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lukem96

Grinding??

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Okay community having massive problems with grinding, i don't think it is the feeder as i have cleaned it, and have adjusted the tension from loose to tight and have had no luck.

I have the problem when i print 2 objects at once (phone cases)

One of them print fine, but the 2nd one it does the first layer then starts grinding, this usually happens when i'm asleep or working so cant tell what actually happens, but it happens all the time now when i try and print 2 and have no idea why.

I've measured the diameter which is fine, i have printed with different temperatures, the fans are working properly, i don't know what else to try, any suggestions?

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In order to have a good first layer the layer needs to be pressed onto the platform. I guess you have leveled your bed to fulfill that requirement (which is good). It might be that due to printing the first object the feeder is now hot and possibly not able to build up the pressure needed to print the first layer. When you normally start the feeder is cold. Due to the direct drive of the UM2 feeder the warm motor can warmup the bold that drives the filament and giving the nature of PLA this might lead to the issues you have.

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Ok, can you please explain a bit about the word “grinding”. You say you are not there, so it is not the sound of “grinding” – it must be a visual thing so what is grinding? (can you post a picture?)

I understand you to be saying that

1st pass - model 1 layer 1

Model 2 layer 1

2nd Pass Model 1 layer 2

Model 2 layer 2

Etc, etc

So I do not understand why you say you are asleep and not beside the printer when the 2nd model is failing???

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Ok, can you please explain a bit about the word “grinding”. You say you are not there, so it is not the sound of “grinding” – it must be a visual thing so what is grinding? (can you post a picture?)

I understand you to be saying that

1st pass   - model 1 layer 1

         Model 2  layer 1

2nd Pass    Model 1 layer 2

         Model 2 layer 2

Etc, etc

So I do not understand why you say you are asleep and not beside the printer when the 2nd model is failing???

 

The filament has been grinded so it can no longer grip it to feed so nothing comes out of the nozzle. Basically if i print 2 phone cases at once, the first once prints fine, but the 2nd one prints the first layer then nothing else prints as the filament has been grinded.

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In order to have a good first layer the layer needs to be pressed onto the platform. I guess you have leveled your bed to fulfill that requirement (which is good). It might be that due to printing the first object the feeder is now hot and possibly not able to build up the pressure needed to print the first layer. When you normally start the feeder is cold. Due to the direct drive of the UM2 feeder the warm motor can warmup the bold that drives the filament and giving the nature of PLA this might lead to the issues you have.

 

It prints the first layer, its the 2nd layer where it fails. Thank you for your reply!!

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Basically if i print 2 phone cases at once, the first once prints fine, but the 2nd one prints the first layer then nothing else prints as the filament has been grinded.

Hi lukem.

Are you fully printing the first case and it grinds when starting on the second?

When you put this into Cura, did you look at the Layers option and see how it does?

it may help if you could give us your settings, speeds and temps.

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I my theory is correct which only an assumption.

For the experiment I would put a fan blowing towards the feeder motor just to make sure it is not the temperature of the motor influencing you results since the first print is fine.

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I my theory is correct which only an assumption.

For the experiment I would put a fan blowing towards the feeder motor just to make sure it is not the temperature of the motor influencing you results since the first print is fine.

 

I have taken the white box off and blown a fan on it, it still happens:( thank you so much for the support guys! having so many problems:(

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Usually the filament gets ground down flat if you have too many retractions. Do you have tons of retractions? I had a part that had 40 retractions in a layer and that caused the filament to grind flat. I changed the "minimum extrusion before retraction) to a higher value and that fixed it. If you set that to say .45mm then it will do no more than 10 (4.5mm / .45mm) retractions on a given spot of filament which should be fine.

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Thank you for the help i really appreciate it.

I am printing 0.4mm nozzle

layer height 0.06mm

bottom layer 10mm/s

infill 80 mm/s

top/bottom 15mm/s

outer 30 mm/s

inner 60 mm/s

printing at 215 degrees

Using reprap Uv sensitive PLA

2.85mm

I will try the retractions, thank you

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Most of the time the problem is in the nozzle and the symptom is at the feeder. An enlarged or lipped PTFE part can cause this since when it retracts, material builds up in the PTFE and cools and makes it more difficult to push on each retraction.

I would do an atomic pull and then if clean and doesn't solve your problem, post a picture of the filament.

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I have done atomic pulls, i have cleaning filament as well, and i have put some thin metal wire up the nozzle to clear anything out of there, and no luck. What is it you specifically want to look at on the filament?

Thanks!

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I have done atomic pulls, i have cleaning filament as well, and i have put some thin metal wire up the nozzle to clear anything out of there, and no luck. What is it you specifically want to look at on the filament?

Thanks!

 

The result of an atomic pull can tell you many things even if clean. Paticularly the section right above the brass nozzle area. Sometimes there is a disk indicating space between the PTFE and brass nozzle, sometimes you have a huge stretch indicating some kind of friction or block preventing a clean 'pull'. There are a lot of clues.

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99% of ALL grinding is down to a blocked nozzle. Cleaning it a few times wont always help, it may need more cleaning than you think. The only other thing that will cause grinding is if you get a tangle printing off the roll. Thats it.

You can still acheive perfect prints with a slightly blocked nozzle, but long prints will result in a slow jam, as pressure is building up ever so slightly, and eventually it just gets blocked, and it will suddenly just stop and thats your print doomed. Always babysit the first layer or two and if you are new to this, print one object at a time until you understand why things are going wrong, as until you do you will always have these issues. Dont worry, it took me 9 months before i figured out all this, especially cleaning my nozzle, which i wasn't doing right for such a long period of time, but due to me using good filament I got away with it.

Cleaning filament in my opinion is a gimmick and a waste of time. Ive never used it and have sorted out my burnt out nozzle everytime with standard atomic pulls. Im still using the same one it shipped with. Just keep doing atimic pulls with pure white filament so you can see the exact shape of the nozzle and examine it for any minute bumps or lumps or discolouration, or burning marks, or scratches or anything. Dont EVER put a stiff wire in to clear the nozzle you will most likely damage your nozzle doing that (by scratching the interior) , then you will need a new one. To put things into perspective i had to do 30+ atomic pulls once to sort my nozzle after burning it out for 15 hours due to a tangle, and a slow jam.

get a chair, put on some netflix and sit by your printer for an hour doing atomic pulls. Then print like it was brand new.....assiming your temps according to your filament are right, and the speed and layer height setting also match. Unfortunately it takes along essay to explain everything and nobody will read and take note of all the things you actually NEED to take care of, so it mainly comes down to experience. You'll get there......eventually.

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That is NOT what an atomic pull should look like. It should look like a perfect imprint of the inside of your nozzle. I made a few vids, but i dont force it in anymore due to hydraulic pressure. Just do it with your hands and ignore me pushing it in real hard.

 

Edited by Guest

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I'm not certain that's a good pull. It should be shaped like the inside of the nozzle exactly. I think this pull is leaving behind lots of filament. Try 5C cooler repeatedly until the pull doesn't work and then go up 5C. It should be about 5 -10 pounds pulling force to get it out.

Having said that, there is another possible cause for gound-flat filament - and that is retractions. You didn't mention if your part was retraction heavy. You can look at the failed layer in Cura slice view and each vertical blue line is a retraction. More than 10 retractions per minute might be enough.

There is a 3rd cause for ground-flat filament and that is heat - if the weather is hot and your extruder motor is hot the filament can soften. I doubt this is the issue as I assume the weather is cool in the UK.

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