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Thomas Sanladerer designed , printed and tested this filament diameter sensor. It could bi used on filament making extruders as a control sensor, or in 3d printers to get better printout results. The work on it is in progress, further accuracy improvements are needed but the current results look promising.































Files can be found at:

https://www.youmagine.com/designs/filament-diameter-sensor


From project description:

This is a proof-of-concept filament diameter sensor, currently intended for an extruder making filament. The filament centerline is 90mm above the mounting surface.
It picks up the filament's diameter between two bearings, amplifies it via the lever by a factor of 3.6, which moves a magnet in front of the hall sensor.
The hall sensor's depth is adjustable and is locked into place via the M3 bolt. Bend the hall sensor's leads 90° to the back and place the sensor in recessed spot. Lead the wires out to the front.
The 6x2mm magnet goes into the matching hole in the lever. The second hole intended for a ballpen spring, which is not needed in most use cases.
For testing, upload the included sketch to an Arduino, connect the hall sensor to 5V, ground and hook the signal pin up to A1 on the Arduino. Connect via serial at 115200 baud, it will start spitting out two values each line, the first one is the smoothed ADC value, the second one the calculated diameter. To calibrate, insert a test object with the maximum diameter you want to measure between the bearings and move the hall sensor carriage until the ADC value just reaches a maximum. Lock the carriage in place and use that value along with the diameter of the object as the last entry in the Arduino's lookup table. Insert two (or more, if you increased NUMTEMPS) more objects of varying sizes (for example the shafts of drill bits) and fill out the lookup table. Use the idle position without anything inserted for the zero-diameter position.
Support might be required for the files as they contain 30° overhangs. If you use Slic3r, you're better off with no support material.

From project forum post:

Low cost filament extruder made from 10 mm ID stainless steel tube, silver soldered inside an ordinary plumber 15 mm copper tube (melt zone) Auger is a 10 mm wood drill bit with the end cut off 5-10 mm in the melt zone. 1 mm hole in a brass endstop at the end of the copper pipe. Aluminium block with a 15 mm hole to fit around the copper pipe. Fixed to the outside of the aluminium two 220 volt 200 degree PTC heaters( I tried 12 volt 230 degrees but the temperature was to high) Insulated with glass fibre cloth. The ptc heaters are available on aliexpress for $1 each)
System driven with a car windscreen motor at the low speed (I have a 2 speed motor - salvaged from scrap yard)
I use the white plastic that is in the inside of the doors of scrap refrigerators. Cut it up with a circular saw and extrude that to a filament of 1.75 mm
I use this filament in my Delta printer on a daily basis.
The trick to have a nice filament is to let the filament run over a copper pipe that is suspended in front of the extruder and let natures G force take over. I fix a weight(clothes-peg) at the end of the filament as it comes out of the hole untill it reaches the floor and then move the end of the filament to the outside of a circle approximately 1 meter away.From then on the G force will take over and produce a nice circular movement of the filament to roll it on the floor .
The slightest air movement or other external force that you apply to the extruded filament will result in a kink in the filament - no fans required.
No fancy electronics involved.
Material cost to should be less than $100
This extruder was only tested with the white refrigerator plastic ( I think it is ABS because it will desolve in acetone ) - no ABS pellets or any other plastic tested.

Source:

http://forums.reprap.org/read.php?1,205005,205005#msg-205005

http://deltaprinter.co.za/filamentextruder/index.html

Russ presents his new home project: he made his own filament extruder. It is still work in progress but it looks good. Almost all parts are recycled from other machines.






Source:

http://www.youtube.com/user/rwg42985?feature=watch

www.RWGresearch.com

























Russ is also well known for his DIY Delta printer build:

http://diy3dprinting.blogspot.com/2013/09/extensive-roctock-delta-building.html