I bought a pro melt - 2 in January..................... It basically detects the temp of the heating element and not the actual alloy.................................
It's only the temp that I have problems with. I wish there was a way I could either reprogram the temp control, or bypass it all together and setup my own PID.
Bottom-pour (BP) v. Ladling: Hoping not to hurt any feelings here, so please take this that way. I personally think that it's 98% what one is used to and 1% mould-specific, 1% learning how to hold your mouth right for either application.
I've done a lot of both with all kinds of moulds (molds too, if you swing that way, which apparently spell-check does). Once I get back into the groove on either, I'm off and running. I do believe that bottom-pour takes some getting used to. I learned on the ladle and eventually got a bottom pour in the early nineties and have stuck with it since, except for a goodly amount of ladle-work (and magma machine-work) helping a commercial caster fried for years.
One strong point I agree the ladle has over the BP is that you can flood the sprue plate on certain moulds, letting the overflow run back into the pot. Do that with a BP and you have a mess, unless you can contain the sprue, which I CAN do SOMETIMES, when everything is going MY WAY. In other words, it's trickier, but can be done. whether it's worth the extra effort and practice is a personal decision.
I have two LEE 10# pots, one of which is over 30 years old and due for a new element. I was online looking for one last night. I MAY buy the t-stat and set it back - and wire the element straight to the cord, because I use a PID unit to control the heat anyway. I didn't have a thermometer and was having fits with some weird "alloy," so I used parts I had on hand and made a controller.
Skip anything with the thermocouple (TC) not IN the alloy. Ive seen some systems made up like you describe and coming from a process heating background, it will not tell you the temp of the alloy unless it's IN the alloy. MAYBE if the hot junction is welded to the outside of the pot, it MIGHT be close enough, but some response time would be lost which just adds work for the PID (the math part). Otherwise, it's as much a trial and error proposition as using the hash-marks on the mechanical controller that comes with the Lee units. Can you make that workd for you? of course, but why pay for the PID system if you're still just guessing? Clean, neat, convenient when the TC is not in the alloy, but it's definitely not ideal. Poke it right down in the allow and get used to it being in the way a little sometimes.
A "well" could be installed in the pot so the TC can be inserted withoiut touching the alloy, but that's more complicated and costly than we hobbyist would tolerate. You coiuld at least get the TC more in the middle of the mass, even though it is so mewhat insulated from that mass, it will catch up. The ones where the TC is just hanging inside the unit near the elelment have air around them - not alloy. That requires an offset*, which any of us would have to determine by trial and error and that would only be good for ambient for THAT DAY and if there were no air circulating.
*"Offset," in this context is sort of a "fudge-factor" on the temp, if that makes sense. Your monitored temp is XX degrees, but it's lower than the actual stuff you're measuring by, say ten degrees, so you add ten degrees to what you're reading. You do it with a fast or slow clock in your head, but can program it in on one of these controllers. "PID controllers" do not control the PID, the PID IN the controller controls a process. "PID" or "PID Controller is more colloquial and can be misleading to the user.
"PV": the temp of the material being processed
"SP": the Set Point, or temp you wish it to reach
"PID, VERY generally speaking, is the math that determines the difference between the SP and PV (which changes as you heat it - a diminishing difference, if you will), decides how aggressively to correct that difference, while paying attention to how close PV is getting to SP, so it can start to slow down and not "skid through the stop light." Think like going through town on a Saturday night "light to light" with a muscle car.
Sorry for all that. Maybe it will help someone, some day, understand that these machines are meant to do the mundane and repetitive math-thinking. One does not need to comprehend the intimate details to benefit from them. They are machines meant to do something we don't want to do. It frees our hands and head to do other things. For me, it allows me to keep tossing my large sprues into the pot and not have to handle a thermometer. Otherwise, I'm a pretty analog kind of guy. Are they NECESSARY? NO. But with the crazier and more unpredictable "alloys" I have to use as my wheel weights from the seventies have been depleted, it is a bit more convenient.
OH! I almost forgot! I would heartily recommend the LEE pots. They are basic, with no over-priced and unnecessary frills, inexpensive and mine have lasted a long time. Replacement parts are cheap and SEEM to actually still be available while nothing else is these days.
I have nothing against ladling and would happily ladle if that's what I had. ONE small consideration is that I ALMOST always have electrical power with which to cast, but I do run out of propane sometimes, and getting to town to fill a tank or two is a major inconvenience even if I am already going to town.
