Re: [CAD_CAM_EDM_DRO] cast iron

Hello Carlos, and Dave:
You are definitely right. In order to get the stress out of big casted pieces You have to age them.
If not after or even during the machining they will twist (sometimes like a bow).
This process can take sometimes a lot of time as bigger the part as longer you need. In lathes Haidenreich und Harbeck near my hometown
back in Germany took 3 to 5 years for
2 meter lathe bodies
A few years ago I had to rescrape a Taiwanese Drill mill. I could not believe it the cross slide
10 inch wide and 3 inch high swivelled on the marmol plate 0,4mm (0.016").

When I have to hurry a casting or need to get rid of stress in long steel bars before machining
I put it into the kitchen oven at 250° to 280° Celsius for 2 to 4 hours and let them cool down slowly
afterwards. This way I was able to make my own calibrating prisms of 45cm with 2 deep V grooves.
They bent only 0,02mm before grinding and after scraping it lasted now 4 years without any further bending.
Also 13 years ago I had been in a factory for 4 meter long rotating industrial scanners. They were the first user of the material what
nowadays is used for machine beds. (they called it artificial concrete) Before that they had to cast 4 years before being able to
machine. With this new material after
4 days the casting was definitely settled.

Hope that helps
Sven Peter

dave engvall wrote:

> Carlos Guillermo wrote:
>
> > List -
> >
> > I've got some questions about some castings I'll be having made soon. There
> > was recently some mention of aging the cast iron before machining, and I'm
> > wondering, how long one should let it age?
> >
> > Carlos Guillermo
> > VERVE Engineering & Design
> >
>
> In Moore's "Foundations of Mechanical Accuracy" pg. 17.
>
> A. proper composition of the iron........ I think implies meehanite
>
> B. "Stability of iron depends mostly on slow, uniform cooling in the mold after casting."
>
> Further down the page the author talks about a Moore jig grinder that had been thru a fire. Melted the aluminum guards. After a
> solvent cleanup. "there was virtually no deviation from the original factory calibration".
>
> HTH
> Dave
>
> p.s. I have heard about shops leaving there casting out in the weather for a few years to age before using them. I suspect Century
> (lathes) did that from the mess behind their shop.
>
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