UP Mini extruder filament guide mod

Support for UP mini. To report a bug, post with a title [BUG REPORT]. To request a feature, post with a title [FEATURE REQUEST]
Post Reply
jeeplvr
Posts: 212
Joined: Sat Jun 08, 2013 5:26 am

UP Mini extruder filament guide mod

Post by jeeplvr » Tue Jul 01, 2014 11:54 pm

I posted this here because I get to help way more folks like me get their Minis working when I post here.
I have redesigned the filament guide (nylon piece inside the extruder with the small bearing) for the UP Mini extruder which has made my Mini print with far less issues than ever before.
Here is the background. I have been dealing with the extrusion issues as many have and have even replaced the entire extrusion head in an attempt to make the Mini work with reasonable reliability. Nothing I have done for the extruder has worked with any great gains.
Here are the issues with the extruder as I see them and they have been discussed on this forum in great detail. Some of these problems I have discovered through investigation and trial and error.
1. Stepper motor heat causes the filament to get soft on long duration prints. This causes the extruder gear to dig into the filament and the filament stops.
2. The filament guide holds the filament too close to the extruder gear. This causes unnecessary friction and drag and the filament is more susceptible to dirty nozzle, uneven filament dimensions etc.
3. The filament guide bearing is forced up against the stepper motor for the extruder. Adds friction and resistance to feed and causes the stepper motor to heat up more than it should.
4. Stepper motor gear is a slip fit on the stepper shaft. The gear can float on the shaft and can cause the extruder to stop feeding filament or cause the filament to extrude intermittently. This is evident by gaps between printed layers. The gear needs to be pushed as far on to the shaft as possible and center punched so it is locked into place.
By far the biggest gain to date is when I redesigned the filament guide inside the extruder. I can print for hours now with almost no concern whatsoever. I can print with crappy filament as well as expensive high quality filaments with no worries.
Has to be a catch right? Well there is a catch. The new filament guide is ABS and susceptible to heat deformation. The new design works flawlessly until the ABS gives out after 5 or six models. So it has to be replaced regularly or you will start to see gaps in the layers of the models. I have printed up to 10 complex models before having to change my filament guide so it is random when the guide gives out.
No matter how you look at it, it is still better than what it was before. Just print yourself 6 or 8 small guides at a time and replace them often.
The combination of the heat bed temp switch mod and the new extruder filament guide design and my Mini is finally the machine I had hoped it would be.
My new extruder filament guide can be found on Thingiverse. https://www.thingiverse.com/jeeplvr/designs

jeeplvr
Posts: 212
Joined: Sat Jun 08, 2013 5:26 am

Re: UP Mini extruder filament guide mod

Post by jeeplvr » Wed Jul 02, 2014 12:19 am

Here is the direct link to the thingiverse file.
http://www.thingiverse.com/thing:381508

roller
Posts: 1622
Joined: Sat Oct 06, 2012 9:09 pm
Location: Brisbane, Australia

Re: UP Mini extruder filament guide mod

Post by roller » Tue Aug 19, 2014 12:18 pm

Great to see someone working on the Mini issues. Just to throw in some ideas that might help to your points:

1. The issue is usually that the heat causes the filament to curl as it's pushed into the hotend ... this bending makes it jam first and then the side gets ripped out of it by the extruder gear. It's not that the filament is softer and more easily tron apart but that it curls up. Therefore, one solution might be bringing the feed path closer to the extruder gear so it has less chance to curl - an idea I've never bothered to test but has helped in other (reprap) extruder designs.
2. I'm not sure what you are saying but the purpose is to jam the filament into the gear as hard as possible to may sure the gear bites into it. Sprung tension solutions worth best. The reason the Up version is fixed though actually makes sense - by getting a consistent depth of bite you actually get the most consistent filament feed volume. If you bite further you actually feed more (overfilling your print) and bite less you feed less (underfilling). The failure in the Up design is that it doesn't consider slightly thicker or thinner (than OEM) filaments.
3. Hmm ... kinda but not really. The friction and stress does not heat up the stepper motor so much as the amount of current applied to the stepper. Try running a print job without filament - you should find the stepper is equally hot. The stepper is doing the same amount of work applying the same amount of holding torque whether the filament is present or not.
4. This gear slipping happens if you are very unlucky and get one not attached well ... otherwise it's a non issue.
5. Consider getting your mod made another way from another material. Could easily order these through a fabber that can micro CNC them... I'd offer to do you're prototypes if I was handy to you.

jeeplvr
Posts: 212
Joined: Sat Jun 08, 2013 5:26 am

Re: UP Mini extruder filament guide mod

Post by jeeplvr » Sun Aug 24, 2014 10:01 pm

Just an update on the guide mod. I have been using the printed guide mods I designed for quite a while now and they do solve a lot of issues. The only issue is that the fail regularly and need to be changed. But until they fail I get great prints. The failure rate is acceptable compared to the jamming issues I had before.

roller
Posts: 1622
Joined: Sat Oct 06, 2012 9:09 pm
Location: Brisbane, Australia

Re: UP Mini extruder filament guide mod

Post by roller » Thu Sep 25, 2014 4:54 pm

Can you post pics of the failed ones to show how they break. Maybe someone else might be able to suggest an improvement to help durability. Looking at your design again, have you tried printing PLA with your mod? The pressure improvement and greater free air space around the drive gear might help with the softening PLA issues. Certainly adding a direct fan would probably solve it.

stormychel
Posts: 241
Joined: Thu Sep 11, 2014 5:13 am
Location: Belgium
Contact:

Re: UP Mini extruder filament guide mod

Post by stormychel » Fri Sep 26, 2014 6:05 am

Thanks for sharing! I ordered a second extruder to switch between stock extruder and filament, and one to test with mods. Will surely try this one!
@stormychel

jeeplvr
Posts: 212
Joined: Sat Jun 08, 2013 5:26 am

Re: UP Mini extruder filament guide mod

Post by jeeplvr » Thu Oct 09, 2014 6:46 am

roller wrote:Can you post pics of the failed ones to show how they break. Maybe someone else might be able to suggest an improvement to help durability. Looking at your design again, have you tried printing PLA with your mod? The pressure improvement and greater free air space around the drive gear might help with the softening PLA issues. Certainly adding a direct fan would probably solve it.
I don't have a picture but the ABS gets hot and deforms letting the bearing move away from the center. It causes the extruder gear to slip on the filament. Since replacing the Nema 14 stepper with a 17 the temperature has dropped drastically and I haven't destroyed a filament guide yet.

roller
Posts: 1622
Joined: Sat Oct 06, 2012 9:09 pm
Location: Brisbane, Australia

Re: UP Mini extruder filament guide mod

Post by roller » Thu Oct 09, 2014 7:10 am

jeeplvr wrote:
roller wrote:Can you post pics of the failed ones to show how they break. Maybe someone else might be able to suggest an improvement to help durability. Looking at your design again, have you tried printing PLA with your mod? The pressure improvement and greater free air space around the drive gear might help with the softening PLA issues. Certainly adding a direct fan would probably solve it.
I don't have a picture but the ABS gets hot and deforms letting the bearing move away from the center. It causes the extruder gear to slip on the filament. Since replacing the Nema 14 stepper with a 17 the temperature has dropped drastically and I haven't destroyed a filament guide yet.
Getting too hot and causig ABS to deform generally means over 80C and more often over 100C ... that is pretty damn hot! I know this s less and issue for you now but perhaps for others not considering a Nema17 upgrade a carboard gasket is often a good option to reduce conduction of heat directly from the stepper.

jeeplvr
Posts: 212
Joined: Sat Jun 08, 2013 5:26 am

Re: UP Mini extruder filament guide mod

Post by jeeplvr » Fri Oct 10, 2014 11:37 pm

I am not sure what the original guide material is but it is very stable at high temperatures and of course the ABS is not. My issue with the original filament guide was the distance between the guide and the stepper where the bearing sits and the distance between the filament and bearing. With everything bolted up the bearing was smashed into the stepper which made the stepper have to work harder. My new design adds a vent hole, proper room and distance for the bearing, and a little side flex for the bearing. The ABS distorts eventually but I get way more print time than before. I was ready to throw this printer in the dumpster before replacing the guide. Now I am moderately happy with the printer. I still have a skew issue that reoccurs now and then for no apparent reason, like today and the occasional controller freak out but it is much better.
Here is the old stepper. You can see where the bearing was wearing into the cover.
DSC02778x.jpg
DSC02778x.jpg (136.09 KiB) Viewed 11383 times

roller
Posts: 1622
Joined: Sat Oct 06, 2012 9:09 pm
Location: Brisbane, Australia

Re: UP Mini extruder filament guide mod

Post by roller » Sat Oct 11, 2014 2:23 am

The old guide is nylon I think.

Post Reply