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Retract @ end of program clogs nozzle

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Since some time I am experiencing issues with the retract @ the end of a program. If I want to start the next print no material will flow through the nozzle.I think the issue has to do with "necking" of the filament just where the material is in its glass state.

This "necking" of the material prevents a firm push from the extruder/fillament (material slides along itself. piece of filament in nozzle and in bowden tube arn't connected no more ) when starting a new print...... Does any one of recognize this problem?

If so is there somewhere in cura/firmware where i can change the amount of retract at the end of a print?

Printer: UM2

Firmware: 15.04.02

Material: PLA metallic silver

Temp: 230 deg

placed new nozzle/hotend

There is no difference with the old and new hotend. I used the atomic pull method with old nozzle/hotend and it came out clean.........

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Usually this should be no problem as this is the standard procedure for most UM2 (that is if they updated their firmware). I guess your problem is the teflon coupler that is deformed and needs to be inspected/replaced. Usually you'd have problems with under extrusion too when the coupler is deformed allowing the filament to expand creating a "plug".

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Thanx for the feedback.


I guess your problem is the teflon coupler that is deformed and needs to be inspected/replaced

@Nicolinux; Yeah mate that was my first guess as well.... sadly I ordered a complete new extruder kit and replaced the whole bunch and still the same result.


I changed the retract at the end of the print from 20mm to 12mm in Ultimaker2Marlin

@Dimensioneer; Thanx mate I will try this one..... Seems worth the try. Can you tell me if this manual covers the knowlage www.extrudable.me needed to change the code????? I will let you know if it worked for me.

Most of all I'me troubled by the idea that more people should have this problem right? I've got the printer now for about 1 year and use it quite often.......


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Hi Guys,

I adjusted the retract to the 12 mm, and uploaded the firmware to the UM2. This seems to help quite a bit..... When starting a new print the material starts flowing sooner, Still It has some trouble (a helping hand/push just before the feeder motor is sometimes needed) since it starts overloading the feeder on occasion.


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