[SwampDonkey]

Im nearly done converting my SX2 to CNC, thanks to many of the members here. I would like to try my hand at tackling one of the major issues with these smaller machines, rigidity and vibration damping. Im thrilled that epoxy granite is being used for this, i work with epoxy and other plastics and rubbers and know how to make it do what I want.
I started by planning to fill the column and base with EG, but have now toyed with the idea of enclosing the column as well. One big L-shaped EG covered frame when done.

One thing I may do is toy with the aggregate formula a bit, I have some ideas...

Back when I was a drilling fluids engineer we used powdered calcium carbonate to prevent our expensive drilling fluids from seeping into fractures in the rock we were drilling through. CC was used because it is exceptionally non-compressible and rigid. It can be purchased as fine as flour. Another interesting mineral is Barium Sulfate. Its extremely heavy and dense(4.2 times as heavy as water) and also available in extremely fine grades.

Of course plain old sand and decomposed granite will be used as well, maybe some of those zeoshperes too.

The moulds are the easy part. MDF coated with RTV silicone will do the trick. Epoxy HATES silicone in that it refuses to bond with it and will bead up like water on its surface.

I need some advice on how to make absolutely sure the column is square and perfect before locking it in place with EG. Once thats done we'lldo the whole project here on this thread. If you have any questions about working with epoxy and what it can and cant do, please ask

[nolage]

Lock the column in place with EG? I wouldn't recommend it.
Instead I'd recommend disasembling the mill, and EG'ing the base and column seperate. This will let you modify later as needed. Things like steel U channel will be more then enough to assist the rigidity at that joint, where vibration dampening isn't the main concern.

[BobWarfield]

nolage is right, you shouldn't lock the base and column together or you'll lose the ability to tram and square the machine.

However, there is one thing you could do that is very close. Create a very small gap between column and base. No more than 1/2" or maybe 1". Needs to be small enough that in height vs width, it is solid because E/G is not as strong as cast iron, though it dampens better.

Now tram the mill in. Make sure it is leveled first as that really affects tram. Once trammed, tape the gap and inject your resin. Ideally you want the base to have a flat resin area that you apply a release agent to so the column won't bind to that area. You're seeking to create a large surface area, very flat, in-tram, connection between these two. If all goes well, you can bolt down that column and as long as the machine stays level, it will be in tram.

I've seen this method described for use fabricating one off machines. They would typically use Turcite or similar, but the resin will work.

Consider it a total experiment though. No guarantees it'll work out well!

BTW, I think you'll like the E/G fill. I estimate it added about 20% to the vibration dampening and overall stiffness of my IH mill when I did it. You can see my pages about that over on CNC Machinists Cookbook: Software and Information.

Best,

BW

[wizard]

Im nearly done converting my SX2 to CNC, thanks to many of the members here. I would like to try my hand at tackling one of the major issues with these smaller machines, rigidity and vibration damping.

I'm not convinced that epoxy granite inside the SX2's column will do a lot for it stiffness wise. It should help a bit with dampening. The columns on these machines are simply to thin in cross section to effectively resist the machining forces involved here.

Im thrilled that epoxy granite is being used for this, i work with epoxy and other plastics and rubbers and know how to make it do what I want.
I started by planning to fill the column and base with EG, but have now toyed with the idea of enclosing the column as well. One big L-shaped EG covered frame when done.

This is an interesting idea if I understand your intentions correctly. Alignment of the machine and maintaining that alignment while the epoxy is molded around it will be difficult. Do realize though that to do any good you will need a huge amount of Epoxy Granite.

One thing I may do is toy with the aggregate formula a bit, I have some ideas...

Back when I was a drilling fluids engineer we used powdered calcium carbonate to prevent our expensive drilling fluids from seeping into fractures in the rock we were drilling through. CC was used because it is exceptionally non-compressible and rigid. It can be purchased as fine as flour. Another interesting mineral is Barium Sulfate. Its extremely heavy and dense(4.2 times as heavy as water) and also available in extremely fine grades.

Please post back with details on how these work out. The big problem for many of us though is getting such materials. Most of us strive to use easily obtained materials.

Of course plain old sand and decomposed granite will be used as well, maybe some of those zeoshperes too.

The moulds are the easy part. MDF coated with RTV silicone will do the trick. Epoxy HATES silicone in that it refuses to bond with it and will bead up like water on its surface.

Interesting, never though about RTV as a mold release agent. Kooning that RTV comes in many grades which do you have experience with? I know of a few free flowing grade that might be good for coating molds.

I need some advice on how to make absolutely sure the column is square and perfect before locking it in place with EG. Once thats done we'lldo the whole project here on this thread. If you have any questions about working with epoxy and what it can and cant do, please ask

Squaring everything up is important, there is plenty of info on the net for that. As others have mentioned though once you do this correcting for squareness becomes a much more involved project. You are basically left with hand scraping as your only option.

This leads me to the following advice, instead of modding this mill excessively, why not use the mill to build a purpose built CNC epoxy granite machine? By doing so you can more easily work with the advantages of epoxy granite. There are some really interesting examples of such machines on the net. I've actually have worked on a few Epoxy Granite machines in the past that used the material as part of the machines frame with cast iron ways bolted in place. On these machines the chunks of the machine (epoxy granite blocks) where still bolted together. There are examples of epoxy granite machines molded as one piece of course but that implies an ability to handle and machine such beasts.

So in a nut shell I'd not rush into this project until a little more though is put into it. I'm certain that you could end up with a nice machine with a bit of thought. Most of that thought needs to go into how do you assemble and align the pieces of the machine.

[SwampDonkey]

I'm not convinced that epoxy granite inside the SX2's column will do a lot for it stiffness wise. It should help a bit with dampening. The columns on these machines are simply to thin in cross section to effectively resist the machining forces involved here.

This is an interesting idea if I understand your intentions correctly. Alignment of the machine and maintaining that alignment while the epoxy is molded around it will be difficult. Do realize though that to do any good you will need a huge amount of Epoxy Granite.

Please post back with details on how these work out. The big problem for many of us though is getting such materials. Most of us strive to use easily obtained materials.

Interesting, never though about RTV as a mold release agent. Kooning that RTV comes in many grades which do you have experience with? I know of a few free flowing grade that might be good for coating molds.


Squaring everything up is important, there is plenty of info on the net for that. As others have mentioned though once you do this correcting for squareness becomes a much more involved project. You are basically left with hand scraping as your only option.

This leads me to the following advice, instead of modding this mill excessively, why not use the mill to build a purpose built CNC epoxy granite machine? By doing so you can more easily work with the advantages of epoxy granite. There are some really interesting examples of such machines on the net. I've actually have worked on a few Epoxy Granite machines in the past that used the material as part of the machines frame with cast iron ways bolted in place. On these machines the chunks of the machine (epoxy granite blocks) where still bolted together. There are examples of epoxy granite machines molded as one piece of course but that implies an ability to handle and machine such beasts.

So in a nut shell I'd not rush into this project until a little more though is put into it. I'm certain that you could end up with a nice machine with a bit of thought. Most of that thought needs to go into how do you assemble and align the pieces of the machine.

Yes, RTV silicone is the go-to mold material when it comes to epoxy resins. Urethane can be used as well with a moud release (silicone spray and Maguires Cleaner Wax work fine). Silicone also shrugs off abrasion due to its yielding nature and slickness.
Inhibitors can be used to slow curing to a crawl and allow the surface to settle to a perfectly flat surface under its own weight. The two rheologic properties we want is low PV (plastic viscosity) and low YP (yield point). Plastic viscosity can be simplified into how thick a substance is, it also typically represents solids and solutes content in solutions. YP represents how newtonian a fluid is, but "stickiness" is a good analog. We want a non-sticky thin liquid RTV that cures fairly slowly to make very accurate moulds. We also want it to be as stiff as possible since we will have but a thin layer and a flat surface to reproduce.

Smooth-On's "Smooth-Sil® Platinum Cure Silicone Rubber" is a good starting point:

Smooth-Sil®940 Food Grade Silicone Product Information | Smooth-On

A bit of thinner and retarder and it would be ideal this application. It also has zero shrinkage, which is the holy grail of mold making.

Barium sulfate is used as an inert weighting agent in fluids. Its cheap too. Im sure we can track some down even though its an industrial material. A 100 lb bag of flour-fine barite is about 20 bucks. Calcium carbonate is cheap too, and comes in a variety of grades. The best thing to do to get it cheaply would be to google Baker Hughes Drilling Fluids, Halliburton, MI Drilling Fluids, or really any of the drilling fluids distributors and ask to buy a bag of each. You should have a warehouse from one of these guys close to you. Thats the plan anyway

And yeah, Im thinking encasing the mill may be a bad idea. Its a LMS Sx2, would this be a large enough machine to make another mill on? I would LOVE to make one that rides on THK rails with an epoxy granite frame.

Edit:
And how do I align the column from top to bottom? And once its aligned, who do I drill perfectly straight holes through the brace and column without another larger mill? Ive seen threads where people do this but they all show them making the brace and BOOM its on the mill in the next picture.