New extruder design

Hey everybody I'm kinda new to 3d printing and if theres anything you guys see anything thats way off please tell me I want feedback on this
So heres the design thered be a worm screw perpendicular to it would be a worm gear mounted on like a nema 17 or something perpendicular to it heres a picture of something like it [static.ddmcdn.com]
see the thing is worm screws arent normally back driven so it would have to be a small gear ratio like 3:1 or 4:1 i think
now please loved to hear some feedback on wether this has been covered aleady or why it wont work

Sorry guys I forgot to say where filament would go
the worm screw would be against the filament so the threads on the worm screw would drive the filament upwards the benifits with this design would be it has more contact points than a normal extruder
Thank you

You simply can't back-drive a worm gear, the friction is too great.

I think what you're thinking of is something like this: [reprap.org]
Where the filament is driven along the axis of a screw.

Edited 1 time(s). Last edit at 08/25/2013 11:11PM by NewPerfection.

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Thanks for the input
So then this is wrong then? Helical worm gear

printerguy1 Wrote:
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> Thanks for the input
> So then this is wrong then?
> [url=http://kmoddl.library.cornell.edu/model.php?m
> =578]Helical worm gear[/url]

I think the text on that page refers to the wrong model, it actually refers to [url]http://kmoddl.library.cornell.edu/model.php?m=572[/url]. I'm not convinced either model is back driveable, it seems unlikely.

Increasing the contact area seems like a good idea, but having used a screw drive it doesn't seem to be much more reliable and takes a lot more space.

Okay makes sense I was kinda thinking of this for bowden type applications where theres a lot of pressure on the extruder, this designI thought would make it have less slipping and might be able to retract faster I thought.

What if we reduced the number of teeth on the gear so there was only 1 square tooth every 1/4 of the way around. ie leave the gear the same circumference but make it so there are bare spots on the gear where there are no teeth. That would reduce the amount of friction wouldnt it.