Attaching a thermocouple to the surface of an AL2024 plate

[khalchris]

I am trying to attach a thermocouple on the bottom surface of an AL2024 plate, basically I a going to drill some holes in my sample and I need to place the thermocouple as close as possible to the hole , i.e. very close to the hole perimeter to measure the temperatures.

any suggestions of which is the best way to do that ?

 

[btrueblood]

You could try spotwelding it. Better may be to make a recess on the alum. plate and hold the TC in position mechanically (a cover plate and a couple of screws).

 

[IRstuff]

Drill a hole, fill with thermal epoxy or grease, put in the thermocouple, and fasten as required.

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[VEBill]

Thermocouples provide very low voltage signals. It's probably best to try to avoid ground loops and common mode noise by keeping the thermocouple electrically isolated from metal plate if possible.

 

[MikeHalloran]

Put the t/c in a shallow drilled hole, and use a chisel or a punch to peen the edges of the hole inward to retain it.



Mike Halloran
Pembroke Pines, FL, USA

 

[controlsdude]

I would look at how a thermowell that are used in industry that holds a thermocouple, might get a better idea on how its done. Or just use a thermowell and attach to the plate by its hardware.

 

[mcgyvr]

You didn't mention an estimated temperate range but I love the loctite 444 tak pak kit for securing thermocouples. I use it all the time for circuit boards/metallic faceplates/heatsinks,etc...

http://www.mcmaster.com/#loctite-444/=mhqy2f

 

[khalchris]

@ mcgyvr I will be doing drilling tests and the temperatures will be around 600 C degrees in the center of the drill and around that temperature around the hole edges

 

[VEBill]

Would an IR temperature sensor (either spot beam type, or an IR camera even better) be a better solution than a thermocouple for this type of test?

Depends on the details of what you're up to.

 

[mcgyvr]

Only problem with IR is ensuring you have the emissivity setting correct.. Or your readings can be off significantly.

Personally for this application now that temps are known the MikeHalloran hole/peen method is what I would use. simple

 

[VEBill]

"Drilling tests" implies a non-steady state situation, so the temperature will vary with exact location and time. A single thermocouple will give you a single data point with some latency and time averaging.

Therefore I'd want to use an IR camera as it would provide the entire picture.

The IR camera can be emissivity calibrate using the aluminum plate heated to the same sort of temperature range. The thermocouple might help with the calibration step.

The value of an IR camera depends on the exact purpose of all this...

 

[khalchris]

@ VE1BLL thank you for your suggestion, I thought of that as well but the problem is that I will not be able to use the IR camera inside the CNC machine as it would be hard to install it and it would be dangerous that liquid nitrogen might fall on the IR camera and damage it, moreover the liquid nitrogen will create some sort gaseous cloud around the drilling are and this will block the ability of capturing clear images from the IR camera.

I thought if I can attach the thermocouple as close as possible to the hole exit I could get an approximate temperature of tool-workpiece interaction.