A downloadable PDF FIle from Mikron Infrared describes the use of IR Thermometers in manufacturing operations using thermoformed plastic sheet materials.

Thermoforming Applications: Thermoforming Temperature Measurement

The Thermoforming Application

Thermoforming is the process of using heating elements and/or cooling elements to mold or shape
some type of material. Typically this material will be a type of plastic.

The process follows a path from extrusion to molding. Most thermoforming companies will use extrusion machines to extrude the plastic, which then will be pulled into an oven and heated until it reaches a certain temperature.

Once this temperature has been obtained the plastic is moved out of the oven into a cooling and molding zone. Usually the machine runs on a timer so the temperature of the plastic varies and is inconsistent within the oven.

The plastic is molded and cooled either by water-cooling or air-cooling. Most applications use water-cooling either sprayed onto the plastic or pushed through the metal mold.

Finally, the plastic is moved to a cutting zone where the shapes are cut out of the plastic. This can be done either manually or automatically as well.

This application has a couple of different sections that are ideal for infrared pyrometers and imaging.

The first area that pyrometers or imaging is appropriate for occurs after the plastic has been extruded as a sheet and before it goes into the oven. In this area the plastic is warm coming out of the oven and has no ability for a thermocouple to be mounted at any point.

Knowing the temperature at this point will allow the operator to slow down the process if the temperature is too warm or quicken the process if the temperature is too cool. Here there is no cover to the plastic that would block the field of sight, therefore imaging or single point pyrometers are appropriate solutions.

The other potential reason to image or gauge temperature at this point is due to the fact that the
temperature variations here can affect the quality of the final molded plastic product.

This was said to be an issue at a certain thermoforming plant where they used an infrared gun to get the temperature at a single point, and they created statistics on the temperature versus quality. However, this is not proven to be an imperative measurement due to the fact that there are many variables that can attribute to temperature changes further down in the process.

Still it is strongly recommended to consider this point of measurement because this temperature still has some affect on the total process. Imaging will allow for an entire profile of the plastic, and allow for possible adjustment of the extrusion die heads if there are areas of the plastic that are warmer than others.

The purpose is to hopefully create a consistent sheet of plastic. On the next page is a picture of a Polystyrene sheet of extruded plastic before it goes into the thermoforming oven:

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This entry was posted on Thursday, April 10th, 2008 at 12:03 am and is filed under Equipment Vendor, Infrared Thermography, Infrared Thermometry. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.