1 Topic by ITman496

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Topic: Weird design flaw for the solidoodle

Apparently if you ground the case to the power supply, the solidoodle fails.

Here is what happened.  The DC jack on a friend's SD3 broke.  Being the work less think more person that I am, I simply soldered a rc style anderson connector onto it via thick cables, one to the positive pin, and one to the outer case of the dc jack after I verified that it was well grounded.

The side effect of this was that the negative (ground!) solder blob on the side of the dc jack assembly was brushing against the metal standoff with the screw going into the case.

When we powered it up, it worked, but if you pulled a lot of current, as in heat the bed, extruder, and arm the motors at the same time, after a few minutes it would lose connection and die.

I checked everything.  No shorts, no heat on the mosfets at all for either one, so nothing was shorted or excessively drawing power.

Then for the hell of it, I figured, well, okay, I'll remove that standoff.  Why the heck it would be affecting it is beyond me, but whatever, I'm out of options.

Sure enough, now it works perfectly.  Does that make any sense at all?

Grounding the case to power supply ground.. makes it stop working.  ??????

2 Reply by eflyguy (edited by eflyguy 2014-09-18 20:30:30)

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Re: Weird design flaw for the solidoodle

Not every system is designed to have a grounded chassis..

Golf carts are one example..

Stock SD4 with 3/16" glass attached to stock (kapton-covered) bed with Aquanet.

3 Reply by grob

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Re: Weird design flaw for the solidoodle

Sounds like there's a noise problem there, I'd suspect a ground loop as the problem appears when you bond something.

But I'm curious as to what could be creating ground loops when the case really shouldn't be tied to anything else in the system. Is there any way the chassis of your computer could be connected to the chassis of the solidoodle? Attached is an image for pondering:

http://www.soliforum.com/misc.php?action=pun_attachment&item=6330&download=0

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4 Reply by ITman496

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Re: Weird design flaw for the solidoodle

Something else to note, on one of the many computers we tried, and all had the same problem, one was a laptop running on battery, its only cable being the usb cable.  So  what you drew would not apply, though you bring up a good point.

And as for not all systems being designed to have a grounded chassis, why would the solidoodle not have one?  Seems weird..

5 Reply by grob (edited by grob 2014-09-19 04:17:12)

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Re: Weird design flaw for the solidoodle

Well, you'd only ground the chassis if it was necessary to prevent an electrical hazard, but as the max voltage presented to the thing is 12VDC (not in most cases hazardous itself - pacemakers, existing medical conditions and extreme misfortune aside) and it's NOT fused, it's actually better to leave it floating (e.g. if it was tied to the neg input, and a 12V power conductor shorted on the case, that could cause a fire - whereas if the case was floating, it takes 2 separate insulation failures to do that...).

Worth noting for those who install mains-powered heaters into the unit: you NEED to connect the chassis to the mains outlet earth. Otherwise, your household circuit breakers (hopefully earth leakage protection also) can't save your life!

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6 Reply by wardjr

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Re: Weird design flaw for the solidoodle

Great point Grob... For those of us with mains powered bed heaters.  When helping others set up a heater of that style I even recommend a ground wire from the chassis to the platform itself as well.

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7 Reply by grob

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Re: Weird design flaw for the solidoodle

wardjr wrote:

Great point Grob... For those of us with mains powered bed heaters.  When helping others set up a heater of that style I even recommend a ground wire from the chassis to the platform itself as well.

Very good - I agree.
My heater is a space heater for the enclosure, so I've been ok just with the chassis so far...

SD3. Mk2b + glass, heated enclosure, GT2 belts, direct drive y shaft, linear bearings, bowden-feed E3D v5 w/ 0.9° stepper
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