This is what I did on a similar project at Armadillo, printed the
channels with FDM in ABS and then electroformed the closeout inside
and out. Then removed the plastic with an ultrasonic cleaner of warm
acetone, which worked surprisingly well at clearing out deep channels
of plastic. The minimum size of a workable engine is set by the
resolution of the plastic printer; an SLA printer would be much better
suited to getting good surface finish and small features.
An x-ray of the part showed that the thickness wasn't consistent, with
a thin area in the throat. Which for hoop stress is ok, but wasn't
intentional. I'm not sure what happened to the part after Armadillo
ended, maybe John or Russ has it.
Mixing the approach with spray deposition might be best of both
worlds: form the regen channels and then close out with sprayed
material for strength.
It is worth mentioning that SpaceX gave up on electroforming nickel
closeouts on copper chambers because the process was too slow. They
switched to explosion formed stainless closeouts that were brazed on,
though who knows what they're doing now. For a hobby project or a
government project slow fabrication processes are probably fine, for a
more agile commercial project it does matter if your complete engine
iteration time is a week or a month.
Ben
Ben
On Mon, Jul 15, 2019 at 12:56 AM Wyatt Rehder <wyatt.rehder@xxxxxxxxx> wrote:
On the getting the cooling channels into the chamber front. Would it be
possible to print the cooling channels into the initial form. Electroform the
channels and the exterior surface onto the form. Then as the secondary step,
remove/burnout the printed form; and then closeout the inside of the chamber?
Or is plating internal structures a no-go?
On Sun, Jul 14, 2019 at 7:11 PM Ed LeBouthillier <codemonky@xxxxxxxxxxxxx>
wrote:
Here's another reference that suggest similar values to what Peter has
suggested:
Modelling and Optimization of Copper Electroplating Adhesion Strength
https://iopscience.iop.org/article/10.1088/1757-899X/204/1/012017
