After-market extruder head

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Mechanizer
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After-market extruder head

Post by Mechanizer » Sat May 12, 2018 9:48 pm

Ok, so here’s a rough concept for adding an after-market extruder head to the cube to be able to print more types of filament. Being able to use different feed gears, idlers and having some adjustment may improve performance. I’m reusing/redesigning the FTF concept above to do this.
CEH1.PNG
I’m using an extruder head from Amazon, some parts form Servo City, and a handful of printed parts. The purchased parts comes to a total of $15.75 (plus shipping). Here are the links:
https://www.servocity.com/5mm-id-x-10mm ... d-in-pairs
https://www.servocity.com/5mm-stainless ... n-shafting

The amazon link doesn't show up for some reason, just search for this and you'll find it:
Iverntech 3D Printer Right Hand MK8 Extruder Aluminum Frame Block DIY Kit for RepRap Prusa i3

The extruder head looks kinda crappy but I could use some of the parts and redesign other portions of it to make it better. But that’s another topic, right now I’m just trying to determine if this concept’s feasible. There may also be better head units available that could be used instead.

Basically, the original cube feed gear slides inside another printed gear and is secured with set screws. So it’s just being used as a driver.
CEH2.PNG
Then the gear ratio is changed via a set of idler gears (this is what the bearings and shafts from Servo City are for) which then drives the extruder head.
CEH3.PNG
CEH4.PNG
I measured between 9.6 and 9.7 mm OD on the original cube gear and the new extruder gear is 11 mm OD. That’s a ratio between .87 and .88, so I’m using 32 and 28 teeth gears which has a ratio of .875. Hopefully that’s close enough, but I have no idea how sensitive it is to changes in filament feed rate.

If anybody has any suggestions to help improve this concept, let me know. Also, does anyone know if it’s possible to change the direction of the extruder drive motor? That would eliminate one of the gears. Thanks.
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MajorOCD
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Re: After-market extruder head

Post by MajorOCD » Sat May 12, 2018 10:09 pm

Looks awesome!! Feel free to redesign the extruder hub any way you see fit.
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MajorOCD
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Re: After-market extruder head

Post by MajorOCD » Sat May 12, 2018 10:24 pm

hobb-goblin-6mm2_1_2.jpg

This type of drive gear works much better. This is the hobb-goblin from E3D.
https://e3d-online.com/hobb-goblin-5mm-drive-gear

Can you adapt it to use one of these? They make it with a 5mm ID and 8mm ID.
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Mechanizer
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Re: After-market extruder head

Post by Mechanizer » Sat May 12, 2018 10:28 pm

Yeah, I saw those. I'm thinking maybe getting the extruder assembly and one of those and swap out the feed gear.
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Mechanizer
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Re: After-market extruder head

Post by Mechanizer » Sat May 12, 2018 10:30 pm

And yeah, I could make the middle gear smaller and even put it off to side slightly
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Mechanizer
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Re: After-market extruder head

Post by Mechanizer » Mon May 14, 2018 10:58 pm

So here's the diameter of the hobb goblin:
hobb goblin.PNG
That number compared with the 9.6/9.7 I measured on the original cube gear is the ratio I need for the gears (I think). But it may take a few tries to get the speed right.
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tprothma
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Re: After-market extruder head

Post by tprothma » Fri May 18, 2018 1:51 am

Hi Mechanizer, good work...
You may want to figure out if there is a way to reduce backlash.
I really don't like our dependence on the cube extruder either.

I was thinking of a version without extra gear but uses a coupling that adapts to the end of the motor and goes directly through hobbed bolt.
We can figure out the gear ratios and tune that with speed adjustments in software.

https://drive.google.com/open?id=1NGdyJ ... HkhS-XAsdG

Thanks,
Tim
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Mechanizer
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Re: After-market extruder head

Post by Mechanizer » Fri May 18, 2018 11:14 pm

Hey Tim,
Thanks, I'll keep that in mind about the backlash - I suppose with retraction that could be an issue. I'm looking at using more purchased parts (gears, plates, etc.) instead of printed parts which may work better. I can get all the hubs and gears I need from Servo City for relatively cheap.

We were trying to come up with a way to do this with the cube software, hence the extra gears, but I like the option of direct drive and 3rd party software as well. I'm not sure if I'll be able to get the speed exactly right with gears anyway, so I may have to go the software route if the gears don't work. I'll try to come up with a direct drive concept as well.
tprothma
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Re: After-market extruder head

Post by tprothma » Sat May 19, 2018 3:52 pm

Unfortunately the extruder gear on the printer is unique, but if it could be reused then that would be sweet. Reuse of that gear may be a way to solve both the ratio and backlash problem all at once. I think the best aspect of direct drive type I've seen on other extruders is the tension capability that we do not have with the cube 3 native design and as a result it seems our printer is intolerant of slight variation in filament thickness. I'm operating under the assumption that the main flaw is the need for tension, and that the gear won't wear out (it may eventually wear out).

I think you're going to find the challenge is coupling to the square drive on the motor to any hobbed gear. But thinking through this a lot of people make their own hobbed gear with bolts.

Good luck, and keep us posted.
Tim
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Mechanizer
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Re: After-market extruder head

Post by Mechanizer » Sat May 26, 2018 9:40 pm

Alright, I got busy with some other stuff but I'm back. Here's what I have on the direct drive option:
Direct Drive.PNG
I still got a couple of details to figure out but it's pretty much done. Now I have to figure out how to change the speed. I know some of you have gotten simplify 3D to work with the cube, but I don't want to buy that. I would like to use slic3r, and I found an old post from someone that claim they created a python program to work with the cube. Here are the links:
http://cube3d.createaforum.com/general- ... ed-slic3r/
https://github.com/spegelius/CubePostprocessor
The post says it's for the cube2, will that work with cube 3? Has anyone tried using slic3r? Can this program be modified to work with cube3?
Any help would be appreciated. Thanks.
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