Description of Problem
• Excessive moisture.
• Heating sheet too hot.
• Heating sheet too fast.
• Uneven heating of the sheet.
• Heat sensitive material.
• Design of the part.
• Sheet too thin.
• Uneven sheet temperature.
• Forming technique.
• Bad plastic sheet. Melt
index of sheet may be low.
Possible Corrective Action
• Pre-dry sheet at the temperature
required for the material you are
• Heat sheet very slowly to forming
• Protect sheet from moisture before
• Cut down sheet forming
temperature. You may be boiling
the stabilizers out of the material.
• Lower element temperatures.
Generally speaking, element
temperatures should not exceed
• Increase the distance between the
heating elements and the sheet.
• Check forming oven for elements
that are overheating.
• Screen out hot spots.
• Check with plastic supplier on
temperature parameters for the
• The overall draw ratio of the part is
too great for the starting thickness
of the sheet.
• The part has specific areas on it
that exceed the draw ratios of the
rest of the part.
• Increase the gauge thickness of the
• Check for air drafts in the forming
• Check for hot spots in the forming
oven. May have defective heating
• Check the sheet for a variation in
• Consider where the part is thinning
and what forming technique would
best address this problem.
• Have physical properties of the