Electro Static Basics

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Electro Static Basics
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Our Purpose

• To help you understand the different type of
  spray technologies, and resulting efficiencies,
  that are currently available. We will also
  identify the features and benefits of each to
  help you increase your transfer efficiency in
  your application.

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Electrostatics -Transfer Efficiencies Comparison
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Mechanics of Atomization

• Airspray HVLP
• Use high air velocity low fluid (material)
  velocity
• Are low (fluid) pressure methods
• Generated particles are
• Medium to small size - High velocity

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Mechanics of Atomization

• Airless Air-Assisted Airless
• Use high velocity fluid low velocity air
• Are high (fluid) pressure methods
• Generated particles are
• Medium to large size - Low velocity

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• Controlling Fluid Flow Rate Velocity
• Low Pressure Methods
• Regulate supply pressure size nozzle properly
• Regulate at point of use
• High Pressure Methods
• Regulate supply pressure size tip properly

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• Atomization Pattern Air Pressure
• Atomization level is the air pressure required to
  create a distribution of spray particles.
• Pattern air pressure is the air pressure required
  to adjust a spray pattern to the desired width.

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Proper Atomization Levels

• Set the atomization level to meet the finish
• requirement.
• Aim for a level that creates a spray pattern with
  a particle size distribution that provides the
  optimal finish quality with the least efficiency
  loss.
• Avoid over-atomizing!

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Low Pressure Fan Patterns

• Adjust the pattern (fan air) to match the target.

Proper fan size allowing 50 overlap
Fan size larger than part
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High Pressure Fan Patterns

• Size the cut of the tip to match the target.

Tips are sized as half the fanexample 4xx is an
8 fan The orifice size is the second two digits
example X13 is a .013 orifice
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Increasing Transfer Efficiency

• Electrostatics is a spray finishing process in
  which electrical charges fields are used to
  attract particles of atomized coating material to
  a target

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Increasing Transfer Efficiency

• Electrostatics - Uniform Coating Effect

Without Electrostatic
With Electrostatics

• Electrostatics can result in a more uniform
  coating because
• particles are all negatively charged. Since
  particles with like
• charges repel each other, particle distribution
  on the target is
• more uniform. Also due to repulsion, particles
  are attracted to
• the areas on the target where the coating is
  thinner.

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Increasing Transfer Efficiency

• Electrostatics - Wrap Effect

• Wrap--the deposition of film on areas of a
  target that are not sprayed directly--occurs
  because electrostatic forces draw back spray
  particles that have moved past the targets
  surface. This a minor, sometimes desirable,
  effect of electrostatics.

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Increasing Transfer Efficiency

• Electrostatics - Faraday Cage Effect

Lines of force create an area which can not be
penetrated

• Sometimes the wrap effect is undesirable. For
  example, it may result in uneven coating on
  targets that have deep cavities because paint is
  drawn to the outermost points of an object. This
  is known as the Faraday cage effect.

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Increasing Transfer Efficiency

• Using Electrostatics Wisely
• Understand mechanics of electrostatics
• Know when conditions are appropriate for use of
  electrostatics
• Economics
• Material compatability
• Substrate (target) compatability

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Increasing Transfer Efficiency

• Other factors include
• Operator skill level
• Target characteristics
• Material condition

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Increasing Transfer Efficiency

• Optimizing Operator Skill Level
• Provide process documentation
• Provide proper training
• Training must be ongoing
• Implement appropriate monitoring procedures
• Engineers and operators should work together to
  implement control and monitoring

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Increasing Transfer Efficiency

• Consider Target Characteristics
• Apply correct atomization type and level for
  target part configuration
• Match target part configurations as closely as
  possible when racking

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Figuring Return on Investment (ROI)

• The purchase of new equipment may be necessary.
  New equipment can solve problems that keep you
  from achieving your goals.

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Figuring Return on Investment (ROI)

• Environmental Problem
• VOC emissions must be reduced to meet
• environmental regulations

• New equipment can
• Improve efficiencies
• Reduce amount of material needed for cleaning
• Reduce amount of material wasted

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Figuring Return on Investment (ROI)

• Quality Problem
• Finish quality, uniformity, and surface quality
  must
• improve to meet customer specifications

• New equipment can
• Reduce costs associated with rework
• Time
• Materials
• Labor
• Help meet new end user requirements