Airtripper Bowden Extruder BSP Edition

by Airtripper, published

Airtripper Bowden Extruder BSP Edition by Airtripper Aug 2, 2013


Full documentation for the extruder is here:

#####Extruder Filament Drive Gear Review & Benchmark

![Drive Gear Review & Benchmark](http://airtripper.com/wp-content/uploads/2013/11/mk8-filament-drive-gear-pulley.jpg "Drive Gear Review & Benchmark")

Airtripper Direct Drive Bowden Extruder BSP Edition
Designed for 1.75mm Filament and Nema 17 Stepper Motor

This is the latest edition of the airtripper extruder series with many improvement tweaks and now is sporting a BSP fitting filament out feed socket.

The extruder has worked well with the MK7 drive gear and was able to push more than 3kg of force with stepper motor type SY42STH47-1684A.

I've not posted any information about the latest extruder design, however, the previous extruder design still provides a good reference.



Recent Comments

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May I ask what is strout part for?

Hmm, reprapworld, I'm currently using Repraper filament bought through filamentenmeer.nl however, and I'm very happy with it. Extrusion temp 200º. The extruder is working quite well now, however it flexes when retracting and extruding. So I'm still thinking of designing my own extruder in the long run ;)

Currently printing with Natural PLA from repraper and it's doing very wel. How consistent is the thickness of the reprapworld filament and did you get the special 'Dutch' variant, or the usual one? Oh, and which color?

I always expected a bevel on stepper motor axles, so the set screw will be an issue on axles without a bevel.

Grounding a bevel yourself should give you the clearance you need if you can get it deep enough. I'm sorry you had to go to so much trouble, but once you get MK8 gear working, the trouble will soon be forgotten.

I just got another delivery of PLA filament from reprapworld and so far it has been perfect for bowden extruders and heated window glass beds. It needs to be extruded at 220 C for best layer bonding and there is no string clean up after printing. It might be worth you trying this filament out if you are looking for better PLA than what you use.

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Full documentation for the extruder is here:

*If you are looking to upgrade from the previous version you would only need to change the extruder main body.*


Skeinforge and Slic3r have been used but Skeinforge seems to provide the best results.

* Infill Solidity (ratio) can be between 0.2 and 0.3
* Layer Height 0.25mm

##Non-printable Parts List

*The parts below may be available as a kit from ebay; search airtripper to find the listing.*

More about the assembly can be found here: airtripper.com/1764/airtrippers-direct-drive-bowden-extruder-v3-bsp-edition/

* 2 x M3 Washers
* 4 x M3 Full Nuts
* 1 x M3 25mm Socket Cap Screw
* 2 x M3 30mm Socket Cap Screw
* 1 x M3 6mm Socket Button Head Screw
* 1 x M3 10mm Socket Button Head Screw
* 2 x M3 45mm Socket Cap Screw
* 1 x 608ZZ Ball Bearing
* 1 x 6mm ID Rubber Hose
* 1 x 1/8" 4mm BSP Push Fitting


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3runo on Feb 14, 2014 said:

May I ask what is strout part for?

Ohmarinus on Feb 2, 2014 said:

Hi Airtripper, I wanted to let you know I've discovered a flaw in the design for the Idler part. It is very important!

The idler bearing gets hit by the little screw on the MK8 filament drive gear, it only hits the edge, but it's enough to push the idler bearing away just a little bit, I've tried everything possible to push the idler further away from the carriage etc, but I think if it is possible to make a slight change in the idler, this can be fixed.

This makes the extruder prone to slipping, and the screw on the MK8 drive gear will show signs of wear since the bearing is much harder.

The fix would be to move the bearing towards the front of the extruder maybe just a mm or maybe even half a mm. I have checked it out and measured it, and it seems that the bearing is much wider than the area it needs to push the filament. Maybe it can be solved by simply adding a few washers behind the idler's part on the bolt that holds the bottom hook of the idler and goes through into the extruder motor. And maybe this problem is caused by the fact that I don't have a 4th bolt in place because no hardware store in my area has a suitable bolt (the short one that is positioned behind the idler).

Airtripper on Feb 3, 2014 said:

Hi Ohmarinus,

I had a look at my extruder and have good clearance between the idler bearing and the MK8 drive gear set screw.

On my MK8 drive gear, the little set screw hardly sticks out at all, it's almost flush with the drive gear boss.

However, I have a flat side on my stepper shaft, which means the drive gear set screw will screw in more then a set screw on a completely rounded stepper shaft.

If you are using the same type of stepper shaft as I, the MK8 must be being shipped with a longer set screw than what I got.

The wide idler bearing is needed for those who want to use the plain insert gear, or any gear that don't have groove to keep the filament running in line.

I'll make a note of what you found for when I work on the next extruder design.

Ohmarinus on Jan 25, 2014 said:

Haha, somebody is making money off of your design:

And they don't even use tubes but springs! Lazy bastards ;)

Ohmarinus on Feb 1, 2014 said:

Is this allowed?

bifbuzz on Jan 24, 2014 said:

I have this extruder all set up and everything. But it is not working. I am trying to push 1.75mm of abs through a tube of non-ptfe hose into a J-head Mark 5 nozzle with a .4mm nozzle. I am using my Rostock 3D Printer.
I am using a Sanyo 103H5208-10U41 stepper motor and the correct drive gear. i've calibrated the stepper motor to extrude exactly 100mm when the command to extrude 100mm is given. It just has not enough strength to force it through the tube and through the nozzle.
I bypass the nozzle and the filament pushes through the hose without a problem.
What do you guys suppose i can do to fix this problem and get printing?

Airtripper on Jan 24, 2014 said:

I use the J-head MK5 myself and when extruding PLA, I only need around 500g to 1000g of force at 24mm/flowrate; so a good spec stepper motor and drive gear should work no problem, I would suggest to push the filament into the nozzle with your fingers to see if you can push with enough force to cause the hot end to extrude.

Remove the bowden tube from the top of the hot end so that you can force feed the filament into the nozzle with your hand. If you are unable to extrude any plastic by hand feeding the nozzle, then there may be a blockage in the hot end.

If there is no blockage in the hot end, you might start next with checking whether the stepper motor has enough current to operate properly.

Ohmarinus on Jan 22, 2014 said:

Hey airtripper, I got everything ready, just checking, do you know what the E-steps/mm should be? In my calculations it comes out as 145.51 steps/mm I will test this later this evening when I have the new hotend in place.

Really curious to see how it will perform!! Didn't have the rubber tube, nor does any shop have that in my area, not even the car-parts shop so now I am still using springs... Don't know yet how it will perform, since the ceramic heater and thermistor aren't in place yet, but it looks pretty solid.

Airtripper on Jan 24, 2014 said:

At 145.51 steps/mm, I guess the stepper motor is set to 1/16. I think with the extruder, it's about getting steps/mm as close as you can. Sampling 100mm will give you better accuracy than sampling 50mm. However, given that a lot of filament is oval shaped instead of round, doing a test print is the only sure way check if the settings are close enough.

You might be able to find scrap rubber sheets, maybe table mats, cup mats, that you can cut up and stack to replace the idler springs on the extruder.

You could continue to use the springs, but design and print a small handle to pull the springs back and aver the idler.

Ohmarinus on Jan 15, 2014 said:

Really nice design, I've been looking at it for months and now, finally, this week, I have ordered EVERYTHING to make my machine eat 1.75mm filament from now on.

I love how the geared extruders work, together with 3mm filament this is wonderful together, but, it was time for me to start working on something new.

This will: A) make my new machine much more stable and B) my old printer will inherit all the 3mm goodness of my new printer ;)

Will let you know how it eventually works, I really hope my push-fittings for the PTFE fit well.
Oh, and that MK8 filament driver better perform!! ;)

nathanstenzel on Dec 14, 2013 said:

Any advice on how to get the spring assembly in place for the tension bearing? Maybe my screw is just too short. I am having trouble.

Airtripper on Dec 15, 2013 said:

Springs don't really work with this extruder design, you need to be using a piece of rubber tube as shown in the picture.
The rubber tube gives free space to allow easy idler removal and assemble when you need to change filament.

nathanstenzel on Nov 23, 2013 said:

I have a SeeMeCNC Rostock Max. It turns out that the 1/8" 4mm BSP Push Fitting bowden tube connector listed with this extruder does not come with the hotend kits from SeeMeCNC. If however a person wants to use the 4mm PTC quick connect fittings that come with the SeeMeCNC kit, it seems that the other hole will hold one well enough if enlarged slightly on the outer few mm. I just figured I would share. I have not tried it yet. I figure either the design would need to be mirrored or the stepper direction would need to be changed in the firmware.

nathanstenzel on Nov 22, 2013 said:

Ok. Black ABS sucks. The ends of the mounting area breaks off a bit easy for me. You may want to enlarge the bit of black plastic at the to try to strengthen it up or avoid black filament for the part and mark it up with a black marker.

nathanstenzel on Nov 22, 2013 said:

Slic3r version 0.9.10 gives me this message about the idler.stl file. I don't know what message is about, but I will just try to print it and see what I get.

"Warning: The input file contains a hole near edge 16.000000,33.000000,6.000000-7.300000,33.000000,6.000000 (not manifold). You might want to repair it and retry, or to check the resulting G-code before printing anyway."

Airtripper on Nov 22, 2013 said:

I use either Skeinforge or Cura to print the extruder and get the best results from Cura.

I've tried to use Slic3r but had issues with infill leaving empty gaps.
I've not seen this error before.

Isos on Oct 28, 2013 said:

Is there any particular reason BSP fittings are used? NPT is much easier to find on this side of the pond.
Thanks for the awesome design!

Enlightx on Sep 5, 2013 said:

lmao i was just thinking i wonder if airtripper has upped scad file yet... upped 4 hours ago :) thanks for the design

Enlightx on Aug 27, 2013 said:

looking forward to the scad file so i can change to 3mm and also change mount holes to 5mm

openhardwarecoza on Aug 3, 2013 said:

Where's the SCAD? (: I can only find 1/4 BSP around here, not the smaller one

Airtripper on Aug 3, 2013 said:

The SCAD file will be uploaded soon after I've checked it. I'm going to see if it will work with the customizer.

ipblythe on Aug 2, 2013 said:

Could you please develop a version for 3mm filament as well, this would widen the market for your extruders.

Airtripper on Aug 2, 2013 said:

I've worked out how to get a 3mm filament version to work with this design and it should be out shortly.
There will be a standard type and also a type to fit a planetary stepper motor.

Ohmarinus on Aug 2, 2013 said:

I'd like to see that too. I have a MK7 drive gear for 3mm filament.

However, I'm currently having more problems developing a nice J-head holder for my Prusa i3 carriage that I'm working on.. Theres not so much bowden J-head carriages around and the ones existing don't work for me :(