Epoxy granite CNC part

Hello,

I like to share some epoxy granite element that I made to my CNC. I decide to made small modernization of my smaller mill. But like always modernization goes to total rebuild of machine.
One of step was to add stiffness and weight to old frame made from aluminium profiles.
Easiest way was to pour out some epoxy granite. When Y and Z axis was easy, because frame was already done, than X axis I have to  build from scratch.
Here I will describe how I made it.

MOLD

This is start point, Y and Z axis are ready. X axis should be easy dismantling, So I mill some aluminum plate that will be bottom of axis and will connect to Y axis.

This will be bottom of mold. Next step is to build form and add some profiles.
20x20 profiles will be poured in cast. They are strengthen mold and after they will be used mount other equipment.

Red "thing" that you can see on walls of mold is wax. I use it as separator for epoxy.
On the top I put two 40 x 40 profiles. After all I will install linear guides on them.

Between profiles there will be cardboard pipe, to create depressions for ball screw. I cover it with silicon grease.

POURING

I used Epolam 2002 epoxy with dedicated hardener. 2,5 kg was used. To fill I use sand with gradation from 0 to 2 mm.  I used about 15 kg of sand. Black dye that is soot from the chimney, it works well and it is free. It was quite hot that day and whole mix have consistency of honey. after pouring out I put it on my vibrating table, and it was working until epoxy harden. lot of bubbles came out.

Unboxing

After 24 hours I decide to remove mold and clean element. It looks that mold was not tight and there are some leakage. But this is not a problem as it can be cleaned.

After cleaning. Full hardness is reached after 72 hours, so I cleaned edges and remove all allowances as fast as possible.
Using silicon grease was mistake. Cardboard pipe glue to epoxy and some part of it left on element. Still it is not an issue.

Installed on machine.

In conclusion:
- epoxy granite elements are stiff and have good weight for dumping vibrations when milling
- use wax as a separator or buy dedicated one
- if you plan to create bigger mold it will be good to pour out with some friend who help you.

Thanks for reading.
Lucas