Beware Melting Connectors on RAMPS boards

Just a warning to anyone making any type of 3D printer using a RAMPS board.

Check your power connector plug - it seems that despite being rated between 12 and 15 amps they overheat easily and melt with obvious risks. Just google 'ramps power connector melted'.

I had a problem with a loose nozzle causing a PLA leak and discounted the smell as burning PLA., when it was actually the connector frying.Luckily it went open circuit as the dodgy connection filled with molten plastic/gummed up with char. It would not have been nice if it has shorted instead - the dividers between the plugs had largely disappeared.

This problem seems to be common to all types of machine as the connector is a standard p[art of the RAMPS board. Prusa themselves say it is caused by not tightening the connectors suffciently. On my connector the wires were so solidly locked in the ferrule they wouldn't pull out, it was poor contact between the pin and socket - as evidenced by the location of melting and scorching, which was away from the screwed connections.

I have replaced my power connections with soldered ones, there are spade connectors in the power lead and these are showing no signs of warmth.

I am also considering putting automotive fuses in the power leads as the ones on the RAMPS board are after the connector.

Neil

Neil,

Thanks for posting this info, I've ordered a 25A DC-DC Solid State Relay for the princely sum of a tenner to take the heated bed load off the control electronics before I do any long print runs,

- Nick

part of the problem is the number of fake / cheap copies of components in the supply chain

the original 1/4" blade connectors used in my mini lathe are made of a too a soft metal

once un-pluged and plugged back in they didn't have enough contact pressure and had to be replaced with connectors made by Lucas ( supplied by my local Motor Factors)

searching for SSR-25 DA 25A solid state relays , I found fakes being sold that only had a 12A triac inside !!!

http://www.ul.com/newsroom/publicnotices/ul-warns-of-solid-state-relay-with-counterfeit-ul-recognition-mark-release-13pn-52/

https://www.youtube.com/watch?v=DxEhxjvifyY

shows whats inside the fake  ssr

John

Edited By john swift 1 on 05/06/2017 22:52:50

I probably have the same one, as I have a different model to the prusa, but it's made by the same Chinese people who originally designed the prusa, I believe they explicitly said on the ebay page of mine, that the board really needs some kind of extra forced cooling to what it comes with if you expect it to work hard!

Depending on how the soldering went, maybe a different connector or the amount of solder used is now dissipating more heat! 

Michael W

Edited By Michael-w on 05/06/2017 22:57:41

The soldering appears fine, it was definitely a poor connection in the plug.

The design of the printer I bought included a small fan blowing directly on the lower part of the RAMPs. it includes a bracket to install another fan aimed at the top, I haven't found this necessary although I have a second fan ready to fit.

Quite so. One of the issues I had with my Tormach CNC mill was an intermittent spindle run problem. I eventually traced it to an 'industrial' push on connector on the control board. The exact same connector, but from a reputable industrial manufacturer, was available from Farnell. I've had no issues since changing the connector. The original connector mated with barely any force needed. The replacement connector needed a significant push to mate.

Andrew

Hi Andrew

it was only last week I read a post on CNCZONE about the same problem with a   Leadshine  3ND883  three  phase stepper driver used on a Tormach CNC machine !!

the connectors are used on a large number of drivers from a variety of manufactures

John

Edited By john swift 1 on 06/06/2017 11:41:38

The green connector at bottom right is a five-pole version of the 4-pole one on a RAMPS.

By any chance is that the one that gives trouble?

Neil

Hi Neil

yes that's the one in the CNCZONE post that's burnt - not mine I'm glad to say !

going by the Leadshine manual its W phase that drives the stepper motor

the same connector is used on some of the infamous TB6560 stepper drivers

( but not the version that featured in Carl Wilson's Arduino controlled Indexer published in the December 2016 issue of MEW )

John

Even with a 15A rating, you may be exceeding that on a typical 3D printer with a heated bed:

• Heated bed - aproximately 10A
• 40W 12V cartridge heater - 3.3A
• 4 x Nema 17 steppers - about 3A
• Nema 17 stepper for extruder - 1A

In total around 17A

Sanguinolo board also has issues with heated bed traces melting, so I offboarded the control of my heated bed.

(Sanguinololu is effectively a Mega + Ramps with a 644 or 1284 chip, but in a much smaller footprint)

I think the connectors are rated 15A per way rather than total i.e. 60A total

Your sums give a total current of 34A - as it comes back out again on the ground pins.

Either way it's a lot to put through a small connector.

Neil

The problem I had was with a connector on the Tormach custom control board, the green connector bottom right:

Although not obvious the PCB part is a header with round pins. The mating half, with the wires, slides over the pins. The circuits are all low current. The problem was poor contact, rather than related heating, due to low insertion force and possibly poor spring contact design.

Changing both halves solved the problem. I also changed the similar connector top left, just to be safe.

Andrew

Edited By Neil Wyatt on 08/06/2017 07:37:42

Hi Andrew

the connectors look like the ones used by Gecko Drive on their stepper drivers (G540 for example)

and your control board looks like its a version of the boards from Campbell designs / Sound Logic Combo Board

http://www.campbelldesigns.com/Combo-board.php

John

Edited By john swift 1 on 08/06/2017 00:24:44

I was thinking more of 17A in on the +ve and 17A out on the -ve power connectors, so still exceeding the 15A per way limit.

But I also think we are violently agreeing with each other.

I'm sure we are, but on a standard RAMPS the supply is split across four pins, two 12V two 0V theoretically 1the biggest current is the heater supply at 10A/way.

Edited By John Stevenson on 08/06/2017 10:12:37