Re: Extruder Heater on MK7

[Joseph Chiu (Toybuilder)]

A true zero ohm resistance cannot heat up. Are you sure you got a 12v cartridge intended for your application? 

I'm assuming there is no obvious short between the leads...

On Mon, Jan 18, 2016, 6:12 PM Thomas Parker <thomas....@gmail.com> wrote:

Hi guys,

I bought a new block and heater for my MK7 on my ToM but it won't heat up. The old heater worked but needed a new block and the cartridge was seized in the hole. The new heater has a resistance of 0.00 Ohm which doesnt look right. The old one was between 6 and 7 Ohms. I bought a new heater to put in there thinking that they had sent me a dodgy one but the new one I got is also 0.00 Ohms. Are they polarised? They are not heating up. I am yet to check output from my board. I checked with an IR temp guage and it stays at room temp.

Any ideas?

Thanks

--
You received this message because you are subscribed to the Google Groups "Vintage Makerbot" group.
To unsubscribe from this group and stop receiving emails from it, send an email to vintage-makerb...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[Thomas Parker]

Sorry not sure why other posts deleted. Doing this from my phone and its not working very well. Turns out my meter is slow. If i hold it there for a while it gradually increases from 000.0 to 002.7 and the guy i bought it from said it should be about 3. So my board isntgiving it power. Hopefully photos will attach.... or not. Will try later from phone. Little board led comes on to preheat bed but not for tool. No power at terminals. Gen 4 display says tool is 27 and bed is 37. RepG says tool is over 1000 and bed is 37.... what the heck?

[Thomas Parker]

23 vs 1023. The display must trim the 1000 off. Thermocouple backwards. Will fix tomorrow :)

[Dan Newman]

> Sorry not sure why other posts deleted. Doing this from my phone and its not working very well.
> Turns out my meter is slow. If i hold it there for a while it gradually increases from 000.0 to 002.7
> and the guy i bought it from said it should be about 3.

These devices are generally +/- 20%. So, while it should be 3.6 Ohms for 40W @ 12V, coming in as low
as 2.9 Ohms would be within spec and yield 50W. However, that you measure 2.7 Ohms and figure that
the leads are contributing between 0.2 to 1.0 Ohms resistance to the measurement, means that you may
have at 2.5 Ohm heater cartridge yielding 56W. May require some PID tuning to work well. (Keep in
mind that most inexpensive multimeters won't measure such low resistances very accurately either.
So, there may be a lot of error in your measurement as well.)

> Little board led comes on to preheat bed but not for tool. No power at terminals.

And the LED's on the safety cutoff for the extruder heater show? It's pretty common for
the extra insulation on the heater block between the block and thermostat to fail and cause
the safety cutoff to trip, thus cutting power to the extruder's heater. Solution was to
slip in a new piece of that ceramic tape which was supplied with the Mk7 assembly kit.

> Gen 4 display says tool is 27 and bed is 37.

And the firmware you are running is? There were plenty of bugs in MBI's Gen 4 LCD display
code.

> RepG says tool is over 1000

Over USB the extruder controller is reporting an error -- that's the error temperature.
Could mean most anything: failure of the EC's MAX6675, failure of the thermocouple, etc.

Dan

[Dan Newman]

On 22/01/2016 5:24 AM, Thomas Parker wrote:
> 23 vs 1023. The display must trim the 1000 off.

Yes, long standing MakerBot bug. 1023 is the error temp. And when that is
triggered, the heater is shut off so no electricity is sent to the heater
cartridge.

Dan

[Thomas Parker]

Thank you I'll try another thermocouple. I run sailfish and dont have a thermal cut off board.

[Thomas Parker]

Yep dodgy heat probe. Works now! Thank you

[Thomas Parker]

Okay so it reads a temperature... But maxes out at about 107/108 and if I check with my multimeter temp probe its up to 450. Might just be poor contact between the bead and the head but its a bit strange. Could the MAX6675 be dodgey and still kind of work? Or would it either work or not work and nothing in between?