Quality engineers in precision and regulated manufacturing collect measurement data in ERPNext through Quality Inspection and Quality Inspection Reading, but the platform stops at pass/fail against a reading value. There is no live control chart, no calculated control limits, no capability study, and no automatic detection of a process drifting toward failure. Teams end up exporting readings into spreadsheets or a separate SPC tool, which breaks the audit trail, delays reaction to special-cause variation, and makes it hard to prove statistical control to an auditor or customer. ERPNext native simply was not built to compute X-bar/R limits or a Cpk against per-characteristic tolerances.

We build a proper Frappe application — its own module, not a pile of loose scripts — that layers a full SPC engine directly on your ERPNext data. New DocTypes model the measurement domain: SPC Characteristic (per item/parameter spec limits, target, tolerance, subgroup size, chart type), SPC Sample and SPC Subgroup for the collected readings, and SPC Control Chart / SPC Capability Study to hold computed results. A hooks.py doc event on Quality Inspection (on_submit) pipes submitted readings into the SPC pipeline automatically, so engineers keep working in the standard Quality Inspection flow and the charts populate themselves. Server-side logic computes control limits (UCL/CL/LCL) for X-bar/R, X-MR (individuals & moving range), and attribute charts (p, np, c, u), plus Cp, Cpk, Pp and Ppk against the characteristic's spec limits.

Out-of-control detection runs the Western Electric and Nelson rule sets — points beyond 3-sigma, runs on one side of the centerline, trends, and zone violations — implemented as whitelisted server methods so results are consistent whether triggered by a doc event or the REST API. A scheduler event (scheduler_events hook) can recompute limits on a fixed cadence and raise alerts (ERPNext Notification, email, or a Frappe Realtime push) the moment a subgroup violates a rule, so the line lead reacts to special-cause variation in minutes rather than at end-of-shift review. The interactive control-chart and capability dashboards are rendered client-side; trend dashboards slice by item, production line, work order, and shift. Access is governed through dedicated role profiles and DocType permissions so operators can record readings while only quality engineers edit spec limits or approve chart resets.

Because every install has different characteristics, tolerances, sampling plans, and reporting needs, this is a build-to-order engagement, not an instant download. After a short scoping call we confirm your chart types, capability requirements, and which inspection points feed the engine, then build and configure the app against your exact ERPNext v15 or v16 site. Typical delivery is one working week from confirmed scope. You receive the installable source, UAT on a staging copy of your instance with a rollback plan, documentation, a training session, and a post-go-live support window — plus the git repository so your team owns the code.