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Bed cable failure - a new one  

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Nikolai
(@nikolai)
Noble Member
Bed cable failure - a new one

Hi guys,

Just had an interesting cable failure which I’ve never seen this way. It didn’t just break as usual. Looks more like corrosion or some kind of chemical reaction. Any ideas what it might be causing this?

 

 
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Posted : 01/10/2019 7:43 pm
Bunny Science
(@bunny-science)
Noble Member
RE: Bed cable failure - a new one

I see dark discoloration of the plastic crimp cover. Also the metal of the crimp looks oxidized. It looks like a failing crimp with ohmic heating that gradually cooked the connection. 

Posted : 01/10/2019 8:47 pm
Nikolai
(@nikolai)
Noble Member
Topic starter answered:
RE: Bed cable failure - a new one

Correct, I make the same observation. But what is the root cause? The cable looks perfectly crimped. Still sitting very tight. Where is the resistance coming from?

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Posted : 01/10/2019 8:53 pm
alan.f6
(@alan-f6)
New Member
RE: Bed cable failure - a new one

@nikolai-r

I had the same issue except I had to replace the entire heat bed.  The corrosion caused a short and during the investigation discovered the contacts on the bed were also torn.   It may have been during disassembly... long story short, Prusa gave me a $15.00 credit which covered shipping but the bed and cables cost about $100.  Not thrilled with the outcome but it is what it is....

The connectors were tight and the cables appeared to be crimped.  The cover I used prevented the cables from moving so I'm not sure why they look frayed.  I'm thinking of using dielectric grease and solder the connectors then put a new heavy duty string tube over them.  Any thoughts? 

Posted : 28/10/2019 5:10 pm
Bunny Science
(@bunny-science)
Noble Member
RE: Bed cable failure - a new one

That definitely looks like moisture related corrosion, not just overheating. Any chance you are getting it wet with a water containing spray like windex or IPA with higher water content like 90% IPA?

 

Posted : 28/10/2019 7:51 pm
alan.f6
(@alan-f6)
New Member
RE: Bed cable failure - a new one

@guy-k2

No.  Very dry climate and never gets wet.  Only clean build plate off heat bed

Posted : 28/10/2019 7:55 pm
eric.s59
(@eric-s59)
New Member
RE: Bed cable failure - a new one

Had an interesting heat bed issue.  I have a heat bed clone I bought from AliExpress.  Been using it on a Prusa MK2S printer for over 6 months.  I replaced the heat bed cable cover with three different designs over the past 6 months in that I have the printer in a Lack enclosure and was trying to optimize cable movement to avoid hitting the back of the enclosure.  After going to replace the cable cover the printer wouldn't allow the heat bed to preheat.  Found the problem to be that on the back of the heat bed area where the heat bed cable nuts for the heat bed cables are secured that the black enamel had worn away exposing copper plating that was shorting out between the ground and +DC cable power leads.  Solution was to put an insulator between each power cable screw nut and the heat bed.

Posted : 17/12/2019 6:14 pm
vintagepc
(@vintagepc)
RE: Bed cable failure - a new one
Posted by: @eric-s59

Had an interesting heat bed issue.  I have a heat bed clone I bought from AliExpress.  Been using it on a Prusa MK2S printer for over 6 months.  I replaced the heat bed cable cover with three different designs over the past 6 months in that I have the printer in a Lack enclosure and was trying to optimize cable movement to avoid hitting the back of the enclosure.  After going to replace the cable cover the printer wouldn't allow the heat bed to preheat.  Found the problem to be that on the back of the heat bed area where the heat bed cable nuts for the heat bed cables are secured that the black enamel had worn away exposing copper plating that was shorting out between the ground and +DC cable power leads.  Solution was to put an insulator between each power cable screw nut and the heat bed.

That's a very poorly designed clone. I'm pretty sure the original part does not have a direct bridge between the two terminals on the bottom side.

Posted : 17/12/2019 6:31 pm
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