|
In plastic fabrication, hot bending is used as an alternative to plastic
welding whenever possible because it is stronger and requires less time
and cleanup than welding. For a sheet thickness less than or equal to
1/2", a single strip heater can be used from one side of the sheet.
Heat is applied from beneath the plastic sheet using a strip heater
(shown at left). In the photograph, it is possible to see the plastic
getting soft where it meets the strip heater. The surface immediately
adjacent to the strip heater will become the outside of the bend.
The sheet is clamped to the work table on top of the strip heater to
assure that the heating of the bend line is straight and level. The
heating must be uniform in order to get a nice uniform bend radius. The
amount of time to make a hot bend depends mostly on the thickness and
the material--thinner materials require less time than thicker ones and
lower density material require less time than higher density material.
The length of the bend line has very little impact on time
requirements.
When the sheet material is softened to about 80% of its total
thickness, the sheet can be bent manually. Once the bend is made, it
must be removed from the strip heater and clamped in position until the
plastic cools completely.
The outside of the bend has a radius a little larger than the
thickness of the material while the inside radius is between 1/16" and
1/8". While there is some "thinning" at the bend there is very little
reduction in strength. |
Molding
- The guide to polymer processing technology,
materials, additives & equipment -
Life insurance