What temp should I trust

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SS2metal
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What temp should I trust

Post by SS2metal » Tue Jan 05, 2021 10:18 am

Good morning All!

Recently incorporated powdercoating into my finishing operations to improve workflow and product life. (I make custom aircraft weathervanes) Since I didn't want to drop a lot of cash initially I decided to use an old oven as everything would fit nicely into it. For part temp measurement I bought a Klein tools IR gun. I've had good luck with basic flat black but my first attempt at a glossy color did not come out very well. My oven temp seems to be all over the place when measuring the internal temperature with the IR gun so I got a cheap inkbird PID and hung the thermocouple in the oven to see what it read. Now I get three different readings and not sure which to trust. When oven set to 400, PID will read 415 and shooting the internal walls of the oven will read 385. I normally have to set the oven at 410 to get my part temps to read 400 with the IR gun and the PID then reads 425. Understand that the oven's temp control is not very fine and the inkbird is a cheap instrument as it the Klein IR gun. Would my best option be purchasing a higher quality gun such as the Fluke? In process now of putting together plans to build a 3 x 3 x 6 oven so I can powdercoat some of my larger creations but want to perform work now to the best of my ability and equipment until I can get the project done.

Attached a couple of the weathervanes
PrimeAirsmall.jpg
PrimeAirsmall.jpg (52.67 KiB) Viewed 335 times
Falcon900Small.jpg
Falcon900Small.jpg (56.82 KiB) Viewed 335 times
BigCubSmall.jpg
BigCubSmall.jpg (77.03 KiB) Viewed 335 times

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Jay V
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Re: What temp should I trust

Post by Jay V » Tue Jan 05, 2021 2:53 pm

Read the temp with the IR gun off of a flat black piece. An IR reading will only be correct when reading from black. Lighter or reflective finishes will read lower than actual.

Preheat the oven to 400F, place in your flat black piece, give it at least 5 minutes to come up to temp (if it's a thin piece), and read the temp. Try different angles to get a consistent temp. Even opening the door may drop the temp on the piece, so check it quickly and recheck if necessary.

Powder can be over-cured a fair amount without issue, under-curing reduces the powder's durability - so err on the high side. Typically you are better staying under 400F and extending the time if needed.

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Crip75
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Re: What temp should I trust

Post by Crip75 » Sun Jan 10, 2021 4:56 am

Nice weathervanes.
Do not believe all that is on the internet.

Mahatma Gandi

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