How Can a Buyer Test Whether Manufacturer Capacity Supports CTQs?

<h2 id="how-to-test-manufacturer-capacity-for-ctqs"><strong>How Can a Buyer Test Whether Manufacturer Capacity Supports CTQs?</strong></h2>

<p>A buyer can test capacity by mapping each critical-to-quality characteristic to a stable process step, a measurement method, and a monitoring or reaction rule. The relevant question is not how many machines a manufacturer owns. It is whether the proposed route can produce the released geometry for the stated lot while preserving datum control, tool access, inspection coverage, and traceability. Capacity evidence should therefore connect equipment, people, material flow, and quality records to the specific part.</p>

<h3 id="start-with-feature-risk"><strong>Start with Feature Risk</strong></h3>

<p>List functional interfaces, datum surfaces, thin sections, deep features, threads, and surface requirements. For each item, state the consequence of drift and the evidence needed to detect it. A ring with an internal profile may need the profile, mating face, and circular relationship reviewed together. Treating only the largest diameter as the CTQ can hide a location or runout problem.</p>

<p>Ask the supplier to identify the setup and datum used for each CTQ. The answer should state how the part is located, what supports it, and when the feature is measured. If a secondary setup is required, the supplier should explain how the datum is transferred and verified. This is process evidence, not a request for proprietary programming.</p>

<h3 id="separate-equipment-capacity-from-process-capacity"><strong>Separate Equipment Capacity from Process Capacity</strong></h3>

<p>Equipment capacity covers envelope, spindle or tooling compatibility, and available production time. Process capacity also includes fixture availability, operator coverage, tool-life controls, inspection access, outside processing, and the time required for records and approvals. A machine may fit a part while the complete route cannot meet the requested lot or inspection schedule.</p>

<table><thead><tr><th>Capacity question</th><th>Evidence to request</th><th>What it does not prove</th></tr></thead><tbody><tr><td>Can the machine reach the features?</td><td>Envelope and access review tied to the drawing</td><td>Finished-part tolerance capability</td></tr><tr><td>Can the setup repeat?</td><td>Fixture revision, datum plan, and first-piece method</td><td>Every future lot will be identical</td></tr><tr><td>Can the lot be inspected?</td><td>Measurement access, equipment, and sample plan</td><td>Acceptance without agreed criteria</td></tr><tr><td>Can the schedule hold?</td><td>Milestones, bottlenecks, and outside-process timing</td><td>A guaranteed date before inputs are released</td></tbody></table>

<h3 id="request-first-piece-and-trend-evidence"><strong>Request First-Piece and Trend Evidence</strong></h3>

<p>The first-piece plan should list nominal, tolerance, actual result, instrument or method, and measurement condition for every CTQ. For a lot, ask how the supplier will look for drift: time order, setup group, tool state, or another documented grouping. A trend is useful only when the characteristic and measurement state remain consistent. A generic statement that parts were inspected does not reveal whether the process is moving toward a limit.</p>

<p>Sampling should follow risk and the buyer's quality agreement. Some interfaces may need every-unit verification, while other dimensions may support an agreed sample. Ask what happens when a sample fails and how suspect units are isolated. Increasing sample size does not repair an unsuitable datum or an inaccessible feature.</p>

<h3 id="test-material-and-flow-constraints"><strong>Test Material and Flow Constraints</strong></h3>

<p>Capacity plans should identify the material form and condition, certificate timing, and any heat treatment or finish between machining and final inspection. Mixed material lots or delayed certificates can change both the schedule and the evidence package. Ask how parts are identified through outside operations and how replacements remain visible in the lot history.</p>

<h3 id="write-a-capacity-acceptance-question"><strong>Write a Capacity Acceptance Question</strong></h3>

<p>Use a sentence that can be checked: can the proposed route make the released revision for the defined lot, measure each CTQ in the specified state, provide the required records, and notify the buyer before a route-changing event? The manufacturer should answer with assumptions and evidence. The buyer then confirms open risks, adds controls where needed, and avoids treating a machine list as a finished-part guarantee.</p>