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PolyBox issues Da Clumsy Noob solved to stop grinding

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Posted · PolyBox issues Da Clumsy Noob solved to stop grinding
11 hours ago, gr5 said:

The feeder on the UM2 plus is identical to the left feeder on the UM3.  Same height.  Same feeder parts.  Same feeder.  Basically I don't like the looks of that hole inthe upper *rear* of that polylbox.  I guess if the filament came over the top of the spool and went straight out.  Better to have the hole near the same corner but on the top face I think - maybe drill a small hole and transfer the o-ring/gasket to the new hole and plug the old hole?  Not sure.  

 

I am cheap so I just use a gallon sized zip lock for nylon and pva and zip the bag mostly up except for a few cm to let the filament out.  I place all of that either on the table behind the printer or on the floor behind and below the printer.

 

Nylon is wonderful in it's flexibility.  Very few filaments are as flexible as nylon so this issue with pva will happen with pla and ngen and pet and cpe and pc.

Are you saying I should use a different hole on the box? like the one through the top and have the spool feeding the other way?

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Posted · PolyBox issues Da Clumsy Noob solved to stop grinding

I choose the hole that makes for as straight a pathway as possible. Any additional angles or turns just adds to the friction.

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Posted · PolyBox issues Da Clumsy Noob solved to stop grinding
1 hour ago, GFlow said:

Are you saying I should use a different hole on the box? like the one through the top and have the spool feeding the other way?

No I'm saying you can simply drill your own hole in the perfect position.  As kman says, place the hole so the filament makes as gentle a transition as possible, eliminating any sharp bends.  Eliminating as much friction as possible.

 

Maybe the hole through the top is in the right spot but maybe not.

 

If you have a drill and drill bits then how hard could it be?

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Posted · PolyBox issues Da Clumsy Noob solved to stop grinding

Yeah I think the one issue, is that I hate having the filament go through the top since it is such a pain to get the lid off with filament running through it.IMG_0179-1.thumb.JPG.4d2e25b1ffe000ce2ad6c4976ee5d909.JPGIMG_0178.thumb.JPG.7509fde2d5c014533a41037e4fbbd6f7.JPGIMG_0176.thumb.JPG.a6d38a07c024693ca0bbf75b8cbf245b.JPG

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Posted · PolyBox issues Da Clumsy Noob solved to stop grinding

So I have been using a 1kg spool of PLA and it keeps binding and getting pulled off the bearings of the polybox and then it starves the printer.  It seems to only happen when the spool is on the lower side.  Has anyone had this issue? should I weight down the spool?

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Posted · PolyBox issues Da Clumsy Noob solved to stop grinding
11 hours ago, GFlow said:

So I have been using a 1kg spool of PLA and it keeps binding and getting pulled off the bearings of the polybox and then it starves the printer.  It seems to only happen when the spool is on the lower side.  Has anyone had this issue? should I weight down the spool?

I am not sure what you mean by 'lower side.' Do you mean when it gets towards the end of the filament? If so, some filaments hold that curve very strongly. As the filament gets to the end, it is more tightly wound and can create more friction. It would also explain why the spool gets pulled up as it is not relaxed enough to allow proper unwinding and wants to stay in shape even pulled upwards. Otherwise, I think it would still unspool.

 

Am I anywhere near the proper starting point with your statement?

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Posted · PolyBox issues Da Clumsy Noob solved to stop grinding

Yes that is correct it's near the end of the spool. And when I say pulled up it actually comes off the bearings of the polybox and is pulled towards exit holes.

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Posted · PolyBox issues Da Clumsy Noob solved to stop grinding

OK. That buttresses my theory that the spool is keeping a bit of super tight coil on there. This is creating friction within the bowden tube as well as not wanting to easily release the spool as it is so tight that it just picks it up. But the feeder should still be able to unwind  the spool no matter what position it is in. If you want to test to see if it is the tightness of the filament coil. Unspool a decent amount and feed it without the spool itself. See if it binds in the bowden tube. That has happened to me when either getting old filament (settled into shape and too much shape memory and a tad bit hardened) and it binds in the bowden tube. And, it may not be old for you, but who knows how long it has been sitting in storage, or maybe just a bad run. I mean I have bought materials at the same time and one will do what you say, but the next one does not.

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Posted · PolyBox issues Da Clumsy Noob solved to stop grinding
On 5/31/2018 at 2:55 AM, GFlow said:

Yes that is correct it's near the end of the spool. And when I say pulled up it actually comes off the bearings of the polybox and is pulled towards exit holes.

 

Maybe you could modify the bearings, so the spool can't be pulled up? Maybe add some sort of cap or guide to the upper part of the bearings?

 

The older UM2 printers (which I have) are sensitive to underextrusion when stiff filament like PLA is near the end of the spool. The filament acts as a very strong spring that resists unwinding (this is one problem), and the narrow bending radius of the stiff filament causes huge friction in the bowden tube and in the print head and nozzle (this is a second problem).

 

A simple solution that eliminates both problems, is to manually unwind a little bit of filament, then wind it around a skater wheel (7cm diameter) in the opposite direction, so that it is straightened. Then I straighten the next few centimeters. After I have done a few meters in this way, I roll the filament up on the spool again. But now it is sitting very loose, with a bending radius of ca. 30...40cm, instead of 10cm. Thus the bending radius is now about identical as that of the bowden tube. So the resistance to unwinding of the spring is gone, and the friction in the bowden tube and nozzle are very low. This straightening takes only a minute, and can be done while the printer is warming up. It works very well for my models, which only require a few meters of filament, and a few hours to print. For huge models that take a long time, or for overnight printing, this method is less suitable, of course.


See the photo. The yellow clamp slides freely around the edge of the spool, and it prevents the filament from falling off sideways, and from getting tangled up. It also prevents the spool from unwinding itself during straightening of the filament.

 

But I don't know if all this is compatible with drying boxes? Or maybe you could develop a derivation of this idea?

 

DSCN5776b.thumb.jpg.04c8093e153fa768024c3c36391f8b23.jpg

 

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Posted · PolyBox issues Da Clumsy Noob solved to stop grinding

The Polybox does not have a spool axle. The spools just sit on the axles and do hot have a way to hold down the spools.

 

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