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TF: Troubleshooting Tips

Faults and Their Remedies in Thermoforming Practice

Sr. No.	Recognized Fault	Probable Cause	Proposed Treatment	Hot Line Bending	Drape Forming	Vacum Forming	Free Blown
Sr. No.	A	B	C	D	E	F	G
1	Apparent bubbles in sheet	Moisture content too high	Pre-drying	+	+	+	+
2	Apparent bubbles in sheet	Working temp. too high	Decrease working temp.	+		+	+
3	Hair fissures, fragile part	Part overheated	Decrease heating period			+	+
4		Mold under-heated	Increase mold temp.			+
5		Late extraction of part	Diminish cooling cycle			+
6		Vacum speed too high	Reduce vacum rate			+
7		Mold corners too sharp	Round sharp corners			+
8		Basic sheet size too small	Increase sheet size			+
9	Webbing	Erratic heating	Prevent hot or cold spots			+
10		Mold lead inadequate	Check spacing-min. depth x 2			+
11		Vacum speed too high	Reduce vacume rate			+
12		Basic sheet size too large	Clamp/mold spacing <50mm			+
13	Blurred or partial detailing	Vacum too weak	Seal leaks/add vacum holes			+
14	Blurred or partial detailing	Sheet rigid, under-heated	Extend heating period/temp.			+
15	Product sticks to mold	Mold overheated	Decrease mold temperature			+
16		Product release delayed	Shorten release period			+
17		Draft angle too steep	Enlarge draft angle up to 4-6°			+
18	Marked zones on product	Irregular finish of mold	Treat mold to consistent finush			+
19		Suction holes misplaced	Install new, better placed holes			+
20		Sheet overheated	Decrease heating period/ temp.	+	+
21	Exterior flaws/ roughness	Dirt/ grime on sheet / mold	Wipe/Vacum-clean mold/sheet		+	+
22	Exterior flaws/ roughness	Suction holes misplaced	Install new, better placed holes			+
23	Inconsistent shape of part	Mold/ brace under-heated	Extend pre-heat of mold/brace			+
24	Inconsistent shape of part	Irregular heating/ cooling	Prevent drafts, fix faulty heater	+		+	+
25	Product release delayed	Shorten release period	Shorten release period		+

Annealing
Cold fabrication, or various thermoforming systems of the PALSUN sheets, may induce detrimental internal stresses, which may eventually cause failure, and have to be relieved by annealing.
Annealing is achieved by heating the fabricated objects evenly in an air-circulating oven up to 120 to 130°C, and leaving them inside for about an hour for every 3mm thickness. (Example: 6 mm thick formed part- 2 hours of “baking”).
After the “baking” period, the parts should be left to cool down slowly to the ambient temperature. It is preferable to let it cool inside the closed oven.

Hot Tips about PALSUN Thermoforming
Consistent part-to-part uniformity is better ensured if the sheet blanks prepared for the thermoforming process are cut from the basic sheet always at the same direction.
Best results in thermoforming are achieved when parts are heated to temperatures just above the HDT (150°C - 300°F).
Thermoforming parts below the HDT temperature induces undue internal stresses.
Secure the cooling area for thermoformed parts against undue drafts. Uneven cooling may result in warping and/or curling of parts.
Assure precise and systematic control over oven temperature and heating time.
PALSUN MR and FR are not recommended for use in thermoforming. The bending and stretching involved during the process will break and crack the protective coating.

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