New to Bowden - Getting started guide? DBot or general
October 24, 2017 04:08PM
I've been printing away on my Original Prusa i3 MK1 for the past year and a half, and over the summer I sourced and built a 300 x 300 x 300 DBot with a number of mods as well as full E3D V6 hot end, aluminum MIC6 heat bed (grounded to AC ground), AC silicone heater pad (184c TCO siliconed to underside), DuetWiFi controller (love how this is set up and works), all running from a GFCI power strip.

Overall, the printer works (yeah!), and I've been working through the DuetWiFi configuration which is mostly complete. I'm now at the point of tuning in general

Since all of my experience to date has been with direct drive, I'm starting to work out the intricacies / unique aspects of working with a Bowden setup.

Was wondering if anyone has any pointers, websites, or a "dummies guide to Bowden Extruders" they could point me to?

My questions are more around the mechanics of just working with a Bowden. Things like:

1. Loading the filament - I assume you just disengage the spring holding the filament against the extruder drive, and feed the filament through the PTFE tube until it gets to the extruder, at which point you re-engage the spring and use a load command to feed the filament through the heated nozzle?

2. Print done, unload the filament? - for my Prusa, if a print was done and I was leaving it for the day or days, about half the time I cut the filament a couple inches above the extruder and put away the roll. Next time I want to print, hit the unload the command after the extruder pre-heated, and out came the tail, then load and go. With the long lead of the Bowden, I've had issues with an unload not completely disengaging the filament, especially if doing it from a reheat after a cold start where the filament was left in. The solution has been undoing the feed tube at the hot end in order to get to the filament and then pushing down to melt some of the filament then pulling up forcefully (almost like a cold pull) to get the filament out. It seems like maybe the PTFE tube isn't down far enough, but it does go in a fair amount before appearing to be seated.

So, fairly basic questions.

My current prints are pretty stringy on the first layer and have sticking issues (PLA on glass with aquanet), but I need to work through some of the basics yet before I reach out for help with that yet.

Any help would be appreciated.
Re: New to Bowden - Getting started guide? DBot or general
October 24, 2017 07:12PM
Hi there,

Maybe i can give you some advice.

What kind of extruder are you using and what filament diameter?

You can used a geared extruder, like a wades or you can use a direct drive extruder, like a bulldog or an mk8.
If you use 3mm filament and want to use a direct drive, you will need a geared Nema motor because it requires alot of torque.

I am using bowden for 3mm filament with a custom bulldog extruder , mk7 drive gear and a clone e3dv6 together with drilled out m6 couplers.
It works fine for abs, but i am unable to print pla because the tension/force blasts out the ring of the couplers. Also my coupler rings grind into my bowden tube, so i have to cut a piece of it every now and then.

This should not be an issue with a legit 1.75mm.

As for your questions --

1 -- If you do it right you should have enough torque to load your filament from your extruder to hot end as is, except when switching pla to abs , then you will probably have to push the filament manually through.
I screw out the coupler and extrude filament so i can push it by hand far enouph to manually extrude till i can screw in the coupler again. Feed it long enouph to get all the old material out if necessary.

It is possible when changing material and you want to retract all filament that it will get stuck after a few cm, this means the end of the filament expanded, manually make it extrude again if needed and then you will be able to fully retract, if not retract, take off the coupler and cut the filament.
(edit: like mentioned by yourself)

My clone v6 is not made for bowden (no smooth edges or ptfe tube inside) it just has tap for the m6 coupler and i can load it from the extruder (make sure the end of the filament is nicely cut right before you load). Your legit v6 should be much smoother as mine.



2 -- I personally leave my filament loaded all the time, for me it doesn't give issues. I would not advice it however.

Feel free to ask further questions at any time.

Edited 4 time(s). Last edit at 10/24/2017 07:19PM by Govahnator.
Re: New to Bowden - Getting started guide? DBot or general
October 24, 2017 08:33PM
I've always kept my filament loaded all of the time without any issues.

As far as the first layer adhesion problems, try using blue painters tape and make sure you set your nozzle height properly.

Edited 1 time(s). Last edit at 10/24/2017 08:35PM by obelisk79.
Re: New to Bowden - Getting started guide? DBot or general
October 24, 2017 10:33PM
Thanks for the feedback folks.

For reference, I'm using 1.75mm filament. The extruder is a printed extruder that is part of the standard DBot build (D-Bot Core-XY 3D Printer, I'm considering looking for something more substantial once I get the basics running.

I have also left filament in the extruder, on the spool for a few days, but it was PLA and when I came back to do something, it snapped off just outside the extruder, due to moisture I assume.

So, just for clarification, if you have filament in the tube / extruder, do you push it all the way out, or do you disconnect the PTFE tube at the hotend, and cut the filament there and then reattach the PTFE tube and push in new filament?

I was assuming that I wouldn't have to be pulling the PTFE tube out of the hotend on a regular basis, but it is sounding like that may not be the case.
Re: New to Bowden - Getting started guide? DBot or general
October 24, 2017 10:57PM
Heat up the nozzle and pull it back through the tube. Yes, if you leave PLA unattended for a couple of days it will become brittle, thus the need for a small stock of desiccant beads. smiling smiley
Re: New to Bowden - Getting started guide? DBot or general
October 25, 2017 02:23AM
You can fully retract the filament by software. If it doesn't retract fully, just do it twice or find the parameter that changes length permanently.
When the filament got stuck in the hotend, you might have to drill out the heatsink to 4.5mm. I've noticed, that the PTFE guide inside the hotend often is too narrow to push the tube down to the heatbarrier.

Make the Bowden tube as short as possible. See my video for inspiration.

Last not least: Don't use glass on a MIC6 bed. It should be flat enough. Get some blue painters tape ( cheap and lasts forever ) or a commercial print surface like Lokbuild, PrintBite, PEI.
Re: New to Bowden - Getting started guide? DBot or general
October 25, 2017 02:49AM
You seem to be getting different advice from different forum users. I'll add mine:

- Some PLA filaments become brittle if you leave them in the printer overnight, others don't. I now use Rigidink PLA and it doesn't have this problem. So I leave the filament in the machine, often for several days between prints.

- For printing PLA I use uncoated 3mm or 4mm uncoated float glass on one of my printers, and PEI stuck on top of glass on the other. In both cases, on top of an aluminium bed plate. If anything the plain glass works better, because the print releases more easily when it cools. The reason for putting the PEI on top of a glass sheet is so that I can remove it from the bed plate and put it in the freezer if the print won't release easily. Also I can start a new print immediately using another glass sheet.



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: New to Bowden - Getting started guide? DBot or general
October 25, 2017 10:12AM
I use ponterface to control my printer and have set up a series of macros that I use to change filament. My printer has two extruders and they are about 550 mm from the hot end. One macro retracts the filament prior to changing the filament and another is used to feed the new filament back to the hot end. I never use PLA so I don't know what it causes. On my printer I use ABS and simply leave it in the hot end when I shut down. I use a Prometheus all metal hot end and have yet to have it plug in almost a year of use.
Re: New to Bowden - Getting started guide? DBot or general
October 25, 2017 04:00PM
Thanks everyone.

Couple of thoughts:

1. I've grown accustomed to being able to remove the glass on my Prusa and get medieval on it if necessary with my removal tool in order to remove the print. Letting it rest for an extended period works as well, and then, with the aquanet, it generally just pops off. I recognize that the plate is just as flat, but, for the time being, I'm going to keep with the glass, just for the convenience. I haven't tried PEI yet, but have a piece for my Prusa.

2. I haven't messed too much with the DuetWiFi macros (which is very convenient inside the web interfaces) for load and unload filament, but will start looking at those and working on how to best configure for my printer to do the load / unload all from the interface instead of manual load / unload. My Bowden tube is probably in excess of 400mm

3. Anyone happen to know how deeply the PTFE tube should be seated in a full E3D V6? My other thought is that I might try beveling the inside of the end of the PTFE tube to see if it will fit better in the hotend.
Re: New to Bowden - Getting started guide? DBot or general
October 25, 2017 07:25PM
Regarding your #3, I was advised to do that by an E3D reseller. First use a sharp knife to cut the end square, then use a pencil sharpener.



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: New to Bowden - Getting started guide? DBot or general
October 26, 2017 08:10AM
Very basic:-
Cut the end of new filament at an angle. This creates an off centre point. When feeding the filament it can snag on joints, ferules etc. This is less likely with the point and if it does you can rotate the filament by hand to get the point away from the joint.
I use ABS and leave the filament loaded. If you are going to extract or retract the filament I suggest you cut the old end off before feeding it forward again as the end has been heated and will be a strange size and shape.
Be aware that using a Bowden will require you to increase the retraction setting. We are talking numbers like 4 - 8mm dependant on your setup.
Using PLA with a Bowden may be a step backwards as many people have been on this board with jamming issues caused by the filament expanding and jamming when retracted - obviously high retraction distances make this worse so a Bowden is probably worse than a direct drive.
Deburr or tapper feed holes. Also check the Bowden tube occasionally. Dust or small scrapings can collect in the tube and cause a jamb.
As O_Lampe says keep the Bowden short but avoiding sharp bends is also important. You also need to ensure free movement of the hot end. So try to avoid the extruder aligning with the hot end AT ALL POSITIONS.
Dependant on your design - Try and ensure you have access to the extruder gear as easily as possible - don't just accept brackets supplied but consider drilling holes etc so you can see or get a tool in to help align the filament with the Bowden tube.
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