Paint line managers of electrostatic paint lines are often tasked to provide plastic substrates with an evenly distributed bright and shiny paint coating and with keeping the painting environment safe.  

That’s easy, right? Most people think that all they have to do is to make sure the substrate is grounded.

 Yes, that is true, but how do you really know if the ground in place provides a consistent low level of resistance?

One way to check the resistance of the plastic substrate is with a multi-meter (after the conductive costing is applied). This will provide an accurate measurement as long as both probes are placed as needed. The problem is that you need 3 hands to hold the two probes plus the meter, while you touch the probes to places that are often far apart. Additionally, the probes are pointed, so caution must be taken to not scratch or damage the plastic substrate which could remove the conductive primer. The process of using a multi-meter to take a consistent reading across the entire plastic substrate can be very cumbersome and time consuming while the line is in full operation.

A much easier and more efficient way to take a measurement of resistance is to use the Ground Analyzer from Mueller Electric. This is a hand- held device that provides the tools to take a quick and easy measurement of the ground effectiveness across the plastic substrate. The Ground Analyzer will take a reading but will also provide a quick go-no go indicator which will allow the paint line manager to know if the substrate is grounded throughout and is ready for base coating. Every paint manager has their own unique requirements for appropriate grounding levels. For some it may be 500Ωs while others may go at 1MΩ or higher. The Ground Analyzer allows for a threshold to be set at various preset levels (one setting is available for user input) and the reading taken will provide a green indicator if the resistance measurement is below the threshold. If the reading is above the threshold the indicator will turn red alerting the operator to the fact that a better ground is needed. For a better understanding of how the Ground Analyzer works you can watch the video or see the PDF here. 

Everyone wants a safe work environment. One of the workplace hazards are explosions and fires due to static discharge, but these can be mitigated by grounding equipment. Proper grounding is the only way to ensure true static protection if you are in any environment where the potential for static discharge exists.

Many places ground with heavy duty cast clips, solid copper clips and clamps of all shapes and sizes connected to a wire and attached to drums and pipes throughout a storeroom, plant floor or pumping stations.  These are referred to as grounding assemblies or “straps.”

These areas may or may not be perfectly grounded. Even though they may look grounded, it’s hard to tell if it’s done properly. An improper ground could mean safety hazards that can lead to fire or explosions.

First and foremost, it must be determined that access to a fully grounded grounding pin or buss bar is readily available. This will be necessary for a solid true ground and will act as the backbone of the grounding system. Keep in mind, however, that the grounding pin and buss bar must be kept clean so solid metal-to-metal connections are made.

The next step in ensuring that something is properly grounded is to make sure the correct connection device is utilized.

Many times a C-clamp or center spring clip will be used for this connection. This would certainly result in a good connection as the C-clamp can bite into the metal pin or buss bar and the clamp pressure on the center spring clamp is strong enough to drive the teeth into the metal pin or bar. It’s important that the clamp or clip is able to pierce any paint that might be on the surface. The connections on the grounding pin and buss bar must be solid tight connections as maintaining continual connectivity is critical for the integrity of the entire grounding system.

The type of cabling used from connection to connection (grounding pin / buss bar to clamp or clip) will depend on the environment being grounded. If the environment is clean such as a paint mixing room, uninsulated stainless steel wire rope or braided copper can be utilized. In other applications where the environment may contain more contaminants, an insulated wire may and should be considered such as THHN (oil and gas resistant).

Now that the connection to the ground source and wire are complete, focus can be placed on the connection to the can, drum, or tank. This connection can be made with a cast clamp with points, C-clamp containing a point or center spring clip with strong clamp pressure and teeth. The type of connection depends on the type of surface in which it is being attached. If the surface is clean and free of dirt and paint, a center spring clip can work fine. The size of the clip will be determined by the size or thickness of the object being grounded. If the container is dirty or painted the connection will need to be made with a connector which will break through those layers to make a solid metal-to-metal connection. Cast clips with points and the C-clamp with a point are perfect for this application.

Once a connection is made to the first container a “daisy chain” method of connecting the remaining containers in the area can be used. This means that a grounding cable can be attached from container to container to maintain a good ground as long as the series of containers is attached to the one connected to the grounding source. Keep in mind that each grounded container must have a solid metal-to-metal connection with the grounding device. It may be necessary in more caustic environments to wire each container directly to the grounding source. This same approach can be applied to grounding pipes for fluid flow, and even grounding work stations.

Following the above steps for creating a solid grounding system should produce good results and create a safe environment.  To confirm that there is good connectivity, take resistance measurements with a multi-meter, ohm-meter or ground analyzer. To ensure entire system integrity, a lead should be placed on the connection on the grounding source (grounding pin or buss bar) and the other on the very last connection in the system. This will incorporate a resistance measurement from point-to-point for the entire grounding system. If the reading taken is zero or approaching zero, the system is well grounded and a safe environment exists. If the reading approaches 1M Ohm then check the connections throughout the system to ensure that there are solid metal-to-metal connections. Once the appropriate measurement is received (zero or approaching zero), you have a good and well-grounded system in place ensuring static protection.         

It may seem like common sense, but it’s important to make sure your grounding and bonding straps are working properly. It is essential that your clips are making a good connection. 

• Ensure your clips are clean and clear of debris.
• Check to see that you are getting a solid metal-on-metal connection. If there is paint on the surface the clips connect to, make sure the clips are breaking through that paint.
• Inspect your grounding equipment regularly and take measurements with a multimeter to ensure there is a low resistance.
• Replace any clips or straps that are too rusted to perform properly

Remember that bonding and grounding serves an important safety purpose, and regularly checking up on the grounding and bonding straps can prevent sparks and explosions.

To read more on static electricity in industry, check out our whitepaper here

If you are interested in custom-made grounding or bonding equipment, you can see our capabilities here

So you’re considering if you need a custom grounding solution for your automated paint/powder coat line, but you still have questions and concerns.  You’ve probably evaluated all your alternatives and realized it may be time to update your grounding process, and maybe you've even read our whitepaper on Static Electricity and Grounding in Industry. But there are still some questions and things to consider.  This infographic addresses the common questions and considerations that people have when evaluating grounding solutions.

 Ready to move ahead with a custom or ready-made solution for grounding to update your process? Click here and fill out the form to get the ball rolling!   

You can also read our free guides to grounding for plastic and metal painting below

When trying to determine the cause of problems encountered with electrostatic painting, it can be confusing. The problem is often solved by updating the grounding process, however this simple solution is often overlooked. 

1. There is a drop in transfer efficiency

Your measurements and output are lower than they should be. 

2. Paint thickness is not what it should be

You may see a reduced paint thickness, uneven paint thickness, or both.  

3. There is a lot of scrap/rework

Lack of a good ground can result in much higher  amounts of scrap and rework than there should be. 

4. There's more paint on the surrounding surface than on the substrate

This can indicate you had a bad ground or no ground at all. 

5. Your cost of paint has gone up

You are going through more paint to coat the same number of items. 

6. Servicing the robots doesn't help

You may have thought there was something wrong with the paint robots, but they are in working order

7. There's a drop in weight

If your substrates come out weighing less than they normally do, this can indicate that less paint is making it to the surface which usually indicates there're something wrong with the ground.

If you think updating your grounding process will help, you can head over to this handy page which addresses the most common considerations and questions for updating your grounding process. 

For more information on grounding, read our whitepaper Static Electricity and Grounding in Industry. 

You can also take a look at our free guides for grounding plastic and metal for painting.

Static electricity is all around us in everyday life and generally refers to an imbalance between positive and negative charges in objects. Most people have experienced it in some form or another whether it be with their laundry being particularly “clingy,” making a balloon stick to a wall after rubbing it on your clothes, or when walking around wearing socks on a carpet and getting a small shock when touching another object or person.

The Science of Static

To understand static, it helps to understand some basic physics with atoms and magnetism.

All objects are made up of atoms which have positive and negative charges, like a magnet. Also like magnets, like charges repel each other (positive-positive, or negative-negative), while different charges attract each other (positive-negative).

Static electricity is a result of an imbalance between positive and negative charges when two objects or materials come into contact. The surface electrons try to balance each other while the two surfaces are together. When two materials or surfaces are touching, one surface gives up electrons and becomes more positively charged while the other object surface collects extra electrons and becomes more negatively charged. When the two materials are separated, an imbalance occurs when the surfaces are left with either a surplus or shortage of electrons, and the surfaces become electrically charged. These charges build up when they don’t have a direct path to the ground, and can eventually build up enough to cause a spark to a nearby grounded or less charged object in an attempt to balance the charge.  

Examples of Static Electricity

When you take off a wool sweater and the hair on your head and arms stand up, the hair acts this way because your body got an extra charge from the friction of the sweater being removed and your hairs are moving away from each other because they all have the same charge.  

With your laundry, your clothes in the dryer are rubbing up against each other (particularly when you have different types of fabrics in there, like cotton and polyester), those charges will cause the fabrics to cling to your body.   

Lightning is another example of static discharge. You see it because electricity is being produced between two clouds or between a cloud and the earth as the static electricity is discharged.

Static in Industry

Static electricity is very important in many industries as can used to our benefit, or it is a problematic issue that needs to be mitigated, reduced, or removed.  

For example, some helpful uses in industry are in pollution control – like air purifiers. The air purifier applied a static charge to dirt particles in the air and then passes the air over an electrostatic plate of the opposite electrical charge. The dirt then clings to the plates and can be easily removed. Factories use this same principle on a larger scale for their smokestacks to keep pollution out of the environment.

Another use for static electricity is for spray painting car parts. This requires a specialized paint gun that applies an electrostaitc charge to the paint. The parts for painting need to be properly grounded using metal clips, clamps and wires. The charge causes the paint to be attracted to the car parts resulting in an even coat, less mess, and less wasted paint.

In other industries, static can cause a lot of problems. Sparks caused by static can cause fires and explosions. While hazards for fires may be obvious with flammable materials, this can also happen in industries where there is dust, like flour mills. Static electricity is also an issue where electronics are used and manufactured.

Static electricity in industry is caused by machinery where this is friction and contact and separation, as well as in instances where there are rapid heat changes. People can build up their own charges simply by the friction created when they walk, so when they move within proximity to a machine, they can receive a shock. Static sparks can be very serious in industry, not only can they cause an ignition or explosion but they can also cause a burn or stop someone’s heart.

Some other sources of static electricity production in industry can be liquid flowing through a pipe, hose or opening, blending or mixing, spraying or coating, filling drums, cans, pails, or tanks and conveyer belts.

Electrical charges can also build up in flammable liquids when they flow through pipe systems or when they splash due to being moved in their storage containers.

Humidity is a significant factor as moisture in the air helps to remove some charge. Dry environments are much more prone to static buildup. Different materials and production speeds also play a role in how much and how fast static is created.

Static Control

Static electricity in industry is controlled by several methods. We will focus on the most common of these methods, Bonding and Grounding. 

Bonding is when two or more conductive objects are connected with a conductor like a wire, which helps to equalize the charge between them. Bonding doesn’t eliminate static electricity but it does ensure that a spark will not happen between the objects. An example of a cable used for bonding is to the left. In this example, two copper clips are on either end of a wire and clip directly to the items being bonded. 

Grounding is when objects that can gain a charge are connected directly into the earth using metal like grounding rods, copper, and steel. Grounding drains the static charges away as they are produced. Grounding and bonding connections are made with connectors using metal clips, clamps and wires.

Grounding Assembly

A grounding/bonding assembly is a clamp or clip with a grounding cable or wire. One end attaches to the item being grounded or bonded. The other end attaches to the ground, whether it be a ground rod or a grounding "bus" mounted on a wall. Ground connectivity of all devices, cables and connections must be checked at installation and regularly afterwards for safety and to ensure the connection is maintained. Many grounding clips and clamps have a paint-piercing ability to ensure a metal-on-metal connection. Check out Mueller Electric's catalog for more examples of grounding and bonding equipment.  

Other Websites For More Reading: 

Uses of Electrostatics on BBC.co.uk

GCSC Science / Uses of Static Electricity