Die Cast Mold

[IdeaMakers]

Hi All, looking for comments and opinions on making a die cast mold for beads that I use. Here's some photos rendered in VCarve of how I think I'll mill the mold but any suggestions would be appreciated.

   

   

Basically this is two pieces of cold rolled steel (4" x 6" x 5/8") and I'm using a 1/4" endmill and ball nose. The rows in the middle are round beads 1/2" in diameter and I'm using a fluting path with a 1/4" ball nose to go a 1/4" depth over a 1/2" length. The rows at the top and bottom are a triangle shape using the same ball nose with a fluting path running from an 1/8" to a 1/4" over a 1/2" length. The channels connecting the beads are 1/8" deep and 1/4" wide and the pour channel in the center is 1" wide by a 1/4" inch deep (1/2" inch when put together).

The thought is to pour metal down the center to flow up the side channels removing the air as it goes up. The beads would then be cut out and a center hole would be drilled. I've milled the surface flat on my cnc and being cautious with it I can mill 0.001 at 70 inches a minute without to much fear of breaking the bit.

I know the large mill at SC could probably go a little faster but only being able to use it 3 hours once a week it would probably take a month to complete, where as I can mill over a 2 week period without driving the neighbors to crazy.

Any thoughts on the design and function of the mold? Being the first one I've tried to make I in that familiar unfamiliar space of doing something new.

John

[ABearden]

Alignment pegs will help with product quality. Multiple pry gaps along the edges will help with release without messing with the sprue surface. Not having a flat "bottom" (to the right) on the sprue would increase material pressure when pouring. Tapering out the top of the sprue will make starting the pour easier. ...and that's as far as my very limited molding knowledge goes.

Aluminum beads?

[IdeaMakers]

Thanks for the suggestions ABearden. I did add some slots for prying the mold open and did have register marks just not shown in the render. Was able to make good progress today, milled the beads out and the channels connecting to the middle pour channel. Started to mill the pour channel also but after two hours and only an 1/8" deep decided I'd give the neighbors a rest. Not sure I can open the pour channel to much more, like to keep a 1/4" of metal between the pour and the outside of the mold at least.

Thanks again, John

[ABearden]

Can't wait to see how it turns out!

[IdeaMakers]

Well the 1/4" end mill is getting a bit worn so had to stop a little short on the pour channel but I think the milling turned out very good.
   

First fire, trying to heat the mold on the furnace. Firing at Dusk always has a nice glow.
   

Like the Blueing but the mold needs to be hotter
   

Mold over the center of the furnace opening
   

Unfortunately not enough clamps on the mold and it began to separate from the heat. By the time I had another clamp on it the metal was ready to pour But the mold had cooled. Got a couple of beads though.
   

With a few modifications I think this will work well. Need to open the bottom U channel to let hot metal flow easier and flare the top also. but so far so good.

[ABearden]

That looks like a great test run.

[Dan]

Super close to having something you can use for production.

your mold looks awesome

[IdeaMakers]

After milling the mold more to open the bottom to let hot metal pool and the top to make it easier to pour, try 3 resulted in only two beads. The ones on the right of the photo are the newest, better alignment of the mold and a little better shape.

   

For try 3 I placed the mold upside down on the furnace trying to heat the mold top to bottom. So for try 4 I placed it right side up trying to get heat into where the metal would pool. Cracking open the mold to peak in I could see there were still only two beads formed. Under the heading of "It seemed like a good idea" I clamped up the mold with C clamps and placed the entire mold into the furnace hoping to melt the copper and let it flow through the mold. The result, a couple of ruined C clamps and two pieces of steel welded together with cooper.

   

The C clamps couldn't hold up to the heat and thus the mold split apart and copper ran out. Back into the furnace with it all to try and melt the copper again and get the pieces apart. I'll pretty much have to remill to flatten the pieces and then back over everything to clean out the remaining copper.

   

So time to rethink the whole idea, begin with something smaller and less complex to see what happens.