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kc-li

Is anyone else having issues with the initial knead of material being pulled into the print

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So I have a UM3 and I've noticed a consistent problem, especially with the PVA material, that is, during the initial extrusion of the filament, the initial knead of material tends to get dragged into the print instead of staying at the location it was extruded in. This happens with PLA as well but at a much rarer occurrence but pretty much happens every time with the PVA. The temp solution I've done to stop this from affecting/ruining the print is to wait for that stage to occur, have my tweezers ready to pull the knead of material away and make sure it doesn't get pulled in. I notice this happens because after the material is extruded, the nozzle moves "into the material extruded and then the hot nozzle sticks to the material and then it's pulled back into the top corner. I have a crappy video of this (link below, apologies for the vertical orientation). I wonder if it's possible to revert back to the way UM2 extrudes materials where it is done at a relatively high height so the material doesn't get pulled into the print. At the very least, maybe adjust the movement so it doesn't bump back into the material during the movement to the top right corner? Also, the PVA nozzle gets nasty real quick as you may notice because of the PVA that sticks to the side over time (is this normal?) and it's extremely hard to clean. I lost the silicone cover (and buying a new one) due to one of the previous attempts and the nozzle was completely clogged outside.

Another issue I've been having is the glass plate seems to be quite warped. This results in me not being able to use the last 10 centimeters of the print area since the material cannot adhere on nicely and results in getting pulled off the glass plate after a few layers. I've tried active leveling and manual leveling but none of this seems to help. I have read in the past on the forum of other users experiencing similar issues with warp glass plates and they at the end sourced one locally to fix the issue. Should I contact the reseller to get a replacement?

Thanks in advance

 

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A similar problem also occurs on an UM2: the priming being pulled onto the printbed, which would sometimes cause problems. Originally I also used tweezers (pincette), to prevent this from happening. Until I found this "filcatch" thing in a post from another user (I don't remember his name). He 3D-printed it, but I made it from inox spring steel, so it lasts forever. This prevents the primed stuff from being dragged around.

I don't know if this method for the UM2 could be adapted to work on an UM3 too?

steel_filcatch1.thumb.jpg.2b3e229fdf742ed53c4aae4fd1e2016d.jpg

steel_filcatch1.thumb.jpg.2b3e229fdf742ed53c4aae4fd1e2016d.jpg

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A similar problem also occurs on an UM2: the priming being pulled onto the printbed, which would sometimes cause problems. Originally I also used tweezers (pincette), to prevent this from happening. Until I found this "filcatch" thing in a post from another user (I don't remember his name). He 3D-printed it, but I made it from inox spring steel, so it lasts forever. This prevents the primed stuff from being dragged around.

I don't know if this method for the UM2 could be adapted to work on an UM3 too?

steel_filcatch1.thumb.jpg.2b3e229fdf742ed53c4aae4fd1e2016d.jpg

 

Love the idea of this! I tend to open my acrylic door at the last second and grab hold of the dripping filament as the head moves to print the first layer.

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I've been having the same problem of the dollop of melted PVA/PLA stays attached to the hot end while dragging and ruins the first layer. I rubbed some of the glue stick in the general area the dollops happen and they actually stayed stuck to the glass the last time I printed. Might have to do this every time I print.

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something like that happens on my ultimaker 3 extended, I raised the ed temp to 65 and cleaned the spot where extruder dumps some material extra well and use gluestick on theese places, then they stay in place and don't end up where they shouldn't, also cleaning the bed with break cleaner works really well, but watch out that you don't get in contact with the liquid

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It was me that posted about my FilCatch addon for my UM2.

You can read about it and watch it in action on my website www.vitalsparks.com where you can download the model file. There are other things there too which you may be interested in.

I have a mk2 version of FilCatch in the pipeline, which is adjustable, and should work on any Ultimaker. I will be providing an update when I am happy with it. I originally thought of making this using the wire from a large paperclip, but thought better of it when I realised that it could possibly get snagged with the nozzle/print head if it was accidentally displaced - hence the safe option of making it in plastic.

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It was me that posted about my FilCatch addon for my UM2.

...

I originally thought of making this using the wire from a large paperclip, but thought better of it when I realised that it could possibly get snagged with the nozzle/print head if it was accidentally displaced - hence the safe option of making it in plastic.

 

Yes indeed, that was where my version was based on.

Being of spring steel (I am not sure if that is a correct English word, meaning: "steel for making springs"), the wire easily moves down when the nozzle passes it. So I deliberately placed it a few mm too high, to get a sort of wiping action. I only need to make sure that I do not position my models in that corner. But even then, it would probably do no damage, or not much (although I am not gonna try it): most likely the build plate will be pushed down when the nozzle tries to put down the first layers, similar to what you have when corners of big overhangs are curling up. The wire is 1 mm diameter.

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@ftoons and @kc-li

There is the option to turn off the prime blob in the new Cura maybe that can serve as a quick fix?

if you go to preferences->settings then under build plate adhesion you can enable the visibility of the "enable prime blob" option so you can then disable the prime blob in your print setup.

There has been some discussion here at Ultimaker about prime strategy and I had a similar problem with the UM2's prime in the air, the blob seemed to be the simplest fix and he best of both worlds in that it sticks to the bed and there can be some variation in amount of material used during priming.

The best would probably be if we could prime next to the buildplate but that's not an option on the UM2 or 3.

We've had a low priority issue for most of a year to change it to something else since the blob is the exact right size to fit under the Z end switch. But as people seem afraid to change this it is taking a while...

Ideas are always welcome!

Should we go back to priming in the air or print a more complex prime structure?

Disable the whole thing and prime in the brim/skirt etc?

Adding hardware like that is not likely to happen though, we've discussed making cleaning flap out of silicon etc but it's not something that is being worked on.

P.S: Since the prime blob is completely my idea and implementation I do apologize for any problems :D

Edited by Guest
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on the bed flatness, yes talk to your reseller

I think there was a test firmware made to measure buildplate flatness, not sure if that is necessary though.

We have come up with a fix for buildplate flatness in software, but it completely changes the active leveling feature so it'll take a (long) while to prove it is working OK, and get it approved by marketing, check the UX designs, etc.

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Each method seems to work in a lot of cases, but not work in some others. Maybe a combination of all good ideas would work?

The area above the metal bed clips can not be used for printing anyway. So maybe it could be used for priming? What about making a small trashbin in silicone (=heat resistant) that can be clipped onto this metal clip? A size of 10 x 15mm and 10mm high might do. Then prime in this bin, and wipe the nozzle against the edge of the bin, so the nozzle is clean and does not drag anything into the print? After completion, the primed stuff can easily be taken out of the little silicone bin, as it does not stick.

This would be a simple add-on (a "clip-on")that does not require hardware changes.

Or something in this direction?

Priming in the skirt would often work, but sometimes a skirt is not desired. And if the prime contains some dirt, or some oil (e.g. from wiping the nozzle with oil to reduce build-up of molten filament, or from lubricating flexible filament), then that could reduce bonding on that area of the glass plate. Thus if "skirt style priming" is done, it would be best to print a thin plate in a corner, I think. For example: 15mm x 15mm x 1 layer, or a 15mm diameter spiral?

Anyway, for me the FillCatch thing shown above works fine on both of my UM2, as it also does some wiping.

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On top of the clip might work, but we'd need to check the stickiness (both ability to remove and initial sticking force of our 9 main material types on the metal of that clip...

What about making a small trashbin in silicone

This gives the added annoyance of you having to tell your printer you have the clip on trashbin, though maybe with a big QR code it could be recognized by the camera?

Even then Cura determines the prime position, so it's in the gcode not completely controlled by the printer. We changed that early on as you might not want to prime both nozzles at the start of a print...

Edited by Guest

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An idea that just occured to me: what about making the prime-method adjustable in Cura? For example let people choose between:

- Prime as extra skirt lines around model (same thickness as first layer).

- Prime as spiral (same thickness as first layer).

- Prime as blob.

- Prime in the air.

In the last three cases, with additional parameters to specify the location where priming has to occur:

x=...,

y=...,

z=... (height above glass plate only for priming in the air)

All with the same material-volume of priming as now.

For each printer, you could set the defaults that work best in your testing lab. And for old printers, you could chose as default the method with which the printers were delivered. For example: "prime in the air" for the UM2.

In this way, people can easily adjust the priming method to what suits their situation best. Maybe there does not exist a "universal best priming method", but only "good priming methods for specific circumstances".

These settings could best sit under advanced stuff, to not overwhelm new users.

Could this be a solution?

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@geert_2 as the priming can be completely controlled by cura, yes this could be done.

"G280 S1" will forward the material (of the active hotend) to the point it should be just at the nozzle tip without extruding (intentionally, it might ooze, the printer tracks retracted length, which can vary)

then Cura can add whatever gcode to prime in the air if needed, re-enabling the paper-clip method :)

In the UM2 priming is done completely by firmware so there is NO way for Cura to change it, so it's not so much a setting in that case as a do nothing...

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