Palram PALSU - Manual (Page 34)

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ƒ PE Masking: When preparing for bending of regularly cladded sheets- peel off the masking on both sides of the sheet along the
bend line for about 100 mm (4 in) on each side in TF prepared sheets. It is possible to process the sheet with the masking on, up
to 5 mm (0.2 in) thickness. For sheets of 6 mm thickness or more the PE masking should be removed along the bending line, as
described above. Always test a few samples before proceeding to production.
ƒ Heaters: Linear IR (Infrared) or resistance wires strip heating elements are used, preferably with heat reflectors. The width of the
heated zone depends on the number of elements used, the spacing between them depends on their specific thermal output and
the distance from the target sheet.
ƒ Bending process: When the sheet has reached the required temperature the heaters are to be switched off. The sheet, held in
pivoted clamps, preferably equipped with a caliper, is then bent to the required angle and secured there until it cools down and sets.
ƒ Note: It is recommended to perform the bend a few degrees tighter than the required angle, as the angle may increase as the sheet
cools. The desired angle may be reached after a few trials.
ƒ Cooling is to be done in ambient air, taking care to avoid sudden drafts. These can cause distortion of the final product.
ƒ The minimal Hot-Line Bending Radius is 3 times the thickness of the bent sheet. Larger radii can be achieved by widening the
heated zone.
Forming - Notes for Consideration
Local hot line bending (or any other localized heating) induces internal stresses in the finished part, reducing the chemical resistance
of the element at the bending line zone. Such treatment is therefore recommended for use in less demanding environments.
Localized heating and cooling expansion/contraction characteristics are unpredictable in many cases. Short elements (up to
1.00m or 3.0’) usually remain flat. Longer elements may distort to a concave shape (the outer edges are longer than the line-
bent side due to uneven contraction).
This phenomenon can be corrected or reduced by simple jigs or frames, which hold the part in the right position during the
cooling period.
It is always advised to fabricate experimental test samples to check feasibility of the bending operation.
PALSUN® Thermoforming Tips
ƒ 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.
ƒ Best results in thermoforming are achieved when parts are heated to temperatures just above the HDT (150 °C- 300 °F).
ƒ Thermoforming parts below the HDT temperature induces internal stresses.
ƒ Secure the cooling area for thermoformed parts against undue drafts. Uneven cooling may result in warping and/or curling of parts.
ƒ Assure precise and systematic control over oven temperature and heating time.
ƒ PALGARD (abrasion resistant) and PALSUN FR (fire retardant) are not recommended for use in thermoforming. The bending and
stretching involved during the process will permanently damage the sheets.