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Soldering wires on hot-end?

Posted by dslc 
Soldering wires on hot-end?
August 06, 2012 12:34PM
Forgive me if this is covered or answered elsewhere, but I'm a bit uncertain about the wiring on my hot-end.

On my last hot-end I used bootlace ferrules to connect the power resistor, but - due to thick leads on certain power resistors - I find this can be quite tricky. So I have soldered the wires this time.

Thing is ... I'm a little concerned that I should be using a higher temperature alloy.

Do any of you solder the connections to the thermistor and/or resistor on your hot-ends? If so, what solder alloy do you use?
Re: Soldering wires on hot-end?
August 06, 2012 03:03PM
i bought some little crimp connectors for a telephone wire , think it was 24 or 26 gauge. i melted the rubber off and used those. seems to work well
Re: Soldering wires on hot-end?
August 06, 2012 03:36PM
If your power resistor leads are decent length, you don't need to worry. Just solder to the end of the wires, they will be far enough away from the high temperature area to not be an issue.

Edited 1 time(s). Last edit at 08/06/2012 03:37PM by NewPerfection.


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Re: Soldering wires on hot-end?
August 06, 2012 06:14PM
Thanks for the advice. The leads on my resistor protrude about 1cm from either side of the hot-end.

I'm only printing in PLA at the moment, so am not too worried, but might take a closer look before I starting printing in ABS.

Re: Soldering wires on hot-end?
August 06, 2012 06:50PM
You probably need high melting point solder then. It melts at 300C. The leads of the resistor get quite a bit hotter than the rest of the hot end because they have a better thermal connection to the element.

Re: Soldering wires on hot-end?
August 07, 2012 12:24AM
nophead Wrote:
> You probably need high melting point solder then.
> It melts at 300C. The leads of the resistor get
> quite a bit hotter than the rest of the hot end
> because they have a better thermal connection to
> the element.

With only 1cm of resistor lead I agree. My resistor leads are more like 5cm long, which is enough that the solder joints don't get too hot.


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Re: Soldering wires on hot-end?
August 07, 2012 01:05PM
Also if you solder, it might seem to work then fail later - I had "successfully" soldered the wires a few cm from my old hot ends resistors, only to have them fall off weeks later, either temperature fluctuations or creep. if you don't have crimps to hand, wire wrap seems to work well, just wrap a few dozen turns of wire around the joint.
Re: Soldering wires on hot-end?
August 07, 2012 02:15PM
Yes even if solder is below its melting point it seems to degrade over time due to oxidation.

Re: Soldering wires on hot-end?
August 07, 2012 06:24PM
Another suggestion for you... if you have some pop-rivets you can use them as joiners. Find some of the desired diameter, snip the head off, tap the pin out and you'll be left with a little aluminium tube that you can use to crimp the wire on to the resistor wire.

There are some photos of my use of a pop-rivets as wire joiners in my hot-end post.
Re: Soldering wires on hot-end?
August 08, 2012 04:03AM
Good advice as always folks. I think I'll re-do it using crimps instead. The only place I can find high temperature solder is Radionics and it's very expensive. Unfortunately my resistor is cemented in using car exhaust putty, so swapping it out isn't an option.

Thank you.

P.S. NumberSix: The clothes-peg springs are holding up well on my idler grinning smiley.
Re: Soldering wires on hot-end?
March 22, 2013 03:09PM
Great topic, I started to wonder if my way of connecting everything would be safe.. Guess I better use crimp connectors instead.

Also, the wires on my stepper motors are rather short, I have been soldering them neatly onto 3M flatcable, but now I found this:

Looks like a great way of connecting my steppers to the flatcable. I was imagining my flatcable to also have one of those cable-ends on it and using the connector pins in between the two cable-ends to have them connect. This way whenever I decide to upgrade my machine I don't have to cut some wires because I can just unplug them and this also makes repairs easier.

Are there people here that put the electronics together without soldering? And what kind of connection did you use? I'm still looking for some kind of holy grail.
Re: Soldering wires on hot-end?
March 23, 2013 07:56AM
Flatcable is too thin to allow running 2 amps through it. You need something at least as thick as the wires coming out of the motor.

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Re: Soldering wires on hot-end?
March 23, 2013 08:47AM
Ai, good thing you say this, you see I have always worked with just a soldering iron, led lamps, small transistors, resistors and just fussing around with my Arduino...

I have no knowledge of all these other requirements. The seller that I bought my parts from told me I could use the flatcables to hook up my stepper motors, but I understand it's not enough?

I will surely replace the wiring on my hot-end for thicker wire and the heatbed, but do I also need to replace the wires on my stepper motors?
Re: Soldering wires on hot-end?
March 23, 2013 09:33AM
the main issue i have with solder is that entire area needs to be wrapped tight to keep out oxygen and even my silver solder melts when i just solder wires together.

i think crimps help isolate the heat.

you want to prevent oxides from growing in the wire, causing higher resistance and then failure. you can just as easily use Symmetry Traditional Picture Hooks such as what is linked to here http://www.walmart.com/ip/Symmetry-Traditional-Picture-Hooks-Brass-Plated-10lbs-6pc/17237099

the metal bends easy and seems to work ok. the issues you need to be aware of are that the leads of the resistors can get up to 80deg c higher than the body of the resistor that makes contact to the heater block. the larger metal crimp acts like a heat sink slowing the heating of the metal on the other side which is usually copper. i would suggest to wrap the first inch of resistor lead with high temp Teflon shrink tubing, as this is the area that is most oxide prone for resistor failure.without shortening the resistor leads, use the crimps and connect to resistor lead ends. shrink the end tubing down,

the next part is just adding 2 sets of heat shrink tubing on the long wires you are attaching to the resistor. 1 a larger tubing, and another to fit over the crimp, you want to crimp the other end and place the smaller shrink tubing over the entire crimp area, preference is as far up as you can go. then melt this tubing to shrink it

this next part may require some additional planning if wired directly and not screwed down. read rest of instructions before proceeding from here:

now for the larger shrink tubing, this is a second barrier against oxide damage, place this tubing down and hopefully at least a half an inch from resistor body on the leads and over the high temp shrink tubing. shrink this down.

also if you want the resistor to last a long time and handle thermal stress better, take a sheet of aluminum foil cut it to 1 inch long strip and about 6 inches in length, align the edges to be at the end of one side of resistor body and roll in up tightly. make it a little bit thicker than the opening of the hole for it to go into. then wrap the excess around the other wire lead, and twist until it is tight. this is the end you will pull the resistor thru the heater block with. it is ok to twist the resistor in, you are trying to form the aluminum to the free space around the resistor. once the resistor is inserted, if it wobbles or wiggles free, then you need to repeat with more aluminum and ask yourself is this the right resistor, is this the correct heater block, how much have i had to drink, and possibly call it a day.

after resistor is installed and it dose not move easily remove excess first from side without the twisted wrapped foil, and then carefully unwrapped the other side and peel off the excess aluminum foil. the idea is to not allow the aluminum to short circuit the resistor. this will provide the largest and most reliable heat transfer to the heater block, you may hear some crackling noises the first time you turn on your heater, this is ok this is from the aluminum foil expanding and reshaping to its confined space. after the first run if the heater block is aluminum the thermal expansion with self annealing will assure proper fit.

never ever use thermal past, nor any glue in the resistor area.

hope this helps.



Edited 2 time(s). Last edit at 03/23/2013 09:36AM by jamesdanielv.
Re: Soldering wires on hot-end?
March 23, 2013 10:15AM

To be honest I think adding two aluminium plates at the point where the crimp goes, will also function as a heatsink. I have bought a few small aluminium coolers that I can connect there, the only difficulty is making sure these coolers don't short-circuit the machine, so I would have to add some sort of isolation.

My hotend is also covered in black thermal paste, I think the seller did this to isolate the heat from the sides of the hotend so the wires won't get too hot.
I will put up an image to show my solution this evening. Oh, and I live in the Netherlands, so theres no Walmart here winking smiley

Edited 1 time(s). Last edit at 03/23/2013 10:16AM by Ohmarinus.
Re: Soldering wires on hot-end?
March 23, 2013 10:51AM
these are available at any hardware store, but so are crimps, in the electrical section. it would be great if you had images. thanks
Re: Soldering wires on hot-end?
March 29, 2013 09:05PM
Okay, I managed to re-do my wiring for the hot-end. The hardware stores here in the Netherlands suck ass, none of them sell any good crimps and now that I found nice crimps, they don't sell the pliers for it.

I'm so done with this country in terms of equipment knowledge.

I am almost ready to start testing, but I can't figure out my Pololu settings for my stepper motors so will figure that out now. Thanks so far for your advice, will update when necessary!

- Marinus
Re: Soldering wires on hot-end?
March 30, 2013 11:52AM
just avoid the pain and go straight for crimps,

car/automotive crimps are easy to get hold of (the red ones)
cut the plastic off the crimp, make up the connections then insulate joint with crapped-on tape (capton)

i used the fabric type of high temperature insulated braid sleeving on mine, the sort of stuff used in floodlights to protect the internal wiring from the heat off the halogen tube, cooker element connections etc. Looks so much better than capton.

you will never look back
trust me
Re: Soldering wires on hot-end?
April 01, 2013 09:12AM
I agree that crimps are the way to go. If, however, you want to try solder, this is a source of relatively inexpensive solder:

Koford M618 High temperature solder. Melting point 598F. Ideal for soldering on pinions for G7 motors to prevent spinning. $4.98 ea. Google it....several on line hobby store sources. It does not wet as easily as 60/40 rosin core so it takes a little gettting used to and a hotter than normal iron if possible.

You get a foot or two of solder...not cheap per inch but you don't have to invest in a whole roll. Koford has a bunch of slot car products including some interesting "high temp" epoxies. Apparently slot car motors get very hot.
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