RepRap: Blog

I have been designing a new printable extruder.  It is primarily intended to be small and light enough to mount directly on Huxley, but it should work on virtually any RepRap or similar 3D printer.


It features:

1. 1.75 mm filament
2. Adaptable mounting plate to attach it to virtually any 3D printer
3. Very compact high-torque NEMA 11 motor
4. Wade-style hobbed bolt filament transport
5. Wing-nut drive to spread the torque loading on the plastic gears
6. Push-fit hot-end parts - no thread cutting
7. Lightweight: 335g (about half the weight of the usual Mendel extruder)
8. Compact design (74 mm x 83 mm x 100 mm)

Here's a video of it working:


RepRap Universal Mini Extruder from Adrian Bowyer on Vimeo.

Documentation and full details being written up here...

Labels: extruders

I have started to design a MicroExtruder for 1.8mm filament.  So far I have just got the non-reprapped parts, shown above.

As you can see, it is about the size of the two end joints of my index finger.

It is a miniaturised version of my standard extruder here, which was based on ideas from Nophead and others, with bits from me.

From the top there is the filament (green - thanks Vik!)  then a length of 8mm diameter PTFE.  This screws into the brass nozzle with an M6 thread.  There is then a PEEK disc with two 2mm holes either side.  Those will take two M2-threaded rods.  The tension in these will resist the extrude pressure.

The brass nozzle is threaded M4, and screws into a small brass heater block.  This takes the normal RepRap thermistor for temperature measurement, and is heated by an 8.2 ohm metal-film resistor rated up to 235 ^oC, which should give 16 watts at 12 volts.

The filament hole down the PTFE and brass is 2mm in diameter.

So far it is untested - watch this space...

Labels: extruders, miniaturisation

The Thermoplast Extruder Version 2.0 - the new pinch-wheel design - has been released. It has these advantages:

• It can be driven faster than the older screw-driven extruder
• It has fewer parts (both reprapped and added from outside)
• It is easier to make
• It can be controlled more precisely and simply
• It can be reloaded while it is working without interrupting a build
• It should be more reliable (only time will tell...)

I've been running it for a couple of weeks now, and it goes very sweetly, particularly with ABS (shown above). And it's really superb with polylactic acid. On my home Darwin I build with that at carriage speeds of 3000 mm per minute, which is fast, and - of course, unlike ABS - it doesn't distort as it cools. This means perfect parts quick - what's not to like?

Labels: extruders

The Java host software is now set up to handle objects made from any (reasonable) number of materials. If you load an STL file, select it with the mouse, then load another the system keeps the relative position and orientation that the two had when they were created. Thus you can design something in several materials, save each as an STL, and then load them all together.

As you can see, the sectioning software distinguishes between the two and creates the correct outline and hatch patterns for each.

So far I have tested this on an Arduino-controlled RepRap with LEDs in the place of the extruder motor and valve (because I only have one extruder here at the moment). The LEDs all seem to light up and go out at the right times.

This is cheating slightly, as the Arduino only has enough pins for one extruder, but if you have two, one of which just needs a motor like our plastic extruder, and the other of which just needs a valve, like our prototype paste extruder, then you can control both.

Next I'll update the paste extruder design and get that working again, and see what we can make.

Then I'll upgrade the Sanguino (more pins...) software so it can genuinely handle two extruders.

This, of course, will allow us to use different support materials, and also fun stuff like silicone rubber and Field's metal.

Labels: extruders, materials