Fixtures are a familiar presence in coating operations.

Hanging workpieces.
Securing workpieces.
Suspending them from a conveyor.
Supporting them so they do not move during coating.
Sending them through a curing oven.
Making them easier for operators to hold.

Fixtures are used daily in these ways.

However, fixtures are more than just auxiliary tools.

Fixtures are essential equipment that determines coating quality.

Poor fixtures cause workpiece positions to shift.
Workpieces sway.
Coating surfaces are obscured.
Grounding cannot be established.
Gun angles become unsuitable.
Film thickness becomes uneven.
Areas are left uncoated.
Operators adopt awkward postures.
Workpieces become difficult to heat in the curing oven.
In robotic coating, the programmed path no longer matches the workpiece.

Fixtures may look like small components of the coating process.
In reality, however, they relate to quality, workability, productivity, safety, and automation alike.

1. Fixtures Keep Workpieces in the Correct Position

The basic role of a fixture is to keep a workpiece in the correct position.

If the workpiece is in the same position every time, the operator can coat in the same posture.
Spray gun distance and angle also become easier to maintain consistently.
Stable workpiece positioning is even more important for automatic coating machines and robots.

Conversely, if workpiece position differs each time, coating conditions will not be stable.

• Gun distance changes
• Coating angle changes
• Film thickness changes
• Areas are left uncoated
• Excessive coating builds up on edges
• The robot path and workpiece position become misaligned

In manual spraying, a skilled operator may be able to compensate to some extent.
However, this compensation burdens the operator.

Stabilizing positioning with fixtures is fundamental to avoiding dependence on operators’ judgment alone for quality.

2. Fixtures That Obscure Workpieces Cause Uncoated Areas

Fixtures are necessary to hold workpieces.
However, obscuring the surface to be coated causes areas to remain uncoated.

Examples include the following conditions.

• Fixture contact areas are too large
• The fixture extends over the surface to be coated
• The fixture enters a recess and prevents paint from reaching it
• The hanger passes in front of the surface to be coated
• The workpiece support location is unsuitable
• The fixture obstructs spraying

In these cases, operators change the angle and try to force paint into the area.
However, awkward spraying leads to uneven film thickness and sagging.

Fixture design must both hold the workpiece securely and minimize obstruction of the surface to be coated.

Simply being able to hold the workpiece is not enough.
It is important to hold it in a way that makes coating easy.

3. Fixture Sway Causes Uneven Film Thickness

A workpiece swaying during coating changes gun distance.

As gun distance decreases, the film tends to become thicker.
As distance increases, the film tends to become thinner.
Sway can also destabilize the spray pattern and cause unevenness.

Causes of workpiece sway include the following.

• Insufficient fixture rigidity
• Inadequate workpiece fastening
• Excessive play in the hanger
• Conveyor vibration
• Movement when touched by an operator
• Sway caused by airflow inside the curing oven
• An unfavorable workpiece center of gravity

Fixture sway is a major problem for robotic coating, as well as for coating appearance.

A robot operates on the assumption that the workpiece is in a defined position.
If the workpiece sways, coating results will not be stable even when the robot moves accurately.

Fixtures serve to suppress sway, as well as to locate workpieces.

4. Fixture Grounding Determines Quality in Electrostatic Coating

Fixture electrical continuity is extremely important in electrostatic coating and powder coating.

Electrostatic coating electrically charges paint particles and attracts them to the workpiece.
The workpiece must therefore be properly grounded.

Grounding connects equipment to earth to dissipate electrical charge.
Put simply, the workpiece must have an electrical connection.

Poor electrical continuity through the fixture prevents charge from flowing properly from the workpiece.
Paint deposition then becomes unstable.

The following problems commonly occur.

• Transfer efficiency decreases
• Film thickness becomes uneven
• Powder becomes difficult to deposit
• Wraparound coverage deteriorates
• The risk of sparks increases
• The electrostatic effect becomes unstable

Old coating buildup on a fixture impairs electrical continuity.
Dirty contact areas also cause poor grounding.

Fixture cleaning and continuity checks are part of quality control in electrostatic coating.

5. Coating Buildup on Fixtures Makes Quality Unstable

Fixtures are used repeatedly.
Paint therefore accumulates on them as they continue to be used.

Coating buildup on fixtures causes the following problems.

• Workpiece positions shift
• Contact areas become thicker, making holding unstable
• Grounding deteriorates
• Coating flakes detach and become dirt inclusions
• Workpieces are scratched
• Fixtures become heavier
• Loading and unloading become difficult
• Fixtures become a source of debris inside the curing oven

In particular, coating flakes that detach and land on the coated surface cause dirt inclusion defects.

Fixtures should not simply be used for as long as they remain usable.
They require regular cleaning and stripping or replacement as needed.

Fixture management is important for preventing debris contamination and poor grounding.

6. Fixture Design Also Affects the Burden on Operators

Operators handle fixtures every day.

Fixture ease of use therefore has a major effect on operator burden.

Poor fixtures cause the following problems.

• Workpieces are difficult to hang
• Workpieces are difficult to remove
• Fixtures are heavy
• Hands can easily be pinched
• Awkward postures are required
• Positioning takes time
• Incorrect hanging occurs
• Hanging methods vary between operators

These conditions fatigue operators.
Fatigue makes coating quality more difficult to maintain consistently.

Fixture design needs to consider operator movements as well as quality.

Can the workpiece be hung with 1 hand?
Does the task avoid awkward postures?
Is the workpiece held safely?
Can anyone set it in the same position?

Fixtures that are friendly to operators are also friendly to quality.

7. Fixtures Also Affect Heating in the Curing Oven

Fixtures also affect drying and baking in the curing oven.

An excessively large fixture absorbs heat itself.
A fixture covering the workpiece prevents hot air from reaching it easily.
Closely packed fixtures impair airflow inside the oven.

This may cause the following problems.

• Insufficient drying
• Insufficient curing
• Uneven gloss
• Uneven temperature
• Longer drying time
• Energy losses
• Insufficient workpiece temperature

When checking curing oven conditions, include the fixture rather than checking the workpiece alone.

In a coating line, fixtures pass through the oven together with the workpieces.
Fixture shape, weight, and arrangement therefore also relate to drying quality.

8. Hanging Methods Change Coating Efficiency

Even for the same workpiece, coating efficiency changes with the way it is hung on the fixture.

For example, is the coated surface oriented so that the operator can see it easily?
Is the angle suitable for gun access?
Is spacing between workpieces sufficient?
If interior or rear surfaces need coating, can the operator reach them comfortably?

Poor hanging methods require unnecessary operator movements.

• Moving around the workpiece to coat it
• Spraying at awkward angles
• Repeatedly changing grip
• Spraying at close range
• Touching up difficult areas at the end

Such work leads to quality variation and operator burden.

Fixture design requires checking on the shop floor how to hang the workpiece for the easiest coating.

9. Fixtures Also Relate to Paint Waste

Poor fixtures can increase paint waste.

For example, poor workpiece orientation makes paint less likely to deposit on the workpiece.
Unsuitable spacing between workpieces increases overspray.
A fixture obscuring the coating surface increases corrective spraying.
Poor grounding reduces transfer efficiency in electrostatic coating.

Paint consumption increases as a result.

Improving fixtures can raise transfer efficiency and reduce paint waste.

Fixtures relate to paint costs as well as quality.

10. Fixture Accuracy Becomes Even More Important in Robotic Coating

Fixtures become even more important in robotic coating.

A robot follows the same path each time.
Unless workpieces occupy the same position every time, coating results will vary.

With manual coating, operators can observe and adjust as they work.
With robots, however, workpiece position errors directly lead to quality defects.

Fixtures for robotic coating need to meet the following conditions.

• The workpiece can be secured in the same position each time
• The workpiece does not sway
• The fixture does not interfere with the robot arm
• The fixture does not restrict the gun angle
• Grounding is stable
• The fixture does not obscure the surface to be coated
• Easy to clean
• Incorrect setup is unlikely

When introducing robotic coating, fixture conditions need to be checked before the robot itself.

Automation will not be stable unless fixtures are stable.

11. Fixtures Also Relate to Product Design

Fixture problems sometimes cannot be solved within the coating process alone.

The product has no hanging holes.
There is nowhere to hold it.
Areas where coating is prohibited overlap with holding positions.
The shape is complex, so fixtures obscure surfaces to be coated.
An unfavorable center of gravity causes the product to tilt when hung.
Fixture marks appear in visible areas after coating.

In these cases, coatability needs to be considered at the product design stage.

Designing products for easy coating can be called Design for Coating.
It means product design that is friendly to the coating process.

Fixture design is not solely a coating shop issue.
Product design, production engineering, quality assurance, and coating operations should work together on it.

12. Fixture Management Should Be Standardized

Fixture condition changes with continued use.

Coatings accumulate.
Fixtures bend.
They wear.
Contact areas deteriorate.
Grounding deteriorates.
Workpiece holding areas widen.
Operators modify fixtures.

Fixtures therefore need management.

The following items should be managed.

• Fixture number
• Products for which the fixture is used
• Number of uses
• Cleaning intervals
• Stripping intervals
• Electrical continuity checks
• Deformation checks
• Damage checks
• Storage location
• Disposal and replacement criteria

Without proper fixture management, quality varies between fixtures even for the same product.

Fixtures are equipment that wears out.
Periodic inspections and standardization are necessary.

13. Common Fixture Challenges in Vietnamese Factories

Vietnamese factories are prone to the following fixture challenges.

Improvised fixtures are made on the shop floor.
There are no fixture design criteria.
Fixtures that obscure coating surfaces are used.
Heavy fixtures place a significant burden on operators.
Workpiece position changes each time.
Fixture continuity is not checked.
Coating buildup impairs grounding.
Fixture cleaning and stripping intervals are not defined.
Fixture storage is not organized.
Fixture accuracy is not assessed when introducing robots.

Coating quality will not be stable under these conditions.

Fixtures need to be managed as essential coating process equipment, rather than small accessories.

14. Basic Items to Check on Fixtures

The following items provide a practical approach to checking fixtures.

1. Positioning

Check whether the workpiece can be secured in the same position each time.

2. Holding strength

Check whether the workpiece sways during coating, conveyance, or drying.

3. Coatability

Check whether the fixture obscures coating surfaces or restricts gun angles.

4. Grounding

Check electrical continuity for electrostatic coating and powder coating.

5. Workability

Check whether loading and removal are easy and whether operators are burdened.

6. Safety

Check for pinch points, falling hazards, heavy components, and sharp edges.

7. Drying performance

Check whether the fixture obstructs hot air in the curing oven or absorbs excessive heat.

8. Ease of cleaning

Check whether coating buildup is easy to clean or strip.

9. Durability

Check whether the design resists deformation, wear, and damage.

10. Standardization

Check whether fixture numbers, applicable product numbers, cleaning intervals, and replacement criteria are defined.

15. The Value of Fixture Improvement According to CoatureVietnam

CoatureVietnam does not regard fixtures as merely workpiece holders.

Fixtures determine coating quality.
Fixtures influence the burden on operators.
Fixtures support grounding in electrostatic coating and powder coating.
Fixtures support accuracy in robotic coating.
Fixtures also relate to paint waste and drying quality.

CoatureVietnam checks fixtures from the following perspectives.

• Whether the workpiece is held stably
• Whether coating surfaces are obstructed
• Whether operators can handle the fixture comfortably
• Whether grounding is established
• Whether coating buildup is causing quality defects
• Whether accuracy is sufficient for robotic operation
• Whether rules exist for cleaning, storage, and replacement

This puts CoatureVietnam’s valued principle, “Coating the Future with Science and Care”, into practice.

Science means checking fixture positioning, electrical continuity, coating surfaces, drying performance, and repeatability to stabilize quality.
Care means creating an environment where operators can produce good quality safely and comfortably without relying on awkward postures or compensation by feel.

Summary

Fixtures are more than simple tools for hanging workpieces.

Fixtures are essential equipment that determines coating quality.

Poor fixtures cause workpiece positions to shift.
Coating surfaces are obscured.
Workpieces sway.
Grounding deteriorates.
Film thickness becomes uneven.
Areas are left uncoated.
Drying becomes uneven.
Operator burden increases.
Robotic coating becomes unstable.

Fixtures therefore need to be designed, managed, and improved.

Items to examine include positioning, holding strength, coatability, grounding, workability, safety, drying performance, ease of cleaning, durability, and standardization.

CoatureVietnam regards fixtures as essential coating process equipment and proposes improvements that stabilize quality, reduce operator burden, support automation, and reduce paint waste.