[JohnMcNamara]

Hi Rotary SMP
Hi ckelloug
Hi RomanLini

Just to set the record straight I did not wish to detract from your or anyone else’s formal study and documentation of the process. You never know when formal research will lead you to the next breakthrough.

This thread has 4460 posts and over 1.1 million reads; rather large and daunting; very confusing for a person who comes upon it for the first time. A few designed and built preferably low cost machines will enable a new convert to the concept of epoxy based casting to get their feet wet and have a go.

From my reading of the literature the Achilles heel of epoxy casting is the epoxy itself; try as we may to improve the properties of the aggregate/fillers we use; the binder (Epoxy) is a significant mitigator of any improvements we may achieve. Yes if building a half million dollar plus CNC machine those improvements are essential to be competitive in a very competitive market.

On the other Hand for the small shop or home builder, a shop that most likely will not have access to micron level machinery and metrology and therefore will not be able to fully realize the ultimate machine. However this level of sophistication is not necessary to enjoy the benefits of this manufacturing method. Epoxy concrete is actually quite liberating. It gives the small shop the ability to produce large castings and parts in house at low cost.

And referring back to my first paragraph re professional research; the same thing applies to more empirically derived shop floor research. Once more people use the process there will be new ideas that germinate from the distributed minds of these designers... we may even get a breakthrough here as well.

Cheers

John

[ckelloug]

John,

I salute your practical work and wish that the others who are doubtlessly build stuff would post their work. Work like yours is why I assume we are here. It doesn't detract in the least.

What I don't like are critics who don't offer anything constructive.

Regards,

Cameron

[castinite]

It is good to discuss theoretical castings, but I have been casting real parts for over 20 years, using a formula I developed. We cast a 18" diameter, 270 deg drum, to .001 ID TIR (AS CAST). We cast a 70,000 lb CNC machining center using a low cost wood mold, and routinely cast grinding machine bases, 4,000 lb to 7,000, using low cost composite molds.

We cast chemical pump bases flat to .002"/36", using wood molds and can cast parts flat to.0005"/36" using wood molds. Our bases are used for a high speed printing machine, replacing a steel weldment, at 50% of the weldment cost. Delivey of a finished base is days, they do not need to be painted and the virbation dampening allows the printer to run faster with better registration.

EG offers a lot of real advantages over other materials, if you know how to do it. If you don't, the results can be bases that never cure or the cure too fast creating air pockets. It is easy to make bad parts.

We do sell the mix for anyone who wants to cast thier own parts.

[the4thseal]

who do i get in touch with to get some?

[vishnu]

It is good to discuss theoretical castings, but I have been casting real parts for over 20 years, using a formula I developed. We cast a 18" diameter, 270 deg drum, to .001 ID TIR (AS CAST). We cast a 70,000 lb CNC machining center using a low cost wood mold, and routinely cast grinding machine bases, 4,000 lb to 7,000, using low cost composite molds.

We cast chemical pump bases flat to .002"/36", using wood molds and can cast parts flat to.0005"/36" using wood molds. Our bases are used for a high speed printing machine, replacing a steel weldment, at 50% of the weldment cost. Delivey of a finished base is days, they do not need to be painted and the virbation dampening allows the printer to run faster with better registration.

EG offers a lot of real advantages over other materials, if you know how to do it. If you don't, the results can be bases that never cure or the cure too fast creating air pockets. It is easy to make bad parts.

We do sell the mix for anyone who wants to cast thier own parts.

Can you please post some pics of the bases you have cast, the problem i have come to know is the availability of materials in my country eg. zeospheres, proper resins & small even aggregates. Do you use vibration setting to release air pockets after casting.

[JohnMcNamara]

Hi Vishnu

Good to see you are having a go yourself.

There is a lot of discussion about air bubbles and the perfect mix. If you are going commercial and want world standard industry best practice, then detailed research and development will be required. Bearing in mind the end product is what defines the specification. It is to easy to get carried away looking for the perfect Mix.

However if you are making a “one off” and want to get your hands dirty quickly, a few small air bubbles are not going to stop you.

The small tool and cutter grinder I am working on is fine there are a few blemishes where the mix did not completely pack down leaving a small void. And there are a few air bubbles.

So what!

I am going to use the same mix in a CNC mill that is next in line to be built. I am quite satisfied with the results of the basic Epoxy mix used in the grinder.

If the mix you use is “basic” Epoxy, aggregate and sand. And it builds a part that complies with your design requirements, why go to the added expense of high tech additives.

The cost of an initial trial of basic materials is so low it is well worth doing it.

What does matter is the casting sound in spite of a few cosmetic blemishes? If the answer to that is “yes”, then don’t worry about the casting and get on with the rest of the project.

Epoxy
I did choose an established Epoxy supplier, Vivacity Engineering in Australia they market “Megapoxy” H and HIPB they gave excellent service and worked with me to get the right medium cure time. there are different hardeners for different curing times. I recommend that a supplier is chosen that has proper technical service personnel. You will have to locate a similar supplier in your area.

Reinforcement
This is not often mentioned in here: There are many purists that believe that the ideal design uses Epoxy alone, apart from a few threaded inserts. This makes no sense to me at all. Deformed steel bar used in concrete reinforcement available from 5mm thick to over 40mm thick is cheap and easy to obtain. It will do wonders for your finite analysis of the structure.

If you study the designs of actual commercially built machinery it is clear that a lot of steel is being used.

Cheers
John

[castinite]

Anyone interested in obtaining the mixture components can email me at [email protected]. We have shipped finished bases and casting materials to India.

[JohnMcNamara]

Hi Castinette

The green grinder casting is interesting….. Particularly the cast in steel ways and the rod or cable ends with nuts. They appear to be the same as those used in pre stressed concrete. Were they post tensioned after the casting had set as is the usual practice?

There is a good discussion of the process here for those that are interested.

http://en.wikipedia.org/wiki/Prestressed_concrete

Also the use of PVC plumbing fittings to form ducts as shown in another photo, they appear to be standard industry practice. I have seen them in a number of manufacturers work. It makes sense, Low cost and easy to customize.

Great job

Cheers
John

[castinite]

John,

The green base is 10 meters long. When picked up on one edge, the deflection on the opposite edge was only .01mm. We cast the steel plates in and had them machined flat to .01mm flatness overall.

You are correct, the base was post stressed. It is filled with several foam cores and has standard PVC pipes cast in for drains along the length in two places. This base was cast in a wood mold.

[romihs]

Castinite,

That is very impressive.

Your last few posts have been very inspiring. Makes me want to go out and build something.. I am very amazed at the accuracy you achieve simply using wooden moulds!

This is not as complicated as I had thought it would be....

Thanks for the info and inspiration.

Sandi

[johnohara]

Terry~

Picture 2: "Bimbo with base"

Bimbo with base?

She seems nice enough. Dresses professionally in an industrial setting. And was certainly willing to be photographed next to your product, with a smile. I'd bet she talks to customers with an upbeat voice too.

Do you realize her image will now be indexed into multiple search engine databases with that caption? (Google, Bing, Yahoo, etc.) Standing next to your product, with your URL and a back link to your cnczone entry?

You might want to delete it before the web crawlers find it -- if they haven't already.

~John

[Steven.ji]

Hi Terry

The steel bar in the green base is almost 6 meters long. There must be bi-metal effect resulting from different thermal expension coeffiencent.

In China, seldom workshop have temperature control system, how to deal with such problem?


Regards

Steven

[RomanLini]

Workers with heaters and thermometers, manually turning the heat on as needed.

Even on small job's I've had some tricky exotherms, needing heat applied for some time to get it moving then grabbing fans in a panic and trying to keep the exotherm under control...

Those non-contact infrared laser thermometers are perfect for casting as they can actually "see" the temperature at the CENTRE of the mold, is it glows in infrared energy from the centre out! Where old fashined thermometers only show the surface temperature and may take seconds to give a change in reading too. I have a number of thermometers in arms reach of the casting bench but the infrared one is the most useful.

[ckelloug]

Hi Roman,

I must admit that my test samples have been a bit small but the only exotherm problems I have ever seen have involved poor choices of hardener. TETA, TEPA, and AEP are very exothermic and too exothermic for E/G.

Isophorone Diamine and Hexamethylene Diamine have low enough activities that they won't even achieve optimal cure properties at room temperature, much less over-exotherm in EG. I've been focusing on Isophorone Diamine as the hardener because of this and doing oven cure at 85C.

Regards all,

Cameron

[yancho]

Hello.Excuse the language but I'm not very good at it.Well there is Google.I have the following question:For epoxy concrete you use gravel and how much.I want to make my machine and generally know how.This product adds a new dimension to the hobby.It removes the foundry and generally heavy mechanical equipment.Castinite-what we produce is great and professional, not a hobby.Thank you all in the forum.Yancho Yanchev

[RomanLini]

Cameron- Sorry I should have qualified that statement as it was not specifically about EG, but other epoxy or urathane casting I do without the aggregate. You can get some nasty temperature runaways depedning on thickness of the cast, mold insulation and room temp etc.

With EG there is almost guaranteed to be the opposite problem, a lack of sufficient exotherm due to the very low epoxy percentage and inert aggregate. An oven cure is about the only way, although you should still watch for exotherm runaway on the centre of the thicker areas as the the temp there will be above oven temp. Maybe an embedded temperature sensor? A LM35 reads linearly in degrees C per volt and is cheap enough to leave inside the casting.

I should have also said re the use of the infrared thermometer "seeing" the inside of the casting temperature that is with no aggregate. A thin casting should see the inside temp even with the aggregate, although I'm not sure how transparent the aggregate is to far infrared so with a thick cast the non contact thermometer may not see to the centre of the casting. There would also be issues with using the non contact thermometer with a curing oven.

Anyway the point I was clumsily trying to make for Steven.Ji was that it's pretty normal to have to take a close interest in the cure and manually have to heat it or cool it, adjusting as needed to get a good cure. Anyone that thinks they can just "mix and wait" and always get a great result is in for a shock...

PS. Even the epoxies will change over storage time and/or with supplier batch and have different exotherms and need different post-cure regimes.

[yancho]

I watched film-Breton SPA-Italy,their machine with such a base.

[Kevin_Johnson]

Hi Terry

The steel bar in the green base is almost 6 meters long. There must be bi-metal effect resulting from different thermal expension coeffiencent.

In China, seldom workshop have temperature control system, how to deal with such problem?


Regards

Steven

Steven, you might consider placing a system of tubes in your piece. You could then circulate cooling/heating fluid to simultaneously drive/regulate the reaction and keep the piece at a more normalized temperature overall. You will probably want a series of interconnecting "manifolds" with multiple external connections. It is similar to temperature regulation in an automobile engine block. With multiple manifolds/circuits you could heat some areas and cool others simultaneously.

By doing this and perhaps insulating the curing piece during temperature extremes you should be able to compensate for an uncontrolled shop environment. Also, the end product should be more valuable because the end user can circulate cooling or heating fluid to bring the piece back to the temperature range that it was manufactured in for optimum accuracy. By creating a grid of manifolds that can be later modified for flow patterns you can allow yourself and the enduser great latitude.

It is a lot of extra expense and trouble, of course. In larger projects such as dams this technique is used because of the great heat released from the large mass of concrete setting.

Good luck.

[Kevin_Johnson]

"A rose by any other name would smell as sweet"

These old eyes read no fundamental development in the change of name from Epoxy/whatever to Mineral Casting

John

It is something to watch and be aware of. In science, the phenomenon of cold or vacuum welding in space has run across issues when effects like galling are considered to be mutually exclusive. As the amount of knowledge increases and fields become more specialized this sort of issue will become more common. Supercomputers may be the best bet to do meta-analysis and keep mere humans more aware of what everyone is doing/defining.

I think anyone that has done interdisciplinary studies can think of a few examples.

[greybeard]

Kevin, I don't want to appear rude, but I have no idea what my quotation you have used above has to do with your erudite comment below.
Could you please explain how my original comment, to be taken exactly as I made it, i.e. what does it matter if you change the name of the topic, the data being discussed hasn't changed, relates to your present thoughts.
I was only suggesting that you need to be aware of alternative names.

Regards

John