Cost of Casting vs MIM vs Stamping vs Machining 3

[gciriani]

I am evaluating the possibility of utilizing investment casting when more cost effective. My parts are AISI 316L for luxury accessories (watchbands) and are typically machined from profiles. Typical dimensions are 20x8x4 mm, with tolerances +/- 0.05 mm, and mirror-polish finish. I know this is beyond the capabilities of Investment Casting, but still think there is some merit for complex parts for which tolerances can be relaxed a bit, and where some final machining can be done on the crucial details. We make at present some parts that take 2-3 minutes each to be manufactured by our CNC machine.

Some parts that are less tolerance demanding we already produce by stamping. Few times in the past we have utilized MIM, but this process has an intrinsic porosity that makes it difficult to reach our mirror-polish finish. Investment casting should prove a much better candidate for mirror-polish finish, and from a chart found at

http://www.daido.co.jp/english/products/casting/casting_applications.html

it would seem less expensive than MIM. Our production orders consist of about 20,000 to 100,000 parts.

In a previous occasion we have requested quotes for investment casting, with traditional pour. However, it would seem that counter-gravity, suction pour in air or vacuum, CLA or CLV, should have definite advantages. Does any one have additional indications on cost benefits of casting, and ball-park figures for percentage savings with CLA and CLV as compared to traditional casting?

I realize that this is a complex question, and I will post it both in the “Metal and Metallurgy engineering Forum” and “Steel Uses & Processes engineering Forum”.

 

[BillPSU]

If the time taken is a total of 2-3 minutes per part on a CNC machine I believe you should stay away from investment casting. Investment casting require many process and expensive equipment to make a part.

Investment Casting Process:
Make wax pattern
Make wax sprues
Attached wax pattern to sprue
Slurry base coat
5-6 Slurry plus refractory coats
Drying between each coat
Dewax tree
Sinter and preheat tree
Pour metal in tree
Remove part from tree
Cleanup

The labor time needed to make an investment castings is greater than 2-3 minutes per part.

 

[gciriani]

BillPSU, your considerations are an important starting point for the trade off. I'm thinking of using a very efficient supplier, one that perhaps can fit hundreds of parts in a tree. At that point you may be comparing 10 hours of CNC versus the operations that you just described.

 

[arunmrao]

gcirani,

Please also consider if the foundry is going to make an additional cost for L grade. Normally in conventional casting units to obtain L grade one needs to use the virgin charge to control carbon. However this is not the case in wrought or rolled products where due to AOD and other refining processes 316 grade also qualifies for 316L grade.

 

[bobdz]

an investment casting could be competitive at the 20,000 to 100,000 pieces per year and could possibly get a part to cost $1 to $3 depending on several things, mostly size and weight.
316L is very common and most cast it, but for your needs they should use certified ingot stock for cleanliness.

The CLA or CLV process makes sense and Hitchiner may be a good place to go to get a quote, they deal with high volume items. We use them and they do high volumes.
I have several other foundries that may be capable of doing this. Let me know if I can help.

Bob Dzugan

http://www.buyCASTINGS.com