thermocouple problem need help

hi repraper!!!! i`m a newbie in this community.
i'm got problem with my 3d printer. last week i bought makerbot replicator clone from the china
yes i want to buy the original but when im compare the price+shipping (i live in asia) cost my budget cannot cover it.
i love 3d printting technology after i spend couple week do some research then i bought non-assembly replicator
but i got problem with electronic part.my idea is about "thermocouple" my bot always show error message "extruder overheat"
at the first time i think im wire it wrong but after i check color code for thermocouple im right in us color code for thermocouple type k is
yellow and red the red is (-) and yellow is (+) after i wire it to mightyboard is workking!!! but only 1-2 time after that the error message come up again

here the something that i notice
1. after turn on the mightyboard it take about 10-15 sec before the error code come up
2. during that 10-15 second im going to monitor mode the temperature of extruder show 653c, the heatbed is normal
3.my thermocouple become very hot!!!! is it normal?

how can i fix this problem i try to change new thermocouple cable but same thing happen
thank in advance

Is it possible that the heater is short circuited to the heat block? I have had that happen and it toasted the thermocouple wires. You should be able to check that with a multimeter.

thankyou Greg Frost for answer my question
i'm a newbie and
sorry about my poor english(my bad) so please give me to ask you in detail

1."heater" is mean heater cartridge?
2."heat block" is it the heat box that connect with nozzle?
3.check "that" what is you mean? sorry but i dont get it is "that" mean thermocouple cable? or heater block?

but thankyou in advance for some help

... you have to measure the resistance of the heating element and the thermosensor and if they are shorted to the metal body ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

thank you viktor
after you told me i went to nearest store to buy digital multimeter
i check measure the resistance of thermocouple between new one and old. the measure came out same number and heater cartidage too.
then i reconect all the wire the error pop up again "extruder overheat"
now i dont know how to check my bot T_T
but thank you anyway

i dont give up but still need help!!!

... wrong measurements can be caused by wrong pin-assignments (wrong board selected or pin assignment in firmware not matching to hardware) or wrong temp-conversion table for your thermistor ...

---

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

thank viktor for give me many ideas.
i try to check everythings re-wire all cable step by step check all the cable where is deflect
but found notthing about the wrong temp table i also twist -/+ to +/- same thing happen
then i try to update new firmware before is 6.2 now is7.0
but the result is same. in monitor mode the extruder temp show 630-640c at first then the error!!

the full error message is
"extruder overheat! software temp limit reached! please shutdown or restart"

any other ways to check or fix this?
or can i re-install all mighty board firmware? format and re-install? factory reset?

VDX Wrote:
-------------------------------------------------------
> ... wrong measurements can be caused by wrong
> pin-assignments (wrong board selected or pin
> assignment in firmware not matching to hardware)
> or wrong temp-conversion table for your thermistor
> ...


Sounds like an error in the firmware somewhere, bad wiring, or bad pin assignment.
1. If the wrong type of thermistor/thermocouple is selected in the firmware, you will get all sorts of weird things happening, temps can show very high and start dropping as it gets warmer, or could read a solid steady incorrect temp, etc etc.
2. a bad pin selection or mis-wire obviously could have unpredictable results.

(I dunno anything about MBot firmware however)

Make sure the thermocouple tip (point/place where you are measuring temperature)is not touching Aluminum parts directly.

What firmware are you trying to load?

it's not the mbot. they claimed as the clone one.
they got many good feed back but only me that bought them non-assembly kit

about the thermocouple i use k type -40c - 300c japan standard
from the research the makerbot use omega thermocouple right? but also the same in k type
alumel and chrome

if it firmware problem.
can i change to reprap popular firmware like marlin? or sailfish?

okaman Wrote:
-------------------------------------------------------
> it's not the mbot. they claimed as the clone one.
>
> they got many good feed back but only me that
> bought them non-assembly kit
>
> about the thermocouple i use k type -40c - 300c
> japan standard
> from the research the makerbot use omega
> thermocouple right? but also the same in k type
> alumel and chrome
>
> if it firmware problem.
> can i change to reprap popular firmware like
> marlin? or sailfish?

Sailfish should work for you as it's partly forked from makerbot firmware anyways...

Was the firmware preloaded?? If so that stinks because you have no way of knowing what was in the files before they compiled it... It would help to have more details about your machine.
If you can get a copy of the firmware they ship on their machines, this could be as simple as changing one value, and reloading the firmware to your machine..

hi all sad news i found the problem T_T

one of ic near the thermocouple slot was burn
if i look carefully i can see the burn point

now question is can it fix?
and if it cannot fix what the electronic can use with gantry style?

There are a couple of ways to use a thermocouple. One is witha chip like the MAX6675 which has a digital SPI interface that must be supported by the firmware. Another way is with a chip like the AD595 which generates an analog signal proportional to the temperature, so can be connected to an analog input on the electronics, but again you would need firmware support to be able to convert the measurements to temperatures properly.

Most people these days use thermistors instead of thermocouples.

thank you greg
my is used max6675 but it's doesnt burn, the small thing near was burn and i can see inside the burn area the electronic line print was torn. is it dead?

and if i change the electronic but want to keep all the part
it still can use?

thank for your help

Yes you can use different electronics but you are going to be doing alot of learning about whatever electronics package you use, as you will be wiring everything manually, you will have to set all of your pins properly in your firmware, and you'll have to setup your firmware to match the mechanics of your machine.
It's not "hard" so much as it is time consuming.

A RAMPS board should have hookups for everything on your machine, But I think your extruder is PWM driven so I'm not sure how you wire that...

And any Reprap electronics package will work with a gantry style printer. It's all about setting up the firmware properly.

sorry for newbie question but what is "PWM"
mk7 cannot use with ramp?

okaman Wrote:
-------------------------------------------------------
> sorry for newbie question but what is "PWM"
> mk7 cannot use with ramp?

Most Repraps use stepper motors for everything including the extruder motor.

If I am correct, I believe Makerbot (and it's clones) are using "regular" motors on the extruders, which are driven with a MOSFET instead of a Stepper Driver.

(PWM is current controlled by pulses to the motor dictating its speed, and a Stepper motor is controlled by moving x number of steps, two different things.)

This is stuff you'll need to consider if you're changing electronics. Perhaps you'd have the easiest time replacing your electronics with the same type you already have.

Hi,
There isn't a lot of comments about the quality of the mbot printer ?
This issue is alone or other guy has issue with the mbot printer ?

I plan to buy the MBot Cube,because it is less expensive than a lot of other ones(like maker bot, close to 50% )
Some people can do some feedback about it?


For guy that would like to buy one I find a 5% discount code here : REFER911 it seems that it is limited to 14 days.
I find also this link that provide a discount code(code promo/reduction code) :
[http://curebit.com/x/RV3UL]

So if some one can give me some feed back quitly, it could be very nice.
Regards,

You could just replace the faulty part of the board, rather than replace all the electronics - take a photo or two and sent it to the company you purchased it from, they may be willing/able to help.

If the company won't help and you aren't confident de-soldering and replacing a single chip, look for local electronic hobby/hardware stores (TV repair shops used to be somewhere to go).