For medical device manufacturers, production does not always begin with a finalized bill of materials (BOM).
During product development, engineering teams may need to assemble functional prototypes, test alternative components, evaluate design changes, and purchase materials before the final product configuration is approved.
The challenge is that manufacturing activity still needs to be organized and documented, even while the design continues to change.
Without a structured approach, companies can lose visibility into which components were used, what changed between prototype versions, how much each build cost, and whether materials purchased for development are suitable for later production.
Managing this transition requires a distinction between engineering builds and released production, along with processes for controlling materials, revisions, and manufacturing records.
This guide explains how medical device manufacturers can maintain that control before the final BOM is released.
Why Prototype Manufacturing Creates a BOM Management Challenge
A traditional manufacturing process begins with an established product configuration.
The production team receives an approved BOM identifying the components required to manufacture the assembly. Purchasing uses that information to source materials, while manufacturing relies on the BOM and associated instructions to execute work.
Prototype manufacturing introduces a different situation.
Engineering may still be evaluating multiple designs, suppliers, component specifications, and assembly methods. A component used in one prototype might be replaced before the next build. Quantities may change, and some materials may be approved only for engineering evaluation.
This creates several operational challenges:
- Material uncertainty: Purchasing may need to order components before final specifications are established.
- Revision confusion: Different prototype units may use different versions of the same assembly.
- Inventory visibility: Development materials can become difficult to distinguish from production-approved inventory.
- Cost tracking: Rework, engineering labor, and experimental components can obscure the actual cost of development.
- Traceability: Teams need records showing what was physically used in each build.
- Production readiness: Engineering decisions must eventually translate into a controlled, repeatable manufacturing process.
The objective is not to eliminate changes during development. It is to ensure those changes remain visible and manageable.
Engineering BOM vs. Production BOM: What Is the Difference?
An engineering BOM (EBOM) represents the product structure and components defined by engineering. During development, it may be revised as teams evaluate alternative designs and materials.
A production BOM represents the component structure used for manufacturing execution. It needs to align with the approved configuration and the processes used to build the product.
| Area | Engineering BOM | Production BOM |
|---|---|---|
| Primary purpose | Product development and design evaluation | Repeatable manufacturing |
| Revision activity | Changes frequently during development | Changes through controlled release procedures |
| Components | May include experimental or alternative parts | Uses components authorized for the applicable production configuration |
| Manufacturing use | Engineering prototypes, test builds, and development activity | Released manufacturing orders |
| Cost evaluation | Estimates and actual development costs | Manufacturing and production cost planning |
| Release status | Working or engineering-controlled | Released for applicable production use |
A BOM does not necessarily need to be finalized across every future product revision before a company can conduct engineering builds.
However, each build should have a defined configuration, and the organization should know which components and instructions were authorized for that specific activity.
This distinction is especially important for medical device manufacturers working toward controlled production and applicable quality-system requirements.
How to Manage Prototype Builds Before Final BOM Release
1. Establish a Defined Engineering Build
Every prototype build should begin with a clearly identified objective.
That objective might involve testing a design modification, evaluating a new component supplier, verifying assembly feasibility, or assessing the impact of a material change.
Before work begins, establish a build identifier and record the applicable product configuration, revision, quantities, responsible personnel, and intended use.
For example, a medical device company evaluating a redesigned sensor assembly might create a new engineering build associated with the updated configuration.
This separates the new activity from previous builds and helps prevent confusion when several iterations of the same product are being evaluated simultaneously.
2. Maintain a Controlled Working BOM
Rather than treating an unfinished BOM as an informal spreadsheet that changes without explanation, maintain a working engineering BOM with identifiable revisions.
The working BOM should indicate:
- Components currently expected to be used
- Alternative or experimental components
- Applicable quantities and specifications
- Engineering revision or configuration identifiers
- Changes under evaluation
- Components approved for a specific engineering build
A working BOM is not the same as a fully released production BOM.
Its purpose is to give engineering and manufacturing a consistent reference for the build being executed while preserving the flexibility required during development.
3. Separate Engineering Materials From Production Requirements
A component may be appropriate for a prototype without being authorized for commercial production.
For example, engineering might evaluate a replacement electronic component because the original part has a long supplier lead time.
That alternative should be identifiable as part of the engineering activity, rather than being introduced into production through an undocumented substitution.
Maintaining this distinction helps purchasing, inventory, and manufacturing teams understand which materials are associated with experimental builds and which are authorized for production.
It also reduces the risk of temporary development decisions becoming permanent manufacturing practices without appropriate review.
4. Record What Was Actually Used in Each Build
The planned BOM and the actual materials consumed during a prototype build are not always identical.
An engineer may substitute a component, use an additional part, or make an approved adjustment during assembly.
Those differences should be documented as part of the build record.
Depending on the organization’s processes and applicable requirements, useful records may include component identifiers, lot or serial numbers, quantities, assembly instructions, changes, test results, and disposition decisions.
The important distinction is between what the team intended to build and what it actually built.
That information becomes valuable when comparing prototype versions, investigating unexpected test results, or deciding whether a configuration is ready for release.
5. Capture Engineering Changes and Their Cost Impact
Prototype development often involves repeated changes to product materials and assembly methods.
Each change can affect more than the engineering department.
A replacement component may carry a higher purchase price, introduce additional supplier lead time, require a different manufacturing operation, or make existing inventory unsuitable for the next build.
Engineering change management should therefore consider both the design decision and its manufacturing consequences.
A practical change review should establish:
- What component, specification, or process is changing?
- Which existing builds and inventory could be affected?
- What additional purchasing or manufacturing work is required?
- What happens to materials or assemblies from the previous configuration?
- Who must approve the change, and when does it become effective?
Capturing these effects during development makes later production planning more reliable.
6. Establish a Controlled Handoff to Production
A prototype that performs successfully is not automatically ready for repeatable commercial manufacturing.
Before releasing a configuration to production, the organization should confirm that the relevant product structure, specifications, manufacturing instructions, quality requirements, and material decisions have been reviewed and approved through its established processes.
The production BOM should accurately represent the configuration that manufacturing is authorized to build.
Unresolved experimental components should not silently become production requirements.
A controlled handoff reduces ambiguity between engineering, purchasing, and manufacturing and establishes a more reliable starting point for ongoing production.
Example: Managing a Medical Device Prototype Through Three Revisions
Consider a hypothetical medical device manufacturer developing a compact diagnostic instrument.
The engineering team is evaluating a sensor board and its connection to the main assembly.
| Build | Engineering change | Manufacturing consideration |
|---|---|---|
| Prototype A | Initial sensor board design | Record components, quantities, and initial assembly results |
| Prototype B | Substitute a sensor component | Identify the alternative, record the change, and retain the build configuration |
| Prototype C | Modify the board and connector arrangement | Evaluate updated materials, assembly instructions, and cost implications |
| Production release | Approve the selected configuration | Release the appropriate production BOM and associated manufacturing requirements |
Without defined build records, the company could struggle to determine which sensor version appeared in a particular prototype or whether the final manufacturing configuration accurately reflects engineering’s approved design.
With structured engineering builds, each iteration has its own record of the components and manufacturing activity involved.
This allows engineering to evaluate changes while giving manufacturing and purchasing the information needed to prepare for repeatable production.
This is an illustrative workflow, not a customer case study.
What Should Manufacturers Look for in ERP Software for Engineering Builds?
Manufacturers evaluating ERP software should look beyond whether the system can store a bill of materials.
The more useful question is whether the system can support controlled engineering activity while distinguishing it from routine production.
Important capabilities to evaluate include:
- Engineering and production BOM controls: Can the system distinguish between development configurations and released production structures?
- Engineering change management: Can users track proposed changes, approval decisions, effective dates, and affected components?
- Engineering build execution: Can a prototype or engineering job reference the appropriate components without unintentionally changing normal production planning?
- Material traceability: Can the organization record the materials consumed during specific builds?
- Cost visibility: Can engineering and finance evaluate the material and manufacturing costs associated with development activity?
- Production release control: Can the organization distinguish engineering-only configurations from components authorized for regular production?
The objective is to connect product development with manufacturing operations while maintaining appropriate controls for each stage.
How Expandable ERP Supports Engineering and Prototype Manufacturing
Expandable ERP includes engineering functionality designed to help manufacturers maintain product configurations, manage BOMs, evaluate changes, and coordinate engineering information with manufacturing operations.
Its documented engineering capabilities include Engineering BOMs, Bills of Materials Maintenance, Engineering Change Management, Product Costing, and Product Data Control.
Expandable also distinguishes between engineering-only, production-only, and combined BOM components.
Within its documented Job Scheduling/Costing functionality, engineering-only components can be included when releasing an engineering job using the appropriate option. This allows designated engineering components to be considered during the engineering build process while maintaining their distinction from standard production components.
The system documentation also specifies that engineering-only components are not automatically included in ordinary MRP processing or cost rollups. Manufacturers should confirm the applicable configuration and job-release procedures during evaluation.
For medical device manufacturers, these distinctions can help establish a more controlled process for managing revisions and engineering activity before a configuration is released for production.
Learn more about Expandable’s engineering capabilities and how its functionality supports manufacturing operations.
Build With Control Before the Design Is Final
Medical device manufacturers cannot always wait until every component and specification is finalized before beginning physical development work.
Engineering builds are a necessary part of evaluating product designs and preparing for manufacturing.
But early development flexibility should not require manufacturers to sacrifice visibility into materials, revisions, manufacturing activity, and cost.
By maintaining controlled engineering configurations, documenting actual build activity, managing changes, and establishing a defined production-release process, manufacturers can move forward with development while preparing for more reliable production.
For organizations evaluating how to connect engineering and manufacturing, Expandable ERP provides documented capabilities for engineering BOMs, change management, and manufacturing control.
Frequently Asked Questions
Yes. A manufacturer can conduct engineering and development builds before a final production BOM has been released, provided the activity follows appropriate controls. A defined working configuration is still important. Even if the design remains subject to change, the organization should identify the components and instructions applicable to the build and maintain suitable records of what was actually used.
An engineering build is conducted for development, evaluation, testing, or other defined engineering purposes. Its configuration may change as the product evolves. A production build follows the applicable released manufacturing configuration and established production controls. The specific approval, documentation, and quality requirements depend on the product, its intended use, and the manufacturer’s processes.
Not necessarily.
Experimental components may need to be purchased and tracked for engineering builds without becoming requirements for regular production.
ERP systems should be evaluated for how they distinguish engineering materials from production requirements and how engineering jobs are planned and released.
The transition should occur when the organization has completed the required reviews and approvals for the configuration intended for production.
This includes confirming the applicable product structure and supporting manufacturing information through the company’s established change-control and release procedures.
The objective is to ensure manufacturing uses the authorized configuration rather than an unreviewed engineering version.