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Re: Epoxy-Granite machine bases (was Polymer concrete frame?)
Hi All - I'm sending some Tetrium to a friend for making into motor mounts. I was going to wait until I had access to a power saw but decided to hacksaw it so I could get it away today. Cuts well. The cross section has been dressed with 80 grit. Now to make a big table so I can make slabs. Peter
Re: Epoxy-Granite machine bases (was Polymer concrete frame?)
But has anybody tried sawdust? Aside from these guys, I mean: https://iopscience.iop.org/article/1...53-1591/ab279e
Re: Epoxy-Granite machine bases (was Polymer concrete frame?)
Hi Flick - i think everything has been tried. But sawdust is not very stiff so is just a filler does not make it any stiffer. Peter
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Re: Epoxy-Granite machine bases (was Polymer concrete frame?)
Hi Buoyen - 400 is a bit thicker than many out there. But it will work. Look up Biresin CR83 via SIKA. 155 mpas and longer gel time. The longer gel time allows the resin to wick into corners and filler better. Peter
Re: Epoxy-Granite machine bases (was Polymer concrete frame?)
Okey, great, thank you!
I'll have a look for CR83. But I can get the BC309 local so that is easy!
Re: Epoxy-Granite machine bases (was Polymer concrete frame?)
Hi Buoyen & welcome to 2020!! - I've just read the TDS and I think you need to send a note to the supplier asking what is the maximum thickness this can be cast in. Its application is for relatively thin floor coatings and 30mins gel is quite active. So if you cast this at say 25mm thick I expect it will exotherm considerably and may burn. By burn I mean it could get hot enough to destroy itself, it turns a very ugly brown and cracks and smells and its structurally destroyed. Thick casts of the wrong resin can ignite in the right conditions as well (or wrong depending on what side of the event you are on). Epoxies are formulate for thin film curing or thick film. I think this is a thin film. Thin film assumes the substrate will absorb the exotherm and being thin film it needs lots of energy to cure (as it sheds heat to atmosphere very easily as its thin) hence the fast gel time, plus thye fabricators don;t want to hang around for hours for this to cure. The filler will absorb heat that's good. Perhaps do a trial cast at your expected thickness and mix but do it outdoors, away from any flammable stuff!! Not on the kitchen table... :) Peter
Re: Epoxy-Granite machine bases (was Polymer concrete frame?)
Ok, thank you Peter for looking into this.
But I guess the granite will absorb most of the heat beacuase a 8% epoxy weight it is relatively low. But I'll maka e test first.
Also the castings I have planned will weight about 70kg and I can only mix about 5kg at a time so there will be several layers.
Re: Epoxy-Granite machine bases (was Polymer concrete frame?)
Question about aggregate.
Would FeO-SiO2-Al2O3-CaO-MgO, you may call it fayalite or iron silicate, be appropriate? I see this is stiffer than granite.
Also would it be possible to combine say this fayalite with quartz, ie I can get hold of
Fayalite 0.2-0.7mm
Quartz 2-3mm
Mixing these ratio should give a fairly dense media.
Re: Epoxy-Granite machine bases (was Polymer concrete frame?)
Hi Buoyen - What is the stiffness of Fayalite? Any mineral mix will work depends on what you can get locally for low cost. Peter
Re: Epoxy-Granite machine bases (was Polymer concrete frame?)
If I read this correct it says 266GPa for Fayalite: https://ocw.mit.edu/courses/earth-at...otes/lec20.pdf
But after looking at the formula it's not fayalite I've found. Don't know what it is, but it is sold as a blasting media and supposedly an olivine sand. To me the chemical composition is not the same as Fayalite or Olivine which should be Fayalite (Fe2Si04), Olivine (Mg2Si04) .
The price for this blasting media is the double of equal size of quartz, but still not the major cost in a machine base made from an epoxy/aggregate composite material.
Re: Epoxy-Granite machine bases (was Polymer concrete frame?)
Hi Bouyen - good article. These sort of crystalline materials have different modulii in different directions. eg the fayanite has a max of 266 but a min of 32GPa so the average will be in the middle somewhere. You will struggle to get more then 50% by volume in the pack so E will be further diluted in the EG. Epoxy is about 3500MPa so does not contribute much. Cheers Peter