Rambo Issues

[TomR]

Hi All,
I am hoping the forum can point me in the right direction. I have had the M2 for over a year with no problems. Recently the extruder clogged so I figured now is the time to upgrade to the V4. Ordered the kit and worked great for a few weeks. Then at the end of a print I got a birds nest. The printer was still running but nothing was extruding. My impression was the extruder stopped heating and the material didn't bond and then stopped melting. Called Makergear and they send a new V4 and said very rare for it to fail and wanted the old one to check out. Got the new one and installed. Same problem, checked the extruder temp and got around 200 instead of 250. The temp in SD3 read 250. MakerGear said the temp if from and Rambo and not necessarily the actual temp. Checked the multimeter accuracy in boiling water and it read 99 so the probe seems to be find. Maker gear then thought it was the Rambo board so sent me a replacement. Installed it and seems like the same problem plus the filament motor worked at first then didn't. Also, the Rambo fan never worked. Not sure if that was the case with the old Rambo. Today the Rambo board is not communicating with the computer. It tries but can not connect. Hopefully the forum can give me some insight before I call MakerGear this Monday.

Thanks,
Tom

[Tim]

It's true that you can't really compare the temperature that the thermistor is reading with the temperature of the nozzle itself. The thermistor is buried inside the heat block, so it reads a temperature that is somewhere in the middle of everything where you can't reach with the multimeter. The v3a and the v3b hot-ends differ by 20 degrees in what gets read back by the thermistor, to get the filament to the same temperature. The v4 temperature readings are similar to the v3b.

When the printer is still running but not extruding, that's either a clog or a jam. That can be caused by the print warping or partially popping off of the bed; if the printed piece presses up against the nozzle, it can block the nozzle and cause a jam. If you're printing at 250C, then I assume you're printing either ABS or PETg, both of which are very prone to warping and shrinkage. That can differ a lot depending on the size and shape of the printed piece.

The RAMBo problems sound like loose connectors, but if you suspect the RAMBo board, then go back to the old one. The original symptoms don't sound like a controller board problem to me.

[TomR]

Hi Tim,

Thanks for you comments. I found out the replacement board had a blown fuse and that is why it stopped working. Replaced it with the original and now it is connected. I believe you are right on the money and it is not the board. What is happening is when the PetG(right again) is threaded into the extruder, the motor has a clicking sound. I push the filament down and it will thread a little and then the sound like a clicking sound starts. It seems independent on the tightness of the screw to control the pressure of the filiment. I originally assumed that it was because the hotend was not hot enough to melt the filament but now it seems the filament does thread a little then stops. I can see about 45mm of gear tracks on the filament with the end melted when retracted.
Does this sound like a motor problem or an adjustment that I am not aware of. Thanks for all your help.

Tom

[Jules]

The clicking sounds like the tension on the Filament Drive screw is too tight. (It clicks as it strips the filament, then stops clicking when it has chewed the filament away enough.) Of course at that point, extrusion stops because there's nothing left to grab.

viewtopic.php?f=3&t=2694

[TomR]

That's what I thought so had both loosened and tighter it but it made no difference unless there is some trick to it. The gear imprint seems the same regardless of tension.

[Jules]

Loosen it completely. There really doesn't need to be much tension at all.

[jimc]

yes that tension especially on a softer material like petg can squish the filament into an oval shape making it too wide to slide easily through the lower hole of the filament drive. it still could be that you have clog in the nozzle as well. tension is my first guess. put the filament in then unscrew all the tension off the drive.

[Tim]

That's what I thought so had both loosened and tighter it but it made no difference unless there is some trick to it. The gear imprint seems the same regardless of tension.

I would guess that if it's refusing to feed regardless of the tension, then the filament is catching on something in either the drive or hot-end, or possibly the extruder drive motor gear is all gunked up with plastic from previous failures.

I can see about 45mm of gear tracks on the filament with the end melted when retracted.

That's about right for the total length of filament through the whole v4 extruder and drive, somewhere around 50mm. Did anything ever come out of the nozzle? If not, sounds rather like a clog. On the other hand, the filament meets no particular resistance until it hits the end of the nozzle, so right at that point anything that's too marginal could cause the extrusion to stop.

One helpful thing is to get some bit of wire that's smaller than the nozzle opening (some people use guitar wire, I use the little needle that comes with 0.3mm lead mechanical pencils for clearing jams) and push it up into the nozzle while the nozzle is hot, to try to remove anything that might be blocking the nozzle opening. If that doesn't help, then disassemble the filament drive, make sure you can push filament through it easily by hand (if not, bore it out with a 2mm drill), check for loose bits of plastic in the way, and clean the drive gear if necessary.

[TomR]

I have tried everything. I used guitar wire to pass through the hot end. Used the cleaning filiment from ESun and tried PLA filiment. Some would extrude a little then stop with the filiment drive clicking. Per Josh I measured the thermistor temp in the hot end and it is at least 25 * degrees cooler than expected. Josh said it should be within a few degrees of the projected in simply3d. I measured the resistance of the thermistor wire and think maybe the connection is the reason. josh said that may explain the reduced temp of the hot end and why it's not extruding. Waiting now for Josh to get back to me.

[TomR]

All fixed!!! Problem was the pinion gear was stripped on the extruder motor. Replacement gear $5.00 from Makergear. Life is good again