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Hot end issue

Posted by Einar Hagerup 
Hot end issue
April 29, 2018 10:57AM
Hi all,

recently i bought myself a Reprap Pro Ormerod 2 printer. I'm using Repetier Host to control the printer. Everything seems fine regarding connecting to the printer, moving the bed etc but I'm having serious issues when trying to print. The problem is that the hot end starts to heat but in most cases, and after a random amount of time, it just cuts off and starts to cool down again. I've tried to replace the heater element, but for no use. It still behaves the same. Anybody else experienced this? I'm about to give up the entire printer, so this is one "last shot". Hopefully somebody is able to help me. :-)

Re: Hot end issue
April 29, 2018 07:55PM
Assuming your thermistor is configured correctly it is most likely due to a heating timeout failure due to stock PID settings. Luckily your firmware can find the correct settings all by itself!

M303 is the command for PID Autotuining EX:
M303 E0 S200 C8
Would make Extruder0 heat to 200 C and cycle above and below that temp 8 times, getting better values with each cycle. When completed the printer will tell you new values you can put in your configuration.h file
Re: Hot end issue
April 30, 2018 05:55AM
Maybe also a power supply issue... if the power supply is a bit weak, all the power goes to the heater and none to the processor, which then stops, which turns off the heater, and the processor then starts up again.

A heater cartridge is about 40W, say 3.5A @12V. Fans and processor and stuff need another amp or so. So you need a power supply that's good for a minimum of 5A, preferably a bit more.

An intermittent short between 12V & ground could also cause the system to reset.

May also be wiring faults; if the heater is on and the thermistor doesn't see an increase in temperature, the printer shuts down for safety. If there's a loose connection, it might not disconnect for some time. This could apply to either the thermistor or the heater. A short across the thermistor would have the same effect. When it is cooling down, is it showing valid temperatures? Does this happen when the print head is kept still, or only if it is moved around?

Toggle the Log Viewer on in Repetier Host and see if there are any error messages there.
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