I Have A Cupcake I Am Working On.

[Ronnie Gould]

Trying To Find Out What Size Nichrome Wire To Get For Mark 4 Heater Barrel That I Am Rebuilding.

[Jetguy]

The one source for it I know of was Ultimachine had the correct stuff.
31 AWG https://ultimachine.com/collections/electronics/products/31-awg-nichrome-wire

[Jetguy]

Also keep in mind, be sure to get the resistance correct (total length of nichrome wire) as that gen3 extruder board MOSFET will fail quite easily with excessive current.
This is a known weak spot in the gen3 electronics design.

[Dan Laskowski]

Is this what you are talking about?

[Ethan Dicks]

On Wed, Mar 14, 2018 at 10:06 AM, Jetguy <vernon...@gmail.com> wrote:
> Also keep in mind, be sure to get the resistance correct (total length of
> nichrome wire) as that gen3 extruder board MOSFET will fail quite easily
> with excessive current

> This is a known weak spot in the gen3 electronics design.

Absolutely. ISTR the limit is around 25W, possibly a bit under.

> On Wednesday, March 14, 2018 at 9:59:03 AM UTC-4, Jetguy wrote:
>> The one source for it I know of was Ultimachine had the correct stuff.
>> 31 AWG
>> https://ultimachine.com/collections/electronics/products/31-awg-nichrome-wire

My own CupCake is presently down for a heater wire replacement. It
worked fine for years with the original wire, then I got my first clog
and had to rebuild the heater. I used insulated nichrome wire from
Maker Gear and it was not the exact same gauge; close, but not
identical. I measured out 30cm of it (the length that worked for the
original) and *after* installation, found out the resistance was off
by about 10%. Something like 6.8 ohms vs 7.5 ohms, and I didn't blow
my MOSFETs, but I can't get it up to temp. It needs another rebuild,
so I put it aside and worked on different printers.

The entire heater construction process always was a PITA - you can't
solder nichrome, so we had this wrap and crimp thing that rarely
worked well and then there was the insulation that got brittle after
first heat... it was the least fun part of the entire build.
-ethan

[multikat]

Thanks For the info.Im going to order some now.

[multikat]

It's actually the wire that wraps around the barrel under the insulation.

[multikat]

Do you know where I can get some of the wrap and crimp things to join the nichrome to the regular wire?

[David Weier]

I don't know if you need it, but I have digital copies of the cupcake assembly instructions including the plastruder mk4 if you need it. It states 31Ga nichrome wire as stated previously by Jetguy (I can remember being helped by Dan L and Jetguy many a times over the years, thanks guys) Here is the section on the wire length from the instructions.

Trim and Strip the Nichrome

The nichrome wire should have a resistance of approximately 6 Ohm. Usually this amounts to about 300 mm of wire,

but use a multimeter to be on the safe side.

Cut the nichrome wire to a length which amounts to about 6 Ohm of resistance (+/- 1 Ohm).

NOTE: It's difficult to measure the resistance of the nichrome until you strip the ends, so cut it long, then trim it down

until you reach 6 Ohms.

NOTE: Make the wire too long, and your heater takes longer to heat up. Make it too short, and you burn out the

MOSFET on the extruder board.

[multikat]

Thanks. I also have the instructions but I have to redo the nichrome to the copper wire connections and since I hear that you can't solder nichrome, what would be the best way to join them. I don't have the original connectors. Maybe use uninsulated butt splices?

[Jetguy]

Yes, that would work. Say take a ring terminal, cut off the actual ring. use the crimp section to crimp your high temp PTFE insulated wire to the nichrome by first twisting the nichrome and stripped end of the power wire together, then place the crimp over and crimp it.

[multikat]

Thanks again for more good advice. Got The Nichrome in the mail today. Will be working on it as soon as possible.