Benefits of a PID

[terryt]

Hi:

I am not familiar with a PID and would like to know the benefits of it.

Thanks,

Terryt

[Mike W1]

In a nutshell you set a temperature that you want, and it'll control it within a couple of degrees of set temperature, and it is repeatable to that same setting. Quite a lot less variation than you get with the numbered dial on the pot Also, dial thermometers do not respond to temperature change as rapidly as the thermocouple does.

[dannyd]

The temp you can use it on any pot. They work great

[wv109323]

A PID works like a thermostat but much more sensitive and better temp. control. The alloy temperature is monitored by a thermocouple that is immersed in the molten alloy. The PID is programmed to a desirable temperature for your casting needs. The PID then controls a solid state relay that will supply voltage to the heating element.
When the thermocouple tells the PID that the alloy temperature is low,then the PID "closes" the relay allowing voltage to the heating element, thus heating the alloy back to desired temperature.
Advantages are:
The PID can be programmed to any temperature desired.
Temperature control is usually plus or minus 10 degrees or better.
All wiring is external to the heat of the pot/alloy, except the two wires to the heating element.
The PID can control other temperatures such as lube temperature(with a thermocouple) located on the lube/sizer. Some are using thermocouples internal to their molds to monitor mold temperature.
There are no moving parts like the bi-metallic strip on a conventional thermostat.
The PID acts like a lead thermometer also.
My problem was about every three years I needed to replace the wiring around the thermostat due to heat destroying the terminations. Also over time my thermostat changed setting points.
When I began using a PID I immediately saw that I was casting with a low alloy temperature when I added alloy to the pot while casting. Adding 2-4 pounds of ingots dropped my alloy temperature from 700 to 560. The PID told me exactly when the alloy reached the desired 700 degrees.
A PID and A hot plate helped my casting quality.

[RogerDat]

A PID can "predict" as it were the future temperature based on past temperature changes, allowing it to provide power to the melting pot in anticipation of when it will be needed to maintain the temperature in a very narrow range. So for example as the pot has less lead in it the rate of heat loss will change, PID will adjust to the changed rate, a numbered dial just keeps cycling on and off at the same temperature points. So if charted temperature is cycling up and down over a range of several degrees. Even 5* temp up and down range can yield 10* difference between casts when the pot is lower on lead.

Not needed but... it becomes one less thing to worry about. You find a mold like your alloy at 678* and you can just set it and know it will be within 1 or 2 degrees of that.

Oh and I think some people use them to control temperature of lube sizers with heaters. I think you can also use with a temp probe in the mold and control hot plate that pre-warms the mold. That assumes one has multiple PIDs but there is something sexy about starting with mold and lead at precise temperature at the first cast.

[JonB_in_Glencoe]

The biggest benefit I noticed was temperature control.

Before I made and installed a PID, I was using a Lee PRO 4-20 pot with a Lyman thermometer in the melt. As the level of molten alloy gets lower, the alloy get's hotter, so to maintain the desired temperature, you need to continually tweak the numbered dial to a lower setting. I've found the temperature can rise as much as 50º, if you don't readjust this setting. This is due to the bi-metallic strip thermostat and it's location.

The PID solves that problem...Just set it and cast til the pot is empty.

>>> another tip to help keep the temperature constant, is to leave a 1/2" layer of dross on top of the melt, it insulates the molten alloy as well as being a barrier, so more dross won't form.

[Walter Laich]

don't forget the 'cool' factor of another piece of equipment on the casting bench. Drives the wife crazy

cr

[dragon813gt]

These are not my best results. But they're acceptable w/ a bullet of this weight.
http://i198.photobucket.com/albums/aa39/dragon813gt/TimeToMakeAmmo/A91B05E2-72CC-45BC-B090-91D8239B73EA.jpg (http://s198.photobucket.com/user/dragon813gt/media/TimeToMakeAmmo/A91B05E2-72CC-45BC-B090-91D8239B73EA.jpg.html)

The main advantage to a PID is that it's one less thing you have to monitor and adjust. It means your attention can be devoted to the other aspects of casting. Chasing temp will typically yield a bell curve w/ a greater span. Focusing on cadence will typically yield bullets w/ less deviation. When you cast 22 caliber bullets every tenth of a grain counts.

I plan on plotting my next casting session that will be a large batch of 10mm bullets. Can still get away w/ a larger deviation. But I like to know how consistent I'm doing. One thing I'm not consistent at is writing down the cadence timing :laugh:

[gwpercle]

You can't cast good boolits without one. It's the only way to fly !

[Morgan61]

I've used a PID from the time I started casting and am glad I did. I got a couple of different K style probes so I can also use my PID to control my powder coating oven and a smoker.

[terryt]

Hi:

Thank you for all of the info.

I liked this answer the best: don't forget the 'cool' factor of another piece of equipment on the casting bench. Drives the wife crazy.

Anything that drives the wife crazy is fine by me.

Terryt

[POP]

Where does one buy one of these PID units?