Monday, November 25, 2019

Casting using Additive Manufacturing

So now off to get them made in brass.  We sent the CAD models to Shapeways and paid some expedited shipping to get them faster.  School was soon to start again!

First brass parts made using the CAD drawings.  First Shapeways 3D printed them in wax and then sent them to be cast via the lost wax process.  Each part goes through additional handling to remove any spouts and and overall brushing.  Later parts would be polished but not at first.
They fit!!  
It was an exciting day when the first parts arrived.  There were many things we needed to 'test' with these early prototypes.  First, would the pegs go through the holes!  Could we tap/smash the pin for the lids to keep them together and keep them rotating.  A big one was if the stopper peg could be bent over without breaking. That was a 90 degree bend and brass can embrittle (I won't elaborate on the metallurgy speak - but there were lots of discussions on this at home and with the brass foundry).  And the big thing - could we braise them together.

So now we get into 'David, your mom is weird and I like her'....David and I had to find some local braising help.  So let's jump into the car and go to an industrial welding supply place and learn things.  They found us funny.  David wandered the isles with huge eyes and begged for acetylene torches for his upcoming birthday while I discussed the intricacies of braising flux with the guys.   No, you can't have a huge torch as the other kids will play with your toys in the basement!!  And you can't have that in your dorm.  So instead we took off for a place my kids graduated to after the LEGO store - a place called You Do It Electronics.  This is a fantastic spot - like what Radio Shack was in the 50's I bet and the same guys still work there.  ha ha.  Of course they would have small hand held butane torches and the flux and
solder we were looking for.  Good enough for our tests and the torch was something that I gave him strict instructions to hide from the younger robot team which is full of 'fiddlers'.  (What's this?? Phoof!).

Give a teen boy a flame and they are happy.  So we spent a day in the basement trying against luck to put these pieces together.  In the end, it was ugly but they were together and we bent over the stopper without it breaking after different experiments heating things up.

Make-shift stand while we are trying to solder this inkwell together
Heating the pin.  This discolors the brass and may have been unnecessary as the cast brass was softer than rolled brass/

Bending the stopper pin over.
Ok, the first result.  Kinda ugly but we learned a great deal.  Not ready for prime time but a step in the journey.

So we had to do some modifications to the pieces, the walls of the bottom were just too thick and unnecessary and would drive up the cost.  So there was thinning of the model and trying to make the pegs still work.  We got on the phone with the brass guys and we all agreed that the round peg bent over just didn't look good at all if you knew what the originals should look like.  It just wasn't right.   So David had to go back and see if he could make a rectangular peg work.

Another round of CAD drawings, 3D prints at home, sending them off to Shapeways and weeks later a set comes back with some of our improvements.  This time I also remembered to have David make a version of the lid for the pounce pot too. Because of how 3D printing works, we were worried that the half dome wouldn't print well as it was unsupported as it prints but it was just shallow enough and small enough to work (we held our breath for the sample coming out of the bag).

Round 2 of 3D prints turned into brasses.  Note the rectangular pin now and you can't see the the base walls are thinner and thus takes less brass to make.

The pounce lid - it worked!!  If you look close, you might see the faint ridges around the rim that are the signs of 3D printing

So now it is a few weeks into school and David's roommate comes to see our place and the basement of wonderful toys.  David had lucked into the best roommate ever!  Someone who likes to tinker as much as he does and they were coming to squirrel away lots of tools and goodies from our stuff.  We actually have to search them when they leave and often while working on the robot and can't find stuff - we blame them and text.  "Yes... I took the soldering iron" (how did I miss that in the backpack!?).

So I had these pieces and asked the roomie if he knew about braising brass?  It wasn't long and they were both downstairs happier than pigs in s*it doing my work testing out the next set of prototypes.  These went much better and I was ready to start ordering blanks that were polished for the next test... engraving.

1 comment:

  1. What a life, Tricia, you have created for your boys!! I love reading about it.