bad contact in END connector

hi,
after a month of use, the extruder did not reach the required temperature. a strong smell of burning plastic (more than usual) felt near the printer. I pulled the power plug and watched the main board. END connector was black. probably the connector was slightly moved and made a bad contact. Now I soldered directly to the main board two thick wires. now no problem. I don't understand why there is this connector instead of the one with the most secure screws like BED & POWER.

Hi, the extruder connections normally cause less problems as they carry much less current than the power and bed connectors. These chinese connectors do not seem to have the surplus capacity that EU and US ones do.

The problem is that:
a) these connectors, including the bed and power ones, are not suitable for connections using stranded wire.
b) the power connector is carrying close to its supposed capacity when everything is working.
c) the green plugs can sometimes give an unreliable connection between plug and pins which can promote arcing.

The screw type connectors are not immune from problems, and I have now seen a number of meltdown pictures of those. What the assembly instructions don't cover, is that you should use crimp-on connectors to terminate the wires. For the plug type ones you should use crimp-on ferrules. You have solved the problem for the extruder by soldering direct to the board, but you are most strongly advised to fit crimp-on connectors to the wires for the power and bed. You should also fit these to the power wires at the PSU end.

The problems arise because, even if you twist the stranded wire end well, it is not solid. It will distort when tightening the screws, and continue to do so with time under the influence of heat and vibration. What you must NOT do is to tin the ends of the wires. Provided that you fit the correct size crimp connector for the wire, and crimp it properly, the strands are fully contained and held tightly in a manner that cannot slacken. The terminal screws, once tightened on the solid end of the connector, cannot loosen and provoke an arc.

You should also keep an eye on the plug connection at the back of the bed that connects the heater power to the bed itself. These have also been known to blacken and heat as a result of poor connections between the plug and the board pins.

There is also a method of reducing the current carried by the power connector. This is to fit a control MOSFET to switch a 12V supply taken straight from the PSU and fed direct to the bed, with the switching signal being provided by the original bed pins on the main board. There are differences of opinion as to whether this fitment is strictly necessary if the wires are correctly terminated as described, but it does have the advantage of keeping the 10A bed current away from the main board.

Edited 1 time(s). Last edit at 12/31/2016 02:03AM by Supermec.

thank you very much for your tips ...

today i'll crimp all screwed connection.
i checked BED plug and look good. there's a safety tab on it.

next i'll consider the mosfet solution to reduce load current in the mainboard.
do you think a IRFZ40 is a good choice ?

Quote
Supermec
Hi, the extruder connections normally cause less problems as they carry much less current than the power and bed connectors. These chinese connectors do not seem to have the surplus capacity that EU and US ones do.

The problem is that:
a) these connectors, including the bed and power ones, are not suitable for connections using stranded wire.
b) the power connector is carrying close to its supposed capacity when everything is working.
c) the green plugs can sometimes give an unreliable connection between plug and pins which can promote arcing.

The screw type connectors are not immune from problems, and I have now seen a number of meltdown pictures of those. What the assembly instructions don't cover, is that you should use crimp-on connectors to terminate the wires. For the plug type ones you should use crimp-on ferrules. You have solved the problem for the extruder by soldering direct to the board, but you are most strongly advised to fit crimp-on connectors to the wires for the power and bed. You should also fit these to the power wires at the PSU end.

The problems arise because, even if you twist the stranded wire end well, it is not solid. It will distort when tightening the screws, and continue to do so with time under the influence of heat and vibration. What you must NOT do is to tin the ends of the wires. Provided that you fit the correct size crimp connector for the wire, and crimp it properly, the strands are fully contained and held tightly in a manner that cannot slacken. The terminal screws, once tightened on the solid end of the connector, cannot loosen and provoke an arc.

You should also keep an eye on the plug connection at the back of the bed that connects the heater power to the bed itself. These have also been known to blacken and heat as a result of poor connections between the plug and the board pins.

There is also a method of reducing the current carried by the power connector. This is to fit a control MOSFET to switch a 12V supply taken straight from the PSU and fed direct to the bed, with the switching signal being provided by the original bed pins on the main board. There are differences of opinion as to whether this fitment is strictly necessary if the wires are correctly terminated as described, but it does have the advantage of keeping the 10A bed current away from the main board.

I don't know anything about that particular MOSFET. I personally believe in not pushing electronic components near to their limits, so I chose a 30A that has excellent connectors and is available from Amazon (look up hotbed MOSFETS). The cost was about £15 sterling. I'm very happy with the quality and it is provided with an excellent heat sink.

Found!
thank you very much!