The "...in large enough amounts to enable 3D printing?" part of your question is, I think, still unknown, but spider silk has been being synthesized in transgenic goat milk for quite a long time already, and I suspect that it's now just a matter of time before the answer to your question is an unqualified "yes."

See 76. Macromolecules, 2011, 44 (5), pp 1166–1176, doi:10.1021/ma102291m

The "...in large enough amounts to enable 3D printing?" part of your question is, I think, still unknown, but spider silk has been being synthesized in transgenic goat milk for quite a long time already, and I suspect that it's now just a matter of time before the answer to your question is an unqualified "yes."

See Macromolecules, 2011, 44 (5), pp 1166–1176, doi:10.1021/ma102291m