Curing multiple parts of varying size in oven at same time??

[Fireblade]

I have a question for you guys that have large ovens, but coat a multitude of different size and mass parts. Do you guys group your parts together according to size and mass during the cure process to get a full cure, and not a over cure? I mean if you put in a 20 pound chunk of aluminum in the oven, and 50 one pound chunks of steel, is this possible to cure at the same time? I have a 4'x4'x8' oven under construction right now, and just wondering how I should go about doing multiple different parts curing in it. If it is possible to do these at the same time, even though I know they take different times to heat up. I dont do mass parts of the same, I do one piece of this with one these kind of deals. Thanks

[non-stick]

well...... congrats on the oven, first off. Sounds like somebody's stepping up into the world. As far as the different masses on ferrous and non-ferrous metals and core temperatures, I can bore you for hours on theoretical and proven times for heat conductivity. Let's go this route instead,shall we?
Aluminum heats faster than steel. This is fact. Therefore the aluminum piece would take less time than the steel even if greater mass (up to a point). Assuming you are NOT doing this in a kitchen type oven, one would coat the steel first, hang it in a cold oven and turn it on. Heat it up to temperature and wait until it starts to get that "melt" about it. Keep checking by cracking the door and looking in with a flashlight ( I told you all we were gonna stay away from the technical stuff,lol). When your part is _just_ cured....take it out and hang in a spot where it can cool down by itself easily enough via air reduction. THEN you put in your aluminum part. When that has cured sufficiently (part metal temperature as indicated by your directions) only then can you open the oven doors slightly, turn the heat off and leave the fan on. The fan will help cool everything down and both pieces will be coated using the most cost effective method. Steel can take a long time to heat up and it can go along for the ride in your oven when coming up to speed (which you were going to turn on anyways). The steel will retain heat longer, so basically you've got to get it out of there toot sweet. Aluminum conducts heat faster, therefore able to take that quick heat up and cool-down in the oven. So basically....there ya go. Both parts done and no oven time ($money$) wasted.
Of course...you listed extreme weights for examples. What would you do in a real world situation where the parts were within like masses? Easy.....coat them all, put in a cold oven. Shut the doors and turn the oven on to temperature. repeat the process for aluminum as stated above. If near same weights and masses, the parts will basically "act" the same in that method. If near same mass (within 5 pounds of one another maybe?) you can heat the oven up and hold at a temperature below the lowest cure ( say maybe 325?) for a while then boost the temp. up to final cure range. You'll note that most thermoset plastics (what you guys use) have a 100% over-cure range in them. Meaning....if your aluminum part is fully cured and the steel is just getting there....and will be done let's say 8 minutes later? It's ok. Your "window" is set nicely so that you can do this. Just work slowly and don't rush,k? It's easier to re-coat or even re-prep whatever your doing than burning/blasting the part off and reworking it,lol. Especially a 50lb hunk of aluminum,right?
That's it in a nutshell, folks. Sorry that I drone on and on at times. But then again...... you guys all ask good questions that need some explanation at times,lol. Take care all..... Russ

[Fireblade]

Trust me, use all your technical savvy all you want, I want to know as much as I can possibly know and more. This is something I want to really do, full on. The more I know, the easier and more cost efficient it is for me to do what I like. I used the extreme variables, to really get a straight forward answer, which you gave, thank you for that. Alot of stuff you read about for PCing, is all from vendors, and they don;t want to tell you anything, but they want you to buy what they sell. That seems to be there answer, which honestly I steer away from. I'd rather learn it the hard way, the way I see it is this. If someone else can do it, so can I, maybe better. Maybe a snobbish approach, but why set low goals? I've been reading your posts, and learned alot from them, keep em coming! Thank you

[non-stick]

lol....trust me. I do this because I love what I do. I thank you all for letting me ramble on. I don't make any money by telling you my secrets and such...but what the hey. What good is it if you can't share,right? I look at it this way..... if it helps you guys get a good looking part and helps Caswell sell thier products, who really loses? As for me....we'll just call it a very inexpensive for of therepy for the moment and leave it at that.