Third Bad Head

[stevnkrn @stevnkrn]

For the third time since September I’ve got a defective head. Large amounts of plastic are accumulating behind the nozzles that occasionally melts and drips all over my parts. This is just a few days after popping my bowden tube for the first time. After three days of waiting for a support ticket response, CEL agreed to send me one of the new bowden’s, which I have yet to receive. While waiting I tinkered with my machine and finally got the original tube to stay in long enought to make a few parts. Unfortunatly I now have what appears to be a valve seal failure. This looks to be the same failure I had on my first head and that was diagnosed by CEL to be a bad seal. My second head was replaced due to the dreaded B-axis stuck error. Has anyone else experienced this blown seal issue? Is it repairable? Is it just bad luck, or is there a serious design defect in this head design?

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[Mark Dee @jabberwocky]

Hi @stevekrn , sorry to hear about your issues:

From the picture you have uploaded, the leak appears to originate from a height higher than the metallic tubes bringing material in.

In simple terms, and I am sure you would agree, this suggests that there is a buildup of molten material without enough being ejected, leading to a busted seal.

I would postulate the causes for this being related to:

1. A blockage in one of the nozzles, even though one is being used, and appears to be working fine. If so, do you eject the filament when printing for the day is over? Or do you leave it in? I have noticed swelling in my filament, and much lower than normal ejection during the initial rubber blade purge and the first few minutes of my prints, when my filament has been left in for a few hours without print.

2. Software settings: Feed rate multiplier, filament multiplier, nozzle partial open values in the settings of the material and print job have an effect on the co-ordination between the externally located extruder and the needle valves, resulting in a knock on effect of too much pressure buildup when out of sync. While I cannot claim to be an expert on this, it is something I am aware of.

3. Bowden tube: I’m not sure what the failure was exactly, but to refer to the above point, a faulty tube position could be having a knock on effect on the sync between the extruder and the needle valves. The Robox has no way of knowing if material is being ejected or not.

There are pros and cons of every model of design, and these are the cons of this type.

As for being repairable, it looks simple enough to clean the area and replace the gasket, but I’d check with CEL to see what their stance is, as it may invalidate your warranty.

Hope this helps.

[Pete @pete My Robox is a Blue Commercial Version]

Repeated faults like this would point to a fault elsewhere, most likely I think is the pogo pins which press against the rear of the head. They should spring back out when pushed. 4 of them are slightly longer than the others by design.

The guys in the support portal are best placed to deal with this.

[stevnkrn @stevnkrn]

I submitted a support ticket before I posted. I’m expecting an extended wait before I hear from them, so I thought I would share my plight hoping that others know what to do about this. I’ve done all I can do to clean off the head and run parts, but the issue of material buildup above the nozzles keeps on reoccuring. Once again I’m at CEL’s mercy for a quick turnaround on “official” diagnosis and replacement parts. This is REALLY getting old.

[Robson @robson]

Hey I’m in the same boat!

This is my printhead from 2 days ago :/ opened a ticket and waiting for a reply.

 

• This reply was modified 3 days, 7 hours ago by  Robson.

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[stevnkrn @stevnkrn]

@robson, I hope you get a faster response than me. It has been 7-1/2 days since I posted my ticket on this, and still no response from CEL. Since this was my second head that exhibited this behavior, and it is happening to others as well, there must be a design or manufacturing defect in these heads. It would not surprise me if others have it, possibly to a lesser degree, and don’t know it yet. They would have to remove the head and look to find out.

[Steve Nicklin @discosteve My Robox is a Blue Commercial Version]

be fair to the CEL guys it is Christmas - I personally would expect nothing to be happening today, yesterday or even a goodly chunk of Christmas Eve - and of course the next two days are weekend

Steve N | Creator of things both virtual (and soon to be physical)

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