The Importance of a Clean Bowden Tube

The Importance of a Clean Bowden Tube

There is a lot of advice out there on the internet for 3D printer fans. Not the kind that blow, the kind that are people. And don't even go there.


Anyway, the advice is copious and varied and often misleading, obsolete, or just wrong. So how can you tell if it is good advice? One way is to see if you can get several authors to give more or less the same advice. Another is to watch a video of the advisor actually doing the action. One last thing (and this applies to the obsolete bit) is to try and figure out if the advice being given is either very recent or  applies directly to the model thing you are working on (for instance, can you see in the video that the parts being serviced look like the parts on your machine).

One common issue that EVERYONE talks about is nozzle clogs. Also sometimes referred to as Hot End Clogs or perhaps as God Damn Fraking Clogs (GDFC).


Clogs seem to occur at joints where various components of the filament feeding system connect to one  another. They also occur in the constricted areas of the nozzle where tiny impurities in the filament can get stuck and accumulate enough to form a partial blockage. You usually know you have something wrong when your prints start to come out weak. They look OK (perhaps) but when you flex them you find that they appear to be made of cotton candy instead of plastic.

Now comes the part where advice got me into trouble. I am watching this video about the printer I just got (The Ender-3 from Creality) and it shows a common problem where the bowden tube connectors near the extruder stepper engine is not grabbing the bowden tube securely enough. Because of this, each time the Extruder Stepper retracts a little (which is often done when moving the head across a No Print area) the connector moves. This movement implies the bowden tube is moving. So instead of retracting the filament, we are just flexing the bowden tube some. Non Ideal.

And now you are saying, "What is he talking about? What is a Bowden Tube?"

The White tube coming from the back left
to the blue extruder on the left if the Bowden. 
Filament roll is off picture left.

On the open license printers, the filament extruder comes in 2 distinct parts, The Extruder Stepper motor (which pushes a carefully measured amount of filament through the hot end) and the Hot End (which is essentially a precision glue gun). On many machines these two parts connect pretty much directly to each other (this is how it was on my original M3D Mini). On the Ender 3, however, the extruder-stepper motor is fixed in place over on one of the side supports and the Hot End is moving around on the X axis Arm. Between  these two parts is a plastic Tube that channels the still hard plastic filament from the Stepper to the Hot End. This is the Bowden tube. One my Ender 3 it is about a foot long.

So anyway, the advice says that any play in the tubing is a bad thing for print precision and you should fix this situation by getting a high quality Bowden Tube and tube connectors. They are like $7.00 on Amazon. So I got them.

Now, one would think that all one need do is to pull off the old parts and stick in the new parts but this is where I ran into problems. The part of the bowden tube that sticks into the hot end HAS TO push up right against the nozzle. Any space in between these parts leaves a place for hot filament to sneak into and cause blockage and bad prints. This becomes hard to work with because the way the bowden tube latching mechanism works is that you press the tube through the connector and then pull back a little to lock it. This pulling back creates a Gap !!

And my advice guy didn't tell me about this.
This meant that not only were my next many prints bad, but I didn't realize the problem and so was doing normal clog clearing things (like a cold pull) and that was having no impact.

So. I went and did more research. I found a guy warning about the distance between the bowden tube and the hot nozzle. He claims it often comes from the factory with this space problem. How to fix it? Pull off the nozzle and insert the tube and visually confirm that the tube sticks just the tiniest bit out in the threaded area of the nozzle. Now when you put the nozzle back in, it will abut the tube and you won't get leaks.

See what I just did there? I gave you advice without the appropriate warnings:

1. Never remove or tighten your nozzle unless you have preheated the head to PLA (200C)
1. this turns out to be a biggie. Who Knew?
2. Don't put your skin against anything preheated to 200C.
1. This is an even bigger biggie. Especially for us Americans used to Fahrenheit.
3. Make sure the Hot End track is cleared of Gunk before you put in the Tube and Nozzle.
1. How? I did it by taking a small extra piece of tube (6 inches) and pushing it all the way through the hot end with the end HOT. It pushed out a huge glob of gunk.
2. Be careful, your piece of tube will heat up quickly. Perhaps wear gloves for this.

Want some more Bowden Tube Advice?

Every once in a while you will get a hunk of plastic stuck in the tube. Right at the end where the tube is hot and the filament melted in it and made a clog. You usually get rid of this by cutting off the end. Many people say, don't snip it with your filament cutters as this will bend the tubing. Other people just go ahead and clip it and don't seem a bit concerned. A third guy says to ether buy the special Bowden Tube cutter, or use a very sharp cutting tool, like razor. That is what I did, I used the blade of a box cutter. 

Does having the new Bowden Tube and the new attachment mechanisms that don't slide matter? 

Maybe.

A little.

But certainly not worth the hassle.

On the other hand. Look how much I learned.....

And now, future Me, gives some even more useful information. Go onto Thingiverse and look around for some Your Machine Specific hot end additions (try here). Essentially, there are measurement devices (yes, you could use a tape measure) and a little gasket that allow you to cut a short piece of bowden tube material and fit it into you printer between the nozzle and the bowden tube attachment fitting. This provides a specifically measured piece of tubing such that you won't ever have that leaking gap again. Work great. Less filling. 

I also have the answer to the question of "Why have  Bowden tube at all?". That is, why not put the extruder right at the hot end and avoid that long path? It is a tradeoff. Putting the extruder right at the hot end (which is called a direct drive extruder) does make for really nice well constrained filament path. It allows you to print flexible, like TPU, and it seems to give very exact control over PETG and PLA (which can make less threading and such). However, it puts more weight and strain out on your moving arms. Which means you may need to move your arms Slower to avoid inertia fracking with you. The direct drive mechanism is also a bit harder to load.  However, that said, I put a direct drive onto my Ender-3 and I love it. (I still have the Bowden on my larger CR10).

Even more Future Me says: Hey, I just put the Micro Swiss NG Direct Drive Extruder on to my CR10 V2 and it appears to work great. The advice to slow the X-axis moves down a little seems to be needed, however.

Adding a MicroSwiss NG Direct Drive Extruder to a CR10 V2

I really like the Micro Swiss Direct Drive Extruders. I got their original for my Ender3 and it was great. It made my prints look a little better and seemed to have better registration and it allowed me to print with softer filaments. In particular, it let me make things from TPU which is really powerful. There are many things that become possible with TPU. For instance, I could print a top for my water bottle with the waterproof washer integrated into the design. When I was printing these things with PLA or PETG I had to use an external washer or they would leak.

My problem was that I really wanted to be able to have just one printer, and my Ender3 is too small to be my only printer. I wanted the direct drive capability on my CR10-V2.  Micro Swiss did not have a conversion kit for the V2, however. They also had this new unit out called the NG which has the extruder set at an angle to the hot end. This evidently provides for a shorter push path (less clogs) and also takes up less room above the hot end, which means you don't hit the top of the Z-direction quite so fast. 

So I waited for them to have a conversion kit for the CR10-V2. They released something just recently for most of the CR10s and Enders, but not for the V2. Sad face.

I contacted there customer support and got a very quick and accurate and helpful response (thanks Paul!!). It said that they had not yet released a complete V2 kit but provided additional instructions (and parts to print) that I could use to figure it out myself.

Challenge Accepted !!

What follows here assumes that you have the current (11/2/2022) NG CR10 kit from Micro Swiss along with the directions they provide AND the extra directions their customer support provides (which I will duplicate some of here). Go Read The Original Instructions. Here is the LINK. No excuses.

The (extremely good) supplemental instructions from Micro Swiss Customer Support that I received are at the end of this blog.

Ready to start?

Print Required Parts

I am going to assume that the only printer you have is the CR10 V2. This means that the first step is to print the replacement fan shroud you are going to need. Here is the one they recommend out on Thingiverse <LINK>. I printed this in PETG and that seems to work fine. I guess I would not recommend PLA, I am afraid it will sag from local heat. Print this with support On BuildPlate Only.  If you try and print it with support everywhere you will get a mess that you can't pull part non-destructively. 

There is also a little part that lets you mount the filament guide tube close to the filament run-out sensor (where the current extruder sits). You should print that too. 

The main difference in this new shroud and the one the kit comes with is the hole for the part fan. OH, and the new shroud is purple. 

The new shroud has a mount for a BLtouch. I don't use a BLtouch because I find that the manual mesh method works fine and I had found the auto bed leveling to be untrustworthy. I will no doubt have to go back and try that again sometime. I suspect that my sensor was faulty.

Disassemble CR10 V2

Getting the shroud assembly off of the V2 is not so simple. There are multiple bolts to be removed from the back of the mount plate. I am assuming that we want to put all of these parts aside and save them in case we don't like the Direct Drive and want to revert. It is helpful to take pictures as you go...

At this point, you can get the two fans off. You can save the screws but I don't think they will help you much attaching the fans to the new printed shroud since these screws are not self tapping.

Now, in order to get the heater and the thermistor out of the shroud, you need to find the 3 allen wrench bolts that hold the two halves of the shroud together. Take them out and crack the shroud open and now you can get to the hot end and remove the heater and the thermistor. A note here, I had a hell of a time getting my thermistor out. I think it was a little glued in. So be careful there.

Remove Roller Plate

This plate comes off pretty easy.  The instructions from Micro Swiss work for this. Note that you are not going to be able to reuse the belt because it is too short.  You also don't need to save anything except the roller wheels. All of the other hardware comes in the NG kit.

Remove Old Extruder

The only real trick here is that you need to remove the tension arm from the extruder first in order to get access to the bolts that hold the extruder to the mounting plate.  Just take it all off. There is nothing here that you are going to reuse. The bolts don't help you since they need something to bolt to.

Attach the NG Extruder and plate to the X-axis arm

I think this is the hardest part of the modification. Not so much the attaching the plate, that is pretty easy. The hard part is getting the new belt on and sized. You did order some new belt as per the instructions, right? To bad they didn't make the plate half an inch longer, then you wouldn't need to do this. (Note: It occurs to me that you may be able to do something really simple like using a short piece of fishing line or other small line to do a little extension on the original belt. The side facing away from the Motor doesn't need to have teeth on it close to the extruder. )

The instructions that I got said to make a loop of the toothed belt and hold that loop in place with zip ties, then just hook the loops you made over the slots in the plate. That doesn't work. You can't make the loops small enough that they don't get sucked into the X stepper motor. And that isn't good. How do I know this, you may ask? 

Anyway, what I found works well is to duplicate the existing CR10 V2 solution of having a stop on the ends of the belt. The stop on the original is a metal staple thing. I found that a zip tie cinched in hard at the end will work just as well. Now you need to get this entire thing sized right and tightened. HINT: Loosen the currently tightening plate that is holding the belt taunt. That is on the X arm at the opposite end from the X stepper motor. Now you can size the belt and then tighten it up by cinching out that arm.

This method of belt attachment DOES NOT WORK

This is a good shot of what doesn't work. 
It just sticks out too far, mainly on the side
close to the X Stepper Motor.

Attach the Hot End.

This is pretty much exactly as the Micro Swiss Instructions describe. Do that.

Assemble the New Shroud

We are now going to put the fans and such onto the newly printed (and perhaps purple) shroud. First, remove the kit included (and probably black) shroud from the NG extruder. We need the 2 screws that hold it in place. Put them into the appropriate and matching holes on your purple shroud (I am just going to call it that to avoid confusion). You are not attaching it to anything yet, but later you will be glad that these screws are already set and waiting in the holes. 

Now you need to attach the two fans. Note that the instructions in the KIT don't work for this as the screws don't fit as directed. Well, the 4 big self setting screws in the KIT for the fans will work for the main body fan. For the part fan you will have to find your own screws that fit. (I just went through my bunch of extra 3D printer fans until I found some that fit).

(Update:I think you want M2.5 x 20 bolt and nut here).

Sorry, I forget where I got these screws

Attach Shroud to NG Extruder Body

It is a little hard to push the fan and heater wires out of the way and get the purple shroud to mate in against the NG extruder. Take your time. This is what makes this hobby fun. Keep saying that to yourself.

If you are like me, this is where you find out that you routed half of the wires under the X-axis arm instead of over it and much cursing ensues.

Hook Up The Control Wires.

The instructions that I got had a lot of detail on how you had to switch the wires on their Extruder Extension cable to make the extruder turn in the right direction. I have 2 things to say about that:

1. If you are doing this NG Extruder hardware mod, there is a good chance you are also burning new firmware into your unit. The latest firmware is certainly better than the stock firmware.  If this is the case, you can do this wire switch with on un-comment in the Marlin code (though I used and recommend the TH3D version).
2. I found that I did not need a wire switch. Things worked just fine with the original direction (yes, this means I switched it in software and then when it didn't work I switched it back again).
3. UPDATE: On taking my CR10 apart to fix some bad wires I find there is a little adapter cable that is about 5 inches long and runs from the cable housing near the where the X-axis cable plugs into the printer out to this extruder control. This little adapter cable has the middle 2 wires switched. That appears to be its purpose in life. Go figure.

By the way, the latest firmware also lets you specify the estep of 400 which is important to get the NG extruder to push the filament out at the proper rate.  The instructions say to use a GCODE override which they provide. That is fine and works fine, but if you put it in your Firmware, it will still be there a year from now when you update to an auto-probe or linear rail or whatever else is cool in a year.

Attach the little guide Thingee

Micro Swiss provides the gcode for this little guide thing that mounts where the old extruder used to be. You will have to find your own screws to hold it down. Also, it has a little tube holder that slides into it. There is an extra one in the KIT you can use.

Is that everything?

I am still having problems printing with TPU. I suspect that my two culprits are: A) Filament Spool is too hard to turn 2) I don't have the NG tension spring adjust tight enough for TPU. Still working that but something to be aware of.

The NG loads and unloads filament like a dream using the Micro Swiss recommended methods.

LOAD: 

1. Heat Hot End
2.  Feed filament up to extruder teeth
3. Start Extruder (do like an extrude of 100mm)
4. Give the filament a little push and let the extruder take it.

UNLOAD:

1. Heat Hot End
2.  using an extruder command to extrude some (say 40mm)
3. Before end of this extrusion, hit the pressure release lever on the NG and pull out the filament by hand from the spool side.

Because of the added mass on the X-axis, I think it may be important to limit the max speed of the X-axis stepper motor. I found this especially necessary during manual Mesh setting, but I have also noticed it during some aspects of a print. Perhaps limit travel rate in the slicer.

Additional CR10 V2 Instructions from the Micro Swiss Customer Support Team

The following was the supplemental instructions I received from Micro Swiss. I hope they don't mind that I reproduced them here.

If your CR-10 V2 does not have a bed leveling probe, then it should be pretty easy to rig our current CR-10/Ender-3 NG Extruder to your printer. You would just need to make these parts/modifications:
- 3D print a fan shroud
- 3D print a PTFE Bracket 
- New GT2 Belt
- Small Zip ties
- Modify the provided Extension Cable

If your printer has a bed leveling probe, then it will definitely need custom firmware with updated Home Offsets and Nozzle Probe Offsets. In that case, the motor direction can also be changed in the firmware instead of modifying the extension cable as detailed below.


Here are more detailed explanations for each of those bullet points.

Fan Shroud
- Needs a custom 3D printed fan shroud for 5015 part cooling fan
https://www.thingiverse.com/thing:5371792

PTFE Guide Tube Bracket
- Print the attached PTFE Bracket (MSDD_PTFE_Bracket_CR10V2.stl)
Instead of feeding the filament into a short PTFE tube on top of the NG Extruder, you will need to connect the original long Bowden tube to the top of the NG Extruder and connect the back end to a printed bracket which will sit in place of the original extruder. This bracket will align the long PTFE guide tube with the CR-10 V2 Filament Runout Sensor.
I've attached a bracket STL file that can be used to hold the PTFE guide tube in front of the CR-10 V2 filament runout sensor. The NG Extruder comes with a spare Bowden Fitting that can be used to attach the filament guide tube to this 3D-printed PTFE Bracket. Also, here is a link for spare Bowden Fittings if needed.
https://store.micro-swiss.com/collections/spare-parts/products/replacement-bowden-collets-for-micro-swiss-cr10-hotend-kit-set-of-3

Belt
-  X-axis belt will be too short and will need to be replaced. To purchase a new belt, search Amazon or Google for "GT2 Belt", they come in long spools. Then use zip-ties to clamp the ends of the belt together as shown in the attached image.

Zip Ties
- You will need four small zip ties to clamp the two ends of the GT2 belt together as shown in the attached image.


Modify the Extension Cable
- You will need to modify the spin direction of the E stepper motor. The NG Extruder comes with a cable that has the specific pinout required to convert a CR-10 to work with the NG LDO motor. When this NG Extension cable is installed on the CR-10 V2, the motor will spin the wrong way. This can be corrected by either modifying the firmware or by modifying the way the stepper motor extension cable is wired. 
 
To check the wiring pinout of the extension cable, connect the two ends of the extension cable together and that will show you how each wire is connected. To change the spin direction, the wires on one side of the connector would need to be swapped around so it looks like a mirrored version of the original pinout. Here is an example to better explain what that means.

Generic Extension Cable Pinout
Pin 1 > Pin 1
Pin 2 > Pin 2
Pin 3 > Pin 3
Pin 4 > Pin 4
A generic extension cable does not change the pinout of the wiring, so each wire will connect back to itself when you connect the two ends of the extension cable together.

Generic Extension Cable Pinout (Mirrored)
Pin 1 > Pin 4
Pin 2 > Pin 3
Pin 3 > Pin 2
Pin 4 > Pin 1

A mirrored pinout looks as if one of the connectors was just flipped 180 degrees. This type of pinout will cause the motor to spin the other way.


The pinout above is of a simple stepper motor extension cable to help explain the concept. The NG Extension Cable has a unique pinout that is required for installing the custom LDO stepper motor onto a Creality printer. The wires will need to be kept in that order, just flipped to the other side of the connector to create that mirrored pinout, in order to change the motor direction.

NG Extension Cable Pinout 
Pin 1 > Pin 1
Pin 2 > Pin 3
Pin 3 > Pin 2
Pin 4 > Pin 4
This is the cable we include with the kit, which basically just has the center two wires swapped around when compared to a generic extension cable. This the the pinout that is required for regular CR-10 and Ender-3 printers, but will cause the motor to spin the wrong way on a CR-10 V2 or V3.


NG Extension Cable Pinout (Mirrored)
Pin 1 > Pin 4
Pin 2 > Pin 2
Pin 3 > Pin 3
Pin 4 > Pin 1
This is the extension cable pinout you would need if attempting to install the NG Extruder onto a CR-10 V2 printer. This can be made by modifying the Extension cable included with the NG kit.