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?

3 comments

3 Comments

abbyk103mo ago

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

claire37827d ago

Maybe the real issue isn't the clay but the grain size difference messing with compaction.

barbarahill3mo ago

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