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I've reached the calibration stage, and seem to blow a fuse after every 3 or 4 thin walled cubes.

Tonight I was trying the calibration plug (my walls are 0.75mm too thick) and I blew both the extruder fuse *and* the motor fuse.


Also, if I put an ohmmeter on the wires from the extruder resisters - and then jiggle it around, it reads a steady 4.12 ohms. There isn't an shorting from my jerking the extruder around. Current from the power supply is 12.27v.

This is the 6th and 7th times I have blown the fuses, I'm at a loss. I feel like the father from A Christmas Story.


thanks,

-sandy

Hey Sandy,

If you are blowing a fuse so frequently I'd stop and recheck all your wiring, there must be a short somewhere... if it's happening during a build. I'd have to guess it's caused by movement so therefore probably located around the hotend, which by the looks of it you have already guessed at that.

I'd recheck, maybe it's insulation melting causing contact, or an unprotected wire making contact during a movement.

Could you explain how you've connected the hotbed and hotend? Do you have fans? Are you using a glass or aluminium plate? Did you follow a particular guide to assembly it?

Oh and are we talking about the RostockMax or other variant of a 3D printer?

Cheers

>If you are blowing a fuse so frequently I'd stop and recheck all your wiring, there must be a short somewhere... if it's happening during a build. I'd have to guess it's caused by movement so therefore probably located around the hotend, which by the looks of it you have already guessed at that.

I'd recheck, maybe it's insulation melting causing contact, or an unprotected wire making contact during a movement.

Could you explain how you've connected the hotbed and hotend? Do you have fans? Are you using a glass or aluminium plate? Did you follow a particular guide to assembly it?

Oh and are we talking about the RostockMax or other variant of a 3D printer?<

Yea, that's my thought, too. This is a RostockMax, I connected the hotend by soldering the resister, thermister and motor wires to longer wires and used heat shrink tubing to cover the solder joints. I can grab the hot-end resitor wires and press on them while shaking the hot end, and the ohmmeter reading stays steady (I clipped the wires that connect to the RAMBO board to the ohmmeter leads for testing), so I guess I should look further along the wires.

I followed Geneb's first (white) build instructions. I'm not using a fan on the hot-end, and I'm using the Seemecnc Glass plate

thanks,

-sandy

Ok I'm not sure on which is the white build instructions, I followed Gene's v1.07, 18th June 2013.

I thought about using heat shrink tubing myself but didn't think it could handle the temperatures required for printing ABS. I'm actually surprised my hotend hasn't shorted, I didn't have enough PTFE tubing so I used insulation from the other wires that I've stripped during the build, until I can find a better and/or nicer solution.

How did you secure the thermostat/resistors in the hotend? Did you use the recommended RTV?

Is the situation pretty constant when the fuse blows (temps, hotend location, time)? What are the temperatures for both the hot end and bed?

Do you have the wires hanging there for a future fan to be connected?

Good luck!!!

September wrote:Ok I'm not sure on which is the white build instructions, I followed Gene's v1.07, 18th June 2013.

In V1 of the manual, Gene built a white Rostock. In V2, he built an orange one.

FYI, the difference between the two is that the white machine was constructed using parts shipped as part of the original Indiegogo campaign. The orange one was built using the current part designs that are going out in kits now. That's why I wrote it (and to make the build order a lot more sane that it was.)

g.

random guess: any chance of a static buildup someplace ... maybe causing a short on the board?

So it turns out I did have a short. Unplugging everything from the RAMPS board, I noticed the hot end thermistor wires white sheilding were bubbled and melted I followed it all the way back to the hot end and the wires I soldered onto the thermistor had gotten pressed together somehow.

I'm surprised to have so little damage. I'm going to replace all the hot end wiring, using the quick disconnect connectors Geneb recommends.

thanks everyone for your help!

-sandy

got a photo of your hotend wiring, ?????sandy

sandy wrote:So it turns out I did have a short. Unplugging everything from the RAMPS board, I noticed the hot end thermistor wires white sheilding were bubbled and melted I followed it all the way back to the hot end and the wires I soldered onto the thermistor had gotten pressed together somehow.

I'm surprised to have so little damage. I'm going to replace all the hot end wiring, using the quick disconnect connectors Geneb recommends.

thanks everyone for your help!

-sandy

I've placed an order for them too, waiting on shipment, probably a few weeks to a month away. What were you using as shielding, the white shielding you mentioned?

I'll try to take some photos tonight.

The white shielding I'm referring to is just the standard wire covering on the thin (24 gauge?) thermistor connector wires that were included in my kit. I used standard heat shrink tubing to cover the solder connections on all my wiring, but, I think I got a bit sloppy with some of it.

-sandy

ok I thought it might be. I don't think that insulation is capable of a high enough heat resistance at least not if you plan to print with PLA... but even then when you do the calibration on the hotend, I think it went somewhere near 250 degrees Celsius.

I've been looking at using heat shrink too, but I think its max temp is around 230 degrees Celsius so again not really sure how it will hold up. Gene's manual recommends PTFE (for the resistors and thermistor), and I think from what I could read it generally handles up to 280 degrees Celsius, my problem is trying to locate the stuff might try searching the web on the weekend again.

Would be interested in hearing back how the heat shrink goes, it's on order waiting on delivery.

PS I think I read around 210, it should be marked on the wire for the white shielding you mentioned.

Try this thread for info: http://forum.seemecnc.com/viewtopic.php?f=42&t=1099

You can get high temperature heat shrink, but conventional stuff won't hold up to hotend temperatures, most conventional wire insulation is also inadequate.
Having said that the thermistor connection should be far enough from the actual hot bit that it doesn't matter.
I usually use Kapton on the thermistor leads, solder conventional wire to the very ends (hooking the wire in to make a better mechanical connection) and make sure the Kapton runs over the soldered joint.
I think on my current hotend I ended up using ferules to make the connection instead of solder, but for the thermistor I've never had issues with solder.

no photo yet? this would help greatly.

September wrote:ok I thought it might be. I don't think that insulation is capable of a high enough heat resistance at least not if you plan to print with PLA... but even then when you do the calibration on the hotend, I think it went somewhere near 250 degrees Celsius.

I've been looking at using heat shrink too, but I think its max temp is around 230 degrees Celsius so again not really sure how it will hold up. Gene's manual recommends PTFE (for the resistors and thermistor), and I think from what I could read it generally handles up to 280 degrees Celsius, my problem is trying to locate the stuff might try searching the web on the weekend again.

Would be interested in hearing back how the heat shrink goes, it's on order waiting on delivery.

PS I think I read around 210, it should be marked on the wire for the white shielding you mentioned.

Try McMaster Carr for the PTFE

Since Mcmaster carr will cut to length the PTFE, the shipping and handling (which is applied after your order *shakes head*) can easily be more than a couple feet of PTFE tubing. I wish I ordered more length to make it feel slightly more worth it.

lordbinky wrote:Since Mcmaster carr will cut to length the PTFE, the shipping and handling (which is applied after your order *shakes head*) can easily be more than a couple feet of PTFE tubing. I wish I ordered more length to make it feel slightly more worth it.

When I backed up molten filament into my Bowden tube (rendering it useless) I decided to get several meters of it, assuming I would mess something up sooner or later, or use it for some other purpose. I haven't been sorry I did.