Life expectancy of cartridge heater ?

[Hans Jørgen Grimstad]

Hi !

The cartridge heater on my MK7 extruder died on me today. The extruder now refuses to heat up. I measured 12 V on the terminals, and 6 Mohms resistance in the catridge... :(

What is the normal life expectancy of these things ? (So far, I have printed approx 4 spools of filament on the ToM)

Regards

Hans Jørgen

[Dan Newman]

The normal life expectancy should be far in excess of 1000 hours.
However, since they're custom parts whose specs we don't know, it's
hard to know. However, yours has certainly failed prematurely. Most likely
due to a wire failing in the core. That's the most common cause
of early death in the things in which the wiring goes bad and fails
open.

You need to contact MBI support and ask for a replacement. And if it's
for a Mk7 on a ToM, be sure to let them know as they appear to be using
a different heater core for the Mk8's on Replicators. And, it appears
that the Mk7's that recently went on sale included that newer core.

Dan

[W. Craig Trader]

Dan ...

I got my second Mk7 a couple of weeks ago, and the heater core is marked 12V40W 1203, which should presumably be good for a TOM.

- Craig -

[Dan Newman]

On 7 May 2012 , at 1:55 PM, W. Craig Trader wrote:

> Dan ...
>
> I got my second Mk7 a couple of weeks ago, and the heater core is marked
> 12V40W 1203, which should presumably be good for a TOM.

Recall the post of 5 May from Jwo Lee where he reported,

The label on the wire of mine says 20V40W, but the engraving on the actual
cartridge says 12V40W. I'm not sure which to believe. It does measure at ~14.5 ohms.

So, if yours has labelling on the wires as well, check it out.

Dan

[Jwo Lee]

Yeah, Makerbot confirmed they shipped me the wrong ones. They are sending out new ones.
As Whosawhatsis mentioned, measuring the ohms is the best way of knowing for sure.
14.6 ohms is for 20V Replicator and 3.6 ohms for 12V TOM.

- Jwo Lee

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[W. Craig Trader]

No label, 4.1-4.3 ohms.  At 12V, that ought to draw ~35W, which should be good.  At some point I'll open up my TOM and measure the first one, but not today.

- Craig -

Dan

[Dan Newman]

On 7 May 2012 , at 2:14 PM, W. Craig Trader wrote:

> No label, 4.1-4.3 ohms. At 12V, that ought to draw ~35W, which should be
> good. At some point I'll open up my TOM and measure the first one, but not
> today.

Keep in mind that unless you have a 4-wire ohm meter, that reading is likely
too high. As such, the resistance is likely under 4.0 Ohms. So, it likely
is 40W as billed. (Yeah, you can "zero" the Ohm meter scale to "remove" the
resistance of the circuit and leads from the measurement, but that increases
the measurement error.)

Dan

[W. Craig Trader]

No circuit involved -- I haven't had time to build the new extruder.  I just opened up the parts bag, took it out, placed it between the red and black probes.

- Craig -

Dan

[Jack Coats]

I did some tire kicking and you can get your own cartridge heater
built to your specs at
http://cartridge-heater-online.com/

They quoted me $21.50, 40W, 12V, 1" long heater, quantity 1

If I wanted 5 they are 13.50 each, and 10.75 each for 10.

If they are consumables (even though some time between), it starts
sounding like ordering a few to have on hand (and share) is cheap.

All plus shipping, but they are light, and ship from NY and CA, and Quebec.

They will also make them with built-in thermocouple.

...

I have not ordered. I told them the quote was for 'tire kicking
purposes, to find second sources'.
Who knows, this may be where MakerBot gets them.

... Jack

[Jeffrey Ballard]

Built in thermocouple sounds awesome did you get a quote for that?

[Dan Newman]

On 7 May 2012 , at 2:32 PM, W. Craig Trader wrote:

> No circuit involved -- I haven't had time to build the new extruder.

The Ohm meter leads and portions of its circuit are measured as part
of the Ohm meter's reading whenever you measure resistance with your
Ohm meter.

Dan

[Jack Coats]

No, I didn't get a quote with thermocouple included, I was trying to
get more of an 'apples to apples' comparison quote, but I doubt it
is much more expensive. ... You can do a quick quote with them
and in a day or so you can let us know :) ...

The way it works, is you fill in the form, they review it and send you
the quote via email.
The same company does all kinds of semi-custom things, like band heaters, etc.

><> ... Jack

[Dan Newman]

On 7 May 2012 , at 3:08 PM, Jeffrey Ballard wrote:

> Built in thermocouple sounds awesome did you get a quote for that?

In the very least, you'd have to change your PID settings if you
used a thermocouple co-located with the heater core. And, you'd
be wondering just how the temp. co-located at the heater core correlates
to the temp of the heater block itself, the latter being a more
important temp given the design of the extruder.

Net, net, I don't think you want to go there unless you feel like
breaking new ground.

Dan

[Whosawhatsis]

Thermocouple built-in sounds nice, but it may not be a good idea for our purposes. There are several theories (in my head alone) about ideal placement of the temperature sensor. Putting it close to (or inside) the heater will give you very fast reactions, allowing for precise control, but the heat of the block will lag behind that somewhat, and due to heat dissipation, will always be a bit lower. The opposite side of the heater block, on the other hand, will give you a better idea of the heat of the whole block, at that moment, but the reading will lag behind the cartridge's own temperature, causing fluctuations in temperature and making precise PID tuning important.

[Shawn]

On 12-05-07 04:32 PM, Whosawhatsis wrote:
> Thermocouple built-in sounds nice, but it may not be a good idea for our purposes. There are several theories (in my head alone) about ideal placement of the temperature sensor. Putting it close to (or inside) the heater will give you very fast reactions, allowing for precise control, but the heat of the block will lag behind that somewhat, and due to heat dissipation, will always be a bit lower. The opposite side of the heater block, on the other hand, will give you a better idea of the heat of the whole block, at that moment, but the reading will lag behind the cartridge's own temperature, causing fluctuations in temperature and making precise PID tuning important.
>

I'm not an expert in this area by any means, but hearing your
description, my brain seems to see an obvious "do both, and turn it into
a software problem"... Of course, I could be way off base here too...