Final testing & I think I have a workable oven... Several questions have 'sorta bothered' me up until now...
*Will one set of heating elements in the top of the oven be enough to bring a full tray to full temp & in a timely fashion?
*Will the delicate PID survive in the control enclosure doing several batches of cast?
*What will be the new bake time starting from a luke warm or cold oven?
I guess, first things first. I need to see if the 204çº temp setting on the PID will agree with my multi-meter reading 400ƒº? I have a reason to want to use the multi-meter.
I cranked it up, empty, and allowed the PID to come to the set temp (with fingers crossed) and it came out close...the control enclosure with the cooling fan running is at a cool 83ļ.
Here's why I wanted to use the multi-meter. Many times the question has come up in the past whether or not the interior of the cast boolits come up to oven temp. and does that affect the quality of the coating getting cured? I have no idea but I'm going to try to answer that question of inside temperature of the cast.
I drilled the bottom of one of the cast so that I can insert the wire end of a thermo-couple.
Inserted the wire and set the cast on it to see if it would stay put? That wire is springy...
So far...so good. Next, to shake up some Lyman 452374 - 225gn. RN's in my 'old lead' blend of PC...
Start stacking the first full tray of 3 that I will bake back to back today...
Loaded the tray and the bare cast with the wire stuck in it's tusch...started the timer running.
**Notice that I almost never get a picture with the PID's numbers fully lit up. I think they blink and at a rate that doesn't agree with shutter speed of this digital camera? Maybe someone has the answer to that, I don't. I have to actually take a short video if I want to show a picture of those numerals lit up & then take a screenshot to show them...a big pain in the tusch!
So far so good again...next thing to monitor is the time elapsed when all the cast's PC coatings has turned to liquid? It's 5 minutes, just as before I started this project...
The interior of that bare cast is already up to 266ļ... (first mistake...I forgot to write down what the actual oven temp. was!) "Oh well!"
It was about 9:30 minutes when I noticed that the interior oven had come up to 204çº (400ƒº) from this point I add 10 minutes bake time and I think I now have 20 minutes total for the cycle time? I switched the on-off/timer switch at the bottom to auto-off and set the timer to 10 minutes...the oven should turn off after a total of 20 minutes.
The PID had overshot and gone up 207çº (the PID is learning for the first time with a full tray of lead) by now the bare cast's interior is up to 367ƒº...
At 20 minutes I expected the bell to 'ding' signaling the end of the cycle, the oven actually turned off at 22 minutes. The interior of the bare cast has settled to 361ƒº and the oven was at 204çº (400ƒº) . . .
I pulled this first tray out and allowed them to cool a few minutes and dumped them and started loading another tray of 3 trays total. I wished I had an extra tray to alternate with but I don't and can't find one to fit this oven..."Oh well."
While they sat there and cooled, the control enclosure fan is off, the temp. in the enclosure rose to 120ļ, that is less than the first time I tested it but today is a mild day of 78ļ in the shop, even after the third tray came out of the oven the control enclosure never rose above 120ļ.
It is looking like I now have a PID controlled oven and that it just may last a while (fingers crossed again!).
Thanks for following this project boys...it's been fun...