Thermoforming w/ Heat Blanket

Technical Bulletin A – 2
Heat Bending (Thermoforming) VERSATEX Using a Heat Blanket

Using a Heat Blanket
Equipment used to heat bend or thermoform VERSATEX Cellular PVC can be purchased directly from Heatcon Inc., 600
Andover Park East, Seattle, Washington 98188-7610, Phone (206) 575-1333, Fax (206) 575-0856. The heat blanket
system comes to you in an easy to transport plastic carrying case and contains the following items necessary to form

VERSATEX Cellular PVC trimboards and mouldings:

  • Two heat blankets 5″ wide by 6″-0″ long with built in thermocouples.
  • One electrical control cabinet with digital program display that provides fast and precise temperature control to
    eliminate overheating.
  • One pair of gloves
  • One manual

The heat blankets can be manufactured longer and wider. The blanket size is dependent on the amount of electrical
power you are willing or able to commit to the heating process. The standard heat blanket system operates off of a
standard 110V outlet. Not supplied, but required materials needed for heat bending are as follows; a pair of safety
glasses, a pair of heat resistant gloves, a digital infrared temperature gun, two (2) pieces of fiber cement siding
5″ x 6′, several pieces of 2 x 4 x 4″ to 5″ boards, two clamps or a nail gun, and a curving jig.

Safety Warnings and Guidelines

  • Do not expose heat blankets to rain or wet conditions or submerge in liquid of any kind.
  • Check the rating on your system to prevent circuit overloading.
  • Ensure extension cord is rated to carry the current your kit will draw.
  • Do not allow the heat blankets to come in contact with one another.
  • Each heat blanket should be rolled for storage. Avoid any sharp turns or bends in the blankets.
  • Do not overlap heat blanket onto itself while plugged in.
  • Ensure the side of the blanket marked “X” is against the product.
  • Never plug the blankets directly into an outlet. Always energize the blankets using the controller.
  • Never leave the heat blanket system unattended when it is being energized.
  • Extend the life of the heat blankets by keeping the operating temperature below 350°F.
  • Extend the life of the heat blankets by avoiding gaps or space between the blanket and the VERSATEX board being heated.

Failure to follow these instructions may result in electrical shock, fire or serious bodily injury.


The thermoforming process is more art than science. The first step in the process is to preheat the cement fiber boards. This is
accomplished by placing several of the small 2 x 4 wooden blocks on a solid surface (table) to properly support the bottom
cement fiber board. Place one of the heating blankets on the cement board. Then lay the top piece of fiber cement board on top
of the bottom blanket followed by the second or top heat blanket. Plug the two blankets into the controller before energizing your system. Finally, insert the plug into a standard 15 AMP outlet. Set the temperature on the controller to 300°F and preheat the fiber cement boards for 15 to 20 minutes, or until the controller reaches 300°F. Once the preheating phase has been completed, place your VERSATEX trimboard to be thermoformed between the two heating blankets, making sure not to allow the heated portion of the blankets to come in contact with each other. Place the second piece of preheated cement fiber siding on the top blanket. Push the run button for 2 seconds. The top screen will display the actual temperature while the lower screen will show the desired temperature. Adjust the temperature to 300°F. Set the timer to somewhere between 10 and 15 minutes. To adjust the timer, push the timer key twice. The lower display will show a “T” and the upper display will show a timer value. Use the up and down arrow key to adjust. Push the timer key once more to exit after the timer is set. When the blankets are within 5
degrees of the desired temperature, the timer will start (timer light will be blinking). At the end of the allotted time, the alarm will sound. Push the run key once to disable the alarm (blankets will still be powered). Monitor the core of the board with the infrared temperature gun to ensure the entire trimboard reaches the set temperature of 300°F. Check the material for consistency. Consistency should be like cooked spaghetti. Be aware overheating may result in a deformed surface and burn marks. When proper consistency is reached, place the material vertically along the left edge of the form or jig. Secure the board to the edge of the form or jig with a clamp or simply nail it to the jig. Gently pull the board stretching it as you proceed from left to right around the form or jig. Be sure there are no cold spots in the product; otherwise the board will not bend properly to the required radius. Instead, the boards will crimp and gather in cold spots. If the product wrinkles or feels rigid especially along the edges, immediately straighten out the piece before it has a chance to lose much heat and place it back between the blankets. Should the top edge curl up use a 2 x 4 block to hold the material against the jig while the shaped board cools. After formed, clamp or nail the other side of the curved VERSATEX board and allow it to cool. Do not put too much pressure on the hot VERSATEX board, since it may leave compression marks. Remove VERSATEX once it is cool enough to maintain its shape.

The process does not affect the cell structure or any other physical property of the cellular PVC product itself. However, the textured appearance will fade away when thermoforming.

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