[Replicator] issues with print support

[Andy]

Howdy folks..

Whenever I print with support I get areas of the support where the extruder doesn't seem to be putting out enough plastic, or stops extruding too early.

I've outlined the section I'm referring to here:
http://db.tt/id3mp7dR

Another pic of bad support:
http://db.tt/83WG36u9

It seems like because the support isn't getting enough plastic the problem magnifies as more layers are printed. Eventually parts of support come off, stick to the print head, and mess up parts of the print or other areas of support.
I printed this model twice, once with the filament set to 1.8mm diameter, and a second time at 1.76mm. I was hoping this would help, but they both have the problem. (each pic is of a different print attempt)
When I print without support, prints usually turn out great. The issue only shows up when I need/use support.

I'm mostly using default print settings with only the changes below:
.2mm layer height
20mms print/travel speed
Printomatic
firmware 5.2, so no acceleration.
1.8mm or 1.76mm diameter filament setting.

Any tips?
Could this be related to my (default) retraction settings?

Thank you!
-Andy

[PropellerScience]

On a positive note your model looks awesome (as seen through the
support material)!
I have the exact problem, and I haven' addressed it yet, so I'd like
to join you in this thread.
Usually the extruder makes wisps of plastic until it builds up, that
gets tangled in the model. It seems like it's going too fast to me. It
just zips here and there, leaving strings as it goes. The first thing
I was going to try was slowing it down when it's laying down support
if that's possible. I don't want to raise the heat because I don't
want the support to become a permanent part of the model.

[Shawn]

Can't say this with authority but...

I saw those sorts of problems early in my printing experiences. My
first crack at using supports was the one piece Serenity model. It came
out pretty badly and showed symptoms similar to what you have (among
many others). But I was still pretty inexperienced then too. When I
took the time to re-level the platform properly all those issues
disappeared and subsequent prints with supports work out as expected.

Failing that, check the general tuning of your repG settings. It might
be as simple as adjusting the filament diameter to make sure you get the
right amount of plastic coming out.

Not sure how much help that is, but here's hoping you can solve this.
Don't forget to report back what your fix was, please.

Shawn

[Joseph Chiu]

I noticed that your raft looks like a big "waffle grid", rather than the tightly spaced raft that I am used to.  I think that may be causing your supports' first layers to not get anchored in the right place.    (Take a look at the raft from my prints for comparison: http://cdnbakmi.kaltura.com/p/695492/sp/69549200/thumbnail/entry_id/0_oizm5eua/width/1024/height/768 )

Perhaps that's the first step in solving this problem?

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[Andrew Russell]

Thanks folks for the suggestions.
re: leveling/tramming
I'm using the leveling jig with a micrometer:
http://www.thingiverse.com/thing:23257

Heres an example of a raftless print of the famous owl:
http://db.tt/0pHkgK74
It was printed after leveling with the jig, using the same
print-o-matic settings as the print in the previous pics, but with a
25% fill vs 10%.

My next steps will be:
* print an object of measurable dimensions (a cube) and validate the
print is the proper size, or at least very close.
* print this thing and see what issues it uncovers:
http://www.thingiverse.com/thing:21268 (I already know my two
printheads are not level, looks like I'll be fixing that tomorrow :) )

I'll definitely report back once I've solved the issue... Hopefully I can! ;)

thanks again for the support,
-Andy

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[Andrew Russell]

Just a question regarding gantry alignment.

I was reading this page about the calibration print:
http://www.makerbot.com/docs/replicator/calibration-print/
Specifically the section about the squiggle that tests for gantry alignment.
Homing my print heads now, I'm only seeing the light on the X endstop
light up, but not the light on the Y endstop.
When the print heads are homed, should both endstops light up? Or I
guess I should ask, when YOU home your print heads, do you see both
endstops light up, or just the X endstop like me?

This page doesn't say anything about the endstop's LEDs lighting up
when calibrated, so I'm not sure it matters.
http://www.makerbot.com/docs/replicator/gantry/

thx!
-Andy

[Andrew]

I was able to sort this one out.

It came down to the restart extra distance value:

skeinforge>dimension>restart extra distance.

A picture is worth a thousand words so here you go:

http://db.tt/0tFODAgI

(the image is 3megs, I didn't want to attach it to this msg for the mobile/email readers out there)

The only differences in the before and after prints are:

* restart extra distance changed from its default -0.2mm to 0.0mm.

* filament diameter changed from 1.8 to 1.79mm

I don't think the filament diameter change affected the support and print holes, but it did seem to help my 1st layer of raft stay a uniform width.

If I run into any issues where objects are printing worse because of these changes, I'll note it in this thread.

Hope this helps people in the future!

-Andy