Automated Certificate Generator from XLSX Templates

Overview

The COI (Certificate of Inspection) Automation System streamlines the process of generating inspection certificates directly from Excel templates. Built for manufacturing and quality-control environments, it replaces manual report creation with a fast, data-driven workflow — ensuring consistent layouts, accurate data, and bilingual output (English-Japanese).

How It Works

Users upload a pre-designed XLSX certificate template containing placeholders such as {lot_no}, {qa1}, {qa2}, {spec}, etc.
When a lot number is entered and QA users are selected, the system automatically retrieves inspection data, replaces placeholders, and generates a ready-to-download file (Excel or PDF).

The interface includes:

Lot Number Search
Export Options (Checkboxes)
QA.1 / QA.2 Dropdowns
Acceptance Status Selection (Accepted / Special Accepted)
Export Excel & Download Buttons
Inspection Results Table

System Workflow

flowchart TD
  A["Start"] --> B["Upload XLSX Template"]
  B --> C["Define Placeholders<br/>{lot_no}, {qa1}, {qa2}, {spec}"]
  C --> D["Select Data Source<br/>CSV / DB / API"]
  D --> E["Map Fields<br/>data.lot_no → {lot_no}, data.qa1 → {qa1}"]
  E --> F["User Inputs Lot No., QA.1, QA.2, Status"]
  F --> G["System Validation"]
  G -->|Valid| H["Generate Filled XLSX"]
  G -->|Error| I["Show Error: Missing Data / Invalid Mapping"]
  H --> J["Convert to PDF (Optional)"]
  J --> K["Provide Download Link"]
  K --> L["Notify User (Email / In-App)"]
  L --> M["Archive Certificate + Audit Trail"]
  M --> N["Finish"]

Key Features

✅ Reusable XLSX Templates – Upload once, reuse for any product or client.
⚙️ Batch Generation – Create hundreds of certificates in seconds.
🧠 Auto-fill & Validation – Ensures QA and lot fields are complete before export.
🧾 PDF + XLSX Outputs – Flexible formats for internal or customer use.
📋 Audit & Archive – Keeps generated files with logs for compliance tracking.
🌐 Multi-language Ready – Supports English, Japanese, and Thai labels.

Interface Overview

Sidebar navigation: Dashboard, Reports, COI Export, Customer Templates, Settings.
Main view:
Related Posts
- Lot search field
- Export options
- QA selectors and status
- Export Excel button
- Generated inspection data table

Output Sample: Certificate of Inspection

Field	Example Data
Customer	Simplico Inspection Co., Ltd.
Product Code	ABC-100X
Lot No.	L24091
Tool No.	T-5523
Inspection Date	2025-10-14
QA.1	John Doe
QA.2	Jane Smith
Status	Accepted

Inspection Item	Standard	Actual	Judgement
Dimension	±0.01 mm	+0.009 mm	OK
Balance	≤ 0.5 g	0.32 g	OK
Appearance	No Defect	Pass	OK
Hardness	60 ± 2 HRC	61	OK

🧩 Technical Implementation

1. Framework & Stack

Backend: Django (Python 3.11)
Frontend: Tailwind CSS + Alpine.js + Flowbite UI
Database: PostgreSQL (certificate metadata, QA user lists)
Libraries:
- openpyxl – read/write XLSX templates
- reportlab / xlsx2pdf – PDF conversion
- axios – asynchronous certificate generation via API
- django-browser-reload – live UI updates during template testing

2. Template Engine Logic

Each uploaded Excel template defines placeholders such as {lot_no}, {qa1}, {spec}.
At runtime:

The system loads the Excel sheet via openpyxl.
It scans each cell for placeholders using regex.
It replaces placeholders with actual values from the database query.
The filled workbook is saved to /media/certificates/.
A signed URL is generated for download or audit logging.

Example (simplified Python snippet):

from openpyxl import load_workbook

def fill_certificate(template_path, data):
    wb = load_workbook(template_path)
    ws = wb.active
    for row in ws.iter_rows():
        for cell in row:
            if cell.value and isinstance(cell.value, str):
                for key, val in data.items():
                    cell.value = cell.value.replace(f"{{{key}}}", str(val))
    wb.save("/media/certificates/COI_filled.xlsx")

3. API Workflow (Flask or Django View)

Step	Endpoint	Method	Description
1	`/api/start`	POST	Initialize COI generation
2	`/api/upload`	POST	Upload XLSX template
3	`/api/export`	POST	Merge data + generate certificate
4	`/api/download`	GET	Provide download link
5	`/api/status`	GET	Check processing or QA approval state

4. Frontend Interaction

The front end uses Alpine.js reactive bindings:

<div x-data="COIReport()">
  <input x-model="lot_no" placeholder="Enter Lot No.">
  <select x-model="qa1">...</select>
  <button @click="exportCOI()">Export Excel</button>
</div>

async exportCOI() {
  const response = await axios.post('/api/export', {
    lot_no: this.lot_no, qa1: this.qa1, qa2: this.qa2
  });
  this.downloadUrl = response.data.file_url;
}

5. Security & Traceability

Role-based access control for QA and Admins
Audit logs stored with timestamp, filename, and user ID
Auto-expiration of download URLs
Server-side template sanitization to prevent formula injection

6. Scalability

Dockerized environment with Gunicorn + Nginx
Task queue (Celery + Redis) for parallel certificate processing
Static file caching for XLSX/PDF templates

Conclusion

This Simplico Certificate Generator automates the most tedious part of quality control — document preparation.
By combining Django’s reliability, Tailwind’s modern UI, and Excel’s familiarity, it creates a fast, secure, and highly scalable platform for generating professional inspection certificates.