MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
you are the third person to say they find a rewinder useful without a MMU. It was not a use I had considered, but I am glad it is helpful to you.
You ABS print is the first one I have heard of and it is good to learn it was a success.
What revision did you print? The v1.1 shaft now has a chamfer thanks to rocky00717's suggestion. Does it need more chamfer, or did you print an earlier version?
50 grams is almost certainly not enough weight. 65 grams seems to be the lowest weight that works reliably based on the feedback I am hearing. You should try some weights between 70 and 90 grams.