A composites manufacturer needed to upgrade their post-cure oven control system. The existing Schneider PLC setup was underperforming — persistent overheat alarms, no reliable data logging, and control logic that did not match the process requirements.
The Challenge
Fiberglass pipe is sensitive to rapid temperature changes. Thermal shock causes cracks, so the heating rate must be precisely controlled at 1°F per minute. The oven has four independent zones, each with inlet and outlet thermocouples, plus additional internal sensors for product temperature verification.
The customer needed:
- Precision ramp control across four independent heating zones
- Two programmable cure recipes — a one-stage cure (ramp to 180°F, hold 6 hours) and a two-stage cure (ramp to 167°F hold 2 hours, then ramp to 200°F hold 4 hours)
- Root cause analysis for persistent overheat alarms the previous integrator could not diagnose
- Time-stamped data logging for customer reporting and quality assurance
- Flexible zone operation — ability to cure shorter parts using only two of four zones with floating walls
Our Solution
We migrated the control system from Schneider to a Siemens S7-1200 G2 platform while retaining the existing Schneider ATV320 variable frequency drives for zone fan control. The project scope included:
- Complete functional design and PLC programming in Structured Text
- Operator HMI with Manual/Jog and Auto modes, real-time temperature display, alarm management
- Multi-zone temperature control with configurable ramp rates and hold times
- Recipe management system for one-stage and two-stage cure profiles
- Safety system integration including E-Stop, over-temperature protection, and door interlocks
- Integration with existing VFDs over Ethernet/Modbus TCP
- On-site commissioning with defined acceptance criteria
Technology
- PLC: Siemens S7-1200 G2
- Drives: Schneider ATV320 (retained, integrated via Ethernet/Modbus TCP)
- Sensors: RTD temperature inputs across four zones plus internal product thermocouples
- Programming: Structured Text (IEC 61131-3)
- HMI: Siemens panel with recipe selection, zone monitoring, alarm history
Results
The upgraded system delivers precise temperature control across all four zones with reliable cure cycle execution. The customer gained full visibility into the process through time-stamped data logging and alarm history — capabilities that were completely missing before.
Industry: Manufacturing / Composites
