re-sprayed work pieces |
Reduce voltage and powder flow, or use specialized gun |
4 |
Insufficient grounding |
Test all aspects of grounding, including gun, high-voltage generator, spray booth and hooks. Grounding wire should be buried at least 2 meters under humid layer |
5 |
Too thick dust of hanging fixtures leads to the insulation between hanging chain and hanging fixtures
|
Clean or replace hanging fixtures regularly
|
6 |
Dry air leads to Faraday effect |
Increase humidity of spray booth and workshop |
7 | Wrong gun-to-part distance or position |
a.adjust gun distance to work piece, approximately 15-30cm b.adjust gun direction to concave parts |
8 | Too much powder output |
Reduce powder output appropriately |
9 |
Too strong air draft of the spraying room | Reduce strength of air draft |
10 | High powder gravity, wrong particle size distribution | Contact powder manufacturer to improve powder gravity and particle size distribution |
Possible Causes | Solution and suggestions | |
1 |
Incomplete coating curing; not completely coating cross linking reaction |
Test temperature with thermometer to inspect whether the curing parameters reach the requirements |
2 |
Over-curing leads to the decomposition of cross linking structure |
Test temperature with thermometer, then lower baking temperature or shorten baking time |
3 |
Poor surface treatment of work piece, e.g. insufficient of degreasing, poor phosphating film quality, phosphating too thick, insufficient rinse |
Check processing equipment and conditioning fluid before adjustment to control the quality of phosphating film |
4 |
Coating thickness too high |
Adjust spray equipment to lower film thickness. It should be between 70µm and 90µm |
5 |
Changes of substrate surface or substrate type
|
Contact substrate manufacturer
|
6 |
Too long storage time leads to the reduction of reactivity |
If powder exceeds its valid storage time, test its properties before use |
7 | Quality of the powder itself | Contact manufacturer to improve adhesion property |
Possible Causes | Solution and suggestions | |
1 |
Incomplete coating curing; not completely coating cross linking reaction |
Test oven temperature with thermometers to see curing curve and parameters; increase temperature or extend curing time |
2 |
Over-curing leads to the decomposition of cross linking structure. Temperature above 220℃ will easily cause bad surface hardness |
Test oven temperature with thermometers; lower curing temperature appropriately or shorten curing time |
3 |
Too low heat up speed; low molecular substances migrate to coating surface, which influence the hardness |
Optimize heat up speed. The usual time from room temperature to the curing temperature is 4 to 5 minutes |
4 |
Poor hardness and abrasion resistance of powder itself |
Contact manufacturer to adjust formula |
Possible Causes | Solution and suggestions | |
1 | Film thickness too high or too low. Film thickness, higher than 120u or lower than 60u, will affect coating flow | Adjust the spraying equipment to control film thickness, generally between 70 and 90μm |
2 | Heat up speed of oven too slow | Optimize heat up speed. The usual time from room temperature to the curing temperature is 4 to 5 minutes |
3 | Intense back ionization effect | a.lower static voltage of spray gun b.increase distance from work piece to gun c.check whether the grounding system runs well |
4 | Roughness of phosphating film | Smooth phosphating film before treatment |
5 | Poor flow of powder coating itself | Contact manufacturer to adjust formula |
Possible Causes | Solution and suggestions | |
1 | Incomplete coating curing | Test oven temperature with thermometers to see curing curve and parameters;increase temperature or extend curing time |
2 | Low heat up temperature of work pieces | Low heat up temperature of work pieces |
3 | Contamination of oven tunnel | Stop using for some time to let off evaporation |
4 | High gloss of powder itself | Contact manufacturer to adjust formula |
Possible Causes | Solution and suggestions | |
1 | Incompatibility with other powder coating | Clean spraying equipment before replacemet of different manufacturers or different types of powder |
2 | Over curing of powder coating | Observe curing parameters; reduce curing temperature; shorten curing time |
3 | Contamination in the oven path, e.g. organic evaporated substances | Stop working for a certain period to eliminate evaporated substances |
4 | exclusive use or over use of reclaim powder | Evenly add reclaim powder into new powder |
5 | Low gloss of the powder itself | Contact manufacturer to improve glossiness |
Possible Causes | Solution and suggestions | |
1 | Coating film too thin | Increase film thickness appropriately, usually a bove 60μm |
2 | Contamination from spraying environment | a.keep spraying house clean; clean surroundings with vacuum b.keep workshop clean ; avoid dust and fiber c.avoid scraps falling into the powder when pouring powder d.Avoid clean the spray tank with paper, washcloth or brooms that will easily lose particle |
3 | Contamination from oven path | Control the blast volume in the oven and clean oven path regularly; use high temperature resistant and anti-rust material for oven path, preferably stainless steel |
4 | Rust or dust from the chain | Clean chains regularly; install anti-dust equipment above hanging fixture |
5 | Deposits on re-cured work pieces | Rough polish then fine polish, and finally clean work pieces with compressed air |
6 | Sands in reclaim powder | Select with #180 mesh and add into new powder |
7 | Insufficient pretreatment; phosphated residue on substrate surfac | Check substrate surface; remove surface defect; assure pretreatment |
8 | Powder itself contains impurity | Contact suppliers |
Possible Causes | Solution and suggestions | |
1 | Mixed with small amount of low surface tension powder or material, e.g. powder containing different leveling agents or silicone oil additives | Test compatibility of powder from different manufacturers before use Clean the whole spraying system if there is incompatible powder Stop using contaminated powder and remove it out of spray houses |
2 | Oil in compressed air | Check the quality of compressed air and air purification core regularly |
3 | Surrounding air contaminated, e.g. silicones,grease and dust, low surface tension evaporated material | Surrounding air contaminated, e.g. silicones, grease and dust, low surface |
4 | Oil and grease residues on work piece | Optimize pretreatment of degreasing |
5 | Poor anti-contamination and craters of powder itself | Contact suppliers to improve powder quality |
Possible Causes | Solution and suggestions | |
1 | Too high or too low curing temperature;different chaining speed | Use constant curing parameters for the same work piece; check oven |
2 | Large temperature differences of different levels of the over | Check oven temperature with oven thermometer regularly |
3 | Uneven distribution of reclaim powder in new powder (esp. metallic powder ) | Evenly add reclaim powder into new powder |
4 | The influence of voltage and airflow leads to different ascending rate of metallic pigment | Adjust spray parameter, e.g. voltage, airflow |
5 | Film thickness varies greatly | Assure constant film thickness |
6 | Different types of work piece in the same drying path, especially obvious when dark color work piece and light color work piece are mixed | Avoid dark color work piece and light color work piece curing at the same time |
7 | Poor temperature resistance and covering of the powder itself | Contact manufacturer |
Possible Causes | Solution and suggestions | |
1 | Formula of theoretical spraying area | Spraying area =(1000/ weight of powder)/thickness of coating film |
2 | Coating film too thick | Control film thickness to increase spraying area (as can be seen from the above formula), usually 70-90μm |
3 | Uneven coating film because of too many recesses of work pieces | Reduce the output of powder Spray recesses first |
4 | Heavy task of re-spraying because of low yield of first spraying | Increase first spraying yield |
5 | Too much waste powder (contaminated powder, unavailable reclaim powder) | Adjust equipment; keep surroundings clean; reduce the amount of waste powder |
6 | Too much fine powder in spraying system | a.Reduce strength of air draft or replace with high efficient ventilation system b.Contact suppliers to reduce fine powder content |
7 | A large proportion of powder or too much fine powder | Contact manufacturers to control particle size of powder |