Not me, the boss.
We just rejected another batch of frame cut because they can see the “bump” where the frame lead in.
Keep this up, I’ll need to find another job.
Can’t machine anything without material.
I assume we are dealing with sand castings here and not investment castings.
Sand castings are notorious for having extra material all over the bloody place.
Do your customer drawings for the castings have cast datums that you are supposed to use for machining purposes for the 1st operation?
If not, then I would suggest you get with your supplier and define some (assuming your customer allows it). Then make sure that gates and other areas that cause a lot of variation are not near these cast datums (again, assuming your customer allows it).
as Fred mentioned,…it does sounds like a harder outer shell layer (skin) on the casting - sand …apply moisturizing cream😄
At present it looks like we’ve chosen “Avoid those vendors” which leaves us with only one for hundreds of castings which does not leave me with warm and fuzzies.
That being said we definitely need to tighten up our casting drawing specs in about every fashion, material call outs, hardness, gate location, casting datums etc etc etc. Right now our drawings are little more than “Well make it generally look like this”…and generally, not surprisingly, that’s what we get.
I’ve been involved with sand casting issues for years. Biggest issues have been from castings from China. However, there have been issues with castings the company I worked for has poured as well, which I think sometimes has to deal with if they are using purchased ingot or re-melted castings. From the manufacturing side: Hardness test, material analysis, tooling geometry design & coatings, feeds & speeds all play a roll. From the foundry side: pattern layout, gating & risers have also made a difference. Even fixturing (how the casting is being held during machining has made a difference.) The best information I’ve gathered is from experienced tool designers, foundry personnel, setup people & operators who pay attention to details.
We are pretty solid on the manufacturing/Fixturing side. What we don’t have is “Casting Expertise”. It’s obvious, in manufacturing and even visibly, that castings from some vendors are not the same as other vendors despite the same material call out, specs etc.
I can walk into a room of our castings and pick out “Good Vendor” and “Not so good vendor” from 10 feet away by surface finish, casting color/discoloration, extra material/lack of material and so on. Chips coming off of one casting are significantly different than the other using the same tooling, speeds feeds etc. Tool life is significantly different as well.
This is also not an issue with “Just one” vendor but in fact we only have one out of half dozen we’ve used over the years that has NOT had similar issues. So “the one” apparently has some trick that makes their castings exceptional by comparison, at least for our application.
These are all sand castings, not investment casting.
It’s usual for Us to request laboratory cylinder for make test about chemical composition or brinell hardnees requirements.
We buy in some companies about the world like Brasil, China and Argentina too. Not always has issues about casting type, but if the casting it’s a little bit more hardener the cost of the bits for milling is on the cost of the supplier.
But we usually uses DIN/EN GG25/GGG60L or GGG70L not another ones. Wich one did you buy on your components?