Re: concrete/molded structural elements

Hello,
I know that concrete type material(Granitan ) is\was used extensively
instead of cast iron castings for the beds of high precision grinding
machines. Also, I have have seen grinding colums filled with similar
material for vibration damping during the grinding of tungsten carbide.
Hope this is of some use.

Regards
John- recent member of the lurking clan




-----Original Message-----
From: DAFcnc <DAFcnc@...>
To: CAD_CAM_EDM_DRO@onelist.com <CAD_CAM_EDM_DRO@onelist.com>
Date: 31 May 1999 08:23
Subject: Re: [CAD_CAM_EDM_DRO] concrete/molded structural elements

>From: DAFcnc <DAFcnc@...>
>
>> Message: 2
>> Date: Thu, 27 May 1999 07:30:06 -0500
>> From: groehm@... (Geoff Roehm)
>> Subject: concrete/molded structural elements
>>
>> Mike Romine
>> wrote:
>>
>> >My CNC is fairly stiff for what I am doing, but I have a huge problem

with

>> >vibration. I am using aluminum and steel extrusions and box channel for
>[]
>> >I think I am going to try to fill my hollow structural parts with a
>> >reinforced polymerized concrete.
>>
>> Not being an engineer, I ask your indulgence if this suggestion is
>> stupid, but how about foam-cored structural members, molded from a
>> Corian-type material? Advantages would be lightness and easy machining
>> with common tools, but would they be strong enough? Would the foam
>> cores help to "increase the damping coefficient" of the
>> material/structure?
>
>I saw formula once for strength in tubular structures, something to do
>with the difference between the outside and inside diameters, and the
>conclusion was that filling a strong walled pipe (in that case it was
>carbon fibre reinforced plastic - used in kites) with lighter, weaker
>stuff (foam?) would not affect the bending coefficients much at all.
>
>So I think your molding will need interior struts to increase the
>damping, which is hard to achieve effectively with a molding process,
>and you might as well make them solid parent material.
>
>> On a related question, how would reinforced concrete work for the bed
>> of a largish (5' x 6') CNC wood router?
>
>I would rather use a welded frame covered with sacrificial chipboard,
>then at least you don't lose router bits to your bed material (so
>often) (-:
>
>Something like the one shown here
>http://www.super-tech.com/root/rr.htm
>
>> Geoff
>> Tennessee
>
>steam and wind
>
>--
> David Forsyth DaForce A-T Iwr.Ru.Ac.Za
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