Casting Multiple Parts from a Single Pattern

I have been using bound sand (both resin and sodium silicate based binders), and if I set up the flask in a mirror-arrangement, it saves me from having to make multiple patterns when I need more than one part cast.

Here is an example of a cylinder mold that was mirrored, and made from a single pattern and snap-flask.

Both molds and cores that are made from bound sand can be cemented together in any number of configurations, and risers can also be made separately and cemented on top of the molds if necessary.

Bound sand is a very flexible way to make molds, and it also produces a much more accurate part since there is no shifting of the sand during the ramming process (since the sand sets), and no changes in the part size due to rapping on the pattern to remove it from the sand.

Although I generally use between 3% and 5% draft angle on parts, I have actually had a good bit of success with parts that have no draft angle (due to an oversight when making the pattern). The worst case has been a slight breakout along part of the top edge, which creates a bit of flash that can easily be removed.

I use a slide hammer to break the pattern loose from the sand, with a light tap on two sides of the pattern to break it loose. A good wax of the patterns after each use is also important with bound sand.

For core making, slit a piece of PVC down one side, fill it with bound sand and harden.
Pry the slit open slightly to remove the core.
No need for a two-part core box for cores.

 

Very nice. What kind of temps can the bonded sand take? Will it hold up to Iron?

 

That particular sand used resin-binder, and it is designed for iron, and works great with it, with an excellent finish.

I am transitioning to all sodium silicate binder, and I am told that SS also works pretty well with iron, but I have not actually tried it.
The SS does not have the fume issues that the resin binder has.
I have some SS that works with a catalyst, so it works just like the resin binder.

I also still use CO2 hardened SS, when I am in a hurry.

 

I still have my homemade SS, the only way it will set up hard is by baking it. Then it gets as hard as a rock. CO2 gets it hard enough to remove from mold but it's still too soft.