Troubleshooting a lifesize skull print

[christax3d]

Hello all,

I'm a new user to the forum and I've been using Simplify 3D for about 3 weeks now (finally found this - http://forum.simplify3d.com/viewtopic.php?f=8&t=2367). I'm not new to 3d printing but I am having some difficulty narrowing down a few consistent issues with this full size child-skull print. I'm attaching photos to showcase these issues:

Using the MakerBot Replicator 5th Gen
1) "Stitching" pattern evident in a loose line on the front-right forehead area
2) Overall "skipping" sort of pattern as evidenced by intermittent small gaps in the perimeter and a strange texture "bumpy" texture in some parts (especially the back-right of the skull).
3) Cleaning off these supports is always a chore. How can I create settings to allow for the easiest clean up without sacrificing too much support? I need to make sure the arch of the top of the skull is supported, but can I avoid an arduous support clean up process? I've been painstakingly adding manual supports by visually analyzing layer changes in the z-axis because I prefer to cut down on the print time as much as possible. I figured auto-generating supports is a good start to take care of most of my 45+degree overhangs, then I can eliminate ones where I know the printer can handle it without supports after seeing the prints come out.
4) How can you cleanly change between different resolutions throughout different process changes? Right now we get tell-tale stripes that show one resolution change to the next. Am I extending to far to think that there should be a way to neatly swap between resolutions on a MakerBot Replicator 5th Gen?

Here is the link to the factory file and attached are some snapshots of the printed results after removing supports. On the top of the skull we had to use a rotary tool to get it off cleanly, but if possible I'd rather everything be done by hand or with a simple pair of pliers.

http://www.megafileupload.com/19vA/Brac ... _4.factory

Already Simplify 3D has given some good advice (thanks Joey!) -

"The stitching below tends to be remedied by a few things. I would suggest increasing your retraction distance slightly in the Extruder tab, then also adding a small wiping distance and coasting distance."

The recommended changes in Ooze Control were:

Increase Retraction Distance from 2.00mm to 2.5mm
Turn on Coast at End with a Coasting Distance of 0.20mm
Turn on Wipe Nozzel with a Wipe Distance of 5.00mm

...I had tried turning on Coast at End with a coasting distance of .20mm but not in combination with these other changes so we'll see how the next skull print goes. I was wondering how much turning on the feature to start perimeters randomly would have to do with this. I tried making them random but I saw no visible difference in the "stitching" pattern we keep getting. Any additional advice is greatly appreciated and I hope I've been clear in framing my questions. Please let me know if any further information is required to assess the issue properly. Thank you!

[JoeJ]

I'm actually already surprised you have gotten that good of quality prints from the 5th gen printers! Their extruders have some issues that can make it pretty tough to get consistently high quality results. So you're already off to a really good start!

For your #4, sometimes you will see the resolution change just because of the solid layers that occur at that interface. For example, when process 1 ends and process 2 begins, you will print the top solid layers from process 1 and then the bottom solid layers from process 2. When printing these solid layers, many times the speed will change due to your cooling settings. Sometimes that can be seen visually depending on the plastic you are using. So if you really wanted to get rid of that, you could try disabling cooling speed slowdown or maybe even decrease the number of top/bottom solid layers at that interface.