1. Got a question or need help troubleshooting? Post to the troubleshooting forum or Search the forums!

Screw-In Thermistor Mod

Discussion in 'Mods and Upgrades' started by JohnStack, Mar 23, 2014.

  1. JohnStack

    JohnStack New Member

    Joined:
    Mar 9, 2014
    Messages:
    139
    Likes Received:
    65
    I was mentioning to Tesseract that I've spent $500 on hot ends for different printers. This mod works with the stock Robo3D as well as the E3D and a few others (like Hot Ends.com). I've known about screw in thermistors for a while but the challenge is that the ones I've found - I can't get taps small enough. Here's my home grown solution - it's probably not original but I haven't seen it...

    Problem: Thermistor shorts, Thermistor blow outs and resulting dead hot ends. As you may know, once you blow a hot end (jam it), you might not ever get it back to normal.

    Important note: This solution works with both the tiny 100k ohm resistors as well as those with the larger glass bead from Ultimachine.

    1. Buy 4MM stainless set screws - length of your choosing, a 4MM .70 thread pitch tap, and a #29 bit by Irwin. I just picked a side where you are looking into the heating resistor hole. The #29 bit won't need a pilot hole since the metal is so soft. (Irwin blades are decent.) Buy an additional bit that fits into the set screw hole. Just make sure it fits into the hole.

    2. Use Pliers or a bench vice...drill. With the #29, Drill enough to go almost into the hole to the heat break. This is the only way your tap will give you enough thread for the set screw.

    3. Get your thermistor set up with PFTE tubing. Push it all the way down to the glass bead. Bend the ends of the leads to keep the PFTE secure.

    3. Drill all the way through the set screw with the smaller bit.

    4. Pull the leads through the hole in the set screw. Keep shoving until the PFTE is through as well. You might have to twist or thread it through. With your needle nose pliers, pull it until the tubing is about 1/4" away from the glass bead.

    5. The Quick Steel takes about 24 hours to fully set. Be sure to knead it really well or it won't set up correctly. Smush some around the end with the PFTE and if your eyes are good enough, use a needle or small screwdriver and shove some into the set screw hole.

    6. Make sure your PFTE is all the way down to the glass bulb. Pull the wire and tubing until it is either into the hole or can't pull through anymore. (If you have the larger glass bulb type, you'll know.)

    7. Thread the set screw into your hot end. Use heat-proof thread locking compound. Caution: Don't tighten the screw so that you'll crack the thermistor. Leave a little room.

    For extra security, I normally use a little Kapton tape and wrap it round the thermistor leads and heater cartridge leads.


    Alternative - take those little screws that you see on PC cards - the ones that cables screw into. Find a matching tap for that and drill and mount. You can use the QuickSteel stuff with it as well. Most hardware stores do not seem to have the right drill and tap for them...I've been to a couple....

    IMG-20140323-00285.jpg
     
    3 people like this.
  2. JohnStack

    JohnStack New Member

    Joined:
    Mar 9, 2014
    Messages:
    139
    Likes Received:
    65
    BTW, some in another forum are buying the whole assy which uses an M3 standoff from an ebayer.

    In this case, you don't need to drill, you just need to tap one of the existing holes on the E3D.
     
  3. Printed Solid

    Printed Solid Volunteer Admin
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    1,605
    Likes Received:
    1,003
    Do you have a link to the ebayer?
     
  4. JohnStack

    JohnStack New Member

    Joined:
    Mar 9, 2014
    Messages:
    139
    Likes Received:
    65
    This was all I saw today. You might be able to contact them. I bought this exact thing last summer. They're a good seller. I never used the one they had. It's still around somewhere.

    Personally, if I were going to go to the trouble, go buy a tap. Not sure which hot end you have but you might not have to drill.

    http://www.ebay.com/itm/221228407572
     
  5. nickster

    nickster Member

    Joined:
    Oct 7, 2013
    Messages:
    82
    Likes Received:
    52
    Be careful to not get PTFE too close to the screw, especially if you want to Polycarbonate at 290C. Some propaganda says PTFE start to pyrolyze nasty byproducts at 240C. Quick Steel is only rated to 260C.

    I did something similar except I drilled out a 3mm Hex head bolt. Hex makes it a lot easier to tighten and extract. Thermistor is held in place with Pro Seal Hi-Temp RTV silicone Instant Gasket which is rated to 371C. Most hi temp RTV will start to out gas nanoscopic amounts of formaldehyde above 250C but there is probably more formaldehyde coming off of any MDF or plywood in the room. Next thermistor I do, I'll coat each lead wire with RTV. Permatex also makes Ultra Copper HT RTV. Both of these are supposed to be sensor safe, but there is some acetic acid produced during cure of the Pro Seal, but I did not notice any odor. If I remember the MSDS the Permatex used a different cure process.
     
  6. Printed Solid

    Printed Solid Volunteer Admin
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    1,605
    Likes Received:
    1,003
    4 people like this.
  7. Ocsff

    Ocsff Active Member

    Joined:
    Oct 28, 2014
    Messages:
    135
    Likes Received:
    40
    Do I have to change the thermistor setting like was required going from stock Robo 3D nozzle to E3DV6?
     
  8. Printed Solid

    Printed Solid Volunteer Admin
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    1,605
    Likes Received:
    1,003
    It is the same thermistor that is installed with the stock robo. If you changed your firmware for the thermsitor that comes with the V6, you will need to change the code back to 1 for the stud thermistor.
     
  9. Ocsff

    Ocsff Active Member

    Joined:
    Oct 28, 2014
    Messages:
    135
    Likes Received:
    40
    Easy enough, thanks
     

Share This Page