Why I skip mold pre-heat on short run casts

I know most people say you must pre-heat molds to prevent cracks. But I think it's not always needed for small jobs. In our foundry, when we do batches of less than a hundred, we pour right into cold molds. For instance, with aluminum sand casts, we've had no issues if the metal is hot enough. This cuts our setup time by half. Some coworkers disagree, saying it risks quality. But in ten years, I've only seen two cracks from doing it this way.

3 comments

3 Comments

noah_kelly601mo agoMost Upvoted

You say you've only seen two cracks, but that still means it happens sometimes. Isn't pre-heat worth it to prevent even those few defects?

noah_kelly601mo agoMost Upvoted

Honestly skipped pre-heat on a small patch job last summer to save time. Big mistake. One hairline crack showed up a month later right along the weld. Now I just do it every single time, even for the quick fixes. It's boring but way less boring than doing the whole job over again.

nancya581mo ago

Yeah that right there would change anybody's mind. Used to think it was just extra fuss for thick metal until I saw a friend's repair fail the exact same way. Now it's just part of the setup, like grabbing your helmet. Takes a few minutes but saves a whole lot of cussing later when the weather changes.