Discrete and engineer-to-order manufacturers live and die by how well they control design changes. In stock ERPNext, a BOM is versioned in a shallow way — you can amend a submitted BOM or create a new BOM against the same item, but there is no formal change-request stage, no approval gate before a change reaches production, no structured diff between two revisions, and no effectivity window that tells the shop floor exactly when the new design takes over. Engineers end up managing change control in spreadsheets and email threads, WIP is built against superseded drawings, and nobody can answer "which revision was released, by whom, and against which ECO?" during an audit. This is exactly where native ERPNext runs out of road for a serious engineering organization.

We build a proper Frappe app — its own module, not a pile of customizations bolted onto core doctypes — that layers a real PLM change-control process on top of ERPNext's existing Item and BOM. New DocTypes model the process end to end: an Engineering Change Request captures the proposed change, affected items, reason, and impact assessment; an Engineering Change Order groups approved changes, links the outgoing and incoming BOM revisions, carries effectivity dates, and drives the release. A revision-history DocType keeps an immutable record of every BOM version with the ECO that authorized it, so the full lineage is queryable. Approvals run on Frappe's native Workflow engine with role-profile-based transitions (Engineer, Reviewer, Approver, Release), so who-can-do-what is enforced by ERPNext permissions rather than convention.

The technical mechanics are grounded in Frappe primitives you can inspect and extend. hooks.py document events (on_submit, before_save, on_update_after_submit) enforce that a BOM only becomes active through a released ECO and that effectivity dates are respected. Server-side whitelisted methods produce the side-by-side revision diff — comparing components, quantities, operations, and routing between two BOM versions and rendering an add/change/remove report inside the ECO. Client scripts drive the in-form experience (revision picker, diff viewer, impact summary), while a scheduler event checks for ECOs whose effectivity date has arrived and flips the controlled rollout so the new revision becomes the default at the right moment — not the moment someone clicks submit. Everything is reachable over the Frappe REST API and the whitelisted methods, so your MES, PLM/CAD vault, or drawing system can push and pull change data programmatically. Drawings and specification documents attach per revision via Frappe's File attachments, so every BOM version carries its own controlled document set.

Because this is build-to-order, nothing is a generic download you self-install and hope fits. We start with a scoping call to map your change-control process, roles, and effectivity rules onto the app, then build against your actual ERPNext instance and BOM structure. Typical delivery is one working week from confirmed scope. You receive the full installable source for your version, a UAT pass on a staging bench with a rollback plan, and a support window after go-live. The app targets Frappe/ERPNext v15 and v16, and the git repository is handed over to you so you own what you paid for.