AS9100 and CNC Simulation

AS9100 is the standard most precision machining subcontractors know primarily as a certification requirement: something audited annually, maintained by the quality function, and associated with a specific set of documented procedures covering material receipt, inspection, nonconformance handling, and delivery. It is also, at its core, a standard about process control — about demonstrating, with objective evidence, that every step in the production of an precision component was controlled, repeatable, and traceable.

The CNC machining process sits squarely within this framework. AS9100 Rev D Clause 8.5 requires organizations to implement production under controlled conditions, which includes the use of suitable equipment, the availability of documented information defining characteristics of the product, and the implementation of monitoring and measurement activities at appropriate stages. For a precision machining operation, "controlled conditions" means that the program running on the machine has been verified before it runs — not assumed to be correct, not reviewed informally by whoever is available, but verified against a defined standard and documented.

Most precision machining subcontractors have some form of program review in place. What they often do not have is a systematic, documented verification step that produces objective evidence of the review — the kind of evidence an auditor can examine, a customer can request, and a quality engineer can point to when a nonconformance investigation asks what controls were in place before that program ran on that part. G-code simulation, used as a formal verification step rather than an informal check, fills exactly this gap.

This article looks at where CNC simulation intersects with AS9100 process control requirements, why the intersection matters for subcontractors specifically, and what changes — in audit readiness, customer confidence, and supply chain positioning — when simulation becomes part of the documented production process rather than an optional pre-run check.

What AS9100 Actually Requires of the Machining Process

Controlled conditions are not the same as careful operators

The language of AS9100 Clause 8.5.1 — "controlled conditions" for production — is intentionally broad, but auditors and customers interpret it in a specific direction for CNC machining: the process must be defined, implemented, and monitored in a way that makes it repeatable and its outputs predictable. A process where the safety of each production run depends on the experience and availability of specific individuals is, by this definition, not fully controlled — it is managed.

The distinction matters practically. A managed process produces good results when the right people are present and paying attention. A controlled process produces consistent results regardless of who is running it, because the controls are built into the process itself rather than carried by the individuals executing it. For CNC machining on structural components, the gap between managed and controlled is often most visible at three specific points:

• Program release: Under what documented criteria is a G-code program considered verified and approved to run on the machine? If the answer is informal review by whoever is senior and available, the process is managed. If the answer is completion of a defined simulation check against specific pass/fail criteria — fixture clearances, probing cycle validation, feed rate analysis — with a record of the result, the process is controlled.
• Setup verification: How is it confirmed that the machine, workholding, and tooling configuration for a given job matches the configuration the program was written for? Informal setup checks by experienced operators are managed. A documented comparison — including simulation of the actual fixture geometry being used — is controlled.
• In-process measurement: When probing cycles run during machining to set origins or check dimensional compliance, how is it verified that those cycles are correct before they execute? Trusting the CAM-generated macro without simulation is managed. Verifying the probe approach path and cycle logic in simulation, with a record, is controlled.

Where simulation output maps to AS9100 clause requirements

The output of a G-code simulation session — the verification record it produces — maps directly to several AS9100 clause requirements in ways that informal program review cannot:

• Clause 8.5.1 (Controlled production conditions): A simulation record demonstrating that the program was run against the actual machine model, fixture geometry, and tooling configuration before production constitutes objective evidence of controlled pre-production verification. This is the clause most directly served by systematic simulation.
• Clause 8.5.2 (Identification and traceability): Simulation records tied to specific program revisions, part numbers, and job orders establish traceability between the verified program version and the parts produced from it. If a nonconformance investigation asks which program version ran on a specific batch, and whether that version was verified before production, a simulation record answers both questions directly.
• Clause 8.6 (Release of products and services): The standard requires objective evidence of conformity with acceptance criteria before product release. For machined precision components, conformity begins with the program that produced them. A simulation-based analysis of residual stock against the CAD model — showing that no material remains where the drawing requires absence of it, and that no material has been removed beyond the specified envelope — is pre-production conformance evidence at the process level.
• Clause 10.2 (Nonconformance and corrective action): When a nonconformance occurs, the investigation must trace the failure to its root cause and demonstrate that corrective action addresses it systemically. A shop that can show simulation records for the program version that produced the nonconforming part — and can compare it to the verified simulation for the corrected version — has a documented corrective action trail that satisfies both the investigative and preventive action requirements of this clause.

Why This Matters More for Subcontractors Than for OEMs

The audit exposure is different at tier 2 and tier 3

Large manufacturing companies and tier-1 primes operate AS9100 quality management systems that have accumulated years of audit history, corrective action records, and process improvement documentation. Their quality functions have dedicated staff, mature surveillance programs, and established relationships with their registrars. When an auditor asks for evidence of controlled machining processes, they can produce layered documentation from multiple independent systems.

a precision subcontractor at tier 2 or tier 3 typically operates a leaner quality function — often one or two people covering the entire scope of the QMS, with direct responsibility for maintaining certification, handling customer audits, managing supplier oversight, and supporting production simultaneously. In this environment, the quality of audit evidence for any given process is often determined by how much that process has been formally documented versus how much it relies on experienced people doing the right thing consistently.

CNC program verification is a specific area where the documentation gap is common. Many subcontractors have a written procedure that describes program review in general terms — programs are reviewed before use, changes are approved, operators are trained — but the records of individual program verifications are sparse or absent. The procedure exists; the objective evidence that it was followed for each specific job does not.

This is not typically a problem when audits go smoothly and customers are satisfied. It becomes a problem in two situations that precision machining subcontractors encounter with some regularity: a customer quality audit that goes deeper than the certification audit, and a nonconformance investigation that asks for process evidence at the program level. In both cases, the subcontractor needs to produce records that demonstrate the machining process was controlled — and if those records do not exist, the response is improvised rather than documented.

Customer audits are asking harder questions than registrar audits

AS9100 registrar audits verify that a quality management system exists and is being followed at a systemic level. Customer source surveillance audits — particularly from tier-1 primes and defense contractors — often go significantly deeper into specific processes, with engineers who understand CNC machining asking targeted questions about how programs are validated before production runs begin.

Questions that arise in these audits include: how does the shop verify that the program accounts for the actual fixture configuration, not just the nominal one? What is the documented verification step for probing macros before they run on a part? How are feed rate conditions validated against the material removal envelope, particularly at re-entrant features? How is residual stock conformance confirmed before the part is unloaded?

These questions have technically correct answers that most experienced programmers know how to give verbally. They have documented answers only if the shop has a verification step that produces records — and systematic G-code simulation is the most direct way to generate those records as a natural output of the existing programming workflow, rather than as a separate documentation burden.

The Four Verification Points That Generate AS9100-Relevant Evidence

For 3-axis machining of structural precision components, there are four specific simulation checks that produce process conformance evidence directly relevant to AS9100 controlled condition requirements. Each addresses a distinct risk point in the machining process and generates a record that answers a specific audit or investigation question.

1. Fixture clearance verification

A simulation run against the actual fixture geometry — with clamps, vises, locating pins, and strap positions modeled as they will be in production — produces a verified clearance record for that specific setup configuration. This record answers the question: was the program confirmed to be collision-free against the workholding used for this job, not just against nominal geometry? For multi-setup operations where the part is repositioned between faces, the record covers each setup independently, with the datum references verified for each repositioning.

2. Probing cycle validation

Simulation of in-machine probing macros — workpiece zeroing cycles and mid-process dimensional measurement cycles — produces a verification record that the probe approach paths are collision-free and that the macro logic will produce the intended measurement result. For AS9100 purposes, this addresses the controlled condition requirement for measurement and monitoring activities: the measurement tool and its operating cycle were verified before they were used to establish the datum from which all subsequent cuts were referenced.

3. Feed rate and material removal analysis

An instantaneous material removal volume analysis generates a feed rate optimization record showing where the program's commanded feed rates are appropriate for the actual cutting engagement conditions and where they create over- or under-load conditions. For AS9100 process control purposes, this is evidence that the program parameters were validated against the actual machining conditions, not just accepted as CAM output without verification. In the context of a nonconformance investigation involving tool breakage or surface finish failure, this record is the starting point for root cause analysis at the program parameter level.

4. Residual stock and geometric conformance analysis

A three-dimensional color-map comparison between the CAD nominal model and the simulated machined state produces a pre-production conformance record at the geometric level: evidence that the program, if executed correctly, will produce a part within the specified material removal envelope. This addresses the AS9100 Clause 8.6 requirement for objective conformance evidence — specifically the pre-production portion of it, which confirms that the process capable of producing a conforming part before the first production unit is committed.

Looking Ahead: IA9100 and the Direction of Travel

AS9100 is currently undergoing revision. The International Aerospace Quality Group has been working toward a successor standard — expected to be designated IA9100 — with publication anticipated in 2027. While the final requirements are not yet public, early IAQG communications indicate the revised standard will place increased emphasis on product safety requirements, risk-based thinking applied more rigorously at the process level, and information security for quality management system data.

The direction of travel is toward more documented process control, not less. The informal verification practices that have been acceptable under AS9100 Rev D in lower-risk machining contexts are likely to face greater scrutiny under a standard that explicitly ties risk management requirements to individual process steps. For CNC machining of structural precision components, this means that the gap between informal program review and documented simulation-based verification is likely to become more visible in future audit cycles.

Subcontractors who establish systematic simulation as part of their documented process now are not just improving their current audit position. They are building the process infrastructure that aligns with where the standard is heading — and demonstrating to customers that their quality management approach is ahead of the compliance curve rather than reactive to it.

The Practical Starting Point

For most precision machining subcontractors, implementing G-code simulation as a formal process control step does not require restructuring the quality management system. It requires defining, in a written procedure, what the simulation check covers, what constitutes a pass, who is authorized to approve the simulation record, and how the record is retained and linked to the job traveler and part traceability documentation.

The simulation itself — the actual verification work — is done in the programming workflow, where it already belongs. The formalization is in the record: making explicit that the check was done, what it covered, and what the result was. This is the difference between a verification activity that happened and a verification activity that can be demonstrated to have happened — and in an AS9100 context, that distinction is the entirety of what an audit is designed to determine.

For a subcontractor where the quality function is one or two people managing a broad scope, the value of this formalization is also operational: it creates audit evidence as a natural output of the programming process, without requiring the quality team to conduct separate verification activities. The programmer runs the simulation. The record is retained. The audit question is answered before it is asked.