Print in-place enclosed movable parts - gap size?

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Print in-place enclosed movable parts - gap size?

MichaelAtOz
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For those who have done a print with enclosed moving parts (e.g. hinge), what size gap have you had success with FDM/FFF filament printers?

I've done a couple on Shapeways, with less success at close to their recommended gap (0.5mm for S%FP, 0.05mm FUD), with 0.53mm & 0.10mm gap respectively they were delivered fused (including a reprint in S&FP), they say they should be able to do both those gaps properly...3rd time lucky...

Anyway, I'm wanting to do design a similar STL for FDM/FFF, what gaps are a good size? Detail of nozzle size/print setting if they needed tweaking would be handy to. I'm trying to make a STL gap as generic as possible without being too lose.
(the shape with be cylinder with a shoulder/recess where the enclosing part with a cylindrical hole wraps around inside the recess)

Thanks.
Admin - PM me if you need anything,
or if I've done something stupid...

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Obviously inclusion of works of previous authors is not included in the above.


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Re: Print in-place enclosed movable parts - gap size?

ednisley
On 07/04/2017 08:01 PM, MichaelAtOz wrote:
> what size gap have you had success with

When I was printing chain mail, I used two thread widths (0.80 = 2 ×
0.40 mm) between adjacent bars and 3 thread thicknesses (0.75 = 3 × 0.25
mm) between overlaid bars. Tighter spacing caused some links to stick
together, at least weakly, and I didn't want that problem in sheets with
several hundred links:

https://softsolder.com/2014/12/05/3d-printed-chain-mail-armor-170x230-mm-sheet/

That's with a 0.35 mm nozzle, (manually forced) 0.40 mm thread width /
0.25 mm thread thickness, neurotic attention to platform alignment &
initial Z-offset, but no fancy slicing setup for either PLA or PETG.

The link caps require relatively long bridges across the lower bars. The
hot plastic has plenty of droop that tightens up as it cools; the 0.75
mm air gap prevents bonding to the lower bars before it shrinks. A
shoulder / recess without much overhang should be do-able with two
threads of clearance.

PLA may print cleanly enough for 1.5 thread width clearance in XY, but
I'd definitely run many small test pieces before depending on it. PETG
tends to produce hairs between parts, although the smallest chain mail
came out well with 2 thread clearance:

https://softsolder.com/2015/04/02/miniature-petg-printed-chain-mail/

 From what I've seen, many (most?) DIY-grade printers aren't
well-calibrated: aggressively tight spacing won't spread happiness.

--
Ed
https://softsolder.com

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Re: Print in-place enclosed movable parts - gap size?

codifies
In reply to this post by MichaelAtOz
depends on material, I found that PLA and PETg needed different
tolerances but then I print PETg without fans (great stuff PETg)

I basically ended up making a print with 4 (was it 6) holes and tried
them with a printed "pole"

bare in mind what will work for you may not work for others due to
different fans, temperatures, layer height etc...

On 05/07/17 01:01, MichaelAtOz wrote:

> For those who have done a print with enclosed moving parts (e.g. hinge), what
> size gap have you had success with FDM/FFF filament printers?
>
> I've done a couple on Shapeways, with less success at close to their
> recommended gap (0.5mm for S%FP, 0.05mm FUD), with 0.53mm & 0.10mm gap
> respectively they were delivered fused (including a reprint in S&FP), they
> say they should be able to do both those gaps properly...3rd time lucky...
>
> Anyway, I'm wanting to do design a similar STL for FDM/FFF, what gaps are a
> good size? Detail of nozzle size/print setting if they needed tweaking would
> be handy to. I'm trying to make a STL gap as generic as possible without
> being too lose.
> (the shape with be cylinder with a shoulder/recess where the enclosing part
> with a cylindrical hole wraps around inside the recess)
>
> Thanks.
>
>
>
> -----
> Admin - PM me if you need anything, or if I've done something stupid...
>
> Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above.
>
> The TPP is no simple “trade agreement.”   Fight it! http://www.ourfairdeal.org/   time is running out!
> --
> View this message in context: http://forum.openscad.org/Print-in-place-enclosed-movable-parts-gap-size-tp21774.html
> Sent from the OpenSCAD mailing list archive at Nabble.com.
>
> _______________________________________________
> OpenSCAD mailing list
> [hidden email]
> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org


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Re: Print in-place enclosed movable parts - gap size?

shadowwynd
In reply to this post by MichaelAtOz
This is my experience also.  I had a working gap in my model, changed filament (all other parameters same) and the part was fused together.  Make a simple "test" model (simple pin hinge, etc.) and try.  This is actually one of the cases where OpenSCAD dominates hands-down - you can make sub-millimeter adjusts, print, tweak values, print, etc. until things come out "right" on your printer, with your filament.

There is a very fine line between "loose" and "fused".