Thoughts about active heating from coil still going on as cartridge drops at end of timer's anneal step. 0.75 seconds is significant relative to overall anneal time with some of the builds where cartridges are running in the 3.0 sec range.
Back on pg 59 of this thread SGK was reviewing his analysis of the coil with his oscilloscope during the anneal step, and he pointed out that it took about 0.75 secs for the coil to decay, and for pretty much that whole time it was at significant power level.
http://forum.accurateshooter.com/attachments/newfile13-png.1065140/
At the time he mentioned it, I didn't really think through the implication of that, but its now sunk in. What that means is as the cartridge is dropping, and moving away from the coil, its still being heated. Furthermore its the tip of the case that's getting most affected, that part that was probably already the hottest.
I don't think its practical to try and stop this from happening, but from a process control point of view (best consistency in annealing) should we give it any consideration?
I feel like its probably a detriment to do something that tends to overheat the tip of the cartridge, so on the flip side should we proactively do something that minimizes that. Has anyone applied any higher temperature Tempilaq (higher than 750) to the tip of the case in order to try and determine how much hotter the tip of the case gets than say the neck? It may be this isn't significant.
I'm waiting on my PS and ZVS to arrive, but I've been playing with my PTR4 timer and seeing how I can work in responses to any problems that might happen like a cartridge not falling into place on the shelf, or the cartridge feeder running empty. I've seen the PTR4 in some other builds and its really quite versatile, much more capability that just a sequential timer. Its limited to 4 inputs, and 4 outputs, so it can never match the ability of the other full service microprocessors other people are using like Arduino, but its a nice in between. Ooops … sorry for the tangent.
Anyways I happen to think about that 0.75 coil decay time and realized with the PTR4 its easy to just add a 0.75 sec pause after the anneal step, and before the cartridge drop solenoid is activated, so that the cartridge is stationary rather than falling as the coil decays. I think that would increase the cartridge to cartridge consistency, as well as eliminate the chance we're doing something to overheat the tip.
Anyones' thoughts are welcome