Heating / Cooling System

Discussion in 'The Projects Forum' started by abuhafss, Aug 17, 2010.

  1. abuhafss

    Thread Starter Active Member

    Aug 17, 2010
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    My objective is to insert a PVC tube in a small (cold) mold. The heater should heat the mold to an ideal temperature to melt the tip of the PVC tube inside the mold (for a few seconds) and then the heater must switch off and the mold must be cooled down immediately by circulating water through the outer sleeve of the mold. All this process should be achieved with a single press of a triggering button. The ideal temperature and time, could be determined after testing various combination of temperature and time settings. I attach my circuit idea for reference.

    Now, please have a look at the mold. It is made with steel for experiment only. I inserted the tail of the mold in a 45w soldering iron as shown in the picture. My test was successful.

    I plan to build a set-up in which I can use molds of various working sizes. I mean, the outer dimensions of the mold will remain the same only the hole diameters would vary to match various sizes of PVC tubes. The actual molds will be coated with chrome or nickle. And, if required, I can change the material of the mold to aluminum, copper or brass for better conductivity. The mold would be installed inside a cooling sleeve, which cover only the body of the mold (excluding the tail).

    After testing the trial mold on a soldering iron, I planned to use a soldering gun which heats the tip more quickly. The secondary coil to be connected to a thick solid copper wire having a few turns round the tail of the mold.

    Now, here I need guidance to accomplish my objective cheaply. We can use induction heating system which gives very high temperatures in seconds. But, I think that I don't need such high temperature for my project.
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    A simple PLC would accomplish all your needs.
    PLC's start at $60 and go up from there. Look into the "Click" PLC.
     
  3. retched

    AAC Fanatic!

    Dec 5, 2009
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    This is a standard process for plastics and food molding. (Ummm, popsicles)

    I agree that you should be able to find the timer/controller for pretty cheap off-the-shelf.

    Following mcgyvy's lead, check this link:
    http://www.aboutplcs.com/click/
     
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    oh and burning/heating PVC is not a good idea as it releases toxic gases (dioxin) that can kill you.
     
  5. abuhafss

    Thread Starter Active Member

    Aug 17, 2010
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    Frankly, I have no experience of PLCs. But, I wonder if I really need a PLC for my project? My circuit is not so complicated, it consists of 2 timers, 12v power supply, relays, aquarium pump and a heating station. The main issue is how to get the appropriate heating set-up. Controlling of that set-up can be done with the help of timer and thermocouple.

    If required, I can acquire a PLC for more precise results. But, right now, I need your valued suggestions to build up a proper heating station.
     
  6. abuhafss

    Thread Starter Active Member

    Aug 17, 2010
    154
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    Can anybody guide me, please?
     
  7. retched

    AAC Fanatic!

    Dec 5, 2009
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    If you want to have precision timers that activate devices (resistive heaters, inductive cooling pumps) You can use a relay board.

    There are OTS (off the shelf) parts that are available that could do this easily.

    Thing is, you want to measure the temperature and if its too low, increase the heating current or time until it is reached, then pump coolant over the mold.

    So, flow-chart the process then go from there.

    If all you REALLY want is 2 timers that operate relays, I would get the relay board and use a software solution that will allow you to change the times.

    This site should get you what you need.

    You can get 2 timer/relay that talk to each other. When you start one, it will power your heater for (x) seconds. then it will open and the other relay will run your pump for (Y) seconds.

    http://www.automationdirect.com/adc...essionid=5e30335f1805c1513ed6857714b1b114885c
     
  8. SgtWookie

    Expert

    Jul 17, 2007
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    Just so you know, this Board is not interactive. Whether or not you receive a reply right away, or if it takes days, is the luck of the draw.

    We seem to have a lot more people asking questions lately than providing answers.
     
  9. abuhafss

    Thread Starter Active Member

    Aug 17, 2010
    154
    2

    Thanks for your guidance. However, my main problem is still there.

    The main issue is how to get the appropriate heating set-up. Controlling of that set-up can be done with the help of timer and thermocouple.

    Please comment on my idea of using the transformer of a soldering gun, as mentioned in my 1st post.
     
  10. retched

    AAC Fanatic!

    Dec 5, 2009
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    Honestly, those things are crap.

    If you are making 1 at a time and waiting 10 minutes between each heat cycle, it MAY work. But these things are NOT meant to run continuously. Also, its the TIP where the heat is generated. The transformer is ONLY a transformer. So there is no need to take a solder gun apart.

    You need a heating element that is made to operate at the temperature you need. There are probably a hundred of these. Plastic forming is very popular WORLDWIDE. Im sure you can find an element that can do what you want quite cheaply.

    Then you need a transformer that can supply the element with the current and voltage that it requires.

    So that is pretty easy. You would then use a relay to switch the element on and off according to the timer.

    After you find out how long the element takes to reach the temp you want (say 10 seconds) then you can set the 2 timers.

    The timers can start at the same time. When you power on the circuit, heating begins.

    You set the coolant timer to count down from 10 seconds. When it hits zero, the coolant starts flowing and the heating stops.
     
  11. abuhafss

    Thread Starter Active Member

    Aug 17, 2010
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    Thanks for your swift response.

    Okay, first let me find some suitable heating element then I shall revert.
     
  12. retched

    AAC Fanatic!

    Dec 5, 2009
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    Good call.
     
  13. abuhafss

    Thread Starter Active Member

    Aug 17, 2010
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    RM

    I have been browsing for the heater element but, am confused among so many kinds. Could you please help which type would be more suitable for my requirement.

    Thanks

    :confused:
     
  14. retched

    AAC Fanatic!

    Dec 5, 2009
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    I glanced through the thread again, but I dont see what I need, or I may have missed it..

    What temperature do you want this to operate at?

    What is the size of the mold?

    Length, and diameter of the area of the mold that needs to be heated.

    I need these before I (or anyone) can find a suitable part.

    Also, where in the world are you located? Where do you need the part shipped?

    AND, Im going to bed soon, so if you get this info soon, I will have something for you tomorrow.
     
  15. abuhafss

    Thread Starter Active Member

    Aug 17, 2010
    154
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    I have already mentioned in my 1st post, I need to melt the PVC tube slightly, I guess it would be around 200' C.

    I had attached the photo of the mold in my 1st post, I attach another photo showing the length of the tail (1.5") that needs to be heated. The diameter is around 1/4".

    I am in Pakistan.
     
  16. retched

    AAC Fanatic!

    Dec 5, 2009
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    Ok. I am going to recommend you build an induction furnace.

    You can probably build it from stuff you have laying around.

    Induction heating only heats conductive materials. Your mold is conductive.

    Your water cooling tubes can be glass or plastic and will not be heated by this process.

    This is good for going from hot to cool quickly.

    READ:
    http://www.richieburnett.co.uk/indheat.html

    You will probably find many uses for this heater.
     
  17. abuhafss

    Thread Starter Active Member

    Aug 17, 2010
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    I have another idea.

    I shorten the tail of the mold, make it a fork-like shape and then slip in the tip of a soldering gun. A copper or aluminum foil can be used to cover up the air gap.

    Awaiting comments.
     
  18. abuhafss

    Thread Starter Active Member

    Aug 17, 2010
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    Please, help me with you comments.

    Thanks
     
  19. SgtWookie

    Expert

    Jul 17, 2007
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    Have you considered injecting boiling water or steam instead of a heating element? You could have a vessel of pre-heated water or steam, force it into the mold, and then cool it rapidly. It could be much faster than trying to use an electrical heating element.
     
  20. abuhafss

    Thread Starter Active Member

    Aug 17, 2010
    154
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    Would you please elaborate your suggestion with some example, as I have no idea about it.

    By the way, the commercial version of my project uses induction heating.
     
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