Hi All,

I have been catching up on my polymer concrete and e/g reading and noticed that no one is using polyester resin to make the base. I searched on the internet and found out the reason. Polyester resin doesn't bond as well as epoxy resin and plus it has less strength.

But I was thinking maybe this way it may work. How about if I contain the whole resin mixed with fibres and stone chips inside a box made out of say steel or aluminium. Basically the resin mix is just to fill up the metal box as filler.

Question is, how strong will the compound be if the resin is used this way. The reason I ask is that where I am, polyester resin is widely used for fibreglass making of boat. Epoxy may be hard to come by.

Thanks.

40081

Polyesters shrink too much and are not a good adhesive,possibly releasing from the steel or aluminum box.Polyesters are also flammable,epoxy's are not.
Larry

Hi Larry,

Thanks for the input. Beside the fact that polyester resin shrinks alot, but if i put in studs all over the aluminium box, will this hold the resin in place? My question is that will I be able to use that as what people will use E/G for mill base and such? Thanks.

I just found a store locally selling epoxy resin. Hope there is only one type of epoxy resin.

The E/Q isn't being used for strength, it's being used for vibration dampening. A "polyester concrete" mix won't add much if any strength to your machine.

I think there are many other products that are better suited as a filler. Even non shrink grout made using portland cement would do pretty well, especially if you used a glass filler. It is relatively cheap as well. It would fair better in larger areas I think rather than small openings like 8020 aluminum. This is what I plan on filling and the epoxy so far, seems ideal. This is along with some sand and gravel.
I think also that the portland cement might have issues if you used coolant. If it always stays moist from coolants, it could have an effect on it's long term curing or stability after cure.

The base for my homebrew mill is a 48" long (x) by 17" wide (y) hardwood box, about 3" tall (6" y motion, 24" x motion, both fully supported). It has a few supports in it to help stabilize the column, but so far it is filled with 160 pounds of concrete, with about .75" to go to completely fill it. I did it almost completely for stability and vibration resistance. The column is actually a 3.5" x 6.5" x ~24" tall hardwood box filled with concrete. It is about 60% full now since I ran out, but its stiffness has definitely improved and now I can only get about .125" deflection at the top by jerking it around before the whole base starts to move. I don't expect to be putting that much force on the mill head, heh, plus I actually have to build another base with two embedded columns instead of one, because I came up with a completely new head design (figured out a way to mount a drill press head accurately and securely). So that will make it stiffer. And then I wil add triangular bracing for more stiffness.

By the way, I just used regular old, $3 per 80lb bag, concrete mix. I will take some pics and upload them when my new laptop comes in... typing this on my phone now, heh.

I know it sounds ghetto, but I can't spend a lot on this as my business gets on its feet. Still, I am confident I can get it accurate to 1mm or less, with at least as much speed and power as, say, and x1, once its all said and done. That will be good enough for most of what I need, and I can then use it to build upgraded parts for itself (since I am now working mostly with wood and concrete, and counting on the dimensional acuracy of steel and aluminum parts for the more important bits of the mill), increasing both stiffness / accuracy, and travel.

*edit*

By the way. I did get some cracking around the edges as it dried, mostly, though, due to not having enough support around the wood frame, causing the sides to swell out due to the weight and moisture of the concrete mix.

The reason I ask is that where I am, polyester resin is widely used for fibreglass making of boat. Epoxy may be hard to come by.


I say go for it. Buy a gallon of resin and do some testing, see if it shrinks. :)

I believe that 50% (if not most) of commercial E/G machine bases are made with polyester resins. In fact, I believe that just about anything can be used- it's the additives that make the difference. Any resin can be made to work. These additives consist of anti-shrinkage agents, de-airing agents, coupling agents, etc. It may not be feasible for DIY and we don't understand how it works- it doesn't mean its impossible.


Here's proof that just about anything can be used for this purpose:


"Machine tool bases have traditionally been made of cast iron, but recently inroads have been made by another material which developers claim reduces the effects of temperature variation and vibration.
The material combines granite and either a resin or acrylic binder cast into a machine tool base, which, developers say, costs the same or less to make than a conventional base.

Although new to many machine tool builders, especially those in the United States, the composite base has been available in Europe for several years. One developer, Fritz Studer AG of Switzerland, first came up with its Granitan S-100 technology in the early 1970s. But it had been kept proprietary until about four years ago.

The granitan base is a mixture of reactable epoxy-resin binder developed by Ciba-Geigy Ltd., Switzerland, and granite or gravel. Granitan produced with sand and gravel was developed specifically for the requirements of machine structure manufacturing, Studer officials have said.

There are other "synthetic granite" products on the market, but they are newer than Studer's technology. Helgard Koblischk GmbH of Germany has developed Motema-AC, which uses an acrylic plastic binding agent. Also, Plastibeton Inc., Montreal, a subsidiary of Lone Star Industries Inc., Greenwich, Conn., has developed Quazite, which uses a polyester acrylic binder.

Another company, Diamant Metallplastics GmbH of Germany, has also developed a process which uses an epoxy acrylic binder, but after about four years of production has left the market.

Despite their differences, all of the synthetic granite developers claim similar advantages over cast iron and steel bases. Vibration dampening is one of the key advantages. In technical publications, Studer officials have explained that machine parts, and particularly machine tool beds, are subject to vibration by the machining process. Effective dampening by the structural material is therefore important. The dampening improves machining quality and steps up production rates, especially where metal is being cut, they said."


http://findarticles.com/p/articles/mi_m3MKT/is_v93/ai_3647171


I would also like to see JMcDonald's base.. It's great to see people experiment and try different things.
_

Hi Guys,

Thanks for the info. I finally got myself a gallon of epoxy and will be starting my test run on epoxy block making in the next few days. Will update if I get the chance.

It isn't the casting epoxy resin. Just your normal epoxy resin for laminating work. But since I am going to mix that with a filler, I won't be using much of the resin so it probably won't get too hot when setting.

I was thinking of using polyester but the shrinkage effect turned me off. And I understand polyester resin doesn't bond as well. So may not bond with the filler or if I have to top up with more resin where shrinkages occurred, it may not bond as well. I have seen wooden boats here with a shiny coat of something and its real tough. Always wondered what it is, now I know. The guy whom I bought the epoxy from said people here use it to put a coat of epoxy laminate on the outside of the hull. It really bonds to the timber once set. So that is good enough for me.

Alex good you found epoxy,The guys on the other thread are using laminating epoxy as well.Polyester and glass shrinks 1or2% making easy release from a mold.Epoxy does not shrink making mold release more difficult.In your case polyester may shrink and release from the steel.
In general polyester is not a good bonding agent.I doesn't stick to anything.Its strength comes from encapsulating the glass fibers Basically polyester fills in the spaces while epoxy glues things together.
Polyester shrinks for years.On 20 years old boats or less you can see the fiberglass print through and gelcoat cracking from stress .
Larry

Cured polyester resin is affected moisture and humidity.