Jhead overheating

Hi Reprappers

I am building prusa mendel with my students from the makergear kit, and have just swapped over to using the j head instead of the makergear head.

We are finding that the temperature of the head is climbing over the set limits. I was wondering if anybody has experienced anything like this on their build?

We are using sprinter firmware and pronterfce with sfact. The power resistor mounted solidly in the head and heats up the head well, just the temp keeps on climbing. The heat bed seems to be working well and the software is controlling it as per normal.

I am assuming this is a firmware of hardware problem as i tried using repsnapper as host but get the same result.
Do you think i need to adjust the power limits going to the head?


Cheers Chris Wood

I found that too but once it got to 230C it then dropped back and started printing, don't know why but it does

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Experimenting in 3D in New Zealand

If you are using PID you will need to re-tune it if you change the thermal characteristics of the extruder.

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[www.hydraraptor.blogspot.com]

HI all,

Thanks for the advice Nophead and NelsonRap your suggestionss are much appreciated.

I let the had go a bit further but it shows no sign of wanting to return to a set temp.
I experimented with turning on the PID settings and reducing the max down to 50 but it did not seem to affect the hot head behavioiur.

I have found the extruder turns on as soon as the printer is turned on at the power for some reason, so makes me think it must be firmware or hardware.

Is it possible to wire the primary hot head up to the secondary set of power leads (for a second extruder) and then allocate this in as the primary hothead power in the firmware?.... if that makes sense!!??

Cheers Chris

You should be able to run without PID control and just use bang-bang control: heat on when temperature is below setpoint and off when temperature goes above setpoint. On Sprinter or Marlin firmware, just comment out the #define PIDTEMP 1 statement.

Yes you should be able to wire your hotend to the HBP or secondary hotend control and then set that as your primary extruder in the firmware. See the config.h file of your firmware for the settings. You may also want to double check that you have the right pins defined in there for the current extruder connection, and check that you don't have the thermistor or hotend connected to the wrong input/output. Though if you are getting temp readings that climb as the hotend heats, that would mean the thermistor is connected right. Did you have the makergear hotend working before you switched?