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Powder Application Problems

 

3. Electrostatic Coating Operation

What is the problem you are facing?

Poor charging inadequate powder build or wrap on part.

Possible Causes Possible Solutions
1. High-voltage source not providing enough KV at charging electrode or grid. 1a. Check 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) insulated by powder build or impact fusion.
1c. Clean electrode (grid) insulated by powder build or impact fusion.
2. Poor ground. 2. Check ground from conveyor rail (or rub bar when used) through hanger to part. All contact areas must be free from heavy grease and other insulating material.
3. Powder delivery (feed) is too high. 3. Turn down powder feed until all material passing through charging carona ( field) is adequately charged.
4. Excessive moisture in powder booth air. 4. Moisture in humid air will tend to dissipate humidity in the powder spray area.
5. Powder too fine. 5a. Too much reclaim added to virgin powder.
5b. Virgin powder pulverized too fine by manufacturer.
6. Powder type or formula. 6. Some resin type charge better than others and some formulas are designed for thin firm applications. Check with your powder supplier.
7. Powder delivery air too high. Powder blowing by part. 7. Turn down air setting or move gun position further away from part.

 

Poor penetration powder will not coat Faraday Cage areas ( holes, grooves, channels inside corners and recesses).

Possible Causes Possible Solutions
1. Powder delivery too high. 1a. Turn up powder delivery air setting.
1b. Use barrel extension.
2. Poor ground. 2. Check ground.
See Electrostatic coating operation 2. Poor ground. - solution.
3. Powder spray pattern too wide. 3. Select smaller deflector or use suitable slotted barrel and cover. ( consult your equipmnet supplier).
4. Voltage too high. 4. Turn voltage setting down so powder builds on part edges and leading surfaces do not repel powder from corner.
5. Powder delivery velocity too high. 5. Turn air setting down so powder/ air stream does not blow powder out of corners.
6. Poor gun placement. 6. Adjust gun position so powder cloud has direct path to recess area.
7. Powder too fine. 7a. Too much reclaim added to virgin powder.
7b. Virgin powder pulverised too fine by manufacturer.

 

Back charging powder layers are repelled from part in spots.

Possible Causes Possible Solutions
1. Voltage too high. 1. Turn down voltage setting.
2. Gun positioned too close to part. 2. Change gun placement away from part.
3. Poor ground. 3. Check ground
See Electrostatic coating operation 2. Poor ground - solution.
4. Powder too fine. 4a. Too much reclaim added to virgin powder.
4b. Virgin powder pulverized too fine by manufacturer.

 

Powder picks up charge through powder hoses. Reverse charging usually through reclaim system.

Possible Causes Possible Solutions
1. Powder booth air too dry. 1. Adjust powder spray area humidity.
2. Poor delivery and/or reclaim equipment ground. 2. Provide ground for all equipment.

 

Powder feed spurting or slugging interrupted powder feed.

Possible Causes Possible Solutions
1. Insufficient air pressure volume. 1. Check air supply. 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.
3. Hoses, pump venturies or guns clogged with powder. 3a. Clean hoses, venturies and guns.
3b. Check air supply for moisture that causes powder compaction.
3c. Check spray booth air humidity.
3d. Check powder supply for contamination. Check reclaim sieve.

 

Poor spray pattern - not a symmetrical powder cloud ( not applicable when using special deflectors for desired effect).

Possible Causes Possible Solutions
1. Worn E/S gun parts. 1. Replace worn feed tubes, orifices deflectors and covers.
2. Impact fusion build. 2. Clean gun parts as needed.
3. Delivery (feed) air too low. 3. Check air supply. Increase air for powder feed.
4. Hoses, venturies or gun blocked with powder. 4.Clean hoses, venturies and guns.

 

 

6. Output of Powder Insufficient to Coat Parts

What is the problem you are facing?

Poor fluidizing properties in the powder hopper.

Possible Causes Possible Solutions
1. Pressure of fluidzing air too low. 1. Adjust (increase) pressure of fluidizing air.
2. Fluidizing membrane is blocked. 2. Clean or replace the fluidizing membrane : see instructions of equipment supplier.
3. Humidity of compressed air too high. 3. Install an air dryer with a corresponding oil-micro filter or another suitable drying system.
4. Humidity of the powder too high. 4. Check storage facilities. Powder shall be stocked at room temperature (30ºC) in closed packing (Maximum humidity 60%).
5. Free-flowing properties of the powder are bad. 5. Contact your powder supplier.

 

Blockage in venturies and hoses.

Possible Causes Possible Solutions
1. Fusing of the powder in the venturi. 1. Clean or replace the hoses ( see instructions of the equipment supplier) if necessary reduce pressure of powder of transport air.
2. Fusing of the powder in the hoses. 2. Clean the hose by bending and breaking up the fused powder if necessary replace it.
3. Fusing of the powder in the hoses. 3. Install an air dryer with a corresponding oil micro filter or an air dryer with a corresponding oil micro filter or another.
4. Bad free flowing properties of powder. 4. Contact your powder supplier.

 

Blockage in the gun.

Possible Causes Possible Solutions
1. Fusing in the gun or gun outlet. 1. Clean the gun according to the instructions of your equipment supplier. When blocking occurs frequently check humidity of compressed air and the free-flowing properties of the powder.
2. Blockage caused by contamination of the powder with dust of other coarse materials. 2. Clean the gun according to the instructions of equipment supplier and determine the reason of this contamination.(check powder pumps for possible impact fusion. Impact fusion particles which break off in the pump could be transported to the spray gun and result in blockage).

 

 

7. Poor of Insufficient Coverage

What is the problem you are facing?

Insufficient wrap-around.

Possible Causes Possible Solutions
1. Poor electrostatic charging of the powder. 1a. Adjust level of electrostatic kilovoltage (Increase). If not possible, check equipment and guns according to instructions of the equipment supplier.
1b. Check for broken electrodes on the spray gun. If found, replace electrodes.
1c. Check for possible frictional transport through powder hose. If evident, consult powder supplier for hose material recommendation.
2. Insufficient ground contact. 2. Check the ground contacts using a measuring device. Correct and insure sufficient earth to ground control.
3. Output of powder too low. 3. Turn up powder delivery air setting.
4. Using an unsuitable powder supplier. 4. Contact your powder type.

 

Poor penetration into corners, flanges, slots, etc.

Possible Causes Possible Solutions
1. Output of powder too low. 1. Turn up powder delivery air setting.
2. Insufficient ground contact. 2. Check the ground contact and if necessary use a suitable measuring instrument.
3. Powder cloud too wide. 3. Narrow powder cloud. If necessary install a more suitable deflector or adjust air for cone adjustment.

 

Poor adherence of powder to part, powder falls from part easily.

Possible Causes Possible Solutions
1. Poor electrostatic charging of the powder. 1a. Adjust level of electrostatic kilo-voltage (increase voltage if not possible, check equipment and guns according to instructions of equipment supplier).
1b. See "Insufficient Wrap around" problem 1b.
2. Powder output too high or the pressure for the transport air too high, which blows the powder from the object. 2. Reduce powder output and/or reduce pressure of the transport air.
3. Unsuitable particle size distribution of the powder or unsuitable powder type for the objects. 3. Contact your powder supplier.