1 Topic by Rincewind

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Topic: J-Head hotend - help?

Hi all,

I'm considering buying a J-Head hotend. However, all sorts of doubts are troubling me. I was already a bit troubled with the connectors (see another post), but now my biggest concern is the heater cartridge. I am afraid that it will have a resistance that is lower than the current one and I'm worried that it will fry my power supply. On ebay and other sources mention a 30W heater cartridge! That's like 10 times the current value AFAIK...

So to whoever switched to a J-Head I would like to ask: what exactly did you do (step-by-step: extra components you needed, did you replace the extruder, did you change the default connectors on the solidoodle? Did you change the wires from the motherboard?)? Where did you buy the hotend from? How does the heater cartridge compare to the SD heating element in terms of resistance/current?

I promise that in return I will write a nice help page on the wiki to help everybody!

Sorry for sounding so dumb, but I thought I'd rather ask instead of just spending a bunch of $$ just to destroy my printer.

Thanks a lot!

2 Reply by IanJohnson

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Re: J-Head hotend - help?

I got mine from hotends.com which came with a resistor, but no instructions.  I follwed the instructions for the Tantillus printer, which also uses a J-Head - http://www.tantillus.org/Build_3.html

I cut the resistor legs shorter, and crimped them on to short wires which went to the connector.  I already had replaced the stock connectors, and left everything the same the rest of the way to the mother board.  I put some thermal paste on the resistor for good measure since I had some on hand.  Some PTFE sleeve would be better for insulating the resistor legs, but I used kapton since I already had that.

I've been given a couple of cartridge heaters, but I haven't tried it yet since it is currently working.  I would be interested in finding out where the resistors are coming from, if they are more reliable than the ones Solidoodle has been getting.

3 Reply by Rincewind

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Re: J-Head hotend - help?

Thanks Ian!

You were my primary hope for information smile

Hotends.com is not very convenient for me, living in Europe, plus it looks like you need to run to get the hotends before they get out of stock. And indeed they ship with 21 or 25W heating resistors. On other sites (eg ebay, but not only), I only found J-Head hotends with 40W heating cartridges. Since your experience is with a 6.8Ohm resistor, I won't try buying such a hotend, as I really have the feeling that it would kill the power supply. Or someone else has a difference experience?

4 Reply by elmoret (edited by elmoret 2013-03-18 18:38:02)

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Re: J-Head hotend - help?

Rincewind wrote:

Or someone else has a difference experience?

Solidoodle's new hotends have 4.7 ohm resistors. That's 31w at 12v. A 40w heating element is just 9 more w, should be fine.

Biggest issue with the 30+ heating elements is that if they fail on (thermistor comes off, etc) it'll get to 500C+

Filastruder - the robust, inexpensive filament extruder
E3Dv6 All Metal Hotend - the premier 3D printing hotend

5 Reply by elmoret

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Re: J-Head hotend - help?

Rincewind wrote:

On ebay and other sources mention a 30W heater cartridge! That's like 10 times the current value AFAIK...

Nope. See above.

Filastruder - the robust, inexpensive filament extruder
E3Dv6 All Metal Hotend - the premier 3D printing hotend

6 Reply by Rincewind

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Re: J-Head hotend - help?

elmoret wrote:
Rincewind wrote:

On ebay and other sources mention a 30W heater cartridge! That's like 10 times the current value AFAIK...

Nope. See above.

Sorry 10x was way off the chart, now I don't even know how I came up with that number originally... If they can reach 30W then it should be ok indeed. I would have not dared to replace 20W with 40, but now the picture is different. Thanks!

7 Reply by JustSomeGuyTN

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Re: J-Head hotend - help?

Hey Ian, what did you use for replacement quick connects on the hot end?  I'm going to replace mine with a Jhead but I can't find matching quick connects.

IanJohnson wrote:

I got mine from hotends.com which came with a resistor, but no instructions.  I follwed the instructions for the Tantillus printer, which also uses a J-Head - http://www.tantillus.org/Build_3.html

I cut the resistor legs shorter, and crimped them on to short wires which went to the connector.  I already had replaced the stock connectors, and left everything the same the rest of the way to the mother board.  I put some thermal paste on the resistor for good measure since I had some on hand.  Some PTFE sleeve would be better for insulating the resistor legs, but I used kapton since I already had that.

I've been given a couple of cartridge heaters, but I haven't tried it yet since it is currently working.  I would be interested in finding out where the resistors are coming from, if they are more reliable than the ones Solidoodle has been getting.

8 Reply by adrian

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Re: J-Head hotend - help?

These are the ones a few people are using to replace both ends of the connector, they are called JST Connectors, widely used in R/C stuff. And example is here: http://www.jaycar.com.au/productView.asp?ID=PT4452

The proper Solidoodle ones are from TE Connectivity and can be had from Digikey or RS Components. http://www.digikey.com.au/product-searc … mp;stock=1 . The different colours are used to denote the differnt wire gauges of the connector - Red is 22AWG, Blue is 26AWG etc.

BUT.. there is a middle road. You can slice a male JST connector on both sides on the top and a central bottom slit and force it onto a TE Connectivity connector. Its not pretty, but it holds and allows you to use the original SD parts as well as '3rd Party' additions.

Anyway, hope that helps.

Adrian

9 Reply by JustSomeGuyTN

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Re: J-Head hotend - help?

Thanks Adrian that helps alot.  You wouldn't happen to know the exact Digikey item numbers that Solidoodle uses would you?

10 Reply by grandpa.dick

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Re: J-Head hotend - help?

"Solidoodle's new hotends have 4.7 ohm resistors. That's 31w at 12v. A 40w heating element is just 9 more w, should be fine."

looking at the specs for SD2 & SD3 they are not using resistors if they are I need to change my replacement order for the newer type.

grandpa.dick

11 Reply by danny

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Re: J-Head hotend - help?

Rincewind wrote:

I am afraid that it will have a resistance that is lower than the current one and I'm worried that it will fry my power supply. On ebay and other sources mention a 30W heater cartridge! That's like 10 times the current value AFAIK...

I'll post a step by step after the weekend, (Building a new hot end then)...

but for now.

the stock nozzle heater is 6ohm.

12/6 = 2Amps = 24W power.
so 40W is a pretty big step up extra 16W. (nearly double the power.) (but only about 1.6 amp more current)

the bed is a 3Ohm resistor as stock, 12/3=4 = 48W,
the steppers don't take huge amounts of current.

This *is* within the capabilities of the power supply to supply a 40W heater.