Molding using a Follower
Here is a part that I need to duplicate. The original is made from two pieces.
The arm is cast and the knob is turned and pressed in. My part will be cast in one piece, useing the original for the pattern.
To cast this in one piece it is necessary to use a parting plane that lies on the axii of the knob and the square hole.
If I only had to make one, I would simply ram it in the drag and carve the sand away to the parting line (cope it out) and then ram the cope.
But, I need to make many, so to save time and effort I prepared a follower, sometimes called a false cope.
I will use a core to create the square hole so I need core prints in the mold.
This square brass bar will leave the necessary core prints in the sand.
Here is the pattern in the plaster follower I prepared.
As you can see, the plaster comes up to the parting line.
Since it simulates the sand in the cope, the first sand rammed in the drag will share this parting line.
The follower and drag are placed on a board and then the sand is rammed as usual.
Here is the drag rammed and rolled with the follower still in place.
The follower is removed, leaving the pattern in place.
A screw hole in the back of the follower is useful, but most times I just dig into the sand a little around the edges and lift it out.
Smooth out any lumps and bumps in the sand and give it a generous dusting with parting compound and you are ready to place
the cope and ram it up.
Here is the mold with sprue and gate cut and the core in place.
After the usual dusting off with the air gun the mold is closed.
(Next batch will have the sprue and gate on the opposite side where clean-up just has to be easier!)
Here are some finished parts in silicon bronze with the iron original.