Paint System Troubleshooting

Paint application system equipment issues can have a severe impact on the productivity of a paint shop.  Paint application systems often combine a multi-trade assortment of equipment whose service and repair challenge even the most experienced maintenance personnel.  Electric and hydraulic machine controls, electrostatics, pneumatics, fluid control and air delivery systems, all designed and applied specifically for paint application, are common system components.  When you realize that the final quality of finish is also affected by pre-treatment, conveyors, paint booths, and ovens, the potential complexity of the system becomes apparent.  

Some common paint application equipment issues are discussed below.  Discussions on paint color change, paint shop throughput, paint overspray, painting robots, and paint defect analysis can be found elsewhere on our site.  NA Paint can help you quickly identify and correct virtually any equipment or system issues.  We also provide maintenance and inspection services to assure all equipment is in good working order.  We can help you calibrate or validate components or systems, and repair, replace, or specify suitable replacements for faulty equipment.  We are experts in fire prevention.

Often with minimal investment, we can add powerful, low cost, self-diagnosing supervisory controls specifically tailored for your existing system that continuously monitor real time process data, analyzing the data to evaluate your systems performance at the component level.  Such controls can detect component degradation and predict failures before they happen.  In the case of detectable failures or system faults, they can tell you which component is broken and which requires maintenance.  When generic problems occur, such as drips or sags, these controls can provide a step-by-step approach for correcting the problem.  

We are happy to discuss how this low cost yet extremely powerful technology can help you efficiently operate and maintain your system.

High Voltage Faults

Electrostatic paint application systems include some method of generating a high voltage potential at the applicator which can approach 100,000 volts.  Paint transfer efficiency, finish quality, and levels of overspray are severely and adversely affected by problems with the high voltage supply, particularly when using bells or spraying metallics. 

Usually high voltage supply systems comprise a controller and a remote voltage multiplier.  This multiplier, also called a cascade, is sometimes integrated into the applicator, sometimes mounted near the applicator, or sometimes located 20 or more feet away.  Regardless of the configuration, all high voltage systems ought to provide a minimum level of safety features.  These include current overload, over voltage detection, ground fault detection, and possibly others like under voltage or corona sensing. 

Assuming that all equipment is installed and grounded properly, over or under voltage faults usually indicate equipment malfunction of either the high voltage controller, wiring, or multiplier, but depending on which power supply is used, not always.  Ground faults occur when there is continuity between the output of the high voltage multiplier and earth.  Usually a careful inspection or isolation of the equipment will reveal the source of the continuity.  Intermittent ground faults can be more troublesome.  Circumstances at the time of occurrence, when monitored closely, can often provide insight to the root cause.

Current overloads occur when the output of the high voltage multiplier is not adequately electrically isolated.  These can be caused by condensation, proximity to equipment at lower potential, contamination of equipment, paint, or solvent, or incompatible materials.

Any fault in the electrostatic control system may indicate a potentially dangerous situation where a spark or fire may occur. 

High Voltage Related Contamination

The presence of very high voltages in paint application systems can contribute to frequent or excessive contamination of surrounding equipment and fixtures.  This contamination, which may be a sign of equipment malfunction, can usually be eliminated or significantly reduced.  NA Paint can assist in diagnosing and correcting such contamination and we suggest that you contact us directly with details. 

Paint Flow Control Systems

Most paint application systems include some kind of fluid delivery control, most of which have no self-diagnostics to help determine if they are functioning properly.  The only evidence of poor or faulty operation shows up in the finished part in the form of light, heavy, or inconsistent film build, runs and drips, solvent pop, orange peel, and in the case of multi-component proportioning systems, incomplete cure or adhesion.  

When these problems occur, the first step ought to be recalibration of the flow controller.  This process ought to validate the controllers accuracy and reveal any defective components.  If flow rate inconsistencies persist, then one must examine the suitability or configuration of installed components for the application.

Sometimes flow meters plug prematurely.  When this happens repeatedly, the meters ought to be disassembled and inspected.  If they are gummed up, then inadequate purging is probably the cause.  If there is no apparent contamination, then the wetted parts ought to be removed and cleaned thoroughly.  If the problem persists, check flow meter specifications and ensure that filtration requirements are met.  Gear pumps are susceptible to similar problems but can be more difficult to monitor for correct operation because no direct feedback for material flow is normally available.

The North American Paint Application Company can implement technology for self-diagnostics and automatic calibration of flow control systems, which enables you to troubleshoot and calibrate your system on the fly, with minimal or no impact to production.

PROBLEMS AT THE ATOMIZER (BELLS AND GUNS)

Rotary Speed Control

In rotary atomizers, the speed of the bell cup or disk is the primary mechanism for paint atomization control.  Proper atomization is so important for optimizing transfer efficiency, producing uniform film builds, and applying quality finishes consistently and repeatably.  If your bell speed control or rotation feedback is defective, NA Paint can repair or replace your equipment, even if obsolete.  If you use rotary atomizers and do not have bell cup speed control, for the above reasons we strongly suggest you consider installing it.

Several methods are used to measure the rotational velocity of discs and bells.  The most common is via a fiber optic cable.  If you have lost the feedback signal, usually it is because of damage, contamination, or improper installation of this cable.  A transceiver, that converts the light pulses to electric pulses, can easily be confirmed functional.  Pulses ought to be generated at low speeds and confirmed with a meter or display if installed.

Disk Paint Build-Up

Under certain conditions, paint can dry and build-up on the rotating disk to such extent that it begins to flake or break off and contaminate the part or parts being painted.  This contamination can cause considerable numbers of surface defects that are noticeable as dirt.

If you suspect this is occurring, the first step ought to be an examination of the disk or bell cup.  If paint build-up is found on surfaces where paint normally does not flow, check the alignment of the feed tube, examine for plugged orifices or foreign material, and for damage to the disc or bell cup.  If paint has dried and built up on a normally wet surface, and there are no plugged orifices, foreign matter, or disk damage, then the build-up is probably  process related.  Paint dries and accumulates during normal or extended painting, which is not uncommon.  There are many ways to prevent or reduce this sort of paint build-up.  Selecting the best solution(s) requires a good understanding of the application process, but could include flushing, chemistry, bell speed control, or other process adjustments.

Paint Spits and Sputtering

Paint spitting and sputtering at the applicator is often caused by plugged orifices, foreign material, applicator damage, or paint supply problems.  Inconsistent flow control or paint pressure pulsations can contribute to it.  In guns, intermittent atomizing or fan air can be a cause.  Kinked hoses in articulating systems might be a source.  Defective valves are sometimes the cause.  A process of elimination usually quickly leads to uncovering the root cause, and correcting it. 

Irregular Spray Patterns

In manual systems, irregular spray patterns may affect the quality of finish, the quantity of paint used, and the level of emissions, but the operator ultimately has the ability to continuously examine the part to ensure it is painted.  Automated systems have no visual feedback and require reliable spray pattern control.  Without it,  inconsistent finish quality will plague production with high touch-up, rework, and/or scrap levels.

Problems with high voltage, flow control, paint, spitting and sputtering, head-to-target distance, bell speed, variations in atomizing or shaping air, or surrounding conditions can affect the size and shape of spray patterns.  Usually, irregular spray patterns and the problems they create manifest themselves during production.  The North American Paint Application Company can implement technology for operator validation of spray patterns on the fly, with minimal or no impact on production.  Combined with our on-the-fly flow control calibration technology, significant improvements in quality control, first time yields, and productivity could be gained, while emission levels and operating costs are sharply decreased.

Feel free to give me a call to discuss . . . Joe @ (708) 980-3758.

North American

Paint Application Company

info@napaint.com

www.napaint.com

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