Why direct drive is not automatically better than bowden tube

direct drive seems all the rage in 3d printing these days so is it automatically better than bowdoin tube well no in this video we'll explore why [Music] 3d printers typically come in two configurations direct drive or bowden tube but there's nothing to say you can't convert between the two in fact i've made several videos showing how to convert to direct drive in the past so direct drive must be better right well like most opposing options each has strengths and weaknesses which we will explore but first we're going to define exactly what each is here are two types of printers one of them bowden tube and the other direct drive we can label the components and see that both machines have two out of the three but let's break it down in more detail firstly we have the extruder drive which was labeled in yellow in the previous diagram this simple creality design has a hobbed gear and then a guide bearing which the spring pushes against the filament helping the extruder drive maintain its grip on the filament and that means it can push it forward through to the printer to be melted and deposited as part of our 3d print of course there are more complex versions of this such as this bond tech bmg which has dual drive extruder gears this is when instead of having a bearing we have a second hopped gear linked to the first and providing grip on both sides of the filament both of these versions however achieve the same thing so that's the extruder drive shown here in yellow but what about the hot end shown in red here are three examples the one on the left is an e3d v6 and the other two are from creality their makeup is essentially the same filament enters from the top through a cold zone kept cool via a fan blowing on a heat sink into the heater block which of course has the heater cartridge where it's melted and then is extruded out of the nozzle on the bottom again there are variations on the design but the purpose is always the same melt and deposit filament as it's pushed through the hot end every 3d printer shares these two components but not all of them have a bowden tube shown here in orange a bowden tube is simply a length of ptfe tube the inside of the tube is hollow which provides a fairly constrained path for the filament to slide through the middle and because ptfe is a low friction material resistance is minimal so that's all of our relevant components in isolation so let's see how they work together for each of these systems our first example is direct drive and it's still common to have a very short length of ptfe tube in between the extruder drive and the hot end however this is short straight and very constrained more modern extruders such as the bqh2 has an even shorter path with filament entry drive gear and nozzle tip all coming in under 60 millimeters here's a direct drive extruder fitted to the machine we feed in the filament through the top through the drive keys and out the nozzle without a length of ptfe tube inside now let's compare the bowden tube setup the same extruder drive except this time a much longer length of ptfe tube in between the extruder drive and the hot end as we feed filament through the system we can see through the translucent tube the filament making its way along to the hot end and here's the same type of system in place on a printer we have our drive gear exiting into some ptfe tube the filament is guided by the bowden tube towards the hot end where it's melted and once again is extruded out of the nozzle here's the whole system extruder drive bowden tube followed by the hot end hopefully that's clear so here's a quiz this setup uses ptfe tube in between the filament spool and the extruder drive so is it a bowden setup the answer is no because the tube is not in between the drive key and the hot end this is what we call a reverse bowden tube and it can be used on either a direct drive or a bowden tube system hopefully if it wasn't clear for you before it's now clear the difference between direct drive and bowden tube with that out of the way let's start to explore strengths and weaknesses we're going to start with assessing a bowden tube setup and these are very commonly found on new 3d printers where achieving good quality isn't really a problem the major strength of a bowdoin tube setup is the lightweight printhead in a bowden setup the moving mass is kept to a minimum and that's because the printhead only consists of the hot end and a part calling fan and that lightweight means less ringing for an equivalent feed rate and acceleration here we see my rat rig printing with the same feed rate but vastly different acceleration as you can see the higher acceleration provides a much more violent movement as seen on the right that fast movement introduces vibration which comes out in the print as ringing the lower we can keep this mass like with the bowden tube the less ringing we should have but there are downsides and it basically comes down to having less control of the filament delivery here's a trunksy corexy 3d printer that i previously reviewed and it had an excessively long bowden tube setup which made retraction a nightmare the end result hard to tune out stringing so why is this so as we saw earlier the filament slides smoothly inside the ptfe tube however if we try to constrain it with a really tight fit it's going to add some friction therefore we need a slightly looser fit to ensure nothing binds and that means the filament is free to flex inside and the longer the bowden tube the greater the disconnect between the extruder drive and the hot end and the more inaccuracy we have to deal with so back to that trunksy with the really long tube no matter how much tuning i did it was very hard to get rid of the stringing that's not to say that you can't eliminate stringing with a bowden tube setup because most of the time you can even with flexible filaments the point is it's just going to be easier with a direct drive setup when we evaluate direct drive we get the opposite attributes the short filament path will give us precise control particularly on modern direct drive extruders where the filament path is only a couple of centimeters long that makes it a lot easier to dial in retraction and things like linear advance a typical retraction distance for a bowden tube setup is around six or seven millimeters but for direct drive it's typically only one millimeter and sometimes even less so this means that if we attempt a retraction torture test print such as chainmail the direct drive extruder is going to be a lot easier to dial in in this case getting a great print on the first attempt of course we have downsides related to the heavier print head because now we also need to move around the mass of a stepper motor this increased mass is relevant any time we change direction and if we try to print faster this increased mass will exaggerate any ringing compared to a bowden tube printer of course each machine is different and these are generalizations but at the heart of it direct drive offers more precise filament control and a bowden tube gives you lighter weight we can of course modify the printer and convert from one to the other so let's explore why you would do that it's nowhere near as popular but why would you convert from direct drive to a bowden tube setup in my opinion the ideal candidate is a printer that already suffers from a lot of ringing possibly due to the print head having a lot of play one such printer i've tested in the past was to see this mark iii as you can see it's direct drive and it's lugging around a pretty big stepper motor despite using linear rails this printer produced the worst ringing artifacts that i've ever witnessed even showing up on a 3d benchy at pretty slow print speeds and accelerations inspecting the assembly gives us our answer as there's just way too much play and i think this would be an ideal printer to convert to bowden tube the cedars mark 3 ticks the first two boxes but this third one might be a little bit tricky for it so let's look at another printer that ticked all three the first 3d printer that i personally owned was a solar doodle 2 and as you can see the factory setup is direct drive this printer was delivered with quite an unusual extruded design made up of stacked laser-cut acrylic pieces and nicked named the jigsaw extruder because this was a pain a community member named tech designed the jigsaw replacement extruder which i then became pretty obsessed with remixing and improving myself initially making the mark ii the mark iii the mach 4 the mark 5 but then finally the mark 5 bowden edition as you can see there was a nice place on the frame to mount the extruder stepper going to bowden tube for the solar doodle 2 gave me a nice increase in print quality unfortunately however the stringing was more prominent so how about the opposite why would you convert to direct drive the most obvious reason is if you're struggling with retraction and because of this the trunks i showed earlier would be an ideal candidate to go direct drive there's also the added benefit of more convenient filament changes with direct drive this manual process becomes a lot lot easier and finally a reason that should be discussed more is that on an i3 style frame with a moving bedslinger y axis that heavy bed mass is going to be a limiting factor anyway for example on the cr-10 max i removed the factory bowden tube setup and instead fitted a much heavier hammer so have i limited the speed of the printer well i would say absolutely not because what really stops me from pushing speed and acceleration is that really heavy moving bed any ringing is going to come from this way before the extra weight from the direct drive the same goes for all of the conversions i mentioned it already done on the channel each printer is different and performing a conversion may or may not be a good fit with that in mind let's look at some current trends for direct drive and bowdoin tube first up why do manufacturers still largely prefer bowden tube from factory just like this coriality cr-10 smart which i've just started reviewing i'd say the number one reason is that it just works particularly if the company has its own slicer profiles where they can dial in retraction tuning and provide something for the user that's already ready to go the second reason which is particularly true for companies like reality is that it's what they know and that means they can continue to pump out designs that are only a slight variation from their last without the need for involved research and development so if photon tube does work then why are direct drive conversions becoming more and more popular i'd say this is mainly due to advances in hardware and design for instance pancake stepper motors are much lighter than regular stepper motors and the scented nylon such as used in the bondtech bmg is both lightweight and strong we're even starting to see the use of less conventional stepper motors that are even smaller and lighter this can be seen in the orbiter as well as the sherpa mini which use such steppers combined with gearing to ensure that there's enough torque to supply sufficient force to the filament here we see a size comparison between the bqh2 all in one direct drive extruder versus end of three components reconfigured to be direct drive not only is the h2 literally half the size but the entire h2 including the heatsink fan weighs less than just the extruder stepper from an ender 3. these lightweight advancements mean we get all of the precision of a direct drive system but the downsides from adding mass are greatly reduced and that makes direct drive as a whole more appealing in short recent direct drive developments minimize compromise offering precise filament control as well as relatively low mass before we finish however one thing you might be wondering if there's a third option a hybrid between bowden tube and direct drive the answer is yes available for a while now we have the flex drive g5 and the zesty nimble with each of these designs aiming to combine the best of both worlds we mount our extruder stepper remotely just like with the bowden tube but then we use a long flex drive cable that goes into a very minimal and lightweight extruder drive which due to its minimal parts is extremely lightweight on paper this approach should be the best setup but for whatever reasons popularity remains limited hopefully you can see now the difference between the two and although new direct drive all-in-one kits are all the rage boat and tube 3d printers still have their upsides and are probably here to stay please head to the comments section and let me know which one that you prefer thank you so much for watching and until next time happy 3d printing g'day it's michael again if you like the video then please click like if you want to see more content like this in future click subscribe and make sure 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Channel: Teaching Tech

Views: 192,384

Keywords: 3d printing, 3d printer, 3d print, 3d printed, bowden tube, direct drive, dd, compared, comparison, evaluation, analysis, creality, ender 3, cr-10 smart, retraction, linear advance, pressure advance, stringing, speed, feedrate, acceleration, ringing, ghosting, mass, weight, test, tested, advantages, disadvantages, pros, cons, strengths, weaknesses, orbiter, lgx, bondtech, dual drive, flexdrive, zesty nimble, tuning, calibration, hemera, prusa, mini, rat rig, v-core 3

Id: ybTbuUBy2-s

Length: 13min 19sec (799 seconds)

Published: Tue Jun 22 2021