Tried a new sand mix for our greensand molds last month and got a wild result

We were running low on our usual bentonite clay binder, so I mixed in about 20% of a different brand of fire clay we had left over from a refractory patch job. I figured clay is clay, right? Wrong. The molds held shape fine for the pour, but the knockout was a nightmare. The sand stuck to the castings like glue, especially on a batch of small bronze gear blanks. It added almost an extra hour of cleanup per pallet. Some of the guys think I should have known better and stick to the proven recipe, but others say experimenting is how you find better methods. Has anyone else had a binder substitution backfire, or found a good backup mix when your main supply runs short?

2 comments

2 Comments

abbyk102mo ago

Our shop tried a 15% fire clay mix last year and it fused to the aluminum castings.

barbarahill2mo ago

Been there, swapped bentonite for kaolin once and ruined a whole batch of iron fittings.