A. General Guidelines
1) Description: A simple bending technique, used for forming local, straight line, one axis bent parts (such as corners, boxes, and machine guards). This type of bending is usually preferable (if possible) to cold linebending.
2) The process: A bending device with localized heaters on one or two sides of the sheet to be bent is used.
The “sandwiched“ two-sided heating method is preferable, since it retains the same temperature on both sides at the time. a one-side heater method requires turning the sheet over a few times during the heating period, to maintain optimal temperature on both sides.

B. Steps & Indications
One-sided heating method may suffice for sheets up to 3 mm (0.12 in.). Thicker sheets or more demanding cases require using two-sided heating. Keeping control of the sheet’s temperature limits of 155-167°C (31-332°F) is of the utmost importance.
Forcing the bend at lower temperatures will render the sheet fragile at the bend. This simple bending process enables working with regular sheets, without pre-drying. Experimenting with small samples before final execution is highly recommended.

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.

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 their specific thermal output and the distance from the target sheet.

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.

Note: It is recommended to perform the bend a few degrees tighter than the required angle, as it may “go back” a little after cooling down. The desired angle may be reached after a few trials.

Cooling is to be done in ambient air, taking care to avoid sudden drafts. These can cause distortion of the final product.

Minimal Hot-Line Bending Radius is 3 times the thickness of the bent sheet. Larger radii can be achieved by widening the heated zone.

C. Notes for Consideration
Local hot line bending (or any other localized heating, for the matter) 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 1.00 m or 3.0 ft) usually stay straight enough. 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. Annealing (see special paragraph) may also correct this problem.
 
It is always advised to fabricate experimental test samples to check feasibility of the bending operation.