Investment casting - Parts bends during casting process
Investment casting - Parts bends during casting process
(OP)
Hi
I have a problem with die-casted stainless steel(316) parts, that tends to bend during the casting process. It resolve in a lot of work on the parts afterwards to fit the tolerances. My idea is that the bending has something to do whit the cooling process. Hope someone can explain to me what might cause this problem.
I am new to investment casting, and the chinese suplier of cast parts my company use, seems to have a lack of knowledge about the process.
If any further informations is needed please ask.
Michael
I have a problem with die-casted stainless steel(316) parts, that tends to bend during the casting process. It resolve in a lot of work on the parts afterwards to fit the tolerances. My idea is that the bending has something to do whit the cooling process. Hope someone can explain to me what might cause this problem.
I am new to investment casting, and the chinese suplier of cast parts my company use, seems to have a lack of knowledge about the process.
If any further informations is needed please ask.
Michael





RE: Investment casting - Parts bends during casting process
RE: Investment casting - Parts bends during casting process
If these are investment castings then you may need to modify the pattern so that the part starts bent the other direction. If you try to stiffen it so that it does not bend it may crack or tear.
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Plymouth Tube
RE: Investment casting - Parts bends during casting process
RE: Investment casting - Parts bends during casting process
Depending on the part geometry, it is likely to be either wax deformation, which is easily solvable by putting in dimensional checks in wax; improper allowances for change of shape/size between wax and metal, which is much more of a trial and error process, contact an experienced die-make; or deformation on cooling. Since 316 is fully Austnintic, it is not as prone to bending during cooling as other steels, so if the parts are fairly small it is unlikely.
Finally, consider that if you are finishing/machining the surfaces of the part post cast, especially without a stress relief cycle, the parts will bend because of this.
What a surprise, a Chinese foundry with a lack of technical knowledge. First time I've ever heard that...
RE: Investment casting - Parts bends during casting process
Basically, a wax form is coated with ceramic slurry, which is then baked and filled with molten metal.
After which, the ceramic must be removed from the finished part, by blasting or tumbling or, uh, beating the crap out of the part with a hammer, which may be an integral part of your vendor's process.
I.e., if the part is at all delicate, it may be distorted by the shell removal.
Mike Halloran
Pembroke Pines, FL, USA
RE: Investment casting - Parts bends during casting process
the most important of them are distortion in was pattern and distortion during solidification.
Preventing and repairing of distortion of was pattern is easy. Using specific fixtures and pre-inserted wax parts and also using ceramic parts as positioning parts can be useful.
however, the great amount of distortion takes place during solidification.
1- Increasing superheat or pouring temperature
2- Increasing ceramic mould preheat temperature
3- Having junction of long and thin sections to a thick section which causes non-uniform thermal gradient. (in this case using insulation cover or chill plate and even using different ceramic shell thickness in different areas can be useful)
RE: Investment casting - Parts bends during casting process
RE: Investment casting - Parts bends during casting process
RE: Investment casting - Parts bends during casting process
Assuming that the method of knock off is not "crack the parts with a hammer" there is rarely any distortion during the process. Most people have the good sense to hit the runner instead, and certainly not to tumble off delicate parts.
Just thought I should comment that, since installing basic gauging in wax, the parts made in the foundry I work at have shown a 75% decrease in scrap for distortion.
And a friend of mine made similar progress using wax setting blocks (his place was making femoral implants)
RE: Investment casting - Parts bends during casting process
What are your performance rules and who is monitoring them on all shifts over there by all people working with each mold over there every time? What training is being done when newbies come in very week from the rice field and the potato farm? So to speak, that is. 8<)