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Hi folks, the machine was running excellent, until I had to walk away for about an hour. Filament must have got caught up around the nozzle and then it reached up into the resistor area. I tried to pull off the filament when it was still hot, but it must have torn off some of the epoxy or un-lodged the resistor.

[img]http://www.redcatrampageforum.com/attac ... entid=7474[/img]

[img]http://www.redcatrampageforum.com/attac ... entid=7475[/img]


[img]http://www.redcatrampageforum.com/attac ... entid=7476[/img]

Do you think I can rebuild the hotend, or is it just easier to get a new hotend with the resistors already installed. I see hotend kits on SeeMeCNC, but nothing pre-built like for the Delta Orion. I am on business travel all next week and would really like to just buy the same thing and install it when I get home.

Any suggestions?

The hotend is only reaching 162 degrees, if that helps.

Those images don't work for anyone not logged into the site they're posted on, btw.


(edit - Looks like you fixed it.)

How are the pics now?

How is the thermistor side? I am not seeing what is wrong in the pics. It "looks" like very thing is still connected. Did one of the wires break but does not show in the pics? Just trying to make sure I understand what might be wrong to try and help help.

If you can only reach 170 or so, it sound likely that one of the resistors is either electrically loose or popped. If you can test the resistance of the resistor pair check to see if the value is about 3.5 ohms or so. If it is in the 6 ohm range, one resistor is not in the circuit either because a connection has come loose or the resistor has failed and is open. Disconnect one end of the Hot End power feed when testing to isolate the resistors.

You can also test the thermistor with one end disconnected. At room temperature the value should be about 100K ohms. Additionally, if the thermistor is not functioning, the Rambo should shutdown and show a "def" error on the LCD indicating that there is a problem or open circuit in the thermistor loop.

There is a possibility that the thermistor was pulled out of the nozzle block and initiated a thermal runaway. This could have overheated the hot end and opened one of the resistors. Running on a single resistor the hot end would not have been able to continue running away and cooled back down. If this occurred there may also be damage to the PEEK insulator.

So once you get the resistance in the heaters back in range, carefully look at the thermistor and assure that it is seated in the nozzle block. Apply power and watch for the corresponding rise in temperature. If it is slow or you see evidence of smoking filament cut the power to the hot end leaving the fan running if possible.

Good luck!

Thanks for the replies. I will start testing resistance and whatnot on Saturday.

I had a thermal runway and overheated my stock hot end. I just ordered the new parts and plan on rebuilding it after a complete inspection. While I was waiting I replaced it with a E3d v6 hot end. Just as easy as replacing the stock one. Now I will have and extra hot end ready to go on the shelf. I have customers waiting, must print parts,must print hehe ...

Yeah, it was the resistor. Cracked in half.

Anyone know what the crimp connectors are called and where to get them?

RAMTechRob wrote:Anyone know what the crimp connectors are called and where to get them?

I think they are uninsulated ferrules and can be found here: http://www.mcmaster.com/#ferrule-terminals/=tn1yjq

Yeah thanks. No wonder I never saw them before. Redneckilicous.

RAMTechRob wrote:Yeah thanks. No wonder I never saw them before. Redneckilicous.

I just hope that you get your machine working. Home depot may sell the ferrules and if they are insulated, just taking the insulation off.
The hardest part is getting the sizing right which is dependent on the wire size.

I will use something else.

I got my non-insulated crimp ferrules at NAPA. They have a blister pack of the #18-#22 size. I think I paid about $3.50 and being NAPA there may be one close to you so you don't have to wait for brown truck. NAPA is also a place to get Permatex Ultra Copper goo.

Yep, got the Permatex in my toolbox. I'm an IPC certified engineer, pretty sure that crimp isn't going on my machine.

When I did my original resister hot-end, I didn't crimp. I used high-temperature solder (old-school 10/90 I already had). Of course that requires having some and a soldering iron that can get hot enough.

These days, my recommendation for failed resistors is to replace with a 40W ceramic cartridge. They're cheap enough and come with long leads already attached.
http://www.ebay.com/sch/i.html?_from=R4 ... dge+heater

That looks like a long term fix for me. Thanks a lot.

Are they all the same size?

RAMTechRob wrote:That looks like a long term fix for me. Thanks a lot.

I think that the cartridge heaters are the way to go. Mine has about 600 hours on it at this point.

I still keep a spare on hand just in case. It is fitted with an XT-60 connector and change out would be less than a couple of minutes.

So you are only using one cartridge heater then?

Only one is needed.

g.

Thanks, that looks like the way to go for me.

teoman wrote:Are they all the same size?

No, they vary in length,,, 6mm x 20mm is what I have in mine.

Somehow I ordered the correct one. Woohoo.