Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor  

RE: Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor

Posted by: vintagepc

I've been running this design and unfortunately I get false runouts.

Well, that's a bummer!  Just to be sure, you have the short bit of PTFE tube above the bearing, correct?  The only other thing I can think of is that perhaps the sensor housing was slightly under-extruded, and therefore things are a bit loose, or over extruded, and the bearing itself isn't spinning smoothly.

What I did to check that the bearing spun well was assemble the PTFE tube, cover, and bearing inside the sensor housing, with a single ink stripe across one part of the bearing (from a sharpie), so I could then insert and move filament through and make sure the ink mark actually moved like I expected prior to assembling the entire contraption.  Maybe try that?  As always, make sure the sensor is clean, too. I hope you're able to get it to work!

RE: Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor

I actually have a slightly different mod but it should have the same effect; I have a reverse bowden setup with an M6 passthrough so I can feed the PTFE down as far as it will go (should be to the same distance as where that little bit would have sat. Bearing does spin freely, I definitely made sure of that, and I can see it protruding into the hole for the filament. 

I'll keep you posted on the results of my experimenting. The sensor should be clean as I inspected it prior to doing the upgrade last weekend.

RE: Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor

I forgot to mention I had the same issue with martin_au's design but at the time I chalked it up to some undersized filament. Perhaps that was not the case and my cheap ebay bearings are just slightly undersized/sloppy. If so the tire should fix it.

It could also be a flaky sensor, I suppose; I've had false jam/runouts  happen in my stock Mk3 design before too... (matte blue, not a known problematic colour.) Experimentation will find an answer!

RE: Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor

Cheap or undersized bearings could certainly cause that, but I'd expect that to be rare - these bearings are so small to begin with! 😀 

I hope you're able to get it figured out.  I've been using this geometry since January and have yet to encounter a false jam/runout (while still being 100% on true positives, too).  Again, good luck!

RE: Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor

Yeah, just grasping at straws here... 🙂

RE: Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor

Might have just got a bit of fluff or dirt in there. It's pretty tight tolerance around the bearing. Nice thing about the newer Mk3s bearing mod is that if there's any problem you only have to reprint that tiny little block. I'm still pondering ideas to improve it, but in a pretty non-urgent fashion.

RE: Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor

No luck with the sleeve/different bearing. It seems in my case the problem happens when the filament's natural curve is away from the bearing. as soon as you hit a bit of undersized filament in that condition, boom, false runout.

In the case of this design I found I need to reprint my sensor cover. The M6 PTFE tube fitting is sitting at an angle (because I was lazy and drilled out the cap and screwed it in... I have one I modified to actually add a thread instead).  Having it lean back that way is definitely not helping this specific situation. 

RE: Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor

I installed this and I'm stoked the path is straight now!  Is this on thingaverse?  Thanks for sharing your efforts!

I was pretty stoked this was as far down as I had to disassemble my extrusion assembly to install the new parts.

Had a few questions...

For the n4-mk3s-plate-1.stl file, can you please flip over the small lever?  It's upside down to print without supports.  I had to cut it out to flip it.

Also, what is the minimum wall thickness on this item?  Slic3r kept putting a hole in a few places depending on what I had set in the settings.

Depending on if 'detect thin walls' was enabled or disabled these gaps would appear in Slic3r.  being a noob, I'm not sure what settings I could change to remedy this in this program.  On the plate however, in the 3D platter view, all looked as it should.  Not your design but a slic3r setting challenge for me.

'detect thin walls' disabled...

'detect thin walls' enabled...

Appreciate any input!

RE: Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor

Even the factory piece from Prusa has this gap!

RE: Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor

Posted by: hans.l4

For the n4-mk3s-plate-1.stl file, can you please flip over the small lever?  It's upside down to print without supports.  I had to cut it out to flip it.

Thanks for pointing this out.  I probably had it right on the initial plate, and forgot to flip the lever to a proper orientation when I uploaded a second version.

As far as the small gap goes, your best bet looks to be to leave thin wall detection disabled.  Closing that gap isn't important for structural integrity, since it just covers the head of a screw.  I didn't change that part of the model at all from the original Prusa CAD parts, so it's good that the factory piece has the gap as well.

I've been considering uploading a .zip file with all parts in their own individual .stl files; I'll try to get to that tomorrow.  That way everyone can print individual pieces as they see fit or as they need.

Thanks for the feedback, and happy printing!

RE: Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor

Awesome, thanks for the reply!  I'm still learning to used Slic3r but did find how to split the object and flip what was needed.

RE: Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor

I think my problem may be a sensor going bad. After reprinting the top I cannot get it to auto-load despite the sensor being enabled. The support menu shows a Yd value that is changing when I move the filament up/down, but it does not seem to trigger anything.

RE: Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor

Posted by: vintagepc

I think my problem may be a sensor going bad. After reprinting the top I cannot get it to auto-load despite the sensor being enabled. The support menu shows a Yd value that is changing when I move the filament up/down, but it does not seem to trigger anything.

Just to follow up - I've jumped ship on the laser sensor. I kept having false runouts, "heating..." pauses (where in pronterface showed it was responding to a filament sensor alert, I think a false jam detect), and it even stopped detecting filament insertions despite the support menu showing that it was registering movement. After chatting with support and verifying my sensor was not dirty/broken I was offered the option to either replace it or get a discount on the 3S kit. I decided to opt for the latter. I may pick up a cheap knockoff replacement to continue to experiment but I wanted to have something more reliable in my back pocket; I'm all for tinkering but not when it becomes an impediment to my enjoyment/use of the item.

Either way, I'll still be running the design here. Just need to reprint some parts to fit the different sensor.

RE: Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor

Also, @butterworthdesign - in your next revision, can you look at the last bullet point in this list:

https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-hardware-firmware-and-software-help/scratched-rods-from-linear-bearings/paged/10/#post-141231

Would be good to verify if that issue still exists in R4/your design and if so correct it...

Much appreciated!

RE: Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor

Posted by: hans.l4

Also, what is the minimum wall thickness on this item?  Slic3r kept putting a hole in a few places depending on what I had set in the settings.

Depending on if 'detect thin walls' was enabled or disabled these gaps would appear in Slic3r.  being a noob, I'm not sure what settings I could change to remedy this in this program.  On the plate however, in the 3D platter view, all looked as it should.  Not your design but a slic3r setting challenge for me.

Appreciate any input!

I'd suggest you decrease the Outer perimeter width in the Advanced section of the Print settings tab until that wall appears. You'll be surprised what range of widths can be printed with a 0.4mm nozzle. Once I used a 0.2mm profile by accident and was surprised the print came out OK.

RE: Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor

Posted by: Vojtěch

Posted by: hans.l4

Also, what is the minimum wall thickness on this item?  Slic3r kept putting a hole in a few places depending on what I had set in the settings.

Depending on if 'detect thin walls' was enabled or disabled these gaps would appear in Slic3r.  being a noob, I'm not sure what settings I could change to remedy this in this program.  On the plate however, in the 3D platter view, all looked as it should.  Not your design but a slic3r setting challenge for me.

Appreciate any input!

I'd suggest you decrease the Outer perimeter width in the Advanced section of the Print settings tab until that wall appears. You'll be surprised what range of widths can be printed with a 0.4mm nozzle. Once I used a 0.2mm profile by accident and was surprised the print came out OK.

I agree, I've been running @bobstro's profiles with "0" in the extrusion widths recently; I've taken a liking to altering the default slightly for parts where possible so that thin walls/sections have an even # of widths to begin with and avoid gap fill.

Also, had some great results printing things in vase mode at 0.8mm width 🙂

RE: Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor

Posted by: vintagepc

Also, @butterworthdesign - in your next revision, can you look at the last bullet point in this list:

https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-hardware-firmware-and-software-help/scratched-rods-from-linear-bearings/paged/10/#post-141231

Would be good to verify if that issue still exists in R4/your design and if so correct it...

Much appreciated!

The bearing axes on both my x-carriage and the original Prusa Mk3S carriage are spaced exactly 45 mm apart.  I pulled the latest .stl direct from the Prusa github repository.

Blue is my x-carriage (the 16T idler version, but the only difference is the positioning of the idler-side belt slot), and red is the original .stl.

If the issue mentioned in that bullet point exists, its not likely to be caused by the CAD or .STL files themselves, and could be due to something else like slicer settings or part shrinkage.

RE: Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor

Also: the original Prusa x-carriage-back.stl (in green) is fine too, with a 45.0 mm axis spacing:

RE: Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor

Thanks for looking - In that thread it was discovered that the spacing in the part is fine but the gap shown between the parts (which makes the bearing cavity circular) can cause the bearing to shift/be pushed out of alignment - especially if the screws are well-tightened

RE: Modified C1/R4 Mk3S parts - Better Filament Path, and a version for Mk3 Sensor

Yeah, I've noted that gap between the two parts before, and I've left it in place in another mod of mine.  I've not noticed any deformation of the x-axis rods (even while cranking things down very tight), and have smooth movement all the way from one side of the axis to the other (resistance isn't increased close to one end or the other, which would be expected if the rods were being squeezed together by even .5mm), indicating that my rods are in acceptable alignment.