ESD shutting down printer

I seem to have some kind of ground loop in my Mendal.

Sometimes, I'll walk up to the printer and touch the filament while it is printing and the machine will stop printing and everything freezes up, including the Ramps and Arduino. Nothing gets damaged and is fine after I reboot everything, but I've lost many a half finished print this way. I thought that I had it sorted out after I wrapped some tinsel around the metal hook that I hang my spool from and hooked it up to an overhead light box, but it has done it since. The only way I can avoid it is to touch the spool itself (I like to roll off some slack sometimes) and turn that. But if I just walk up to the machine and touch the filament itself - zap! (silent zap, but deadly)

Has anybody else had this problem?

Does anybody know where the loop might be and how best to create a drain for it?

Have you considered wearing an ESD wrist strap and grounding that? Should eliminate your problem.

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

How about grounding the printer. It sounds like you have a floating ground.

tmorris9 Wrote:
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> How about grounding the printer. It sounds like
> you have a floating ground.

I guess that's what I mean by a ground loop.
Do you mean wire the frame to ground?
I'm guessing the boards are grounded since the ESD goes through them.

Yes, I mean hook the frame to "earth ground" not just negative side of the power supply.

Is your power supply properly grounded?

tmorris9 Wrote:
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> Yes, I mean hook the frame to "earth ground" not
> just negative side of the power supply.
>
> Is your power supply properly grounded?

My power supply is well grounded and I have hooked parts of the frame to it's chassis.
The problem with grounding the Mendal frame is that all of the rods are inserted into plastic parts, which of course are di-electric. I'd have to take apart the entire machine to electrically join the rods in some kind of meaningful fashion. I'm not sure how I'd securely connect to the hardened steel smooth rods...

I wrapped my tinsel around the two upper rods that the filament passes between and connected the other end to the power supply, and it has frozen up since then.

Has anyone else had their machines freeze up due to ESD?

I havnt had mine freeze but I scramble my lcd on a regular basis just by touching my machine

What seems to have worked for me on my MendelMax is to connect all the extrusions together with wire and then ground the frame to the power supply ground. I've also made a connection between the power supply's V- and its ground. Lastly, I wrapped the ribbon cable from the display to my Sanguinololu in aluminum foil and packing tape as a shield, then grounded that to the frame. Note that the aluminum oxide film that forms on the extrusions from anodizing is electrically non-conductive. Even non-anodized aluminum will form a natural, non-conductive, aluminum oxide layer in the atmosphere. You need to screw into the aluminum to get a proper ground. I used sheet metal screws and spade lugs on the wire.

Since I've done all this, I don't think I've had a single freeze up and rarely scramble the display.

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ΜΟΛΩΝ ΛΑΒΕ

I've had my mendel stop mid print most recently the other day but what I touched was the usb cable to the melzi electronics.

Ben

Plastic in the event of friction is a big cause of static electricity. That is why dust collectors need to be grounded if they use plastic lines. Try using a piece of brass as a wiper and connecting it to ground, preferably at the outlet.

I have seen this occasionally too (printer freezes mid print). I run the printer using a laptop which has a brick supply that is not earthed (the supply has a power connector with only 2 prongs). The 12v supply for the printer is also a brick style (12v 6 amp) which has no earth connection. My heat bed is a 240 v bed controlled by an SSR. The bed is connected to the earth of the heat bed power lead, but as far as I can see, that is the only earth in the whole system. Seems crazy looking at it now.

What should I be connecting to earth to make things more stable?

As far as I can tell, it seems to be the USB connection that is shutting down, because the firmware still seems to be happily managing nozzle and bed temperatures.

Edited 1 time(s). Last edit at 04/24/2013 06:11PM by Greg Frost.

Well, I sure am glad to hear that it is not just my machine.

I know that plastic will conduct if the voltage is high enough, and turning on a spool can generate that. My spool is suspended from the ceiling 4 feet above the printer.

I too am using a laptop (netbook actually) but I think that it might be the Arduino that is locking up.

I guess I could link every metal object in the printer together and connect it all to ground, but that would kind of take away something from the whole printed plastic parts concept for me. I'm sure it's a ground loop and if it's form can be discovered, it could be drained away from a single point.

I am using a 100 amp 12 volt server power supply that is well grounded. (Yes, I know that's a bit big, but it was dirt cheap).

Maybe it would help if I put the machine inside a metal box? Or would that just trap the static more?

I have never seen anything like that on my printer, but assuming you use a resistor heater.. What if some of the resistor windings have shorted with the hotend, that could send noise up to the electronics via the heater circiut..

Should be easy to check with a multimeter.

Just a thought..

Ralf Wrote:
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> I have never seen anything like that on my
> printer, but assuming you use a resistor heater..
> What if some of the resistor windings have shorted
> with the hotend, that could send noise up to the
> electronics via the heater circiut..


Thanks Ralf, but I use a ceramic heater and it's not shorting.

This happens in an exact way each time. If I've been out of the room it's in for awhile, and then I walk in while it's printing and then grab the filament, it stops printing the instant my fingers touch the filament. I touch it about two feet up from the moving hot end. I've gotten into the habit of first grounding my body by reaching up and holding onto a big metal light box in the ceiling. That seems to be working fine.

In the winter I wear an ESD foot strap in one slipper otherwise I get a big spark when I walk up to a machine and touch it. Whether you generate ESD depends mainly on how dry the air is, what the soles of your shoes and the flooring is made from.

Odd that touching the filament does anything as it is normally almost a perfect insulator. If I re-spool ABS with an electric drill while passing it through a duster it works like a Van de Graff generator and makes sparks about 30mm long. It also sparks though the casing of the drill and gives me a shock,

Perhaps grounding the nozzle with an independent ground might work. I.e. you don't want the the ESD pulse flowing down the ground of the machine. Sometimes adding a 10M resistor works better for discharging ESD without creating a big ground current pulse or air-born EMP.

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[www.hydraraptor.blogspot.com]

nophead Wrote:
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> In the winter I wear an ESD foot strap in one
> slipper otherwise I get a big spark when I walk up
> to a machine and touch it. Whether you generate
> ESD depends mainly on how dry the air is, what the
> soles of your shoes and the flooring is made from.
>
>
> Odd that touching the filament does anything as it
> is normally almost a perfect insulator. If I
> re-spool ABS with an electric drill while passing
> it through a duster it works like a Van de Graff
> generator and makes sparks about 30mm long. It
> also sparks though the casing of the drill and
> gives me a shock,
>
> Perhaps grounding the nozzle with an independent
> ground might work. I.e. you don't want the the ESD
> pulse flowing down the ground of the machine.
> Sometimes adding a 10M resistor works better for
> discharging ESD without creating a big ground
> current pulse or air-born EMP.

Thanks for your suggestions Nophead, I'll try the resistor.
Where I live, it rains all winter and the humidity is pretty high, so that's likely not the cause.

I have over the years worked repairing Xerographic equipment, and they use polymers (similar plastics) in granular form that churns in an auger manipulated trough (It's called developer material). The voltage created by this churning is critical to the printing process and is pretty predictable, and is on the order of thousands of volts. Even vacuuming that stuff up will give me some pretty bad shocks. I know from that knowledge that plastic can be a very good conductor under the right circumstances. From how it's been explained to me, and I'm no physicist, the static accumulates on the exterior of the plastic and forms a conductive skin of sorts.It is that electrical skin that is the conduit that conveys it down the filament. I'm guessing that from the nozzle, it travels to the Arduino and locks that up. I've only ever seen it do this when I walk in the room and phycically touch the filament, and since I live in a high humidity area, I'm thinking that I'm actually draining the static away, rapidly, and causing a flow through the system, rather than adding anything to it. I think the spool turing is the source of the static.

Hey Tek, did you work for Kodak (or maybe Xerox?)

waitaki Wrote:
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> Hey Tek, did you work for Kodak (or maybe Xerox?)

I've been trained on both, along with several others....