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Slow Heating of Hotend

Posted by b-irwin 
Slow Heating of Hotend
July 29, 2020 05:11PM
I am having an issue with the hotend not heating up quickly enough.

I start the Printer and then set the hotend temperature to 200 C. It starts to heat up but after some time I get a message saying "Heating fault on heater 1, T = 196.8 C; still not at temperature 200.0 after 150.484131 seconds." I can get past this by resetting the hotend while it is still hot and setting the temp again but this doesn't fix the issue.

During printing, it is also dropping the temperature by 10 to 20 C when it starts to print quickly. But the prints seem to come out fine despite this.

I think this is caused by the hotend heating up slowly and not being able to keep up with the amount of material that it is extruding.

I have had this printer for a while and it has only started doing this recently. Could it be a firmware issue? Is there anyway to change the hotend temperature check so it can heat up quicker?

FYI, I have just changed the hotend and the whole heatsink assembly because the same was happening to the old one so I don't think that was the issue. Also, I am not sure when I updated the Firmware last or if this started after a firmware change.
Re: Slow Heating of Hotend
July 30, 2020 06:28AM
After you changed the hot end, did you tune the heater? [duet3d.dozuki.com]

Check that the heater wiring is in good condition with no signs of overheating at the connectors.

Check that you have set the correct thermistor B parameter in the M305 command for the heater.

Edited 1 time(s). Last edit at 07/30/2020 06:33AM by dc42.

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Slow Heating of Hotend
July 30, 2020 08:59AM
I'll take a look at this. Thanks.

I haven't done any tuning to the heater as far as I can tell. I can't remember doing any tuning when I built the machine so I didn't realise I needed to.

I replaced most of the wiring loom and checked it so I am pretty sure the wire is still good.

I haven't checked the thermistor B parameter but I am not sure what it is supposed to be. The printer still works so I assumed this was correct.
Re: Slow Heating of Hotend
August 08, 2020 04:16AM
I picked up the same problem several years ago and it turned out to be the MOSFET TR4 IPD036N04 (Duet 0.6). The gate had become leaky

With the heater turned on I measured approx 4.3V gate to ground where the +5V rail measured 5V. The voltage should have been around 4.95V.

I also noticed that TR4 heated up but not enough to burn the PCB.

With the damaged gate I was surprised that that the MOSFET switched at all let alone partially.

The printer was still under guarantee and RS Components insisted on changing the printer so when I built the new printer I confirmed that T4 gate voltage was almost 5V.

Hope that helps.
Re: Slow Heating of Hotend
August 08, 2020 02:39PM
I just tried Tuning the Hotend and it came up with the message Invalid M Code: M303. Does that mean the firmware is not the latest?
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