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Printrbot Jr. Upper & Lower Filament Guides (1.75mm)

by phraust, published

Printrbot Jr. Upper & Lower Filament Guides (1.75mm) by phraust Mar 11, 2013
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Summary

I was having issues with my filament slipping out of the teeth of the hobbed bolt halfway through a print (Too much twist while unspooling, I guess...). So I came up with a fix that guides the filament directly into the hobbed bot. It also replaces the lasercut piece of wood for the extruder idler, and includes pockets for the nylocks (I hated having to bust out a wrench and a screwdriver to tighten those).

I was also having issues with the lower half of the extruder, it looked like there was too much wobble in the channel below the hobbed bolt and above the extruder, so I added in a lower filament guide as well.

Instructions

Upper Guide

  1. Print. I used 10% Infill, 2 perimeters, 0.2 layer height.

  2. You may have to scrape out the inside of the guide to allow the filament to pass smoothly. A jewelers flat-head screwdriver works great.

  3. Note the location of your nylocks, you'll probably be pretty close to that when you replace the idler latch.

  4. Replace the idler latch.

NOTES

I admit, it's a bit of a pain to thread in new filament. I unclip the idler, pull the old filament out, thread the new filament in and raise the latch to the almost locked position, so I can push the filament through the extruder and see it come out the nozzle, then latch it.

I may be working on this again if any other problems manifest, but for now it works pretty well for my needs.

LOWER GUIDE

HEADS UP

This is a major pain in the ass to install, since (for me at least) it required I break down the entire laser-cut extruder. I had to remove the extruder motor and gear, the hobbed bolt and big gear, the idler assembly, and the front two laser cut plates. That let me see how far down into the extruder I had to place the guide.

  1. Print. I used 10% Infill, 2 perimeters, 0.2 layer height.

  2. I had to file down the inside and outsides to get a nice snug fit. Clean it up a bit now, and it's that much easier later. Make sure you try running filament through it, I double checked to make sure it slid through easy.

  3. It's designed so that the channel faces to the right, away from the hobbed bolt. Once your extruder is dismantled, try fitting it to see how well it slides. The two little wings are meant to sit right on the little ledge by the hobbed-bolt bearings. It's designed long, so it can be trimmed to fit. I ended up taking about 1CM off the bottom, and rounding the tip (just the tip). Make sure to test your filament through it again. The guide shouldn't move, and you shouldn't feel any resistance.

  4. Once that's all set, reassemble it all and try it out. With both of these pieces in place, I've had to change how I load & unload filament. I unlatch the idler, feed through the filament through the idler till about 2CM is sticking out, then slowly begin closing the idler latch. When it's almost closed, I can slide it in the bottom guide, and push it through till I see it extrude. Lock the latch, good to go.

NOTES

I lucked out, this worked on the first try (yesterday), so your milage may vary. It's been a major pain having longer prints fail because of tangling inside the lower extruder, and I still have no idea what causes it. Too many pauses? Not a high enough temp (i've been running PLA at 220)? High ambient temperature/humidity? Phase of the moon/Solar Flares? Who knows... I made this, and so far, it seems like it's fixed (finished a 10 hour print yesterday, and it's half-way through a 20 print today).

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phraust -

Big dumb question. I printed a similar part for my Printrbot Jr that came with the 3.0 mm Extruder + 3.0 mm PLA. When my 3.0 PLA runs out I will be switching to the 1.75 mm ceramic Ubis extruder and 1.75 mm PLA. In addition to the 1.75 mm extruder and your filament guide, is there any other part that I will need to make the change? For instance, I am worried that the serrated bolt that grabs the 3.0 mm filament today won't grab the 1.75 mm PLA.
I am sorry for asking here but I don't feel that the printrbot forum really lends itself to old legacy "woodies" like the PB Jr.

Jan 12, 2016 - Modified Jan 12, 2016
cfg - in reply to cfg

Me -

Answering my own question on printrbottalk.com (that I just found today) :

Transitioning from 3.0 mm PLA to 1.75 mm PLA
http://www.printrbottalk.com/forum/viewtopic.php?f=21&t=10646

Hobbed Bolt comparisons
http://www.printrbottalk.com/forum/viewtopic.php?f=21&t=10630

Hello !
Can you make it for 3mm filament too ?
Or I just have to drill the piece ?

Worked perfectly with no mods on a Printrbot LC v2.

I'm interested in these things as the filament frequently bunches up on my Printrbot Jr. However, there are no flat sides to these things and I can't figure out how to lay them on the print bed.

How do you print them? Thanks.

I just printed this with support. Normally I dislike doing that, but this print doesn't really have to look pretty.

I was having so many issues with my jr until I added this! I had to file it down in order to fit but i think that is due to the fact my machine isnt perfectly calibrated. I didn't even have to install the bottom guide, it works wonderfully without it. Thank you so much for this!

Phraust - seriously...you saved my life man!! I was so bloody fustrated of the extruder getting jammed all the time. I figured that the quality of the PLA means a lot. The filament that came with the printer worked just fine, but I bought some cheap-ass stuff from china that jammed all the time (too soft). It was the lower guide that made the magic (I also needed to do a lot of filing - the scaling does not seem right) - for all of you with this problem - IT IS WORTH IT TO TAKE THE EXTRUDER APART TO INSTALL THIS!!

I guess it is worth mentioning that after install you have a "1.75mm machine only"

Phraust - seriously...you saved my life man!! I was so bloody fustrated of the extruder getting jammed all the time. I figured that the quality of the PLA means a lot. The filament that came with the printer worked just fine, but I bought some cheap-ass stuff from china that jammed all the time (too soft). It was the lower guide that made the magic (I also needed to do a lot of filing - the scaling does not seem right) - for all of you with this problem - IT IS WORTH IT TO TAKE THE EXTRUDER APART TO INSTALL THIS!!

I guess it is worth mentioning that after install you have a "1.75mm machine only"

yeah, i'm still going strong with this upgrade. Best one to date. About 30 prints in with it, no more jamming, all filament issues gone.

Thanks again!

Actually I had to do a slight modification of your upper fillament guide as well. I could not get the "channel part" to fit into the 5mm gap. I simply sawed that part off and printed a smaller guide that I glued onto your part (If I find time I will make a completely new part)...and it works like a charm.

I have now done several prints with "soft" PLA and with no issues at all.

Brgds from a very happy printrbotter :)

Thanks for posting this. I've been using something similar but with a 3mm filament hole. (Even though I use 1.75 filament)
As for your filament twist, I set my filament to come from the bottom of the spool instead of the top and all of my twist problems went away, like magic.

Ah, that's one thing I never tried! XD

I ended up making a lower filament guide as well, so that it can't wiggle back and forth in the laser-cut slot. On longer prints, it'd bind and cause a tangle. I've been testing out the lower-guide for the last two days, and it's taken care of a 10 hour print with no problems, and currently 3 hours into another one, so I'll probably post it up here as well.

Okay, I installed the lower guide. It needed some shaving for sure. I had to cut 8.25 mm from the bottom, and shave 5 or 6 layers off of the side. For those that want to attempt this upgrade, you have to take your extruder apart. But it's worth it!

please please do, i have the same issue.

There ya go! Good luck :D

Thanks for the model phraust. I printed it up and tried to install it, but couldn't figure out where it goes. When placed in the obvious place, it looks like it will block the bearing from pressing the filament against the hobbed part of the bolt.

Okay, I've added in the picture now, so you can see where it's at. :D

You've gotta cut or file off some of the end near the nozzle, so it'll fit the whole way down. It's a tight fit, and I intentionally made it long so I could get it as close as possible by hand once I had it all apart. I'm still printing right now, but I'll take a picture of it installed as soon as I get a chance.

Thanks for the extra photo, that helps a lot. Did you disassemble the entire extruder to get it in or just slide it in? I'm taking mine apart right now.

Yeah, I had to pretty much disassemble the whole front-half so I could slide it in the filament slot. Once it's in there, try sliding some filament through it, to makes sure it doesn't have any issues, and make sure that the opening and those little"wings" are right where they are supposed to go so there aren't any issues with loading or with the hobbed bolt.

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