automating coating process

Automating the Coating Process Presented by:

Nguyen Quang Vu Business Development Manager

Finishing Brands UK

Automating the Coating Process

• 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

Automating the Coating Process

Air Atomization Technology

Conventional Air Spray

• Low Volume High Pressure

• 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

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

Conventional, HVLP, LVMP • Comparison of air consumption, efficiency and particle size

Particle Size

20 40 60 80 100

Transfer Efficiency %

Conventional, HVLP, LVMP

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

Hydraulic Atomization Airless & Air Assisted

• Air Assisted Airless

Typically 300 - 1500 psi

Air used to improve spray

pattern uniformity

Applicator Technologies Hydraulic Atomization Airless & Air Assisted

Air and Hydraulic 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.

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

- - - - -

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

Transportation Wood Metal 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

Large -------------------------------------------- Small

Atomized Droplet Size

Airless Air Assist

HVLP LVMP

Conventional

Disk Bell

Classification of Atomization Technologies: • Transfer Efficiency

Conventional -------------------------------- Rotary

Applicator Technology

Airless Air Assist

HVLP LVMP

Conventional

Disk Bell

E-Stat Gun

Classification of Atomization Technologies: • Speed of Application

HVLP ------------------------------------------ Airless Spe

Airless

Air Assist

Conventional

Applicator Technology

Comparison of Rotary and Air Atomization Technology

Normal: 200 – 250mm

Normal Spray Pattern Cut-in Areas

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

• Long Stroke Reciprocators 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 Travel A

14 ft 1min

12in 1 ft

1 cyc 12 in

X X @ 50% Overlap

• Long Stroke Reciprocators

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.

• Long Stroke Reciprocators

“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

Calculating Coating Volume Needs

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

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