How do you know you're not under curing or overcuring??

[Guest]

I hear some people say they bake 15-20 mins past flowout, and some people say 15-20 mins after the part reaches temp. For me those 2 would be way, way different lengths of time.

Personally, I always bake 15-20 mins (or whatever that particular powder recommends) after the part reaches temp, checking with an IR thermometer. But when I stick my parts in the oven, it's probably less than 10 minutes before the powder starts to flow, but at least 20 until the part reaches temp. So there's a variable of at least 10 minutes there, usually more for me.

What's the "right" way??

[Guest]

Re: How do you know you're not under curing or overcuring??

All cure times are at PART METAL TEMPERATURE

[Guest]

Re: How do you know you're not under curing or overcuring??

So then all those people who just bake past flowout are undercuring there parts by like 10 mins, that's a considerable amount of time!

[Guest]

Re: How do you know you're not under curing or overcuring??

Yes, they are. I know the heat up temps for all of my parts (for the most part) since I do a small group of parts. So it takes my oven 15m to heat up most valve covers to cure temp and then the timer starts from there.

Those that are curing a few mins past flow out are badly under curing IMO.


Steve

[Guest]

Re: How do you know you're not under curing or overcuring??

ALSO follow the recommended cure time and temperature. Do not try to make your own up or cure everything at the same time and temp.

Some powders cure different than others. Pay attention to your packing receipts from PBTP, it will tell you the time and temp for each powder.

[Guest]

Re: How do you know you're not under curing or overcuring??

Metal temp. at recommended time. Almost all powders have 100% overbake stability so you are better off airing on the side of over cured than undercured. Gotta watch those IR guns they can give pretty odd readings if the surface you are hitting is very reflective.

[Guest]

Re: How do you know you're not under curing or overcuring??

Thank you Dr. Faraday

[JW450R1]

Re: How do you know you're not under curing or overcuring??

yeah, i learned my leason with my i/r gun

[Guest]

Re: How do you know you're not under curing or overcuring??

Good info to put back up....

[Guest]

Re: How do you know you're not under curing or overcuring??

when it says PMT (part metal temp.) what exactly does this mean? i usually start timeing the part once it reachs the cure temp( ie: 10 min. at 400). i check the part with an ir gun also.

[Guest]

Re: How do you know you're not under curing or overcuring??

PMT (part metal temperature) means when the part reaches the prescribed temp. For example if it says 10 min at 400, once the part itself reaches 400 then cure for 10 min. That is my understanding.

[Guest]

Re: How do you know you're not under curing or overcuring??

when it says PMT (part metal temp.) what exactly does this mean? i usually start timeing the part once it reachs the cure temp( ie: 10 min. at 400). i check the part with an ir gun also.

Here is what I do.

When the substrate is in your oven wait for about 3-4 minutes depending on the size and thickness. Check the part with your IR gun about 1 inch from it. (Mine worked better this way yours might be different) The IR gun should give you PMT. If you are using a chrome it might be difficult because the laser will reflect to something else. You can try different angles OR when out gassing the substrate check to see how long it takes to reach PMT without powder. I would add a couple of minutes to the cure time if you do it without powder.

[Guest]

Re: How do you know you're not under curing or overcuring??

A simple test to see if your part is under cured - take a cloth with a little bit (NOT TIM THE TOOL MAN) of MEK and swipe it over the part..do not RUB just swipe...if your cloth has paint in it, you are under cured !

[Guest]

Re: How do you know you're not under curing or overcuring??

A simple test to see if your part is under cured - take a cloth with a little bit (NOT TIM THE TOOL MAN) of MEK and swipe it over the part..do not RUB just swipe...if your cloth has paint in it, you are under cured !

Gotta ask the dumb question. You guys wouldn't think it was me if I didn't.

If you rub the part with MEK will the powder come off on the rag. This is why only swipe it, am I right or did I just go duh again?

Harley

[Guest]

Re: How do you know you're not under curing or overcuring??

I hear some people say they bake 15-20 mins past flowout, and some people say 15-20 mins after the part reaches temp. For me those 2 would be way, way different lengths of time.

Personally, I always bake 15-20 mins (or whatever that particular powder recommends) after the part reaches temp, checking with an IR thermometer. But when I stick my parts in the oven, it's probably less than 10 minutes before the powder starts to flow, but at least 20 until the part reaches temp. So there's a variable of at least 10 minutes there, usually more for me.

What's the "right" way??

Part temp is the right way.
I do it with the I.R. gun and usually go a few extra minutes on the cure time. Alot of powders have good overbake stability built in (time wise, not overtemp). You could always do some panels and do the rub test or cross hatch test.

Whats the cross hatch test? I suppoose it's in the manual I haven't finished reading yet.


Harley