Keeping a consistent temperature

[mookiie]

I am new to casting and I am having trouble getting and maintaining a consistent pour temperature. How do you pros do it, have any tips?

[ipijohn]

Buy or make a PID. Frozone (a member here) makes them.

[theperfessor]

Or at least get a quality thermometer.

[mookiie]

What is a PID?

[mookiie]

Or at least get a quality thermometer.

I have a good one.

[Shiloh]

Or at least get a quality thermometer.

Thats what I did.

I cast from about 750 800 usually less than 800.In winter I have to go hotter cuz the set up is in the garage.

Shiloh

[AggieEE]

Mookiie, I'll try to answer this in a nut shell. PID stand for Propotional, Intergral Differental controler. If you get a quick temp change the Differental part of it generates a large signal which slams on the heat. The Intergral part take a small temperture offset and evens it out over time. The Propotional part is if a 10* difference results in 10% heat then 20* gives you 20% heat. The standard thermostat is a on/off only so you have some large overshoot/undershoot on some units. If you have one of the older AC units in your house it is either full on or full off. If you had a sensitive enough thermometer you would see the over /under temp swing. The mass of the air and contents of your house makes it easier to control temps as it streches out the on/off times. All industrial processes that require tight temp control use PIDs. I don't have one yet but it is on the list and worth it.
AggieEE

[Fishman]

Bottom line is that a PID attempts to keep your melt temp consistent. It will unless you add ingots. When you do, it will turn your heat coil on in your pot to bring the temp back up. I have one of Frozone's units and really, really like it. It has really improved my boolit quality and minimized frustration.

[Cane_man]

PID is the only way to go, imo... certainly can cast fine boolits without it, but it sure helps alot and takes the temp control part of casting out of the equation... you can use the PID to control lead temp, preheat molds, anneal brass, heat lube and it is a good investment if you are going at this for the long term...

[montana_charlie]

I am new to casting and I am having trouble getting and maintaining a consistent pour temperature. How do you pros do it, have any tips?
If you aren't fiddling with the thremostat, the temperature of your molten metal will stay fairly constant.
What is much more critical to good bullets is having a consistent mould temperature.

What indications are you seeing that make you think your 'pour temperature' is varying?

CM

[fredj338]

I set my pot on the desired temp, then keep filling it w/ small amounts, like 1# ingots, to keep the alloy about the same temp. I don't see much diff in casting +/- 50deg.

[mookiie]

What indications are you seeing that make you think your 'pour temperature' is varying?

CM

I have some that come out with sharp bases while others come out with rounded bases and corners.

[rsrocket1]

Prior to adding a PID control to my Lee 4-20, I was constantly fiddling with the temperature control and spout adjustment as the pot went from 7/8 full to 1/8 full (my usual limits).
The thermometer was showing that a fuller pot required a higher setting on the thermostat than a near empty pot. I know that the thermostat is probably a simple bi-metal switch that turns on and off at a set temperature, but for some reason, I did have to adjust it down as the pot emptied or else the lead would climb well above 800 as the lead level went down.

After reading the threads about PID's, I made mine out of spare parts (I'm an EE so I do have these things as spares) using an Omega CN9000a temperature controller (http://www.omega.com/pptst/CN9000A.html), a Crydom a1210 (http://www.crydom.com/en/Products/Catalog/AdvancedWebPage.aspx?CategoryText1=Panel%20Mount&CategoryText2=AC%20Output%20SSR&CategoryText3=Series%201%20240%20VAC%20-%20Ratings%20from%2010A%20to%20125A%20@%2024-280%20VAC%20-%20AC%20or%20DC%20control) Solid state switch (a 10A switch is a little small, but it works and it cost me nothing) a 6' extension cord and some crimp lugs. If you had to buy your parts, you can buy other parts which are just as good for much less money than these parts.


With this setup, I can set the pour rate once and it keeps an even flow from the top of the pot to the bottom and I never have to set the dial thermostat. When I add more ingots, I just take a break and let the thing heat up until I see the readout get to the proper temperature.

[montana_charlie]

What indications are you seeing that make you think your 'pour temperature' is varying?
I have some that come out with sharp bases while others come out with rounded bases and corners.
That may or may not indicate a temperature problem. It may simply be a variance in pouring technique.

Do you cast with a dipper, or from a bottom spout?

CM

[mookiie]

It is a bottom pour.

[montana_charlie]

It is a bottom pour.
Personally, I have never learned the knack of using a bottom spout with a technique good enough to get 'keeper' bullets.
But, many have.

Be sure your sprue plate is loose enough to allow venting of the base area of the bullet, and don't bear down on the plate so hard that the looseness that you put it is negated by you forcing it to stay in contact with the mould blocks. It will settle flat on it's own, before the alloy solidifies ... ensuring a flat base.

Alternatively, you may want to 'pressure pour' when filling the cavity.
In that case, it's necessary to ensure base venting by actually creating the groove the air will travel through.
To do that, you bevel the top edges of the blocks on both sides of the cavity.
BUT ... and this is important ... by 'bevel' I mean to just 'break the edge' of the corner. After both corners have been 'broken' they should form a groove so small your fingernail won't catch in it.

With that 'vent', air can escape from the base corner even if you are pressing the sprue plate down as you maintain contact between the sprue hole and the bottom spout.

That's about all I can tell you about 'technique', and it is pretty generic.

But ... getting back to 'temperature' if your sprue puddle doesn't take about five seconds to solidify, something is too cold.
If you suspect your metal is low, crank it up a bit and look for improvement.
If you believe you are using an adequate pot temperature, speed up your casting rythmn to get your mould hotter.

Once you get sprue solidification up to the five second point, try to maintain a cadence which keeps everything at that temperature.

If you are in a situation where the sprue takes considerably longer than five seconds to solidify, you may be way hotter than necessary. If it is under a condition like this that you get rounded bases and corners, it's because that happens when things are too hot.

Between five and seven seconds on the sprue puddle is a good indication that your temperature is okay ... even without a PID.

CM

[10mmShooter]

Mookie

I like the PIDs but don't find them necessary, here a few pointers to keeping temps constant,

1. Keep pot at a least 60% full all the time.
2 Let the full pot stabilize at the desired temp for me thats 700 on my thermometer, for my Lyman mag20 the themostat setting is 8 1/2 for stabile 700 degree pot.
3. Cast away,
4. Collect your spures to the side, I melt mine on a small hotplate and then once melted, I add them back to the pot, this keeps the pot temp from dropping crazy.
5. In my Mag20, I can add 2 one pound ignots to at a 50% full pot and that wont drop the temp below 675, there by I can keep casting as my temps come back up to 700.
6. Just try to time adding lead in 1-2 pound increments to avoid big swings in pot temp 700.
7 As mentioned, in the 675-700 temp range watching your mould temps is just as important as the pot temp. A hotplate really helps when you need to bump up the heat on your moulds, I find once I get going the molds stay plenty hot....actually I find I have to slow the pace periodically if the bullets are coming out a little too frosty.

[dverna]

Good advice. I am also a firm believer in keeping the level of lead in the pot over 50% and adding ingots a bit at a time to reduce melt temperature swings. If you can afford it, a PID is a nice to have; but it will not help you if you run the pot down to 25% and add 5 pounds of ingots - it takes time to get that new metal up to temperature.

So the first thing is to try keeping your pot level up and start adding ingots when it drops to say 75% full. You have a thermometer so you can tell how much your melt temp is changing. If you are still having fill out issues, bump your "normal" temperature in 25 degree increments but do not go over 750. If you are still having issues, add tin (up to 2%) and see if that helps.