Re: Material for milling big products

From: Delft Spline Systems (
Date: Wed Dec 24 1997 - 12:27:41 EET

Jan Willem Gunnink wrote:

>Dear RP-world,
>At the moment we have some projects running for which we need to mill
>rather big models (L: 1300 mm W: 800 mm H: 25 mm). At the moment we
>are using OBOmodulan 302 for it. Really nice stuff to mill
>(feedrates: 24 m/min, Tool diam: 10 mm, n=30.000 omw/min) but also
>rather expensive. Is there anybody out there who knows some materials
>which are cheeper than the stuff we use ? For the record stuff like
>Polystyreen like for Lost Foam or the packing industry is not dense
>enough because of the break out of the little foam bubbles.
>I hope to hear anything from anybody !!!! (i like to beat my
>collegeaus with their LOM 2030H)

Marshall Burns and Ralph Milone added:

>Have you tried RenShape (RenBoard?) from Ciba?

Steve Farentinos added:

>Rayite 100 (a machineable plaster) from U.S. Gypsum.


Hi Jan Willem,

I will try to bring some more clarity in this matter.
As you can imagine we are allways very interested in beating a LMT based
RP system by a CNC system.

Renshape is the US brand name for what in Europe is called Cibatool
tooling board (manufactured by Ciba Polymers, Duxford, UK).
It is fact the same material as OBOmodulan, Hexelite, SikaBlock and
some other brand names (I can give you some Dutch importers names).

Most manufacturers do supply the material in various densities, from
say 60 kg/m3 until ca 650 (the 'normal' tooling board). The less dense
forms are in fact just PUR foam. The lightest can be easily damaged,
the more heavy cannot. A suitable density should be available for your
application, at a lower cost than what you use now.

The same PUR foam can be bought from isolation-foam suppliers,
at a much lower price than from the model-foam suppliers. However do
take care that you get foam with small bubbles only.

PUR foam is easier to machine than Polystirene, as the latter material
in most cases is expanded from small grain, and these grains can break
out during the milling.

I do not have experience with the 'powder materials'. They are advocated
to have the advantages of easy cutting and almost no dust production (the
latter in contrast to the above materials). A disadvantage seems to be that
you will have to mould your own blocks before you can start milling.
Anyone present having experience ?
Comments from Steve ?

>From a rainy Holland (not much chance for a white Christmas here):
best wishes to you all for the next year, a good health and a succesfull

Lex Lennings.

Delft Spline Systems, The Netherlands.
Active in CAD/CAM, Rapid Prototyping and NC milling

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