UM2 filament grinding, fails after ~10 layers

[valcrow 145]

Instead of hijacking the other thread, thought I'd make a new one since I'm not sure it's totally related to Cura/firmware anymore.

Here's my current issue:

________

I'm getting failed prints due to filament grinding after around 1mm of printing, around 5-10 layers. The base layer lays down really nicely, and everything looks fine up until a certain point and then the filament gets grinded down and no longer extrudes.

Here's 4 fails in a row:

So from left to right here's what I tried:

1. First fail (Cura 14.06 | 0.2mm layer | 20% infil | 0.3mm first layer)

2. Second try same settings (thought it was a fluke)

3. Disabled retraction | 25% infil | 0mm first layer

4. Disabled retraction, tightened extruder tension screw, 50% speed

5. Cura 14.03 (not shown) | played with tension screw, normal print settings THIS ONE PRINTED SUCCESSFULLY.

I thought it was fixed by using 14.03 but not so...

Here's a few new failed prints. same issue. (the bottom smaller pieces)

Any ideas?

Thanks!

 

[Dim3nsioneer 557]

Do you use a different speed for the outer shell than for the rest?

edit: forget it, this is not the cause... I was mislead by the 'good' print... sorry!

 

[valcrow 145]

I usually do 40mm/s Perimeter and 50mm/s infil, but for the latest test I made them both 40mm/s thinking it might be it...

It's kinda bizzare because either it fails like this or it prints beautifully. There's never any inbetween like underextrusion throughout.

 

[illuminarti 18]

Could it be a firmware related partial-grind at start up that finally makes its way to the apex of the bowden, or the hotend, or something, and gets stuck?

Are you getting the motor skipping back, or just renewed grinding? If grinding, try increase the tension on the spring a bit - the motor should be able to grip the filament well enough that it skips, before it gouges the filament.

 

[anon4321 16]

Just a shot in the dark but I'm having a problem where the bottom layers separate and I think it is temp related (on a UM1).

However, it go me thinking on this. Since you are getting good first layers, are the fans coming on for later layers causing something to cool, underextrude and grind?

How far do you get if you switch the fans completely off?

 

[valcrow 145]

Could it be a firmware related partial-grind at start up that finally makes its way to the apex of the bowden, or the hotend, or something, and gets stuck?

Are you getting the motor skipping back, or just renewed grinding? If grinding, try increase the tension on the spring a bit - the motor should be able to grip the filament well enough that it skips, before it gouges the filament.

 

So I sat and watched the extruder for a good 5 minutes. I think you're right, the grinding starts to happen in the beginning of the print. It still extrudes fine, but the filament is not actually moving up it's like it's just using the front loaded pressure that's there.

I helped it a long a bit after about the 3rd layer and pushed the filament up to get past the grinding area and it seems to be working now, no new grinding areas so far... but we'll see.

There is no bolt slippage where it does the snapping back thing. It does that sometimes when loading material though.

I had installed your custom firmware, I guess we have to wait till daid gets it in the next one?

 

[gadgetfreak 7]

I like anon4321s comment.

Once I had a misdirected fan on an UM Original which made the nozzle never come up in temperature.

Valcrow, do you have an UM2 or an UM Original. If you have an UM Original, is it with a heated bed.

For UM2 the fans would come on full at 0.5mm into the print as per standard however I can't remember whether this is the case for an Ultimaker Original with a heated bed as well?

Like anon4321, check the fans!

 

[valcrow 145]

I did a science fail, I changed 2 variables and now I don't know which is making it work... after your comment I disabled the fan, but I've also helped the extruder a bit by pushing the filament manually so now I don't know what's making it work. :-|.

I'll test without touching the extruder and deactivating the fan next so I know if it's the fan or the extruder.

Thanks for the ideas. Oh it's the UM2 btw.. I'm trying to print a UM1 fan shroud on my UM2... sorry for confusion.

 

[anon4321 16]

If it is the fans, look for something misaligned that causes something to cool that shouldn't. I don't know the UM2 and the head design is very different than the UM1 so I wouldn't even want to guess what is getting cooled.

 

[illuminarti 18]

One thing to check is that the fan shroud isn't pressed up against the nozzle; make sure that the nozzle is centered in the hole in the fan shroud.

 

[valcrow 145]

Ok, so it's not the fan, I just did a test without the fan on and didn't touch it. It failed in the same place.

It does the extruder skippy thing.

 

[valcrow 145]

Ok so for some reason it's fine now... Either Cura 14.07 fixed it, or increasing extruder pressure worked. Apparently I was tightening for more pressure, but when I should have been loosening the grub screw... who knew?

Anyways, it works now so yay!

 

[blenny 0]

Hey Valcrow,

What temperature have you been printing at?

How far did you loosen the pressure screw?

I have been having exactly the same problem for my last half dozen prints.

https://www.dropbox.com/s/wq1r54t6rqry6z1/2014-07-05%2021.42.17.jpg

With any luck I can copy your fix exactly.

 

[valcrow 145]

Those little blobbies look weird. you sure it's not PLA clogging your nozzle?

Anyways, I loosed my grub screw until a little after the 1st click. and using the new Cura .07

 

[valcrow 145]

Ok so for some reason now, it'll be ok for the first few objects and then do the grindy thing around the 3rd! whyyyyyyyy!

*edit* ok I figured it out, my filament was tangled on the spool. I feel like a fool.