Installing a PID on my Lee Pro furnace

Discussion in 'The Ammo Can' started by Cranium, May 5, 2011.

  1. Cranium

    Cranium XDTalk 100 Member

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    Let me start off by saying that I'm fairly new to casting. When I decided to get into it, I bought the Lee Pro 4 20 Lb Furnace because it was inexpensive and had good reviews in the user community. The only downside to using this furnace was temperature control. It has a rheostat with numbers from 1 - 10 for controlling the amount of current going to the coils to heat up the lead.

    This created an issue for me. In order to tell what temperature I was at, I bought a VWR Traceable Workhorse Thermometer 4425. I would constantly have to check the temperature and could only maintain it within 20°F - 30°F of my desired 700°F. It was a pain to do and time consuming. Occasionally, I would find myself way above the desired temperature resulting in burning off my tin and causing some nice colors to form on top or I'd find myself way too low and my pours would slow down to a trickle. There had to be a better way other than buying another pot that had temperature control.

    The solution is to install a proportional–integral–derivative (PID) controller to the pot and let it maintain the temperature for me. As a coffee geek, I had heard of people using these to control the brew temperatures of the espresso pours to within 1°F accuracy. I almost bought this for my Isomac Millenium espresso machine but then learned it isn't very effective on heat exchanger type machines such as mine. I had also heard of people using these for Sous Vide Cooking and almost bought one for this, but didn't. So now I thought this is the perfect opportunity to finally get to use a PID controller to solve an issue that I was having.

    As I researched this, and not to my surprise, I found others had already done it. Through postings of others, I was turned on to a website auberins.com, Temperature control solutions for home and industry. It had all the equipment I needed at and at reasonable prices to achieve my goal. I placed my order for my parts and got them in yesterday. Now the project begins...

    The goal is to have a furnace that I can set the desired temperature and this temperature will be maintained with no interaction by me to within 10°F. The PID controller should maintain it within 1°F so my goal should be easily met. My other goal was to install this as part of the furnace rather than as an external box that the furnace plugs into. The external box is simple and can be easily used for another purpose so there are benefits to it but I want a clean single unit to plug in, melt lead, and store.
     
  2. Cranium

    Cranium XDTalk 100 Member

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    Here is my somewhat dirty Lee Pro 4 20 Furnace that I am starting with.

    [​IMG]

    Here is the equipment that I bought from auberins.com, Temperature control solutions for home and industry.
    It includes:
    • 1/16 Din PID Temperature Controller (SSR control output)
    • 25A SSR (Solid State Relay)
    • Heat Sink for SSR
    • K type high temperature thermocouple
    • Compact extruded aluminum box for 1/16 Din controller
    • Panel mount for K thermocouple
    • Flashing Buzzer
    [​IMG]
     
  3. Cranium

    Cranium XDTalk 100 Member

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    First step is to disassemble the Lee Pot controller housing. This consists of removing just a few screw on top and the bottom. As you can see, there isn't much to them inside. It is mostly just empty space. A rheostat and wires to the heating coil. I was glad to see this because it meant I had room to work with on my project!

    [​IMG]

    I had been wondering where I was going to mount the relay and heat sink and after I had the Lee housing apart, I found that the relay barely fits within it; but not the heat sink. So I decided to mount the relay to the base of the Lee Pot and allow the base to act as a heat sink. The heat sink I bought came with some thermal coupling grease so I lightly coated the bottom of the SSR, drilled a couple of holes and screwed the SSR to the Lee.

    [​IMG]
    [​IMG]
     
  4. fredj338

    fredj338 XDTalk 10K Member

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    I know some guys that have done sim work. I think you are chasing your tail a bit w/ the Lee pot though. One reason it fluctuates so much is there is no insulation around the pot or between the rheostat & pot. The more expensive RCBS or Lyman or even more exspensive Magma have an inch or more of insul mat'l. It helps the therm work more efficiently. Keep me posted how it works out. I have been quite happy just running the Lee around 6 after initial melting & add alloy as it get down to 2/3 full, seems to keep casting temps close enough. IMO, a 30deg diff isn't going to affect the weight or size of your finished bullets much.
     
  5. Cranium

    Cranium XDTalk 100 Member

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    Don't be raining on my parade at the very beginning now! heheh

    This is as much a fun project for me as an attempt to solve an issue.

    PID controllers shine in the realm of temperature control and 'learning' about how the equipment performs with overshoots and undershoots. It adjusts itself to perfection and doesn't care about insulation or how full the pot is.

    Read a few paragraphs on it here and maybe you'll change your opinion. PID controller - Wikipedia, the free encyclopedia

    Or just wait for the results and we'll all find out how well it works about the same time.
     
  6. fredj338

    fredj338 XDTalk 10K Member

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    Ok, but what is this costing you? If it's just an excersize in learning, doesn't matter, if it's to build a better pot, then there are better pots.;) If it's cost effective, I wouldn't mind setting mine up just so I didn't have to check temps as often. I am happy though casting anywhere from 675-775deg for most alloys.
     
  7. Cranium

    Cranium XDTalk 100 Member

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    Cost isn't the point here (haven't you learned that about me by now? ;)) It is a fun project that I am learning on.

    With the items I ordered, the total was $140.71 with shipping. I've already determined that about $25 of the order was in unnecessary parts that I probably won't use so figure $115 total for the project. If you go with your own housing instead of the aluminum one I bought, it would save an additional $22. Regardless, this is still much cheaper than purchasing a Lyman Mag-20 or RCBS Pro-Melt.

    More to come tomorrow...
     
  8. fredj338

    fredj338 XDTalk 10K Member

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    Yes, but not much. Still, I understnad the DIY aspect, after all, it's why we reload & cast. I run a MagmaCaster on occasion, so I know abotu spending some money on casting.;)
     
  9. Cranium

    Cranium XDTalk 100 Member

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    I was watching a video on the master caster as I read this.
    Star lubrisizer + master caster = consistent, high quality, high volume lead bullet production. Magma engineering has some great products.
     
  10. Szumi

    Szumi XDTalk Newbie

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    Sounds like a case of great minds think a like. I scrounged a Omega Engineering controller out of some machine that was being scrapped and tied it to a 6 buck relay that so far hasn't failed. Add a thermocouple that was cut short by someone routing it int the wrong place and I was up and running for time and 6 bucks.

    I keep the Lee t/stat in the loop as an overtemp saftety of sorts in case my mechanical relay contact welds.

    The set up worked great for casting.

    I don't do a lot of handgun bullet casting casting now since I work too much O/T and buying commercial cast gives me time to actually shoot on rare occasions when I don't have to work.

    I do plan to get my 03-A3 out and cast some rifle bullets for it. I can find time for that.

    Szumi
     
  11. libertad

    libertad XDTalk 100 Member

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    Not familair with your particular controller, but it probably will benefit from some tuning. Most of them do not teach themselves and arrive programmed with Proportional Integral and Derivative factors that will minimize overshoot but stabilize slowly. Since it appears the pot is not well insulated, you can handle a bit of overshoot and shorten how long you have to wait to cast. You won't want to get too aggressive, though. Your mass (and thus the response) will be constantly changing as you take molten metal out of the pot. Aggressively tuned controllers will cause oscillation when something changes the response rate. I have programmed furnace controllers in the past, and it was pretty fun (but completely nerdy).
     
  12. fredj338

    fredj338 XDTalk 10K Member

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    Mine is nice, bought it years agou when they were "affordable". It isn;t any faster than a Lee 20#BP & 6cav mold, but you can cast for hours if you want, just pull the handle. Magma also makes some nice molds, but only two cav. Yes, I use a Star luber/sizer too. I don't have that much time & the Star is eaily twice as fast as any other.
     
  13. Cranium

    Cranium XDTalk 100 Member

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    Next step was to determine where to mount the aluminum housing for the PID Controller. I decided to mount it on the back of the Lee housing and low enough so that radiant heat won't have a direct effect on the PID controller face. I attached it with a couple of screws and then drilled a hole to pass a couple of wires for powering the PID and controlling the SSR.

    [​IMG]
     
  14. Cranium

    Cranium XDTalk 100 Member

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    Now, I'm ready to start wiring it up. First was to get power to the PID. I soldered the wires onto the existing power wires to keep things simple and allow me to remove it easily if needed in the future.

    [​IMG]

    Next, I wired up the heater circuit to add the relay into the loop. Again, I did some soldering for a couple of wires and put heat shrink (green piece in pic) over the connector that used to go to the other coil contact.

    [​IMG]

    Finally, I ran a wire from the PID relay output to the relay and hooked up the thermocouple to the PID. Now it's all wired up and ready for re-assembly.

    [​IMG]
     
  15. Cranium

    Cranium XDTalk 100 Member

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    Re-assembly consisted of installing 8 screws for the PID housing and 7 screws for the Lee Pot housing. Quite easy and no left over hardware. :) The thermocouple wire was way too long for my needs so I coiled it up and tucked it in the PID housing.

    Here is the final assembled Pot with the PID controller attached from all four angles. I still need to come up with something to hold the thermocouple in the pot and just off the bottom. I'll take care of that tomorrow.

    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
     

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