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  1. #1
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    Default Luthiers bending iron with PID controller

    I’m making a two part bending iron with a PID controller. The reason for it being in two parts is so I can unplug the bending iron and plug in a bending blanket. I decided to make my own as the only one I found available in Australia looks to be rudimentary by design electrically. I am not going to go into detail of the wiring of this device here. Just thought I would show what I have come up with. The basis of the iron itself is a solid 80mm diameter block of aluminium 200mm long, I have drilled a hole through the length of this to install a heating element which is 500 Watts, thermal paste has been added also. I have also drilled holes to reduce the thermal mass of the aluminium. Drilled and taped 3 m8 threads to mount the block to the box, the aluminium sits on a piece of cement sheet and the bolts have fibre washers and a sheet of mica to protect the malamine from heat. There is also a taped thread for the thermocouple. I found some connectors from RS Components that were a little more unique than just using 240v plugs and plates, this was to stop anyone plugging whatever to the controller or to the iron. The thermocouple has its own unique connection also. I have used high temp wire and ceramic connectors in the bending irons box, it is also vented. I have created a tunnel in the sides of the box (fully enclosed to keep the wiring away) to clamp it to a bench. I will add an on/off switch to the controller box also.
    Here are some pics





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  3. #2
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    Looks good. How long does it take to get to temp?
    Those were the droids I was looking for.
    https://autoblastgates.com.au

  4. #3
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    It's been a week and it's still not warm [emoji1]will find out once I finish getting it together.

  5. #4
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    Dec 2011
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    This is probably a dumb question and all - but why "temperature control" a bending iron. I get why people do it with bending blankets (though I quit using temperature control on mine and just bend when the wood relaxes. My bending is now quite a bit better without the controller..)...

    But on an iron - the critical bit is the wood, not the iron.. And the wood doesn't stay in contact with the iron for extended periods of time... The main reason I can come up with is to simply keep it from getting too hot and burning up your heater or scorching oily wood too quickly... A PID would serve admirably in this case... And probably a lot easier to find/hook up than a bimetal deal out of a toaster oven..

  6. #5
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    Not a dumb question at all. As I am a novice when it comes to bending wood I wanted to remove a variable to aid in consistent results, and as the son of a fussy electrician I thought the PID would do a great job for both the bending iron and the blanket. I don't want to burn up the element, which from the reports I have seen on some of the irons available, it has happened. My thoughts are that the off/on type thermostats used may contribute to shortening the life of the element, much like turning a light on and off regularly (I may be wrong here). The PID just seems like an easy solution for me and I like to fiddle with electronics! There will be at least 2 people using it so I hope that it will make life a little easier for both of us. Will see what happens I guess [emoji848]

  7. #6
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    Oct 2014
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    Nice work Cal.Looks well thought out and safe.
    let us know how it goes.
    Interested to see what you have done here as I want a temp control for my blanket so I can use it for repairs.

    A comment to truckjohn : one of the necks i have been making has truss rod rattle and i need to remove the fretboard to fix it.
    I have used an iron in the past to do this and not been happy with the process, so being able to use a controlled low heat to slowly
    heat the fretboard up seems to be a good reason to have temperature control.

  8. #7
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    Thanks Mase, yep thinking safely with this AC can be a nasty beast when handled wrong that’s where my father comes in also. He gave me the ceramic connectors and a few words of advice but knows I am on the right track after explaining what I was doing. I am going to put some warning labels on both boxes so if something happens to me in the future then there is less of a chance someone will try to plug the wrong thing into either of them, it’s just too risky doing nothing. Here is a link to the controller itself PID Controller ITC-100 | INKBIRD there are a few YouTube vids of them being used in beer brewing, a couple of really good ones by an American chap. Hope to get a bit more done this week and double check everything then give it a run, I am also thinking of putting a timer on it just in case I forget to turn the power off. There are DIN timers of the same size as this for not much money, set it to switch off after an hour or so. It would save me from burning the shed down!

  9. #8
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    Here's the thing with these.... Even with the modern controller - you must never ever leave it plugged in unattended... Do not even leave them plugged in and turned off unattended.... If you have to walk away - unplug it. No exceptions.

    I personally know several luthiers who had 100% losses on their shops due to bending irons and heating blankets catching fire... One inadvertently left his bending blanket turned on all night and lost the entire shop... Luckily his shop was not connected to his house.

    Best of luck with your build. It looks like a neat setup.

  10. #9
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    Could not agree with you more John, there is never a single plug left in a powerpoint for longer than I am using it at any given time in my shed. And the last thing I do before I leave the shed each time is to check all power points again just to be sure I have not left anything plugged in. Did I mention I'm the son of a fussy electrician? My mentioning of a timer is added protection just in case. It's not a fall back or failsafe by any stretch.
    Cheers Cal

  11. #10
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    It's alive! I have success, took appropriately 15 minutes from 18 degrees C to reach 140 degrees C. Bent a small piece of claret ash 2.3mm thick, I think it will work well. I will have to resaw some wider stock and see what happens.


  12. #11
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    May 2014
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    South Africa
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    G'day all not sure if I am posting in the right place but I saw the word LuthierI have started building a 34 string celtic harp.I have no experience and would appreciate any help.

  13. #12
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    Quote Originally Posted by trevor1944 View Post
    G'day all not sure if I am posting in the right place but I saw the word LuthierI have started building a 34 string celtic harp.I have no experience and would appreciate any help.
    You got close Trevor, one level up out of this thread and you can create your own thread. Would be good to see what you are doing! Cheers Cal

  14. #13
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    Default Luthiers bending iron with PID controller

    Well I finally got a chance to start making a guitar and using the bending iron. I started at 140 degrees C and that worked well for the shallow radius but upped the temp to 160 which worked better. I ended up with one small split on the inside towards the front of the guitar and have glued with titebond, it will be fine.
    Now for the other side which has a much tighter radius in one section, will try wrapping with foil to see if I can get it to sweat a little more on both sides to help with the tight bend.







    I will make up some cauls for the jig to better keep the form of the sides, I didn’t get a chance today to do it.

  15. #14
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    The bending is complete on this one


  16. #15
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    That's a good looking guitar there.
    What size plantilla is that?
    And that wood is pretty... What is it?

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