Solved Filament snagged, now clicking/crackling noises + layer problems

Okay, I am so fed up with this thing. I finally fixed the last problem -- by completely replacing the hexagon hotend, then attaching a new 25mm heat sink fan to replace the broken one (which required cutting the line and soldering on the new one)

Started up a print, was working okay so left the room for 15 minutes... come back and the thing is making clicking noises, and the layers are all off. The whole print is screwed, because at some point the filament snagged (it somehow got tangled in the spool itself? Like it was running under other wound portions, creating a sort of knot/snag)

So, I cancel the print (which was failed at that point, though the bottom several layers had printed perfectly), and restarted it. Now the printer doesn't work. For some reason, it's like it's not moving up the z-axis appropriately. It keeps making clicking/crackling noises (can't tell where they are coming from), and the layers are wider and goopy... it is either over-extruding for some reason, or suddenly just not moving up like it should be... I'll post pics in a few minutes. Basically, the interior framing gave away that there was a problem... instead of nice, thin lines, it is flat, widened-out globs.

Is there any way to ship the printer to RoBo and have them fix it? This has turned out to be a nightmare...

 

Where would these switches be?

 

If I'm thinking about the same switches, the are the ones attached to the Z screw nuts.... I had a similar problem earlier in the week with one of my prints. The "switch clamp" screw that tightens around the Z nut was loose, so the switch and whole carriage on one side had clibmed about 1/8" higher than the other. Had to cancel the print, reset the switch/carraige and tighten the phillips head screw. Good ever since. I've had my printer since last Tuesday, and that has been my biggest failure so far.

 

Now I go to test things out again (with print setting on Low), and it utterly fails. Won't even print the first layer.

So I test it by raising up an pressing Extrude button. Nothing comes out. Not at 210, not at 200, not at 205, not at 220.

So then I look more closely. Sonofabitch, it's LEAKING again. Just like my last Hex head did. And I made sure to tighten this one.

The Hex seems to be seriously flawed. I'm done with it. I'm ready to drop-kick this printer into the highway.

Anybody want to buy a used RoBo 3D?

 

giving it one more go, but this hotend really is the bane of my existence. I think the problem all boils down to the fact that there is not going to be an air-tight (or PLA-tight) seal between the steel screw end and the aluminum heater block. (Additionally, the level/rate of expansion of those 2 different metals is likely to cause problems for the threading, as well. This is why plumbers can't just screw 2 different types of metal pipes together and call it a day...)

 

I might try the E3D... wait, extruder or hotend? I'm assuming you are referring to hotend.

If I keep having trouble with the hex, I am going to try the E3D. I've already replaced the hex (with another hex). This is the brand new one I put in!

 

Something else is going on. I'm not sure what. I never used to have this problem, until now... after I tried to fix the old problem (leaking filament, broken heat sink fan)

Now I have replaced Hex hotend, replaced the heat sink fan, etc. I thought the failure occurring here was because of filament snag, but maybe not? Because the filament is no longer snagging, but the same issue keeps happening every time I try to print: it does about 1/4" up just fine, then fails. The layers are off... and then the head starts jamming into/rubbing it as it moves (the print lifts, or the head does not lift enough... not sure which)

Here are some photos:

https://drive.google.com/file/d/0B2Q1ZSqb8_UaYzlnZ1BQeVNCTkE/view?usp=sharing

https://drive.google.com/file/d/0B2Q1ZSqb8_Uaa3dfenMwaWFScms/view?usp=sharing

https://drive.google.com/file/d/0B2Q1ZSqb8_UaU1ZmYzQ0RHpGWlk/view?usp=sharing

You can see how a layer gapped/lifted, and then all subsequent layers are rubbing/smearing due to contact with nozzle...

 

What would cause a print to be going fine, and then suddenly fail and print gaps/lifts and overhangs (wider layers) after printing 10-15 perfectly fine layers?

That's what I keep experiencing, over and over about 5 times in a row now. It will be good for about 30-40 min. of printing, then the print fails.

Here are some pics.... I can take more of the other prints if it helps. It doesn't always fail at the exact same spot, but close (somewhere between 1/8 to 1/2" of vertical rise/layers); I have tried changing filament, temperature, and layer widths, etc. Always happens regardless of any of that. I even shrouded the printer under a sheet (my ghetto version of an "enclosed case" ) and set bed temp to 65 to try to raise the ambient temperature, in case the filament was cooling too quickly and thus not adhering. That didn't fix the issue. It just keeps happening, I can't get a print out of it...

https://drive.google.com/file/d/0B2Q1ZSqb8_UaYzlnZ1BQeVNCTkE/view?usp=sharing

https://drive.google.com/file/d/0B2Q1ZSqb8_Uaa3dfenMwaWFScms/view?usp=sharing

https://drive.google.com/file/d/0B2Q1ZSqb8_UaU1ZmYzQ0RHpGWlk/view?usp=sharing

 

How can I check the firmware version? (Or load a new one on)... I haven't been able to find that info, even searching on the forum.
I'm using the MatterControl software that came with it.

Here's the thing -- as far as I know, I am doing everything exactly the same way as I used to... and the prints worked. (and I would think if it were an issue of metric vs imperial, it would cause a problem long before getting 1/8-1/2 inch up. Also, it's not consistent... sometimes it does this 1/8" of the way up, other times it's closer to 1/2")

Then there was a heat sink fan failure, and a leak in the hex end, so I had to remove the hotend (tried to clean it, but the threading stripped the heater block on reassembly, so I replaced it entirely) and solder on a new fan. So, I put the new hotend and fan back in.... and now I am getting these problems.

There was another issue on the first print I tried after reassembly, where the filament was tangled in the spool and snagged during printing. Could that have done something to break or bend or strip components on the printer itself?

 

that looks to me like the heatsink is getting hot and causing the filament to expand and jam. The hexagon has a pretty small ID so it's more vulnerable to that. When it jams feel the heatsink and see how hot it is. If it's warm to the touch I think the fan might be underrated. Were these included by RepRapDiscount when you got it?

 

Yes, everything seems snug. (at one point the hotend came loose, but I then mounted it pretty tightly after that)

Here's why it is especially weird: the shape I am printing is very, very basic. If you look at the photos, that 2nd one shows the shape of my model -- all the way up. It's just a vertical extrusion of that shape.

I would think if it were a loose belt or something, it wouldn't make it through 10-15 layers of that shape no problem, then suddenly slip... would it?

I'm going to try some other models and see what happens I guess. Maybe some calibration cubes.

 

Yeah, the fan is the one that came with the heat sink.

Just curious... how would expanding/jamming cause these artifacts? What it looks like is that a layer suddenly gets wider -- it ends up overhanging at both ends. Now, if that was just extra filament leaking out, wouldn't it sort of correct itself on layers after that? But it doesn't.

It's really hard to even touch the heatsink, but it does seem pretty cool (barely warm) to the touch...

 

Could the filament snag have caused a stripped gear in one of the motors? That was one thing I was considering...

 

Well then my first hunch was wrong and it's probably the obvious answer of it just needs an in-line oiler.

As for jamming theory I think there's a couple main issues.

The first is chemical based. As Polylactic Acid (PLA) is a derivative of corn/sugar based products it has similar chemical properties similar to their starting ingredients. If we think of how sugar behaves when heated up inside metal pan it will stick to the wall and begin to crystalize, especially at points of high temp flux.

The plastic probably has similar characteristics. Metal is actually very rough on a microscopic scale and will be abbrasive to PLA. Once it starts to shear off the plastic it will sit in pores and begin to crystallize. This is commonly referred to as burnt on gunk.

The way to prevent this is the same as to prevent sticking while cooking, you coat the metal in an oil and then heat the oil to a point that it begins to polymerize. This creates a super slick coating of polymers allowing for your plastic to pass through unmarked.

The reason for jamming and partial clogging is these burnt on plastic crystals break off and get stuck in the small orifice. That's why you use something like a nylon cold pull to grip these crystals and yank em out.

Generally you use an in-line oiler to prevent these crystals from breaking off. The oil will more or less scrape off as the plastic passes through the small orifice so you're left with a negligible amount at the end.

The second is thermal expansion.

I believe the hexagon has a 1.8mm ID which only leaves 0.025mm of tolerance around the filament. This may have changed, you'd need to measure.
As the filament enters into the heated area of the extruder it begins to expand. If you're not heating it up rapidly you can get a bulging effect where the filament requires more force than usual to pass through the extruder. This usually manifests them as "weak" layers or porous, almost sponge like. With enough force your extruder can overcome this, but it generally results on grinding of filament or even the deformation of a section of filament. The filament can be ground down enough that the extruder no long is able to push the filament and "jams." The other results in the deformed section of filament catching on something, causing a jam or improperly extruded filament


It could very well be either or both judging by your picture. An in-line oiler is a good place to start though. Especially if the fan keeps the heatsink sufficiently cool.