At MS we know there are a lot of issues that want to know what the cause is. Here we have added a selection of typical issues and corrections that may help
Grounding
Cause | Correction |
---|---|
Poor conductive hose material, causing friction and charging of hoses (sparking) | Use manufacturer’s original powder hoses |
At the injector due to insufficient grounding | Ground injector |
Between object and hose due to bad grounding | Strip buckets and hoes of paint |
At the handgun due to too little grounding | Do not wear rubber soles or gloves |
Decrease in System efficiency
Cause | Correction |
---|---|
Too much powder accumulation in system components is often associated with leaks in the recovery system (absolute-filter, cyclone, hose connections, etc.) | Check for leaks |
In cyclone systems, peristalticfeed pumps or powder feed pumps can wear or clog | Check powder recirculation system for function and leak-tightness |
Clogged sieve mesh can substantially minimize separation | Clean powder sieve regularly |
Coating issues
Cause | Correction |
---|---|
Particle size distribution too fine | Consult with powder suppliers |
Moisture in the powder due to improper storage | Powder must stored dry at processing temperature |
Sintering at the baffle plate and the nozzle due to excessive conveying air pressure Damage to nozzles by too high an air pressure of the feed air |
Reduce conveying air or Check for wear on the injector - collecting nozzle |
Poor fluidization in the powder tank due to moist compressed air or blocked fluid plate, fluid tubes | Check compressed air for contamination, replace fluid plate or fluid pipes |
Picture frame effect
Cause | Correction |
---|---|
When using structure powder in Corona guns, the so-called picture frame effect may occur | Effectively countered by the new MS controller with adjustable and variable amperage control. |
Conductivity
Cause | Correction |
---|---|
Poor conductive hose material, causing friction and charging of the hoses (sparking) | Use manufacturer’s original powder hoses |
Insufficient grounding at injector |
Ground injector |
Between object and hoe due to bad grounding | Strip buckets and hoes of paint |
At the handgun due to too little ground | Do not wear rubber soles or gloves |
Fluidization
Cause | Correction |
---|---|
Powder fluidizability has a major impact on coating quality | For difficult powder, additional vibration of the powder tank is recommended. Retrofitting with a vibration table is simple. |
If lumps occur in the the fluidized powder, the powder was stored for too long or exposed to temperatures above 35° |
Use new powder and check the storage of the powder or Sift powder |
Poor fluidization of the powder can result from a fluid air pressure setting that is too low | Check the fluid air pressure settings |
Excessive fluidization can also significantly reduce powder output | Reduce air supply pressure |
Powder clumping
Cause | Correction |
---|---|
Workpieces insufficiently grounded | Clean buckets |
Powder with insufficient resistance | Discuss with powder suppliers |
Excessive field strength | Change voltage and distance |
Powder is blown out of the corners and recesses due to excessive air pressure | Reduce air pressure, use proper nozzle |
Too little penetration in the corners and niches due to excessive voltage or the use of an incorrect nozzle |
Reduce voltage and use appropriate nozzles. or See also nozzles |
Poor pre-treatment | Discuss with supplier |
Poor oven setting (too high / too low temperature) | Set oven temperature according to paint supplier |
Inadequate powder quality | Switch powder, change admixtures |
Dirty base, oils etc. | Check pretreatment |
Brightness / gloss
Cause | Correction |
---|---|
If powder emerges with dull / matt surface finish from the fcuring oven, specifications for powder curing have not been observed. | The different curing temperatures of various powders must be observed. |
Powder escape from booth enclosure
Cause | Correction |
---|---|
If powder escapes from a properly configured booth, and the pressure monitor of the exhaust system displays normal values, the fault can usually be found in the external vicinity of the booth. | The most common cause is drafts in the system building, through open doors or windows. Watch for cross drafts from auxilliary equipment such as air conditioners or general ventillation systesm in vacinity of the booth. |
Fat Edges
Cause | Correction |
---|---|
Excessive powder cloud, distance between gun and workpiece too far. | Minimize distance, use correct nozzles, or increase dosing air. |
Excessive distances between the objects. | Use automatic gap control, part recognition |
Nozzle selection
In order to obtain an optimum coating result, the choice of the nozzle must be adapted to specific coating needs. One size and type may not be applicable to all jobs. |
Round nozzles
The baffle plate produces a homogeneous powder cloud, which slowly approaches the grounded workpiece and therefore acts with good throwing power. The cloud can only be controlled under certain conditions and the penetration potential is small. It is used for flat parts, pipes and high surface services. |
Flat nozzles
The flat nozzle generates an elliptical cross-section and can be be well-aligned with the object. It is used for more complex parts (profiles) with wells. |
Pinholing
Cause | Correction |
---|---|
Often the use of silicone in the coating area is the reason for a dirty coating |
Since all powder has an "allergic" reaction to silicone, it must never be used in the coating area |
Level probe
Cause | Correction |
---|---|
Sensor probe not adjusted properly | Adjust immersion depth of probe to meet needs. |
Orange peel effect
Cause | Correction |
---|---|
If powder layer on the object is too thick, this results in an uneven surface. |
Use the powder supplier’s settings for the powder coating or Use less electricity (µA) |
Gun arrangement
Cause | Correction |
---|---|
The ideal gun arrangement depends on the range of parts, booth configuration and exhaust system. | A cabin with filter recovery is particularly suitable for the horizontal gun arrangement. Booths with central suction and quick color change systems should be built short as possible. In such cases, vertical arrangement is preferred. |
Gun function
Cause | Correction |
---|---|
An active powder gun not only produces voltage, but also draws current. | Power increases at the work piece as the gun approaches. Too much power causes back-ionization and orange peel finish. The current can be reduced by configuring µA settings. |
Gun powder surging
Cause | Correction |
---|---|
Pulsation during powder supply results from incorrectly configured conveying air or an incorrect dosing ratio | Check the conveying air setting and dosing ratio. For powder output of less than 80mg / min, a 10mm powder hose should be used. |
Powder deposits on the object
Cause | Correction |
---|---|
Too much powder output quantity per gun resulting in inefficient powder separation | Reduce powder output quantity and reduce chain speed |
Powder propulsion generally too high | Increase powder hose diameters |
Excessively long powder hoses | Shorten powder hoses or increase diameter |
Powder output irregular
Cause | Correction |
---|---|
Powder air speed too low | The ideal amount of air should be in the range from 4-5 Nm3 |
Fine powder/powder with poor flow properties | Use a powder container with fluid air and vibration |
Short periods of high compressed air consumption can cause pressure fluctuations | A compressed air reservoir before the powder plant solves this problem |
Too small cross sections or too small radii in the powder hose routing | The radii must be at minimum150-200mm |
Incorrect ratio between fresh powder and recovered powder | Use fresh powder |
Excessively high/low emissions | Adjusting the coating parameters |
Contaminated injectors | Injectors are often neglected during daily cleaning |
Powder container
Cause | Correction |
---|---|
The fluid air pressure or the amount of air are too high | The fluidized powder should “boil” only slightly but evenly. Prolonged use may lead to the partial closure of the fluid plates, which must be compensated for with a high amount of fluid air. In this case the bottom must be replaced. |
Recovery
Cause | Correction |
---|---|
Clogged return feed system | Clean |
Clogged sieves | Clean or replace |
Back-ionization
Cause | Correction |
---|---|
“Back-ionization” occurs when the powder layer is too thick. |
Reducing powder flow often prevents back-ionization, but results in a reduction of the transfer efficiency. Back-ionization also depends on the temperature and humidity. Very difficult powder materials may require air-conditioning of the coating zone. See also, orange peel effect. |
Sieve problems
Cause | Correction |
---|---|
Sieve clogs quickly | Sieve with larger mesh size |
Insufficient sieve mesh size | Replace sieve |
Surface impurities | Use a sieve with a smaller mesh size or use an ultrasonic sieving system |
Striping / banding
Cause | Correction |
---|---|
There is a fundamental mathematical relationship between powder feed speed, lgun motion velocity and number of moving guns to form and avoid banding on the workpiece. | Determine manufacturers recommendations. If the time of using a double stroke of the gun is less than the time it takes for the conveyor to pass through the width of the spray cloud, no banding or striping will occur. |
Yellowing
Cause | Correction |
---|---|
White powder reacts by yellowing excessively when exposed to high curing temperatures or excessive time. | If pure white powder is used, the curing specifications of the powder manufacturer must be strictly observed. |
Flow disruption
Cause | Correction |
---|---|
Particle size distribution of the powder is too coarse. | Contact powder suppliers. |
Contamination. | Contamination by foreign powder can be avoided by careful cleaning of the plant. In addition, different powders should not be mixed. |
Too high or too low film thicknesses. | Adjust powder output. |
Too wet or too hot workpieces. | Check drying and temperature of the workpieces. |
Powder deposits accumulate on nozzles. | Maintenance! |
Drop formation occurs when the powder flow is too strong. | Verification of the voltage and the distance to the workpiece, or the addition of thixotroping agents can help. |
Contamination
Cause | Correction |
---|---|
Inadequate sieve machine. | If a smaller mesh size is not sufficient, a sieve machine with ultrasound must be considered |
If the conveyor is not cleaned regularly or inappropriate lubricants are used. | Clean regularly, attach a cover if necessary |
If powder is blown-off in the curing oven. |
Check the air currents in the building |
Powder residue in the oven. | This can be prevented by regular cleaning |
Poorly clean recovery. | Regular cleaning |
Dirty air is sucked into the booth. | Here, the coating plant may need to be separated from production areas |
If several booths are operated together, cleaning may cause an impairment may occur. | In this case, the booths must be separated from each other |
Degree of cyclone separation
Cause | Correction |
---|---|
Squeeze valve running too slow or too fast | Set the time according to the manual |
Squeeze valve not open completely | Check squeeze valve for fatigue and hose inserts for correct assembly, or replace. |
Daily maintenance
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Weekly maintenance
- Check grounding inspection
- Check whether the compressed air is clean, dry and free of oil
- Check guns for voltage output
- Check electrode for wear -
- Check fan nozzle / baffle plate for wear
- Check powder hoses for sintering and kinks
- Check lifting and display
- Check filter systems
Economy
Cause | Correction |
---|---|
Check squeeze valve for material fatigue and check hose inserts for correct assembly, or replace | If new parts are integrated into the range, in most cases it is worth performing a review of the system parameters. If the objects are complex, a review of the gun assembly may also be worthwhile. |