As I was cruising ebay I found this  http://www.ebay.com/itm/Wire-Measuring-Machine-/331157067818?pt=LH_DefaultDomain_0&hash=item4d1a7fd82a  And looking at the design

As I was cruising ebay I found this http://www.ebay.com/itm/Wire-Measuring-Machine-/331157067818?pt=LH_DefaultDomain_0&hash=item4d1a7fd82a And looking at the design I thought “Why cant we make an active filament measuring device similarly?”. This design would use a spring, 2 x 623vv bearings, a sliding pot, 3 x m3 screws, 1 x m2 screw, and the rest printed. Alternately a second axis, turned 90 degrees, could be added. Calibrate distance from the filament to the nozzle and away we go. My issue is this: my Arduino skills are non-existent. That and lack of firmware support which falls back on my issue again. I made this in all one part with enough space .1mm for each item to be separate. I exported to .stl and cura separated most of it except the top bearing. Any thoughts, ideas, help?

The ebay link measures length, I assume you want to measure diameter. Maybe this could help: http://airtripper.com/1473/airtripper-extruder-filament-force-sensor-design-3d-print/

Looks like a good idea! I think it could be made a lot more compact. I wonder if it could be built into the extruder idler?

How accurate are cheap linear pots? I guess we want around ±0.05mm accurary, ideally ±0.01mm?

@Liam_Jackson awesome idea. I’ll look into that.

These guys are talking about similar systems https://plus.google.com/communities/107859862288161234107