Switched to a new green sand mix for a big job and the cores crumbled

We had a rush order for 50 cast iron flanges and I swapped our usual bentonite blend for a 'fast-bond' type I saw online. After ramming up, the cores just fell apart when we tried to lift them... like dry cake. I learned that saving an hour on setup can cost you a full day on scrap. Has anyone found a good middle-ground mix for high-volume work that still holds shape?

3 comments

3 Comments

xena_kim26d ago

So what was the actual moisture content when you tested it? Those fast-bond mixes often need way more water than the bag says, especially in a dry shop. Did you do a squeeze test on a handful before you even started ramming, or just trust the specs?

vera_lewis27d ago

Ugh that's the worst. Did you try adding ANY extra water or binder to the new mix before you rammed it up, or just go straight from the bag?

charlesb8914d ago

Yeah, those fast mixes are tricky. We run a 70/30 blend of our old reliable bentonite with the new fast stuff, and we always add about 10% more water by volume right in the mixer. You have to get it to where it just barely sticks together in your fist without dripping.