automating coating process

Automating the Coating Process
Presented by:
Nguyen Quang Vu
Business Development Manager
Finishing Brands UK

• Applicator Technologies
• Spray Characteristics
• Automation: Reciprocators & Robotics
• Product Presentation
• Production Requirements & Cycle Time
• Calculating Coating Volume Needs
• Selecting Automation

Applicator Technologies
 Air Atomization
 Hydraulic Atomization
 Centrifugal (Rotary) Atomization
 Electrostatics

Air Atomization Technology
 Conventional Air Spray
• Low Volume High Pressure
 HVLP
• High Volume Low Pressure
 LVMP (TransTech Compliant)
• Low Volume Medium Pressure

Conventional, HVLP, LVMP
• Functional mechanics are all the same
• Air impinging on fluid stream to create droplets
Atomization air exits
from center holes of
air cap and creates
droplets
Fan (Pattern) air
exits from horns of
air cap and shapes
pattern into elliptical
shape

Conventional “Air Spray”
• The most established method of air
atomizing used on spray guns
• Uses high pressure and low volume of air
to provide good atomization of the
material
• This process creates a high particle velocity
resulting in lower paint transfer efficiencies
due to “bounce-back” and “overspray”
generated.

HVLP (High Volume Low Pressure)
• Compliant technology developed in the 80’s
when environmental legislation was first
introduced.
• Uses larger compressed air volumes at lower
pressures to atomize coating materials.
• Can yield higher transfer efficiency than
conventional air spray, however, quality of
finish may be negatively impacted.

LVMP (Trans-Tech Compliant)
• Introduced in the 90’s and is a combination
of Conventional and HVLP atomization
methods.
• Trans-Tech utilizes more compressed air for
the atomization process producing smaller
droplet than HVLP.
• Can yield higher transfer efficiency than
conventional air spray, with better quality
than HVLP.

Conventional
• Spray at Any Pressure / CFM
• Air cap pressures typically 30 – 60 psi
HVLP
• Meets USA Regulatory Requirements
• Air cap pressure less than 10 PSI
• Requires air cap test kit
LVMP (TransTech, Compliant)
• Meets European Requirements
• Air cap pressures typically 20 – 40 psi

• Comparison of air consumption, efficiency and particle size
Particle Size
150
300
450
600
750
900
20 40 60 80 100
HVLP
LVMP
Air
AirConsumption(l/min)
Transfer Efficiency %

Hydraulic Atomization
• Material at a high pressure is forced
through a fixed orifice.
• The material is atomized by shear
• Spray pattern size is based on angle
ground into tip
• Flow rate is based on fluid
pressure developed by pump

Hydraulic Atomization Airless & Air Assisted
• Airless
 Typically 1000 - 4000 psi
 High flow capability
 Used with wide variety of
coating materials

• Air Assisted Airless
 Typically 300 - 1500 psi
 Air used to improve spray
pattern uniformity

Air and Hydraulic Atomization

Centrifugal (Rotary) Atomization
• Rotary atomizers were developed
by Harold Ransburg in the 1940’s.
• The term “Bell” comes from
the shape of the original
atomizers that were driven at
low speeds 900 -1800 rpm
with electric motors.
• The rotation was used to distribute coating
evenly around the perimeter and the
atomization process was purely due to the
electrostatic charge applied to the “bell”.

• High speed rotary atomizers, utilize mechanical
shearing action to atomize coatings materials.
• Rotational speeds vary from 15,000 – 100,000 rpm

• Atomized droplet size is
based on bell cup diameter
and rotational speed.
• Various diameters used
based on flow rate and
coating materials
• Bell cup design vary
Serrated edge
Non-serrated edge

• Shaping air is used to provide forward
direction to the spray pattern
• Various shape air technologies used
 Single shape function
 Dual shape function
 Vortex style
 Combinations
• lower particle velocities associated
with higher transfer efficiencies
when compared to air atomization

• TurboDisk operates at speeds of
6,000 - 40,000 rpm
• Various disk platters available
 Serrated edge conical available in
6, 9 or 12”
 Smooth edge uni-disk available in
6, 8, 10 & 12”
• lower particle velocities associated
with higher transfer efficiencies
when compared to air atomization

• TurboDisk is a specialized applicator
that works well with
 High production systems
 Minimal color changes
 Batch run parts
• Markets used in:
 Aluminum Extrusion Industry
 Door manufacturers
 Propane or cylinder manufacturers
 Car or truck filter
 Shock absorbers
 Sporting equipment

Electrostatics
Definition: Method of paint application in which a
high voltage charge is used to dramatically increase
transfer efficiency.
• Coating is negatively charged
as it is atomized
• Product coated is at ground
potential, and appears to be
opposite charge
• Opposites attract - coating is
drawn to grounded product.
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Electrostatic: Two Methods
• # 1 Process: External or Indirect Charge
Fluid supply and
application
equipment at
ground potential
Wire grid is
electrically charged
Product coated
is grounded
through
conveyor system

• # 1 Process: External or Indirect Charge

• # 2 Process: Direct Charge
 When first developed, atomization
process was based on electrostatic
repulsion, like particles repel.
 Optimal atomization was obtained at a
maximum fluid flow rate of 10 ml/inch of
circumference
 Today atomization process is either
mechanical shearing action (rotary and
hydraulic atomizers) or air impingement.

• # 2 Process: Direct Charge
 With disk and bell applicators, charge is
transferred from disk platter or bell cup.
 Air atomized applicators utilize an
electrode in the fluid stream

Electrostatic Applicators
• All atomization technologies are
available with electrostatics in manual
and automatic versions

Non - Electrostatic applicator applying coating
material to tubular target.
Back side of tube targets
after being coated
Fluid flow rate set at 200 cc/min
Non-Electrostatics Application

Electrostatic air atomized applicator applying
coating material to tubular target.
Fluid flow rate set at 200 cc/min Back side of tube targets
after being coated
Electrostatics Application

Electrostatic rotary atomizer applying coating
material to tubular target.
Fluid flow rate set at 200 cc/min Back side of tube targets
after being coated
Electrostatics Application

Electrostatics
• More forgiving application
• Better uniformity
• Electrostatic “wrap” as opposed
to “line of sight”
• Increased transfer efficiency
 Decreased coating cost
 Decreased booth maintenance
 Decreased emissions
 Decreased waste disposal
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0
20
40
60
80
100
Bells Air Elec. Air Conv.
Min
Max
0
20
40
60
80
100
Bells Air Elec. Air Conv.
Typical Transfer Efficiency
on Metal Substrate
Typical Transfer Efficiency
on Plastic Substrate
Electrostatics

• Increased transfer efficiency
• The best way to reduce coating usage is to minimize
the volume of material that is sprayed.
Electrostatics
• You pay for paint 4 times!
 You pay somebody to buy it
 You pay somebody to apply it
 You pay somebody to clean it up
 You pay somebody to dispose of it

Electrostatics can effectively be used on
non-conductors

1. Conductive Sensitizers
2. Conductive Primers
3. Conductive Adhesion Promoters
4. Inherent Conductivity (moisture content)
5. Misting
6. Imaging Techniques
7. Conductive Additives
8. Metal Deposition
Electrostatics: Eight techniques used to
make non-conductors conductive:

Spray Characteristics
Applicator technologies can be used across a
wide range of markets and applications
TransportationWoodMetal Special Coatings
 Urethanes
 Latex
 Two-Component
 Epoxies
 Toners
 Stains
 NGR Stains
 Topcoats
 UV Materials
 Primers
 Base Coats
 Clear Coats
 Aerospace
specific coatings
 Waterborne
 Adhesives
 Mold release
 Ceramics
 Enamels

Classification of Atomization Technologies:
• Finish Quality
Rough------------Fine
Large -------------------------------------------- Small
FinishQuality
Atomized Droplet Size
Airless
Air Assist
HVLP
LVMP
Conventional
Disk
Bell

• Transfer Efficiency
Low---------------High
Conventional -------------------------------- Rotary
TransferEfficiency
Applicator Technology
Airless
Air Assist
HVLP
LVMP
Conventional
Disk Bell
E-Stat Gun
Note:

• Speed of Application
Slow----------------Fast
HVLP ------------------------------------------ Airless
SpeedofApplication
Airless
Air Assist
HVLP
LVMP
Conventional
Disk
Bell
Applicator Technology

Comparison of Rotary and Air Atomization Technology
43

Normal: 200 – 250mm
Normal Spray PatternCut-in Areas
44
Dual Shaping Air Spray Pattern - can be optimized for coverage
into deep recessed areas or larger surfaces.
Cut-in: 75 – 100mm

Automation: Reciprocators and Robots
Machines and robots installed in spray booths
must be approved for operation in hazardous
area (Class 1, Division 1).
• Machines Hard Automation
 Short Stroke Reciprocators
 Long Stroke Reciprocators
 Smart Reciprocators
 Special Machines (Rotary Spray)
• Robots Flexible Automation
 Electric robots, highly reliable

• Short Stroke Reciprocators
 A reciprocator increase the effective
coating area of the applicator.
 Typical stroke range 7 – 14”
 Blends round spray patterns together
providing very good coating uniformity.
 Improves coverage by changing
presentation of the applicator to
the part.
 Rotary atomizer, 30 cycles per
minute
 Air atomizers, 60 cycles per
minute

• Long Stroke Reciprocators
 A reciprocator increase the effective
coating area of the applicator.
 Typical stroke length 3’ – 14’
 May be equipped with “toeing”
feature that angles applicators in
direction of travel.
 Rotary atomizer, 180 ft/min
maximum
 Air atomizers, 280 ft/min
maximum

12 cyc
1 min
50% Spray Pattern Overlap
 Machine must be
synchronized with conveyor
to get uniform finish
 50% or 75% spray pattern
overlap most commonly used
 50% overlap: conveyor speed
(in) / pattern width (in) =
machine cycle rate
 75% overlap = above X 2
 Assume:
• 14 ft/min
• 12 in spray pattern
Conveyor TravelApplicatorTravel
14 ft
1min
12in
1 ft
1 cyc
12 in
XX @ 50% Overlap

 Used with disk system
 Typical stroke range 3’ – 24’
 Recommend a minimum of
4 strokes on part while in
disk loop
 Maximum speed 4ft/sec,
recommend slower.

 “S” loop conveyor configuration
 Allows access to both sides of part

• Smart Reciprocators
• Special Machines (Rotary Spray)
 Similar to long stroke style reciprocator
 Additional axis of movement incorporated
 Variable stroke length
 Multiple atomizer mounted
on rotary axis
 Product coated conveyed
on belt beneath atomizers
 Integrated system to
reclaim material

• Robots
 Flexible automation, programmed to accommodate product
coated.
 Ability to maintain optimal distance
between applicator and substrate.
 In most cases more cost effective
than designing custom “hardware”
solution
 Robot selection made based on
work envelope “reach” and payload
capability

• Robots

Product Presentation
Product presentation is most often dictated by
• Manufacturing process
• Size or weight of the product coated
• Desire to coat new product in existing system
Conveyor Systems
• Overhead
• Floor mounted
• Chain on edge
• Power and Free (indexing)
• Horizontal belt or web

Part Presentation
• Single or multiple parts per fixture
• Fixture may index on 90˚ or 180˚
increments
• Fixture may continuously rotate
• Rotation may be reversed in each
spray zone

Part Presentation
• Repeatability
• Grounding

Part Presentation

Production Requirements
• Following information is need to make
equipment recommendations
 Conveyor speed (ft/min)
 Rack centers (ft)
 Parts per rack
 Hours per shift
 Shifts per day
 Days per week
 Weeks per year of operation
2’

Calculating Coating Volume Needs

65
Comparison of application technology impact on
transfer efficiency
Calculating Coating Volume Needs

Evaluate the “Givens”
• Greenfield project?
• New program in existing finishing system
• Production requirements
Selecting Automation
Prioritize the requirements
• Finish quality
• Production level
• Coverage
• Transfer efficiency
• Environmental

Bring in the Experts
• Use equipment suppliers applications labs
Selecting Automation

Thank-you
Nguyen Quang Vu
Business Development Manager
Finishing Brands UK
0933993335

automating coating process

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