New aluminium extruder

Once again it has been a while since I updated last, but I still haven’t just been sitting on my butt while touching myself… Instead, I have made this.

 

A new extruder for my 3D printer made out of aluminium, a new and more flexible groove-mount system for the hotends, and I also got a new design of X carriage in the oven.

When I designed this I had some things I wanted from it:

  • 3mm filament, 1.75mm optional (not tested yet)
  • Easy to change filament
  • No tools needed (no tools needed to adjust or changing filament)
  • As open as possible to allow access to the drive pulley
  • Simple to machine (so it can be made on a manual mill)
  • Durability (the whole point of making it in metal instead of plastic)

The extruder is made out of multiple parts, the first is the L shape which is the base of the extruder. This holds the motor, the pinch arm and also bolts onto the groove-mount. The pinch arm is rotating around a brass tube with a build-in spacer to keep the right distance from the body to the center of the bearing which presses the filament into the drive pulley.

Next up is the bolts which holds the motor on,  are countersunk so they are flush with the surface behind the pinch arm, and they are also cut down to a custom length for optimal contact. With these custom lengths I managed to get the M3 bolts going 7mm into the face of the gearbox, which is just over 2xD which is considered to be perfect for most operations.

The pinch arm got about a 2.8:1 ratio to multiply the force provided by the spring, and from what I calculated, the ball bearing applies 4,6 kg of pressure against the filament, so without it being difficult to open and change filament, it still got quite a bite on the filament. The pinch arm is rotating around a brass sleeve with a spacer build-in, this is so it wont tear or get worn from the small movements under pressure which can occur in operation.

Here is the very first thing printed with the new extruder.

Over all the quality is fine, but there are still a few places where the layers are not consistent enough. Those inconsistencies between the layers might however be a temperature problem instead of extruder problem. (Update: The problem got narrowed down to being the filament, faberdashery filament gave a close to perfect surface.)

BOM:

  • 3x M3 x 18 bolts, cylindrical head
  • 4x M3 x 15 bolts, countersunk head (must be grinded down to about 13mm for perfect length)
  • 1x 625 Deep Groove ball bearing (16 x 5 x 5 mm)
  • 1x Compression spring (31 x 10 x 1 mm)
  • 2x M4 x ??? (used to bolt it to the carriage)
  • 1x 5.18:1 geared Nema17
  • 1x Drive pulley with 8mm ID

Extruder machining drawings:

   

Groove-mount machining drawings:

Printed accessories:

2013-03-19 22.27.45 (Medium)
Filament guide – This helps making changing filament on the fly easier. To change filament you just cut the old while still printing, then press the new in just behind it.

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