designing a new extruder

I'm currently designing a new extruder that combines the best design-details that have emerged since Wade's.

* It will gear down the stepper like Wade's does.
* Use herringbone-gears to reduce backlash and noise like some others I found.
* Use a spring-loaded lever to make filament changing and adjustments of pressure easy and keep the pressure constant as the nut does not loosen after a while.

my own ideas:
* integrate a filament cleaning-sponge into the extruder to keep dust and dirt out.
* integrate the mounting-holes for the stepper-fan into the extruder-design.
* add an optional rotary encoder to detect failures and pause the print for later resuming if no filament is actually transported (grinding, blocked nozzle or simple no filament left)
* keep the center of gravity down and mount the toolhead at 3 points to keep it stable when the ToM is transported and reduce any possible shaking/backlash in XY.
* be compatible with multiple existing hot-ends (I want to use it on the ToM with Makerbot -hotends and on the Repman with pre-fabricated and self-assembled BitsFromBytes hotends.)
* allow 2 mirrored extruders to be mounted side by side on the ToM for multi-color/material prints
(no need for this on the RepMan as that natively supports up to 3 toolheads)

[marcuswolschon.blogspot.com]

Does anyone have additional ideas, I could integrate?
Any problems I may not have thought through yet?
Feedback?
(The rendering is only a very, very early draft. It will change. Especially the rotary-encoder is not included yet.)


I'm posting this on the Makerbot Operators group, the BfB-forum and the RepRap-forum as all 3 groups are involved and may have ideas about making this as good as I can make it.

Marcus

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Instead of relying on springs, there should be a printable spring apparatus to perform the same function.

Ducting for the fan should be integral to the design.

Since you are considering the use of an encoder AND dual extrusion, I would opt for using the encoder coupled with a second stepper to turn a cam shaft loaded with two or more 608 bearings. Along with this you would need a stackable method for mounting additional hot ends. Then it would simply be a matter of clocking the cam to select the nozzle to extrude from.

jcabrer Wrote:
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> Instead of relying on springs, there should be a
> printable spring apparatus to perform the same
> function.

What would be the advantage?
(I'm not aiming at a maximum percentage of printed parts.)
I don't think
a) 3 people printing the same spring on 3 printers with
3 brands of ABS will get anywhere near similar results and
b) that an ABS-spring can store enough energy compared
to a metal one.


> Ducting for the fan should be integral to the
> design.

Why that and where to duct the air too?
Could you explain the advantage and intent?
Currently the fan sits right atop the stepper motor.
The stepper being open to the air on all but the front
side. In the current ToM this works very well and in the
current RepMan the larger stepper has no active cooling
at all and works reliably since years now.


> Since you are considering the use of an encoder

What does the suggestion below have to do with
the encoder (that is detecting that the right amount
of filament is actually pulled in and pauses the
printer upon detecting a failure to do so to improve
reliability in unobserved prints.).

> AND dual extrusion, I would opt for using the
> encoder coupled with a second stepper to turn a
> cam shaft loaded with two or more 608 bearings.
> Along with this you would need a stackable method
> for mounting additional hot ends. Then it would
> simply be a matter of clocking the cam to select
> the nozzle to extrude from.

Interesting idea.
However I don't think I'll do that.
Too complicated compared having one extruder with
one stepper and the option of mounting a second one
next to it.
Feel free to design such one! It sounds like a lot of
work but could be a huge improvement.

Marcus

Edited 1 time(s). Last edit at 07/04/2011 10:07AM by MarcusWolschon.

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The issues I've had with existing designs:

1) Access to the mounting screws - Wade's design buries the mounting screws under the motor and filament clamp, which makes it necessary to disassemble the extruder in order to remove it from the carriage. With my own (Techzone) printer, this problem is compounded by the design of the carriage, which put the mounting holes directly over the carriage rods, making clearance difficult.

2) I'm also currently trying to figure out the best location to attach a quick-disconnect for the wiring - I'm using an 8 pin Microphone connector, and need to position it so that it doesn't reduce the x-travel of the carriage. It would be nice if your design had an obvious location for such a connector.

You mean something like THIS?

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

rhmorrison Wrote:
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> You mean something like THIS?

That's an interesting location for it, but it seems like you'd have to be very careful with your carriage design to avoid conflicts there.

Personally, I'm considering the area directly above the motor, between the motor and the filament, but since I'm currently using Greg's Wade as a starting point, that's a difficult place to put it.

I mounted to the wade LIKE THIS.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse