Having hot-end clogged problem, need advice

During my printing the hot end stop extrude material ( I use PLA ) . So I have to stop the print half way.
I check the hot end temperature at that time it already cold, first i though it is electronic may be the heater or the
Duet's FET that control the Hot-end heater so I turn off the power and unplug the ethernet cable
(the print was through web interface) bring my laptop and plug usb cable then start pronterface. I turn on the power
and check the temperature the heater is working I can see the temperature rise and stable around 198 to 203 according
to my setting of 200 so i try to extrude the PLA but nothing come out of the hot-end. I retract the filament out then
feed it back with no success. Please advice how is this happened. I already print on this printer for more than 20 hours
Produced 10s of parts include the extruding gear and z axis gear upgrade found in this forum.

Thanks

Inside the extruder, has the little feed wheel come unscrewed from the long M3 screw/shaft?

Is the motor turning when you command it to extrude?

Command "motors off" and with the head hot, try turning the extruder slowly by hand.

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Another RS Ormerod Mk1 meets the world

Retired now but I used to make....
CNC Machined Mk1 aluminium bed support plates for the Ormerod
CNC machined X-plates and ribs for Mk1 & Mk2 Ormerods
CNC machined bed support arms for the Mk2 Ormerod.
Dual Hot-End heatsink blocks.

Motor is ok i can retract and extrude but it struct after it reach the hot end

Have you tried repeating a few times the procedure to extract filament from the hot end? That is bring to working temperature (195) then retract 10mm, then set temp to 100, wait till it gets there then retract filament right out and out of extruder. Often this brings a tail of filament with it and can help to clean out any debris.

Thanks all for good advice, i found a tip in this forum very helpful.
I got my ho-tend fix according to @bobtidey advice, did it once not working so i asked.
Repeat a few tries and it start to extrude material out of the hot-end. The problem seem to solve now.
I still having a question through. Why the hot-end heater stop working during that blockade happen.
Are there any safety mechanism to prevent the heater to heat up if the hot-end blocked.
If my pc connected to web interface was on power saving mode during print the printer will still print or stop
How can i prevent this to happen again during print?

Sorry for my silly question.

I can think of at least two causes of hot end blockage:

1. Contamination with something that doesn't melt. e.g. PTFE shavings from when you assembled the hot end. If you are lucky, you can extrude backwards and pull the contaminant out with the filament.

2. If the fan cooling the heatsink is intermittent, or the printer is turned off when the hot end is still very hot, then filament will melt further up the nozzle than is intended. When proper cooling is restored, the plastic solidifies there and blocks the top end of the nozzle. So you must never power down the Ormerod after a print until then hot end has cooled down. This is why the fan controller on my Ormerod sensor board runs the fan whenever the hot end is 40C or higher.

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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].

For the PC stop/sleep question: my preference is to upload file to SD card through web interface drag/drop and then initiate print by clicking that. I know it is very convenient to print direct and skip the upload, but the upload speed is quite decent now and the benefit is that printing is then completely self contained in the printer. The web interface is then acting purely as a monitor and printing will continue without any dependence on PC.

Thanks guys,
I found another cause also. During the print the wire-loom connecting to all components of the hot-end
(Fan, heater and temperature sensor) is moving all the time until finish the print.
Mine having some issue during the print causing the heater intermittently disconnected but the fan still blowing.
This cause the melted filament to cool-down and harden blocking further extrusion to be continues.
I guest i may need to repair the wire loom and connector somehow to resolve this problem.

You might like to check out my hot end board for the Ormerod. This provides a modulated IR sensor which avoids the main problem of the standard IR sensor, thermostatic fan control, lighting, optional experimental ultrasonic height sensor, and a more reliable and more easily dismantled hot end connector.

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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].