Should you use a Reverse Bowden? 

For me, the mod with the biggest quality jump was making a low-friction spool holder, I made one of the many skateboard bearing based spool holders on Thingiverse. It made my layer lines noticeably more consistent. Though the reverse Boden could be useful to me since I have the spool holder screwed to the rafters 4' above the printer.

So Anker can sponsor a video on a 3D printing channel, but won’t send a review unit of their 3D printer to the same channel. Interesting.

I prefer to us a PTFE tube with 3mm inner diameter for the reverse bowden to get less friction.

ive been doing this for years and it lets my Direct drive pull evenly on the spool at all times and its not those sudden hard pulls that happens with travel movement. A must have for large printers.

Thomas, thanks for all of your informative videos. One other advantage of a reverse Bowden, I have converted to a direct drive and wanted to continue to use my Smart Filament Sensor without adding the sensor to the print head. Using a reverse Bowden allows me to place the sensor on the printer frame and off of the moving part of the hotend.

Been using one for ten years on my Hypercube. I have the filament spools mounted on the side of the printer, with a little funnel like feeder with a filament out switch on it, where a 4mm PFTA tube plugs into, and another adapter on the top of the Titan direct drive extruder that the other end plugs into. Has always worked flawlessly.

Interesting idea. Ironically i do this as well from my dry boxes to my printers. I do want to add you might have missed sone additional forces. Restriction through a bowden does provide resistance and possibly worse then an open spool. Depending on the length of the reverse bowden (or as i call it a feed tube since it doesnt really work like a bowden imo). Also if that add on tube has any coils or bends in it that is going to add to drag. I got all my Teflon tube from a 3d supply store and it came from a spool. So it was already coiled. I have found this to add a ton of drag so straightening the tube is advised.

Reverse bowden actually made a big difference to my prints when using 3kg spools on my ender 5. The cartisan printer carrige is more susceptible to issues due to drag and the drag on a 3kg spool is much higher than a 1kg one. When I switched to a 3kg spool my failure rate went up to about 30% from about 10%, and with the reverse bowden it went back down to below 10%. The main reasons for failure being under extruded layers or jammed filament.

Normally I'd be annoyed by such a long ad, but that power brick thing actually looks pretty awesome.

I found this video perfect, I printed a Prusa spool holder and mounted it in my Anker M5C to get rid of the idiotic and weak stock setup and I was running with only a 1” piece of ptfe that I bellmouthed to help guide the filament into the direct-drive extruder. The filament roll was flopping around a bit and tugging but like he showed, it didn’t cause any issues and now my cardboard spools roll smoother as well.

I have always wondered if the force would be enough to deflect, this is interesting for sure! From the sides maybe, but like you showed, I have not seen a degradation in print quality by having my spools above and forward of my printers.

Reverse Bowden? You mean a filament guide tube? Been using one for years, didn't know it had a fancy name! Great video again!

When I switch from direct to Bowden and back I started using the tube on the direct extruder. Found that it worked pretty good so I just left it that way.

Don't use 2mm ID, use 3mm ID, you really don't want that extra drag in a reverse bowden.

I have a spoolholder/storage for 15 spools at a time but my rollers aren't optimal, so my drag is a lot higher than on most normal holders Reverse bowden is a must especially at higher print speeds

Im 100 percent agree that the tube is IMPORTANT! I have it on both of my printers (both direct drive) and this drastically improved the print quality and reliability!

I have a modified Ender 5 (Direct Drive) that uses 2 BMG Extruders. One is for DD itself and one is attached to the frame to help feeding filament. It works pretty well and I have some extra time to add a new spool to the feeding system without any kind of issues in the process.

I used a 'reverse bowden' setup on my custom CoreXY printer (direct drive) that has a canopy so it's totally enclosed. It worked but would often result in the extruder jamming with larger prints. After unsuccessfully trying different PTFE tube sizes, the final solution was to have a connector at the filament end that is free to rotate 360 degrees so that the bowden tube is better able to release tension and not grip the filament at extreme positions.

Im sure you know this now, but that visual stuff you were trying to get rid of is prusa 602 and is caused by the bondtech drive gear being eccentric due to manufacturing tolerances

@Thomas, you may want to double-check your Prusa z-axis assembly. On the three Prusas (MK3) I have access to, when I apply a reasonable amount of downwards force to the top of the extruder stepper (a few pounds), the extruder deflection is imperceptible - much less than what this video shows.

We stuck a 5kg roll of filament in a dry box under a table, then ran a 4mmOD-3mmID PTFE tube up to the Prusas. Never had to change or deal with filament problems for several months (in a free-use university maker-space)!

You've presented some motivations in favor of reverse Bowden I hadn't considered before. Personally, I dislike them because they negate one of the biggest convenience improvements of direct drive: not having to load and unload filament through a Bowden tube. I think some of the benefits can be retained by using one or more pulleys with bearings (specially designed not to drop the filament under loss of tension, using some tricks with TPU) rather than Bowden tube.

I've been using reverse bowden for a while! For the reason of having my filament mounted lower than the printhead.

Thanks for your Video. I am printing a lot ABS lately and always had my Fillament outside my Tent in my dry box and wasn't considering that as a problem. A week back I didn't need my Fillament dryed an had the spool on top of my Printer and was surprised by better Prints. At that time I wasn't exactly sure why but after this Video it all makes sense. Honestly my steup with the tent on the ground and the dry box on the Table is kind of getto but I was surprised that it Realy made a visual difference.

For reverse bowden it makes sense to use 4mm OD 3mm ID tube instead of 2mm ID that Thomas recommends. Reverse bowden does not need the filament constrained as much as regular bowden and the looser internal diameter reduces friction thus needs less pulling force by the extruder.

Also great for run-out detection based on actual movement of filament (vs. the ones that just detect a break). Without it, the movement of the head makes it harder to detect if actual filament is being used.

I did this to my CR-10 Direct Drive and it definitely helps!

I've had a reverse bowden for years because 1) Repbox setup that is in a wacky location. 2) I use a Mosaic Palette which not only does it's own reverse bowden but a mount of some sort was needed on the extruder to hold it (like the slip on that Tom used) and that didn't have to only be used with the Palette... so

The Prusa Mk3s with multi-material upgrade already uses a both a normal and a reverse bowden system. It uses a normal bowden system to load filament to the toolhead, and after the toolhead detects the filament, it takes over and the filament loader/selector disengages. The system then acts as a reverse bowden. It actually works pretty well in my experience.

I've had a reverse bowden tube for ages, just because I had tubing left over when I converted my printed to direct drive and thought it looked "naked" without it!

I have a bowden hotend, and i added a bowden tube from the extruder to my filament box/dryer to protect it from dust and humidity. Since I installed it I had 0 clogs or problems at all.

i have been using it like that since i switched to a direct drive setup, because the filament spool sits inside a drybox on the side of the printer. without a bowdentube the printhead would pull on that every time the x axis moves...

Have you ever considered making a test about Silica Gel in DIY drybox vs. filament dryers? You have a video about cooking filament to dry it out, but multiple sites suggest that leaving filament in boxes with silica gel for more than 24hours would render the same result. Thougts on that?

Does anyone have a link to the reverse bowden parts? I like the way it mounts but I'm not having any luck finding it.

Hi Tom, it would be very interesting to see you trouble shoot the weird extrusion pattern

I never imagined someone would use a direct drive extruder without a reverse Bowden. But then my printer's spool mount is sideways so it really is necessary.

This was a super helpful breakdown - thank you! My space is very limited and I need my filament to sit next to my Prusa 3 instead of on top. Thanks to this video, I know exactly how to swirl my space, and why!

Hey Thomas! Design up a way to always have slack between the DD printhead and the filament roll. I have always wished there was a way to somehow motorize/other, the filament roll to always have some slack. On fast retractions/movements sometimes the filament roll will wind and unwind (roll out/roll in) which ends up putting bad pressures on the extruder. I own a 3d Printing retail business/farm/service and this is something I have always thought about. I ended up making all filament roll Holders with a more Clutch style assembly. Bearings roll too smoothly etc. Thank you for your content!

I've used a "reverse bowden" for a long time as a filament guide. Very handy. I didn't notice any change in print quality though.

Agreed, the reverse bowden is a necessary upgrade. However, filament retraction will separate poorly coupled tube ends due to the bowden tube/filament internal friction. Rapid retracts exacerbate the tube decoupling nearest the extruder. I've had to add a PTFE fitting on top of my Ender 5 with the direct drive extruder conversion.

Very long reverse bowden adds quite a bit of friction. Best to use 3mm ID teflon tube.

Reverse bowden was great just for filament guiding on my Ender 3 knockoff, and it's even more critical now that I'm using both an enclosure and drying box.

I have been using this because I did not want the lazer runout sensor on my print head. my flashforge creator had this stock.

Wdym there's no way to avoid reverse Bowden in an enclosure? I can't see why I'd need it when the entire spool is inside the enclosure

fore sure, I have been adding that to every printer I have ever touched for years. It does really help.

but how could you fix those ripples, got htem myself and cant find a thing ot that

The drybox scenario is what i do with my normal bowden setup. Interestingly, the bowden tube fit perfectly in the little hole of the drybox and ensures the the filament doesn't rub away the enclosure hole. The friction of the hole and the bowden tube is perfectly enough to keep the tube in place. On the other side, the tube pushes against the extrude inlet and stabilizes the position by itself. This allows me to have clean filament fed and "going around corners" from the drybox placement without any weird kinking and pulling of the filament at odd angles. On retractions, the bowden tube pushes away a little from the extruder, so the filament doesn't get pushed back through the whole tube back into the drybox. This also allows for easy pulling away and out for filament changing. Pulling friction through two tubes is not noticable to me, retraction only has friction through one tube as before. In that way, it is not a reverse bowden setup as you showed, but similar enough when you just look at it.

Why not also do tests when the spool is not on the top? How big of a difference will the tube make?

I have an hemera modded ender 3 v2 and Ive often wondered if I could do exactly this if I was to take my spool holder off the top and have in on the ground... Question answered. Thnaks heaps bud 👍

Tom, can you please share with me the STL for the bowden tube clip and the revised extruder cover? I want to use the mk3 inside of a Ikea Lack enclosure, but obviously the spool holder will not fit. I have the Prusa Mini on top, so I want to put the filament inside on rollers, and use this setup. PLEASE :)

i use a closed loop for nylon printing using the mmu2 m6 pc extruder cover

5:26 OMG that MILULOYO!

What i'm missing here is the issue that some filaments like PLA will break after only a few days without use in these tubes. While this is not a big issue with bowden systems, it is kind of annoying in reverse bowden systems.

What about routing bare filament over the back over an empty spool?

Did it years ago. Can I put a link to it? It shows a Mechanism to adjust for retraction when using this type of feed.

Yet another nice video and what a coincidence. I was thinking about exactly this yesterday for my Ender 3 S1!

Shouldn't the weight of the spool turning on the smaller diameter spoolholder be the main cause of the issue? Because of friction?

Interesting ! I've been using Reverse Bowden intuitively when going from Bowden to Direct Feed. Though, my prints don't show the artifacts yours do...

The even more sophisticated method is, if you use a second (bowden style) extruder together with the direct drive extruder, simultaneously. I call it twin-extruder and I use it on every big machine I have. The bowden extruder has an independent mounting from the printer frame, so the filament dragging forces are not affecting the frame at all (think of 8kg spools...). Another advantage is, that if the two extruders are working together, the bowden extruder can help out the direct drive one if it would come out of juice, by pushing the filament into the gears. Hereby you can gain ~ 20 to 40% more flow compared to only one (direct) extruder.

Large extrusion retraction values might push the tube out of the socket.

With the drybox behind the printer, it looks like adding a reverse bowden setup would mostly help the filament not be so easy to snap.

​I tried something like that for a ewhile, and it negatively impacted the quality of the print, I think there was too much friction. I should revisit but set it up properly....

Should be obvious it's not needed to combat forces (which is more suitably solved with bearings), if anything it just adds drag to the filament path. I used to use a short piece as a guide path to direct my filament into the extruder to prevent snagging. Since I upgraded to direct drive I use a length to constrain the filament path to avoid it getting caught in the X or Z axis.

My extruder needed the filament to be inserted really carefully and precisely. You even needed to cut it sloped to help guide it in. So I don't think this would work for that extruder.

I can't say I've ever had any issues but I've only been in the 3D printing game for almost 2 years now. I have an i3 Clone and don't have those elements in the prints. I believe they are caused by the stepper motors and their harmonics dealing with the steps themselves. The only artifacts I get are some slight ringing. I'll keep this in mind but for now I like my setup.

I use an older reverse config on the office MK3S+. I can then position a spool on a bearing-type spool rack behind the printer and thread in the filament. I was never a fan of Prusa's "tug the filament right against the frame" setup.

Nice i did something simlar but i will improve after seeing this

had a rbt setup with my ikea enclusure mk3 - removed it - added way too much drag and did not improve anything...

My extruder cover looks different than yours, did you print a special cover for this?

ive been doing this for a while from my multi-spool dry box to the filament sensor on my ender 3s1. it works a treat... just have to make sure the filament unrolls nicely from the spool or we have a bad day

Where do we find those parts you showed in the video?

I don't know... On this one, looks like a spool holder with bearings would take care of all the problems easily.

Thomas the Reverse You-Bowden-Tuber. This video is a tropical storm. Thank you Thomas.

Haven't thought about that too much but always interesting to see these experiments. I tried to have my spools at an ideal " drag roll" ratio. Meaning it is very easy to unspool but they dont get into the motion of doin that by themself. They did before I removed the bearings. All working nice but I have those same lines in that light direction. I told my self that this is how it looks when you build something from many layers. Still considering to go to .6 nozzles :)

Hi Thomas, the inconsistent extrusion that you showed on the two pink parts is a problem that I have aswell on my Prusa. Were you able to solve it otherwise? Also thank you for this video. Very informative as always!

ha, anker are sending me the 535 and the solar array, I should have asked for the big boy :P

The Anker looks amazing....until I saw the price! I'm not saying it's not worth it, but it's well out of my budget.

Someone knows what's the name of the artifact shown at minute 6:05? I have the same issue but I have no idea how to fix it

Where did you get the model?

You should add a US Amazon link for the add. That one turned my Amazon to Germany 🤣 and it took me a while to figure out how to get it back.

Its more like guide tube if it used just to guide the filament...... I actually use 6mm tube (internal diameter) for that. There is less friction. With short tube that not important but I have tube almost meter and half long. First I did use genuine Capricorn tube but the friction there was a bit too much friction

You're right! Prusa did pay a lot more to pretend that their printers are better! "Reviewers" took the payment and here we are!

A mini Voron 0.1 has a 'reverse Bowden' tube to manage its direct drive filament path.

I know this is an old video but if by any chance you see this Tom, I have exactly the same print quality as the parts you showed in this video and have been killing myself trying to fix it. Did you end up resolving this issue and if so can you point me towards a video where you or someone explains the fix you used?

it also keeps the filament dry on its way from the spool to the hotend, especially when you print out of a dry box.

does anyone know where the best info or troubleshooting can be found??? I can not get my A10 32bit upgrade to work 100% My extruder shuts down after 10mins??? tried open case with a Fan, I'm not sure it's heat related now as that made no difference....?

Watched several times. I don't get it. Doesn't adding a bowden introduce more friction? I get it for spools not mounted on the printer's frame but otherwise, huh? Haha. Thanks

Neat, Thanks Thomas!

I run my printers on garden variety (i.e. lead acid) uninterruptible power supplies. I have an inverter so I can back those up with my car (which happens to be an electric car but doesn't have to be).

Your physics explanation at aprox 4min in is not right. The bowden tube purpose is only to give a narrow path to the rather unstiff filament. Since its like pushing on a string it need to be restrained in a tube. The fillament then will have a typical sinus wave or spiral buckle behavius inside the tube. This give friction points that add adtional axial loads (therfore the tube is fixed at each point.) There is no cancelation of extruder push forces from the tube. The forces need to be absorbed by the frame either way. Direct drive hotend will aslo need to pull on the spool either it have a tube or not. Its purpose is then to give a better path to the hotend, nothing more.

We must attach the filament spool to the hotend!

I used this for the m3d micro, where it made a huge difference because the printer is very flimsy.

could you turn 2 ender 3s into an ender 6?

Huh? Giving an old solution a new name? Stick a bowden tube on a direct drive extruder to see that it has no effect on print quality but does help with guiding the filament? I did this experiment years ago.

I wish I could get back the time I spent watching this. You spent so much time talking without actually saying anything or answering the question in the title.

What keeps the tube from slipping during retracts?

Wait, what’s up with the West Virginia shirt?

if you use a steel bar ziptied to your printhead and block its mvoement completely you can absolutely get rid of that ghosting

Reverse Bowden? Today we're on the channel of Doppelganger Thomas aka Reverse Thomas.

With 2,6 kg spools it can be a real difference. Some extra slack from starting / stopping a print (printhead moving up / down / corners for print bed leveling / manual filament change) and a perfectly wound 2,,6kg Dasfilament spool can become loose enough to create a snag, with that the printhead will lift up. Have been there, have done that.