AirSprayTech Academy

Finishing Quality—From Spec to Sign-Off | Article 01 of 28

Quality Begins with the Specification

How to turn customer requirements, drawings, standards, and coating instructions into work the finishing line can understand and verify.

No Spec. No Standard. No Sign-Off.

The finishing line cannot meet a requirement nobody has clearly defined. Before the first part is cleaned, masked, sprayed, coated, cured, or inspected, the shop must know what success is supposed to look like.

There is an old temptation in finishing: get the parts moving and sort out the details later. The order arrives, production needs the work, and somebody says, “We have coated parts like these before.”

Maybe so. But “like these” is not a specification.

A professional finishing operation begins by translating the customer’s requirements into measurable shop-floor instructions. That means more than knowing the color and coating type. It means understanding the substrate, surface preparation, pretreatment, film thickness, appearance, cure, performance tests, inspection frequency, documentation, packaging, and final acceptance requirements.

What Is a Finishing Specification?

A finishing specification is the collection of requirements that defines how a product must be prepared, coated, inspected, documented, and accepted. Those requirements may be found in several different places.

• Customer purchase orders
• Engineering drawings and drawing notes
• Approved coating-system documents
• Product and process specifications
• Coating manufacturers’ technical data sheets
• Safety data sheets
• Customer quality manuals
• Industry test standards
• Approved samples, color standards, or appearance panels
• Written deviations or engineering changes

The problem is that these documents do not always arrive in one tidy package. Requirements may be scattered across a purchase order, drawing, email, technical data sheet, and customer manual. One document may also refer to another document that the shop has not received.

Start with the Order of Authority

When several documents apply to the same job, the shop needs to know which document controls when two requirements disagree. This is sometimes called the order of precedence.

For example, a coating manufacturer may recommend a particular film thickness, while the customer’s drawing requires a different range. The shop should not quietly choose one. The difference must be reviewed and resolved by an authorized party before production.

The governing order may vary by customer and contract, but it commonly includes documents such as:

1. Contract or purchase-order requirements: Commercial and quality requirements specifically accepted for the job.
2. Approved engineering drawings: Part-specific dimensions, masking, coating, color, appearance, and inspection notes.
3. Customer specifications: Requirements covering approved materials, processes, testing, and documentation.
4. Approved process instructions: The shop’s controlled method for performing the work.
5. Manufacturer instructions: Mixing, reduction, application, flash, bake, cure, storage, and safety information supplied with the coating or chemical.
6. Referenced test standards: The specified procedures used to measure or evaluate results.

Never assume that this example is the governing order for every customer. The correct order must come from the contract, customer, or approved quality system.

Turn Words into Measurable Requirements

A specification may contain dozens of instructions. Those instructions become useful when the shop converts them into a requirements matrix, traveler, control plan, inspection plan, or another controlled working document.

Each requirement should answer four questions:

• What must be done?
• How will it be controlled?
• How will it be inspected or tested?
• What record will prove it was completed?

Identify the Critical Requirements

Not every requirement carries the same risk. A small cosmetic variation on a hidden surface may not have the same consequence as inadequate coating thickness on a corrosion-critical part.

Critical requirements should be easy to recognize in the job documentation. They may include:

• Restricted or customer-approved coating materials
• Surface cleanliness and pretreatment requirements
• Minimum and maximum film thickness
• Masking boundaries and electrically conductive contact areas
• Color, gloss, texture, and approved appearance standards
• Cure temperature and time requirements
• Adhesion, impact, hardness, flexibility, or corrosion testing
• Special traceability and certification requirements
• Prohibited repairs or limitations on rework
• Customer inspection or hold points

Once identified, these requirements should follow the job from receiving through final release. They should not live only in an office file that the operator never sees.

Do Not Let Ambiguous Language Reach the Line

Words such as “adequate,” “uniform,” “smooth,” “fully cured,” and “free from defects” may sound clear until two people disagree about what they mean.

If appearance matters, define the viewing distance, lighting, viewing angle, approved sample, and surfaces that will be evaluated. If thickness matters, define the range, number of measurements, measurement locations, and method. If adhesion testing is required, identify the procedure, acceptance rating, and test frequency.

A measurable requirement gives production a target and gives quality a fair basis for acceptance. An ambiguous requirement gives everyone an argument after the parts are finished.

Control Revisions and Changes

Having the correct specification is only half the job. The shop must also make sure it is using the current revision.

Controlled documents should identify:

• Document title or number
• Revision level and revision date
• Customer and part number
• Approval status
• Effective date
• Who reviewed and approved the document
• Where obsolete copies are removed or marked

Changes made during production must also be controlled. A phone call may help explain a problem, but it does not provide dependable authorization for changing a customer requirement. Obtain written approval from the appropriate authorized person and attach that approval to the job record.

Create a Specification Review Record

The specification review does not need to be complicated, but it should be documented. A useful review record confirms that the appropriate people examined the requirements before the job was released.

Depending on the work, the review may involve sales, estimating, engineering, production, quality, purchasing, maintenance, and the finishing department.

• Customer and purchase-order identification confirmed
• Part numbers and current drawing revisions confirmed
• Coating materials and color standards confirmed
• Surface-preparation and pretreatment requirements confirmed
• Masking and plugging requirements confirmed
• Film-thickness requirements confirmed
• Cure requirements confirmed
• Required inspection and testing methods confirmed
• Sampling frequency and acceptance criteria confirmed
• Certification, traceability, and reporting requirements confirmed
• Packaging and handling requirements confirmed
• Open questions resolved before production release

The Practical Lesson

Quality does not begin with the inspector holding a gauge over a finished part. By then, most of the work—and most of the expense—has already happened.

Quality begins when the shop understands the requirement, confirms that it has the capability to meet it, and translates that requirement into instructions and controls that people can follow.

A finishing specification should never be treated as paperwork standing between the shop and production. It is the agreement that tells the shop what to build, tells the inspector what to verify, and tells the customer what may be accepted.

The first step toward sign-off is knowing exactly what you agreed to deliver.