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Plastic comes out at the top

My left nozzle got clogged, so I changed my right nozzle to the left to continue printing. But after changing the plastic comes out at the top (see picture). How is this possible and how can I resolve this?


1 person has this problem

My guess:
The brass nozzle needs to be tight up against the end of the threaded barrel so that it seals.
If the threaded barrel is a little too high into the heater block, the nozzle will stop before it seals against the end of barrel. That's allowing plastic to leak into the threads.


hm normally that place on top is welded, I think it is busted.. you probably need a new extruder

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I have had this issue, simply screwing the nozzle back in was ineffective. The face where the nozzle back met the thermal block had an orange powered which I assumed was locktight but trying to get the right amount in there and still screw the nozzle back in the full way was problematic. Due to the seal being broken, as others have said it is most likely to require a new head.

In these extruder heads the top is not welded. I still got a new hotend from them though.

I would think it has to do with screwing the nozzle all the way back. If this is not the case then I really do not know how to replace a nozzle.


We have the exact same issue after changing the nozzle from 0.35 to 0.5. Could someone advise how to solve this issue?

I am not sure it helps but I would do as follows:

Take the entire hotend off. Then screw the heatelement+heatsink+temperature sensor all the way up. After that, screw your nozzle on until it is really tight. Then screw the heatelement etc back down until it is tight to the nozzle.




Will try , thanks Marcel

We will try to fix this issue with heat resistant silicone that hardens when dried,will report the results in a few days

Hi Luka,

I currently am having this issue and wonder how your test with the heat resistant silicone went?



Hi David It worked out really well, we had some heat resistant black silicone, and stopped the problem. Check the temperature on the back and I would recommend ordering a spare one because this is only temporary solution

Hi Luka,

Thanks for the reply. Unfortunately I am having a lot more problems with my printer than just leaking plastic, I have attached a photo of the right hand hot end.

I sadly have a total of 8 open tickets registered into Leapfrog Tech Support and maybe likely raising another about a new-ish issue.  A number of the issues are moderate but several a quite serious and as such I do not have a printer that works reliably or consistently any longer.  This is a huge frustration to me as I am unable to use to support my intended business activities, especially with a non-functional printer.  More so it is the consistent lack of reliability that cannot seem to be 'permanently rectified.

Though I will be sure to let you know how I go resolving this in the future.

Kind regards,


(1.05 MB)


I have been having issues with this printer since I got it.  It is an HS and has never consistently worked correctly.  I have 2 other printers and some good experience - although not an expert by any means.

I have yet to get 3 consistent prints to finish - let alone get the quality or speed correct.  Since I got the machine I have had to replace - the warped bed, the main board, the nozzles twice and new hot ends.  My hot ends looked like your picture and I have to say that the new ones they sent me seem to be different and they are working a bit better for the last 2 prints anyway.  I am assuming that is because of the new hot ends and the new firmware upgrades.

I do see a difference after installing the new firmware and other updates just released.

I have my fingers crossed.

I am a bit frustrated about them drooping simplify 3d for Materialise and wanting to charge us for the software change....

1 person likes this

Dear KEN petschauer ,

If you would upload the factory file of a print you want to make so I could have a look at the settings you are using so I can adjust them and see if I can`t help you get the quality you want.

I also attached a gcode I printed today and you can agree it is not a simple looking model and you can also see pictures of the results I got.

Could you also give it a try and send me pictures of the print?

(9.84 MB)
Mircea Thanks for the offer but I have been through this with some of your colleagues many times. The major issue now seems to be the cooling issue in the stepper motors causing jamming. Discussing this in another thread and awaiting a fix from your engineers. Thanks
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