Mk3 Appears to have a serious design flaw and no Prusa response
 
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CybrSage
(@cybrsage)
Honorable Member
Re: Mk3 Appears to have a serious design flaw and no Prusa response


20180527_232116.jpg
and yes you can flex it without destroying the bonds

regards Joan

Just wanted to say that I love your nails. 🙂

Publié : 19/06/2018 12:02 am
dimprov
(@dimprov)
Noble Member
Re: Mk3 Appears to have a serious design flaw and no Prusa response


But you must just be very lame if you cannot manage to make anything but shitty prints.

Let's please not resort to name calling. It doesn't solve anything.

Also, maybe if the OP rephrased his post in a way that he could be helped....? Like give the specific details of his particular situation and what's going wrong there. I'm assuming he wants to be helped. Otherwise, this is all moot.

Publié : 19/06/2018 1:04 am
mkopack
(@mkopack)
Eminent Member
Re: Mk3 Appears to have a serious design flaw and no Prusa response

Sorry, but I'm more than happy with the print quality I'm getting out of my Mk3 kit. It's literally fantastic!

Publié : 19/06/2018 1:21 am
JoanTabb
(@joantabb)
Veteran Member Moderator
Re: Mk3 Appears to have a serious design flaw and no Prusa response



Just wanted to say that I love your nails. 🙂

Thank you,
they have changed colour now...

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK

Publié : 19/06/2018 2:07 am
CybrSage
(@cybrsage)
Honorable Member
Re: Mk3 Appears to have a serious design flaw and no Prusa response

Still waiting for this list of serious design flaws.

Publié : 24/06/2018 10:23 pm
StefsEngineering
(@stefsengineering)
Eminent Member
Re: Mk3 Appears to have a serious design flaw and no Prusa response

Quite a bit of information and a long list of topics (and posts in them). As it seems that the topic starter hasn't listed the "serious design flaw" yet, I want to give it a try.

Based on what I've seen in those topics I'd like to define the design flaw or "null hypothesis" as:
- The chosen extruder motor for the prusa I3 MK3 is not able to sustain continous work under normal to high operating conditions

During usage this can cause:
- The extruder motor gets really hot (possibly outside operating temperature range)
- The hot extruder motor softens the extruder body
- The hot extruder motor heats up the filament to the point that it is too soft to be extruded correctly

(my opinion/assumption)
The first one seems plausible (but I think it has to get out of it's operating temperature range to do so)

The second one seems to me rather unlikely because the extruder gear is only for a very short time in contact with the filament. The contactsurface is very limited and changes all the time, and just like with the first possible cause it requires the motor to get well outside of it's operating temperature
(I looked up some common operating temperatures and it's usally in an ambient temperature up to 50C with a motor temperature up to 80C. The isolation is commonly rated up to 130C)

I am curous though what print settings where used when these printers failed. Especially the printing speed and if the stealth mode is activated. At higher speeds the motor can get quite a bit hotter (comparing 2000mm/m -> 5000mm/min -> 10000mm/min) This may also be the reason why I've jet to have my first failed print. It has been working for months reliably and with great results.

At this point I think the issue isn't necessarily the one defined above but that instead the recommended printing speeds and advertised maximum speed is too high for this printer. Not only for the extruder motor but the entire printer. Using these settings not only causes the motor to get too hot but also significantly affect the print quality due to lack of rigidity in the frame and mechanics. (please note! this is based on assumptions I haven't had any issues so I cannot speak from experience)

I saw a few posts back that when you state "great results" that a picture is much appreciated so here is mine:

SDcard is added for size reference

Publié : 24/06/2018 11:04 pm
Kyle
 Kyle
(@kyle-2)
Membre
Topic starter answered:
Re: Mk3 Appears to have a serious design flaw and no Prusa response


Quite a bit of information and a long list of topics (and posts in them). As it seems that the topic starter hasn't listed the "serious design flaw" yet, I want to give it a try.

Based on what I've seen in those topics I'd like to define the design flaw or "null hypothesis" as:
- The chosen extruder motor for the prusa I3 MK3 is not able to sustain continous work under normal to high operating conditions

During usage this can cause:
- The extruder motor gets really hot (possibly outside operating temperature range)
- The hot extruder motor softens the extruder body
- The hot extruder motor heats up the filament to the point that it is too soft to be extruded correctly

(my opinion/assumption)
The first one seems plausible (but I think it has to get out of it's operating temperature range to do so)

The second one seems to me rather unlikely because the extruder gear is only for a very short time in contact with the filament. The contactsurface is very limited and changes all the time, and just like with the first possible cause it requires the motor to get well outside of it's operating temperature
(I looked up some common operating temperatures and it's usally in an ambient temperature up to 50C with a motor temperature up to 80C. The isolation is commonly rated up to 130C)

I am curous though what print settings where used when these printers failed. Especially the printing speed and if the stealth mode is activated. At higher speeds the motor can get quite a bit hotter (comparing 2000mm/m -> 5000mm/min -> 10000mm/min) This may also be the reason why I've jet to have my first failed print. It has been working for months reliably and with great results.

At this point I think the issue isn't necessarily the one defined above but that instead the recommended printing speeds and advertised maximum speed is too high for this printer. Not only for the extruder motor but the entire printer. Using these settings not only causes the motor to get too hot but also significantly affect the print quality due to lack of rigidity in the frame and mechanics. (please note! this is based on assumptions I haven't had any issues so I cannot speak from experience)

I saw a few posts back that when you state "great results" that a picture is much appreciated so here is mine:

SDcard is added for size reference

This is one issue but the primary one I was referring to was the jamming in the heat break. The only solution in the threads I posted was to buy a new one.

I did discover today though that boosting the speed of the print resolves the problem. My theory is this prevents the slow heat creep up the heat break. Right now I've tested at 200% and it works for at least this one particular print. I'm on a time crunch to produce a lot of copies this week so I'm not going to do anymore experimentation on print speeds. I did order a heat break and will report back if this resolves the issue (it did for several other people in the other threads.

Interestingly enough my filament sensor just stopped working. Leads me to seriously believe they did no significant testing on this model prior to release. Some searching of the posts reveals this to be a fairly common occurrence with some instances of the filament sensor melting!

Publié : 25/06/2018 5:17 am
CybrSage
(@cybrsage)
Honorable Member
Re: Mk3 Appears to have a serious design flaw and no Prusa response

I have only ever run mine quickly, even boosting the default speeds in Slic3r (which runs much slower than the S3D profile posted by Prusa).

I did have a lot of problems with my filament sensor being DOA, and the next two replacements were also DOA, but third time's the charm. They now have a new version of it as the old one had manufacturing issues (tolerances too tight for mass production, worked fine in partial production).

Publié : 25/06/2018 6:13 pm
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