Manufacturing Change Control for Custom Parts: Drawings, Samples and Supplier Approval

Custom parts rarely remain unchanged forever. A designer adjusts a hole position, a material becomes unavailable, a supplier replaces a cutting tool, a coating source changes or inspection reveals that a tolerance needs clarification. Each change may be reasonable, but an uncontrolled change can create mixed revisions, assembly failures, undocumented process differences and disputes over which product was actually approved.

Manufacturing change control is the structured method used to propose, review, approve, implement and verify changes to a part or its production process. It protects the connection between engineering intent and the physical items delivered by the supplier.

This guide explains how to establish a manufacturing baseline, control drawings and CAD, manage supplier changes, distinguish deviations from permanent revisions, validate first articles, segregate inventory, preserve traceability and prepare a clear change package for custom CNC-machined, cast, molded, formed and 3D-printed parts.

What Is Manufacturing Change Control?

Manufacturing change control is a documented workflow that ensures a proposed change is evaluated before it affects delivered product. The workflow normally answers six questions:

1. What is changing?

2. Why is the change needed?

3. Which parts, assemblies, tools and documents are affected?

4. What risks does the change create?

5. Who has authority to approve it?

6. How will the new condition be verified and traced?

Change control is not intended to prevent improvement. It allows useful changes to happen without losing configuration, quality or accountability.

Why Change Control Matters for Custom Parts

A custom component is defined by more than its nominal 3D shape. Its performance may depend on material grade, temper, heat treatment, datum relationships, surface finish, coating thickness, tool orientation, molding gate, casting porosity control, print orientation, assembly torque, inspection method and packaging.

A seemingly small change can affect:

• Fit with mating components.

• Structural strength or fatigue life.

• Corrosion resistance.

• Sealing or pressure tightness.

• Electrical conductivity or insulation.

• Cosmetic appearance.

• Thermal behavior.

• Regulatory or customer documentation.

• Service parts and field interchangeability.

• Cost, lead time and tooling life.

Without change control, a team may discover a problem only after parts reach assembly, finishing or customers. The cost of sorting and rework then exceeds the cost of reviewing the change properly.

Establish the Approved Manufacturing Baseline

Before changes can be controlled, the team needs an approved baseline: the specific combination of documents, product requirements and process conditions that defines acceptable production.

A baseline may include:

• Part number and revision.

• Released 3D CAD model.

• Controlled 2D drawing.

• Material specification and condition.

• Bill of materials for assemblies.

• Approved finish, color and texture.

• Critical-to-quality characteristics.

• Manufacturing process and approved supplier location.

• Tooling, fixture or mold identification.

• Approved sample or first-article report.

• Inspection plan and measurement method.

• Packaging, labeling and traceability requirements.

• Customer-specific or industry requirements.

The baseline should be unambiguous. If the drawing says Revision C but the purchase order links to a Revision B model, the supplier does not have a reliable manufacturing definition.

3D CAD and 2D Drawings Have Different Roles

The 3D model usually defines the complete nominal geometry. The drawing communicates requirements that geometry alone does not fully express, such as tolerances, datums, materials, finishes, notes, inspection requirements and revision history.

For reliable control:

• Use the same part number and revision on related files.

• State whether the 3D model or drawing governs nominal geometry.

• Identify model-based definition requirements if no conventional drawing is used.

• Avoid emailing an updated model with the old filename.

• Remove obsolete files from active supplier portals and work instructions.

• Include a change summary with every release.

• Preserve prior revisions in a read-only archive.

Changing CAD without updating the drawing can leave tolerances and notes attached to the wrong geometry. Updating a drawing without sending the corresponding model creates the opposite problem.

Revision Control Basics

A revision identifies an approved configuration of a document or part. The revision system can use letters, numbers or another controlled convention, but it should be consistent.

Each released revision should record:

• Revision identifier.

• Release date.

• Description of change.

• Change authorization reference.

• Person or function approving the change.

• Effective condition or serial/lot boundary when applicable.

Avoid descriptions such as “updated drawing” or “minor changes.” A useful revision note identifies the affected feature and the nature of the change without requiring the reader to compare every dimension manually.

Revision control is not the same as file version history. A cloud drive may save dozens of drafts, but only a formally approved revision should authorize manufacturing.

Engineering Change Request, Order and Notice

Organizations use different names, but three concepts are common.

Engineering Change Request

A request describes a proposed change and why it should be considered. It is an input to review, not permission to manufacture.

Engineering Change Order

An engineering change order, or ECO, is the approved instruction that defines which documents and configurations will change. It normally includes approvals and an implementation plan.

Engineering Change Notice

A notice communicates that the approved change is released or effective. It tells affected teams and suppliers what action is required.

Small companies may combine these steps in one form. The important distinction is between proposal, approval and implementation.

Common Types of Product Changes

Geometry Changes

Examples include a relocated hole, thicker rib, larger radius, adjusted clearance or modified thread. Geometry changes require updated CAD and usually an updated drawing.

Tolerance and GD&T Changes

A nominal feature may remain identical while its acceptable variation changes. Tightening a tolerance can alter process capability, tooling, cycle time and inspection cost. Relaxing one can influence fit and interchangeability.

Material Changes

Changing alloy, resin grade, temper, hardness, supplier or recycled content can affect strength, stability, machinability, mold shrinkage, finish and certification. “Equivalent material” should be defined by an approved specification, not by informal similarity.

Finish and Coating Changes

Coating chemistry, thickness, pretreatment, color, gloss and masking can affect dimensions, appearance, adhesion, corrosion resistance and electrical contact.

Assembly Changes

Fasteners, adhesives, inserts, torque, cure schedule, sequence and fixtures can change joint performance even when component drawings remain unchanged.

Documentation-Only Changes

Correcting a spelling error may have no product impact. Clarifying an ambiguous note may affect product. Classify the actual consequence rather than assuming every text change is administrative.

Common Types of Supplier and Process Changes

The supplier may need to change how the same drawing is produced. Examples include:

• Manufacturing at a different facility.

• Moving work to a sub-tier supplier.

• Replacing a machine or production line.

• Changing CNC program strategy or setup sequence.

• Replacing a fixture, mold insert, die component or cutting tool type.

• Changing heat treatment, plating, painting or passivation source.

• Modifying a casting gate, vent or runner.

• Changing an injection-molding gate or process window.

• Changing 3D-print build orientation, machine model or post-cure.

• Changing raw-material manufacturer or stock form.

• Revising inspection equipment, program or sampling.

• Changing cleaning, handling or packaging.

• Repairing or refurbishing production tooling.

Not every process adjustment needs customer approval. The quality agreement or purchase terms should define notification thresholds based on risk.

Customer-Directed vs Supplier-Initiated Changes

Customer-directed changes originate from design, quality, cost or product teams. The customer controls the released product definition and should provide the updated technical package.

Supplier-initiated changes originate from manufacturability, obsolescence, capacity, process improvement, tooling repair or supply-chain conditions. The supplier should submit a change request before implementation when the change can affect fit, form, function, reliability, appearance, traceability or an agreed process condition.

A supplier should not silently interpret a difficult feature away. A customer should not expect a supplier to manufacture to an informal phone discussion without controlled documents. Both parties need a written approval trail.

Change Classification by Risk

A risk-based classification determines the review and validation effort.

The table is an example framework, not a universal standard. Each company should define classes appropriate to its products and obligations.

Evaluate Form, Fit, Function and Risk

A change review should consider more than whether the new part looks similar.

Form

Does the change affect geometry, surface, color, texture, mass or visible appearance?

Fit

Does it affect interfaces, tolerance stacks, assembly sequence, fastener engagement, seals, connectors or interchangeability?

Function

Does it affect load, motion, fluid flow, heat, electrical behavior, wear, durability, safety or service life?

Manufacturing and Quality Risk

Could it change capability, inspection, porosity, distortion, burrs, contamination, traceability or defect detection?

Supply and Lifecycle Risk

Does it create obsolete inventory, replacement-part incompatibility, lead-time impact, a new single source or loss of repairability?

A good review documents the reasoning. A checkbox marked “no impact” without analysis is weak evidence.

Permanent Change, Temporary Deviation and Waiver

These terms are often confused.

Permanent Change

A permanent change updates the approved baseline. New documents receive a revision, and future production follows the new condition.

Temporary Deviation

A deviation authorizes production or delivery outside the current baseline for a limited quantity, lot or time. It defines the nonconforming or alternate condition, risk, controls and expiration.

Waiver or Concession

A waiver or concession accepts a known nonconforming condition, often for already-produced material. Terminology varies, so companies should define it in their quality system.

Temporary authorization should never become an undocumented permanent process. Include an expiration, quantity limit and disposition plan.

What a Supplier Change Request Should Contain

A complete supplier change request should state:

• Supplier name and manufacturing location.

• Customer and supplier part numbers.

• Current revision and proposed condition.

• Clear description of the change.

• Reason for the change.

• Whether the change is temporary or permanent.

• Proposed implementation date.

• Affected tools, processes, sub-tier suppliers and facilities.

• Inventory and work-in-progress status.

• Risk assessment.

• Comparison data or supporting evidence.

• Proposed validation plan.

• Cost and schedule impact.

• Requested customer decision date.

Attach marked drawings, photos, process-flow updates, material data, sample results or simulation as relevant. Do not force the reviewer to infer what changed from two large CAD files.

Use Redlines and Change Maps

A redline or change map highlights each affected feature. It improves review speed and reduces the chance that a secondary change is missed.

Useful formats include:

• Ballooned drawing with old and new dimensions.

• Before-and-after section views.

• CAD comparison screenshots.

• A table listing feature, old requirement, new requirement and reason.

• Updated process-flow diagram with changed steps identified.

• Photographs of tool or fixture modifications.

If one change creates downstream updates, show the chain. For example, a thicker wall may change mass, molding cycle, sink risk, cooling, packaging quantity and assembly force.

Drawing and CAD Release Checklist

Before issuing a new revision, verify:

• Part number and revision match across files.

• The model and drawing describe the same geometry.

• Units and scale are clear.

• Material and condition are correct.

• General tolerances remain appropriate.

• Datums and GD&T still reflect assembly function.

• Finish and coating notes are current.

• Threads, inserts and hardware are defined.

• Critical characteristics are identified.

• Revision notes are specific.

• Obsolete notes and dimensions are removed.

• Referenced specifications use the intended revision.

• The approval record is complete.

Release all related files as one controlled package whenever possible.

Purchase Orders Must Reference the Correct Revision

Even a perfectly released drawing can fail if the purchase order references an obsolete revision or none at all. The order should identify:

• Part number.

• Revision.

• Quantity.

• Required delivery.

• Applicable specifications.

• Inspection and documentation requirements.

• Approved deviation or change authorization when relevant.

Blanket orders and scheduled releases need special attention. State the effective revision for open quantities and whether the supplier must stop, convert or complete old-revision work.

Control the Effective Date and Cut-In Point

Approval does not by itself define when the new condition starts. Establish an effective cut-in rule such as:

• All orders placed after a defined date.

• First lot after approval.

• First serial number or date code.

• After existing inventory is consumed.

• Immediate stop and replacement of old revision.

• Phased implementation by product or region.

The cut-in decision should consider field interchangeability, service inventory, tooling readiness, test completion and business urgency.

For traceability, record the last old-revision lot and first new-revision lot. If revisions can be mixed safely, state that explicitly. If they cannot, require physical segregation.

Inventory and Work-in-Progress Disposition

A change can affect raw material, unfinished components, finished goods, assemblies, service stock and items in transit.

For each inventory group, decide whether to:

• Use as is.

• Rework to the new revision.

• Use under deviation.

• Restrict to specific applications.

• Return to supplier.

• Scrap through an authorized process.

Record quantities, locations and financial responsibility. Do not leave obsolete material on the production floor with an informal note; it can re-enter the supply chain months later.

Identification and Segregation

During transition, clearly identify revision status. Methods may include:

• Separate labeled containers.

• Controlled warehouse locations.

• Lot or serial numbers.

• Temporary color tags.

• Updated barcode or traveler.

• Physical marking on the part when permitted.

• Distinct certificates and packing lists.

The method should survive normal handling. A label on an outer carton is insufficient if parts are later separated and lose their identity.

First Article Inspection After a Change

A first article inspection confirms that a new or changed production setup can produce a part that meets specified requirements. It is often appropriate after:

• A design revision.

• New tooling or major tool repair.

• A manufacturing-location change.

• A new process or machine family.

• A long production interruption.

• A material or critical sub-tier change.

• A significant process-layout change.

The first article scope should match risk. A minor marking adjustment may need only focused verification. A new mold or facility may require a full dimensional report, material confirmation and functional tests.

First article approval is not the same as ongoing process capability. It shows that inspected samples conform under the sampled conditions.

Delta First Article vs Full First Article

A delta first article inspects the changed features and related characteristics. A full first article evaluates the complete drawing or product definition.

Use a delta approach when:

• The change is localized.

• Unchanged tooling and setups remain controlled.

• Risk analysis shows limited interaction.

• The customer accepts focused inspection.

Use a full approach when:

• The production location or major process changes.

• New tooling replaces the original.

• Several interacting features change.

• Traceability to the earlier baseline is weak.

• Customer or industry requirements call for full submission.

Document why the selected scope is adequate.

Dimensional Validation

Dimensional validation should cover the changed feature and any characteristics that could be influenced by the manufacturing change.

For example:

• A new fixture may affect datum relationships across multiple faces.

• A mold-gate change may affect shrinkage and warpage far from the gate.

• Heat-treatment-source change may affect distortion.

• A new print orientation may change hole location and flatness.

• A revised coating thickness may alter fits and threads.

Use a ballooned drawing and identify the measurement method. When results from different equipment disagree, review datum setup, probe access, filtering, temperature and measurement definition before deciding which result is correct.

Material and Process Validation

Depending on the change, evidence may include:

• Material certificate and heat/lot identity.

• Chemical composition or grade verification.

• Hardness or heat-treatment records.

• Coating thickness and adhesion.

• Surface roughness.

• Passivation or plating certificate.

• Print build and post-cure records.

• Casting X-ray or leak test.

• Mold-process parameters.

• Weld procedure or operator qualification where required.

• Cleaning and contamination results.

Certificates alone may not prove that the finished part meets functional needs. Combine documentation with testing appropriate to the risk.

Functional Revalidation

If a change can affect performance, repeat the relevant functional tests. Examples include:

• Assembly fit and insertion force.

• Static load or torque.

• Leak or pressure test.

• Thermal performance.

• Electrical continuity or insulation.

• Cycle life and wear.

• Drop or vibration performance.

• Chemical or environmental resistance.

• Cosmetic approval under controlled lighting.

Do not automatically repeat every historical test. Use the change-impact analysis to identify which requirements could be affected and justify the scope.

Capability and Production Trial

For high-volume or critical characteristics, conforming first articles may not be sufficient. A production trial can assess whether the changed process is stable and capable over time.

Review:

• Variation across cavities, tools, shifts or machines.

• Warm-up and steady-state conditions.

• Tool wear.

• Material-lot variation.

• Measurement-system suitability.

• Process parameters and alarms.

• Yield, rework and defect patterns.

The sample quantity and analysis method should be defined by the organization responsible for product quality. Do not claim capability from a handful of selected parts.

Approved Samples and Golden Samples

An approved physical sample can communicate appearance, texture, feel or assembly characteristics that are difficult to define completely on a drawing. It is useful for paint color, gloss, polishing, engraving or tactile response.

However, a sample has limitations:

• It may age, fade, corrode or become damaged.

• It represents one result, not the full tolerance range.

• It may not have complete material or process traceability.

• Different observers may judge it differently.

• It cannot replace measurable engineering requirements.

Control the sample with part number, revision, approval date, signatures, storage conditions and replacement schedule. Use objective specifications wherever practical.

Tooling Change Control

Molds, dies, fixtures, soft jaws, gauges and assembly tools influence the product. Maintain a tool record that includes:

• Tool identification and ownership.

• Approved drawing or design revision.

• Cavity or station identification.

• Maintenance and repair history.

• Modifications and approvals.

• Sample results after significant repair.

• Storage location and condition.

• Expected or measured life.

After welding, insert replacement, cavity repair or major refurbishment, inspect the characteristics that could be affected. A tool may appear restored while producing a shifted datum, flash or cosmetic mismatch.

CNC Program and Setup Changes

CNC programs frequently evolve to improve cycle time, tool life and chip control. Many program changes are normal supplier process control, but a change becomes customer-significant when it can affect an agreed characteristic or validated condition.

Risks include:

• Different datum pickup.

• Setup consolidation that changes positional relationships.

• Tool substitution that changes corner geometry or finish.

• New clamping force that distorts thin walls.

• A changed deburring path that affects edges.

• Reordered operations that release residual stress differently.

The supplier should maintain internal program revision, backup and approval controls even when customer notification is not required.

Casting and Molding Process Changes

For die-cast or molded parts, changes to gates, runners, vents, cooling, cavity inserts and process windows can influence internal and external quality.

Review potential effects on:

• Fill pattern.

• Weld or knit lines.

• Porosity.

• Shrinkage and warpage.

• Fiber orientation.

• Residual stress.

• Gate witness and appearance.

• Ejection marks.

• Dimensions across cavities.

• Cycle stability.

A tool repair that changes only steel geometry can still require new samples and dimensional or functional validation.

Additive Manufacturing Process Changes

3D-printed part properties can depend on machine, material batch, layer parameters, build orientation, nesting, support strategy and post-processing.

Evaluate changes to:

• Printer model or facility.

• Powder or resin specification.

• Reuse or refresh practice.

• Build orientation.

• Layer thickness.

• Exposure or energy parameters.

• Heat treatment or post-cure.

• Support removal.

• Surface finishing.

• Machining allowance.

The nominal CAD may be unchanged while strength, dimensional stability or surface condition changes materially.

Sub-Tier Supplier Change Control

The direct supplier remains responsible for controlling outsourced processes within the agreed supply chain. Plating, heat treatment, painting, material conversion, testing and special machining are common sub-tier activities.

The quality agreement should state:

• Which sub-tier changes require notification or approval.

• How approved sources are identified.

• What certificates and lot traceability are required.

• How nonconformities are communicated.

• Whether the customer may audit critical sub-tiers.

A supplier should not treat a new plating source as invisible simply because the purchase order remains with the same direct company.

Emergency Changes and Supply Disruptions

Material shortages, equipment failure, damaged tooling or logistics disruption can create urgent pressure to approve an alternative. Speed is important, but emergency status should not eliminate risk control.

Use an accelerated process that still documents:

• Reason for urgency.

• Proposed alternate condition.

• Risk assessment.

• Limited scope or quantity.

• Verification before shipment.

• Identification of affected product.

• Expiration and recovery plan.

• Required customer approval.

If full validation cannot be completed before use, state the residual risk and define containment. Do not describe an unverified substitution as equivalent merely to meet a schedule.

Communicating Changes Across Functions

A released change can affect engineering, purchasing, quality, planning, production, service, sales and logistics. The change owner should identify recipients and required actions.

A communication plan may include:

• Supplier acknowledgment.

• Updated purchase-order text.

• New inspection plan.

• ERP and bill-of-material update.

• Work-instruction revision.

• Tooling modification schedule.

• Inventory disposition.

• Service-parts review.

• Customer notification.

• Training for operators and inspectors.

Silence is not acknowledgment. Require confirmation from functions that must implement the change.

Avoiding Mixed Revisions

Mixed revisions occur when old and new configurations lose identity. Prevent them through:

• Clear cut-in rules.

• Physical segregation.

• Updated travelers and labels.

• Revision on certificates and packing lists.

• Supplier shipment authorization.

• Receiving inspection of transition lots.

• ERP controls.

• Reconciliation of old inventory.

• First and last lot records.

If mixed revisions are functionally interchangeable, document that decision. If not, consider a visible marking or serial trace to protect assembly and service operations.

Change Control for Low-Volume Prototypes

Prototype teams often move quickly, but configuration control still matters. Without it, test results may be linked to the wrong CAD file.

For rapid iterations:

• Use a unique revision or build identifier for every manufactured version.

• Include the identifier on the purchase order and packing list.

• Mark each sample when possible.

• Record material and process differences.

• Do not overwrite the tested CAD file.

• Link test data to the exact sample configuration.

• Summarize what changed between builds.

The system can be lightweight, but it must preserve the relationship between design, sample and result.

Change Control for Production Parts

Production change control requires greater attention to inventory, capability, documentation and repeatability. Before approval, define:

• Implementation lot and date.

• Required qualification samples.

• Production-trial quantity.

• Inspection frequency during launch.

• Temporary containment.

• Capability or yield acceptance.

• Shipment release authority.

• Review point after initial deliveries.

Early production after a change may need increased inspection until evidence confirms stable performance.

Supplier Quality Agreement Topics

A quality agreement or purchase terms can prevent later disagreement by defining:

• Documents that form the product baseline.

• Order of precedence when documents conflict.

• Change-notification requirements.

• Approval authority.

• Restricted processes or sources.

• First-article triggers.

• Record-retention expectations.

• Traceability and lot control.

• Nonconformance and deviation workflow.

• Sub-tier control.

• Tool ownership and maintenance.

• Right of access or audit where applicable.

• Counterfeit and material-identity controls.

• Packaging and preservation.

The agreement should fit the risk and commercial relationship. Overly broad approval requirements can slow ordinary process improvement; vague requirements leave critical changes uncontrolled.

A Practical Change-Control Workflow

Step 1: Describe the Change

Identify current and proposed conditions using clear documents and redlines.

Step 2: Identify Affected Items

Review parts, assemblies, tools, programs, specifications, inventory and suppliers.

Step 3: Assess Risk

Evaluate form, fit, function, quality, compliance, service and supply impact.

Step 4: Define Validation

Choose dimensional, material, functional and production evidence appropriate to the risk.

Step 5: Approve or Reject

Obtain authorization from the defined engineering, quality, commercial and customer functions.

Step 6: Release Controlled Documents

Issue the revised model, drawing, specifications, process documents and purchase requirements.

Step 7: Control Inventory and Cut-In

Define disposition, segregation, first new lot and transition identification.

Step 8: Manufacture and Verify

Produce samples, complete inspection and tests, and resolve deviations.

Step 9: Authorize Production Shipment

Release the changed configuration only after required evidence is accepted.

Step 10: Review Effectiveness

Monitor early production, assembly feedback, defects and field performance.

Change-Control Checklist for Buyers

Before sending a change:

• Confirm the business and technical reason.

• Update both model and drawing.

• Mark every affected feature.

• Review mating parts and tolerance stacks.

• Identify open orders and inventory.

• Define old/new interchangeability.

• Request cost and lead-time impact.

• Define sample and validation needs.

• Set the desired implementation date.

Before approving supplier implementation:

• Review supplier feasibility and risk.

• Confirm tooling and process readiness.

• Approve updated quotation if required.

• Verify first-article scope.

• Confirm material and finish documentation.

• Approve inventory disposition.

• Establish transition identification.

• Record formal approval.

After implementation:

• Verify first new-revision shipment.

• Confirm drawing revision on reports.

• Review inspection and functional results.

• Monitor assembly and quality feedback.

• Close temporary containment when evidence supports it.

• Archive the complete change record.

Change-Control Checklist for Suppliers

Before requesting a change:

• Describe the current and proposed process.

• Explain why the change is needed.

• Identify product and documents affected.

• Evaluate risk and sub-tier impact.

• Check inventory and work in progress.

• Propose samples and validation.

• State cost and schedule effects.

• Wait for required written approval.

During implementation:

• Update internal programs and instructions.

• Train affected personnel.

• Segregate revisions.

• Record tool and process changes.

• Produce traceable validation samples.

• Complete agreed inspection and tests.

• Do not ship before release authorization.

After implementation:

• Identify the first changed lot.

• Include revision on documentation.

• Monitor process and defects.

• Report unexpected effects promptly.

• Retain evidence according to agreement.

Common Change-Control Mistakes

Manufacturing From an Email Attachment

An engineer emails a new model, but the approved portal and drawing remain unchanged. The supplier no longer knows which instruction governs.

Reusing the Same Filename

New geometry is saved over an old file without a revision. Earlier test and quotation records become ambiguous.

Treating a Supplier Substitution as Equivalent Without Evidence

The material or coating has a similar name, but critical properties, certifications or appearance differ.

Approving a Sample Without Defining the Baseline

The sample looks acceptable, but its material, process settings or drawing revision are not recorded.

Forgetting Open Inventory

The new design is approved while old parts remain in transit, at finishing or in the warehouse.

Validating Only the Changed Dimension

A process change affects related datums, warpage or surface condition, but inspection covers only one edited callout.

Allowing a Temporary Deviation to Continue Indefinitely

The quantity or expiration is not controlled, so the exception quietly becomes the production standard.

Skipping Supplier Acknowledgment

The customer releases a revision but does not confirm that purchasing, planning and production at the supplier received it.

Information to Include With a Revised RFQ

If the part is being re-quoted after a change, provide:

• Updated 3D CAD and 2D drawing.

• Part number and new revision.

• Redline or change summary.

• Current approved process and requested alternative.

• Existing tooling status and ownership.

• New prototype and production quantities.

• Inventory and open-order information.

• Critical feature and inspection changes.

• Functional test requirements.

• Material, finish and documentation changes.

• Target sample and production dates.

• Required first-article or validation package.

The supplier can then separate one-time engineering or tooling cost from recurring part cost and identify the true schedule impact.

For an accurate initial package, use the CNC Machining RFQ Checklist. To request a DFM review or revised quotation, send the controlled files through the Aluprototype request-a-quote page.

Frequently Asked Questions

Does every drawing change require a new part revision?

Every released change should be traceable, but whether the part revision changes depends on the organization's configuration rules and product impact. Administrative corrections may use document revision control, while geometry, tolerance, material and finish changes normally require clear product-revision control.

Can a supplier change a machine without customer approval?

It depends on the quality agreement, risk and validation status. A routine move between equivalent controlled machines may be internal supplier control, while a facility, process type, validated line or capability change may require notification and approval. Define the threshold before production.

What is a supplier change request?

It is a formal proposal describing a supplier-initiated change, its reason, affected products, risk, timing, inventory impact and validation plan. It is not authorization to implement until the required customer approvals are complete.

What is the difference between a deviation and a revision?

A revision permanently changes the approved baseline. A deviation permits a limited temporary departure from the baseline for a defined quantity, lot or time and should include controls and expiration.

When is a new first article required?

Common triggers include a design revision, new or repaired tooling, a manufacturing-location change, a significant process or material change, or a long production interruption. The required scope depends on product risk and customer requirements.

Is an approved golden sample enough to control quality?

No. A physical sample is helpful for appearance and feel but represents only one result and can age or become damaged. It should supplement drawings, measurable specifications and traceable process requirements.

How should old and new revisions be separated?

Use controlled inventory locations, labels, lot or serial identifiers, updated travelers and clear cut-in records. Define the last old-revision lot and first new-revision lot, and prevent loose parts from losing identity.

Can old-revision parts be used after a change?

Only after an authorized disposition determines that they are acceptable, reworkable or usable under deviation. The decision should consider interchangeability, performance, service needs and customer requirements.

How much validation is needed after a process change?

Validation should match the potential effect. It may range from focused inspection to a full first article, material verification, functional testing and production capability review. Document the risk analysis that justifies the scope.

Who should approve a manufacturing change?

Approval authority depends on the change. Product engineering, manufacturing, quality, purchasing, regulatory functions, the supplier and the customer may all have roles. The quality agreement or internal procedure should define who can release each class of change.

Conclusion

Manufacturing change control protects custom-part quality by keeping design intent, supplier processes, physical inventory and validation evidence aligned. It begins with a clear approved baseline and distinguishes a proposed change from an authorized one.

Reliable control requires matched CAD and drawing revisions, specific change descriptions, risk-based review, supplier notification rules, appropriate first-article and functional validation, controlled cut-in and traceable inventory. Temporary deviations need quantity and time limits; permanent changes need an updated baseline.

For prototypes, the system can be lightweight but must connect each sample to the correct design and test result. For production, it should also address capability, tooling, sub-tier suppliers, open inventory and early-production monitoring.

When sending a revised custom-part request, include the new CAD, drawing, redline, reason for change, affected quantity, inspection needs and implementation date. Clear change information helps the manufacturer respond quickly without guessing which condition is approved.