The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Lamination in Aluminum Diecastings

2002

I work for a diecasting company that makes transmission cases for automotive OEMs. We are currently seeking a finishing process that will remove lamination (or delamination depending upon your terminology) from aluminum diecastings. The lamination is typically at the bottom of a hole that is an inch in diameter (25mm) and approximately 3-4 inches deep (75-100mm). The lamination is an onion peel layer of aluminum that isn't removed in our current shot blasting process.

Please respond with ideas or suggestions, I would be deeply grateful!

Thank you.

Adrian Cole
diecasting. - Shelbyville, IN, USA

---

Very interesting quandary, let us know if any suggestion works out. But I don't think you are going to find a chemical or electrochemical answer. My first thought would be to end mill the hole, removing the skin in question whether it has onion peeled or is still adherent.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

---

If you are not talking about a lot of volume and only a specific location that has to be worked, what is wrong with drilling hole or holes? Most inexpensive mechanical processes will not work unless the abrasive or media can get into work area and then the abrasive must apply pressure to that area in a controlled pattern.

AF Kenton
retired business owner - Hatboro, Pennsylvania

---

How about a) modifying the dynamics of the injection stroke, or (b) modifying the die, or (c) both of the above, so that the defect doesn't occur in the first place?

Bill Reynolds [deceased]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.

We are trying to modify the tooling to eliminate the source of the problem but I just wondered if there was a specific finishing process to deal with this. Additionally, it is not possible to drill the location, this would be in violation of the customer print, but thanks for the advice regardless!

Adrian Cole
diecasting - Shelbyville, Indiana, USA

Why not try a profile on the tip of the core , such as a wave or cross-hatch, even a full semi-sphere.

Alternatively keep the core hot so that the injecting molten metal doesn't set and form laminations on the core. Another alternative is to use a ceramic core or simply coat it with ceramic coating as in gravity diecasting, wish you luck.

Regards,

ALAN BUTTERWORTH
CASTINGS - BACUP, LANCASHIRE, ENGLAND

---

Lamination problem most common for thin section castings as well as specific thick section parts. In your case I think air entrapment is the problem , you have to provide better system for effective entrapmant in the die as well as concentrate the molten metal cleaning process. can have a photo copy of the issue.

Thanks,

S.K.Elengo
- Coimbatore, Tamilnadu, India