Message Board Thread - "using IR in molding industry"

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using IR in molding industry gendron1 4/29/2008
i am a beginner in thermography. i have been certified in building sciences but i am encountering something new with my full time job. i work at an injection molding factory that is using an IR laser type thermometer to check the temperature of a mold at ten feet away from the target. I am not an expert but i dont believe what they are finding is accurate due to emissivity , apparent temperature, and also the distance at which they take the temperature. Now is there a camera made to deal with checking temperatures on reflective surfaces in the molding industry? or is there a certain technique I could use with a B-cam? thanks
 
Re:using IR in molding industry jvoitl 4/30/2008
Your probably correct that they they are not reading the correct temperature. See this link.
http://www.itcnewsletter.com/2006/2006-06_page2.htm
 
Re:using IR in molding industry Toolman 4/30/2008
gendron1,

There are several issues that need to be taken into account to get a correct reading:

Emissivity -
As you surmised, this is critical. You need to know the emissivity of the object to be measured and either modify it or correct for it(article jvoitl referenced explains it well). If doing emissivity correction, you also need to be able to accurately determine Tref.

Object size/distance/IR device spot size ratio-
A spot radiometer is essentially a one pixel IR imager. If it's spot size ratio is 12:1, that means that at 10 feet, the displayed temperature is the average of a 12" diameter spot. To get an accurate measurement you need to be close enough to insure the object of interest entirely fills the active measurement area of the device, while at the same time being able to insure that the IR device is, in fact, accurately aimed at the target - this can be tough to accomplish at longer distances.

Temperature-
Most injection molding processes operate well above the 100C maximum calibrated temperature of the BCAM, so it probably won't work well, if at all, in this application. An Infracam/E/T series would be a much better choice. The emissivity of some materials can also change significantly with temperature. A measured object that is significantly above ambient/Tref also has some benefits. Flir has some good material on IR theory in their manuals that explains this, and the new T series manual also has an excellent section on the measurement formula used in the IR cameras....maybe Gary can post a link if some of this is available online......

Finally, if you're going to be looking at these types of applications, I'd recommend you get your employer to send you to a level I class - the things you learn will be extremely helpful.

Sorry for the length - hope you find this useful...
 
Re:using IR in molding industry gendron1 4/30/2008
Toolman wrote:
1,

There are several issues that need to be taken into account to get a correct reading:

Emissivity -
As you surmised, this is critical. You need to know the emissivity of the object to be measured and either modify it or correct for it(article jvoitl referenced explains it well). If doing emissivity correction, you also need to be able to accurately determine Tref.

Object size/distance/IR device spot size ratio-
A spot radiometer is essentially a one pixel IR imager. If it's spot size ratio is 12:1, that means that at 10 feet, the displayed temperature is the average of a 12" diameter spot. To get an accurate measurement you need to be close enough to insure the object of interest entirely fills the active measurement area of the device, while at the same time being able to insure that the IR device is, in fact, accurately aimed at the target - this can be tough to accomplish at longer distances.

Temperature-
Most injection molding processes operate well above the 100C maximum calibrated temperature of the BCAM, so it probably won't work well, if at all, in this application. An Infracam/E/T series would be a much better choice. The emissivity of some materials can also change significantly with temperature. A measured object that is significantly above ambient/Tref also has some benefits. Flir has some good material on IR theory in their manuals that explains this, and the new T series manual also has an excellent section on the measurement formula used in the IR cameras....maybe Gary can post a link if some of this is available online......

Finally, if you're going to be looking at these types of applications, I'd recommend you get your employer to send you to a level I class - the things you learn will be extremely helpful.

Sorry for the length - hope you find this useful...
thanks for the information. I will have to look into the level 1 class. thanks again and any other advice or wisdom would be appreciated
 
Re:using IR in molding industry Apprentice 5/19/2008
Im curious to know the materials in the mould ? that also as i have learnt,could impact the precision of your measurement with the B-Cam.
 


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