Airtripper’s Direct Drive Bowden Extruder V3

The Airtripper’s Direct Drive Bowden Extruder is now at version 3 with the design files ready to download from Thingiverse. A lot of work went into the design to improve the usabillity and the look of the extruder. The design is stronger with a much cleaner 3d printed finish, and filament changing is now much easier than before.

The bowden extruder was originally designed to fit the Sumpod 3d printer to replace the bulky MDF extruder housing that was awkward to use. However, the bowden extruder can be used for other 3d printers making use of it’s simple bracket, and the extruder has been popular with the Rostock delta 3d printer. A tube bracket is now availble for attaching to the bowden extruder to help guide the filament from the filament spool. more about that here at Sumpod 3D Printer Filament Handling for Bowden Extruder.

You will find more about this bowden extruder on the following page: Bowden Extruder Upgrade Part 3.

The popularity of The Airtripper’s bowden extruder was boosted when the extruder was included in the development of the awesome Rostock 3D Printer (delta robot 3D printer). To see the bowden extruder in action on the Rostock, watch the youtube clip below.

Click here to view the video on YouTube.

Bowden extruder V3 Update Details

A number of updates were made to the bowden extruder design with some minor updates on the strut and idler housing.

To get a better fill between perimeters around the screw holes, the rounded ends on the strut have been increased to 10mm in diameter to improve print quality on wider 3d printer settings.  A small taper was added to the edge of the idler bearing housing to make it easier to slide the rubber tube over the preloader hook.

1. The filament drive gear housing has been filled-in to improve overall print quality by minimizing stringing.
2. Filament guide funnel size increased and angled for (a) a more gentle filament bend around the drive gear and for (b) easier filament threading.
3. Holes opened up and angled to give the idler preload screws better clearance from the idler housing hooks.
4. M4 nut for bowden cable (PTFE tube) now drops in to position much easier than before, also, reduced filament snagging when threading into the bowden cable.
5. Screw column housing lowered and widened at the top to minimize shrinkage and deformation. The M3 screw now drop in without drilling out, although a 25mm screw is now required instead of a 30mm. However, a 30mm screw will fit with a washer so the screw cap does not drop into the recess.
6. Holes removed from the fixing bracket to improve overall 3d print quality.
7. The filament in-feed bracket is re-designed for a much cleaner look and is now attached to a screw column for added strength.
8. A spacer is added so that extra washers are no longer needed.

Bowden Extruder V3 Parts List & Files

Most of the items below can be acquired cheaply from Ebay. The MR105ZZ Ball Bearing is optional but recommended, and the Rubber Diesel Hose can be replaced for coil springs. The M6 nuts, bolts & washers are for attaching the extruder to the Sumpod 3d printer or any other printer with similar fixing arrangement, just decide what length of bolts you need.

Extruder 3D Design Files

All the files for this extruder project are on Thingiverse for download. I’ve Supplied STL files that combine selected 3d objects for printing in one session. This is good for the smaller 3d objects because the printed layers will be given more time to cool. You can download the files from here:

http://www.thingiverse.com/thing:35404

Special Parts

• Nema 17 Stepper Motor. Since this extruder is a direct drive type, a powerful stepper motor will be needed. Point your browser to http://reprap.org/wiki/Stepper_motor for a good source of stepper motor information.
  
• Filament Drive Gear. For direct drive extruders, I can only recommend the MK7 drive gear at this point. If this does not work, you probably have Hot End issues. Starting with a tried and tested drive gear will help with your extruder system trouble shooting.
  

Screws, Nuts & Washers

• 1 X   M3 x 25mm S/S Cap Screw Allen Bolt.
• 2 X   M3 x 30mm S/S Cap Screw Allen Bolt.
• 2 X   M3 x 45mm S/S Cap Screw Allen Bolt.
• 1 X   M3 x 6mm S/S Button Head Allen Bolts.
• 3 X   M3 Stainless Hex Full Nuts.
• 1 X   M4 Stainless Hex Full Nuts.
• 2 X   M3 washers.
• 2 X   M6 S/S Hex Head Bolts.
• 2 X   M6 S/S Flat Form B Washers.
• 2 X   M6 S/S Hex Full Nuts.

Ball Bearings

• 1 X   608 ZZ [8 x 22 x 7] Roller Skate Ball Bearings.
• 1 X   MR105 ZZ Model Miniature Ball Bearing 5 x 10 x 4mm.

Tube

• 1 X   PTFE Tube 4mm x 2mm.
• 1 X   1/4″ 6mm id Rubber Diesel Hose Tubing Line.

Printing the Bowden Extruder

Direct Drive Extruder 3D Printed Parts

As a guide for printer set-up, I’ll list some of the settings used to compile the G-code. The toolchain I normally use includes OpenSCAD, Skeinforge, Printrun/Pronterface and Marlin. The settings listed below will be those used in Skeinforge, just the notable settings are included that works for this 3d print. Printing thicker layers and adding extra shells could create gaps in some surface layers, especially around screw holes that are close to a surface edge.

• Carve: Layer Height = 0.25
• Dimension: Filament Diameter = 1.75
• Fill: Extra Shells on Alternating Solid Layers = 2, Extra Shells on Base Layers = 1, Extra Shells on Sparse layer = 1, Infill Solidity (ratio) = 0.25

The STL files should be all you need to print off the extruder successfully, and I’ve provided extra STL files that will allow you to print a pair of selected items or all the items in one go.

3d model images have been uploaded to Thingiverse to help identify which STL files have multiple objects in them. The STL files rendered to images by Thingiverse don’t clearly show the files with multiple 3d objects.

Assembling the Bowden Extruder

The original assembly instructions are still valid for this bowden extruder update and you can find it here: Extruder Upgrade Part 3.

To add to the original instructions

The bowden extruder V3 bill of materials is slightly different from the last version because of a couple of small changes made to the extruder main body. However, all the parts used to assemble previous versions of the extruder will still fit the new version without buying new parts.

As mentioned above (bowden extruder update details), an M3 x 25mm screw is now required for one of the screw posts for attaching the extruder to the stepper motor. However, an M3 x 30mm screw can still be used if a washer is added to the screw before inserting in to the screw column. This will shorten the screw enough to fit the stepper motor body.

Direct Drive Extruder Stepper Motor with Gear, M5 washers and Ball Bearing. Notice the bearing with electrical insulation tape to increase diameter.

The bowden extruder features an axle bearing support for the optional MR105 ZZ ball bearing to spread the load on the stepper motor shaft. Because of variations in 3d printer outputs, it may be necessary to add a bit of extra diameter to the ball bearing. When assembling the bowden extruder, take note of the amount of contact between the ball bearing and the bearing support. If you don’t think there is enough contact, try a piece of electrical insulation tape to add some diameter to the ball bearing. Add as many tape layers as needed to get good contact.

Some types of filament drive gears, after lining them up with the filament on the stepper motor shaft, will leave a gap between the ball bearing and the drive gear. For proper stepper motor shaft support, the ball bearing should be positioned at the end of the shaft. This position can be maintained by adding M5 size washers to fill the gap between the bearing and the filament drive gear.

Related Topics

Sumpod 3D Printer Filament Handling for Extruder
Bowden Extruder Upgrade Part 3
Bowden Extruder Upgrade Part 2
Bowden Extruder Upgrade Part 1

Airtripper’s Direct Drive Extruder V3 Assembled View from Front	Airtripper’s Direct Drive Extruder V3 Assembled View from Back
Airtripper’s Direct Drive Extruder V3 Fitted without washer on M3 x 25mm screw	Airtripper’s Direct Drive Extruder V3 Fitted with washer on M3 x 30mm screw
Raptor Universal Filament Drive Gear from QU-BD, CNC machined from a brass alloy and shipped with the MBE Extruder.	Airtripper’s Direct Drive Bowden Extruder V3 Fitted to Sumpod 3D Printer

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