Circular gaps, only occurs when printing small gears for extruders

Hi everyone,

I have a Prusa i2 which has been successfully printing for a while now, but I've noticed a problem.

One of the first prints I tried, months back, was a small gear for a Wades extruder. It had an odd problem where the teeth would have a small, about 1mm, gap from the inside of the shaft. This being the only print this happened on, I forgot about it.

Recently I've been wanting to print some new herringbone gears, but when I printed the small gear, the problem happened again.

Seeing as it has happened on two different gear STLs (plain and herringbone) and at various fill densities (I have tried 100% fill).

Attached picture is of the recently printed herringbone gears.

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-Richard

[tynan.me]

Hi there. Just curious, but what slicer program are you using?

I only ask because I was encountering similar issues with gaps on the top layers when small perimeters are involved (like the small gears) when using Slic3r. I fiddled with the settings but nothing I tried would change anything. When I slice the small gear using Cura, the solid infill at the top is much more robust, filling all the gaps completely. I'd suggest trying a different slicer and compare the results. I'm still pretty new to this, so just trying to help by throwing out a suggestion that worked for me.

Here's a comparison picture. The gear on the bottom looks similar to your issue...it's a Makerbot gear (printed on accident, shaft hole is much too large) sliced with Slic3r. The other two gears are normal small extruder gears, the one on the right sliced with Slic3r and the one on the left sliced with Cura, identical settings otherwise.


Edited 1 time(s). Last edit at 08/19/2013 12:39PM by mycarlooksfast.

I am using Slic3r, yes. That looks like it could be the problem, the bottom gear looks identical to one of mine. I'll try a different slicer soon, as my extruder is currently broken and waiting for parts, and then post back.

Thanks!

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-Richard

[tynan.me]

Thanks mycarlooksfast, good problem I.D..
I borrowed your image for the PTPG [www.reprap.org]
.

try playing with the solid infill setting in slicer, say 0.2mm to start with, see if it fills it. Also check you solid infill threshold area setting ( I think default is ~70)

A quick way test different silcer settings before printing, is to slice and then load into Repetier, run through the layers in the model and see if the new settings are having the desired effect, can save a bit of plastic & time.

Hi rptynan! You can solve the problem reducing "Perimeters (minimum)" to 1 in the case you are using a height 0.4. If you use for example 0.2, then you need to reduce extrusion widths under "advanced > extrusion width". Try 50% in infills.

That small gear must have a 100% infill, i suggest circular, but try rectilinear too.

Regards,
Pato

Edited 1 time(s). Last edit at 09/24/2013 05:36PM by patriciorivera.