TL;DR
Sheet sag before forming is usually the heater temperature too high, sheet tension too low, or a slow oven-to-form transfer. Lower the heater temperature in small increments and optimize the transfer time.
What you might see
- sheet sags excessively before reaching the forming station
- formed parts thin in the center
- sheet touches heating elements or oven frame
- forming depth varies across the sheet width
Likely causes
Heater set temperature too high relative to the sheet material softening point
Sheet chain or clamp tension insufficient to hold the heated sheet taut
Transfer time from oven to form station too long allowing over-softening
Non-uniform heat across the oven causing one zone to over-heat
Required tools
- IR thermometer or contact pyrometer
- Wall thickness gauge
- Heat-resistant gloves
Safety first
- Oven heaters and sheet surfaces exceed safe contact temperatures. Wear heat-resistant gloves when working near the oven.
- Hot softened sheet can fall or slump suddenly. Keep face and hands clear when the sheet exits the oven.
Procedure
- 1
Measure the sheet surface temperature at the oven exit using an IR thermometer or contact pyrometer at five points across the web.[1]
- 2
Compare the measured sheet temperature to the recommended forming temperature for the material type in the process guide.
- 3
Reduce the highest-reading oven zone temperature by 5 C increments. Allow the oven to stabilize between changes.
Warning: Do not reach into the oven with bare hands while heaters are on. Sheet and oven surfaces exceed safe contact temperatures. - 4
Check the sheet chain or clamp rail tension. Increase tension per the machine adjustment if the sheet is not held taut across the web.[1]
- 5
Verify the transfer timing between oven exit and form station descent. Reduce transfer time by 0.5 second increments if practical.
- 6
Run 10 trial cycles and measure formed part wall thickness at center and corners with a wall gauge.
- 7
Accept settings when wall variation is within the part specification.
Sources
Brown Machine Brown Aclo / Quantum Thermoformer general technical documentation, Brown Machine
Brown Machine thermoformer operator manual, process setup and temperature adjustment guidelines (general)
More guides for Brown Machine Brown Aclo / Quantum
How to identify and replace a failed heater element on a Brown Machine Aclo / Quantum thermoformer
A failed oven heater element creates a cold spot in the web, producing thin or incompletely formed parts in one zone. Identify the failed element with a clamp ammeter before replacing.
How to fix parts sticking in the mold on a Brown Machine Aclo / Quantum thermoformer
Parts sticking in the thermoforming mold indicate insufficient air-eject pressure, too-short cooling time, or worn draft angles. Increase cooling time before increasing eject pressure.
Stop fixing the same fault twice.
Dovient turns guides like this into your team's shared playbook, with AI that catches recurring issues before they break the line.