Engineering Specifications and DMR Build for Medical Devices

Design Output to DMR — Where Theory Meets the Production Floor

ISO 13485 §7.3 and FDA 21 CFR 820.30 both require that design outputs be transferred to production in a controlled way. The bridge between design output and production is the Device Master Record (DMR) — the structured set of specifications, drawings, manufacturing instructions, packaging instructions, labeling, and quality acceptance criteria that defines how the device is built and inspected.

In well-run organizations, the DMR is a living, versioned, traceable object — typically held in PLM, drawn into MES for production execution, and audited as the authoritative source of "what we build."

In less-disciplined organizations, the DMR is a folder of PDFs that may or may not match what manufacturing actually does. That gap is the most common finding in MDSAP and KGMP audits of design transfer activities.

This guide covers the practical mechanics — what goes into engineering specifications, how the DMR is structured, when DFM/DFA reviews happen, and how Korea KGMP audits this area.

Engineering Specification Components

A complete engineering specification set for a medical device contains:

Mechanical Drawings (GD&T)

Drawings follow ASME Y14.5 (US) or ISO 1101 / 14405 (EU/global) Geometric Dimensioning and Tolerancing. Every dimension carries:

• Nominal value
• Tolerance (per drawing or per general tolerance note)
• Datum references
• Surface finish (where applicable)
• Material reference (linked to material specification)

Drawing release controls — title block, revision history, signatures — establish the legal authority of the document. A drawing without proper release controls is engineering reference, not a production specification.

3D CAD Models

Native CAD models (SolidWorks, NX, CATIA, Creo) serve as the source of truth for geometry. Drawings are derived. The 3D model itself is a controlled artifact — released, versioned, signed off.

A common configuration: CAD model is the authoritative geometry source; STEP file is the released exchange format for suppliers; PDF drawing with annotations is the human-readable specification.

Material Specifications

For each material used in the device:

• Material identifier (often a generic spec linked to approved suppliers)
• Composition or grade
• Mechanical / physical properties (where critical to performance)
• Biocompatibility class (ISO 10993 series compliance)
• Sterilization compatibility (where applicable)
• Approved supplier list cross-reference

Patient-contact materials warrant the most detailed specifications. A device with three patient-contact materials typically has three material specs plus three biocompatibility test summary references.

Electrical Schematics

For active devices, schematics released per IPC standards. Each component carries:

• Reference designator
• Value or part number
• Tolerance class
• Approved supplier (or supplier list reference)

For safety-critical components (those identified in ISO 14971 risk analysis), additional controls — second-source qualification, lot traceability requirements, incoming inspection criteria.

Software Specifications

For devices with software components:

• Software requirements specification (SRS)
• Architecture specification
• Module specifications
• Coding standards reference
• Build environment configuration
• Source code repository reference (with controlled access)

For SaMD or software-driven devices, the SBOM (Software Bill of Materials) is part of the released software specification set — see our SBOM Template Pack for FDA-aligned structure.

Packaging Specifications

For sterile devices, the packaging specification is part of the validated sterile barrier system:

• Primary package material and configuration
• Secondary package design
• Seal parameters (sealing temperature, dwell, pressure)
• Aging and shipping testing references
• Sterilization compatibility validation reference

Labeling Specifications

Labels and IFU follow regulatory labeling requirements per market. For Korean operations specifically, see our Lean IFU Documentation and UDI Implementation Guide for the Korean labeling specifics.

The DMR Structure

A complete DMR contains:

Section	Content
Device specifications	Drawings, models, material specs, schematics
Production process specifications	Work instructions, in-process inspection, equipment specifications
Quality assurance procedures	Acceptance criteria, sampling plans, test procedures
Packaging specifications	Sterile barrier, secondary, shipping
Labeling specifications	Labels, IFU, UDI, market-specific variants
Installation, maintenance, service procedures	Where applicable for the device class

The DMR is the legal "build sheet" for the device. ISO 13485 §4.2.3 and FDA 21 CFR 820.181 explicitly require its maintenance.

Bill of Materials Structure

The BOM is the structural backbone connecting specifications to production. A working BOM has:

• Hierarchical structure — parent assemblies contain sub-assemblies contain components
• Effectivity dates — when each version of the BOM applies
• Make-vs-buy — internally manufactured vs purchased components
• Approved supplier links — for purchased items
• Specification links — each line links to its specification document

For ERP integration, the BOM serves as the source of truth for materials planning, costing, and procurement. The integration is bidirectional: BOM changes in PLM trigger ERP updates; ERP cannot create new BOM entries without PLM approval.

A common architecture issue: BOM maintained in both PLM and ERP without strict source-of-truth designation. Result: drift between the two, and the device that gets built doesn't match either record.

DFM and DFA Review

Design for Manufacturing (DFM) and Design for Assembly (DFA) reviews happen at structured points in the design lifecycle:

During design (formative). Engineering and manufacturing collaborate on tolerance feasibility, supplier capability, assembly sequence. Changes here are cheap.

At design freeze (summative). Formal DFM/DFA review with manufacturing engineering, production, supplier quality. Outcome: either design is releasable to production, or specific changes are required before release.

During production ramp. Continuous review based on yield, scrap, rework data. Changes here are expensive but sometimes necessary.

For first-time MFDS submissions, the DFM/DFA review should be complete and documented before submission. KGMP auditors specifically check that design transfer activities were reviewed and approved — an undocumented design transfer is a finding.

Korean KGMP Audit Specifics

KGMP audits of design output and DMR have several emphases worth knowing.

DMR completeness check. Auditors pull samples from the DMR and verify that:

• Every drawing in the DMR has a current revision
• Every material referenced has a specification
• Every component has a supplier qualification
• Every process step has a work instruction

Gaps in any of these surface as findings.

Korean manufacturing site specifics. If the manufacturing site is in Korea, the DMR must be accessible in Korean (or in bilingual format) at the production location. Korean operators reading English-only work instructions is a recurring finding.

Korean import scope. For foreign-manufactured devices imported into Korea, the DMR remains in the manufacturer's home jurisdiction. The KLH does not need a complete copy — but the KLH must have access for KGMP audit. The KLH agreement should specify how this access works (typically electronic access to a controlled portion of the manufacturer's PLM).

Change control on Korean labeling. Labels and IFU for Korean distribution are part of the DMR, with Korean variants explicitly versioned. Changes to Korean labeling must follow the change control procedure and, where material, trigger MFDS notification.

Six Practical Recommendations

1. Treat the DMR as a structured object, not a folder of PDFs. PLM-based DMR with effectivity dates is the working pattern.
2. Integrate PLM and ERP with one source of truth for the BOM. Drift between the two is among the most common audit findings.
3. Conduct formal DFM/DFA review at design freeze, with cross-functional sign-off. Document the outcome.
4. For Korean manufacturing sites, ensure the DMR is accessible in Korean at the production location.
5. For Korean imports, structure the KLH access to the DMR via electronic access to controlled PLM portions. Avoid sending paper or unmanaged copies.
6. Audit the DMR yourself quarterly. Pull random samples and verify completeness. Finding gaps internally is cheaper than finding them in an external audit.

Where Leanabl Plugs In

The Design Output service handles engineering specification and DMR build for medical device organizations, including PLM/ERP integration design. For Platform PLM and Platform MES deployments where DMR sits in the platform, the design output work integrates with the platform configuration. For Korean manufacturing or import operations, the DMR work coordinates with Korea QMS Foundation and KGMP Certification.