[probinson]

Thanks for the backup on this Bloefeld,

Anyone who has done epoxy work that demands perfection can tell you how important degassing truly is. When someone says it won't outgas we can't control the urge to jump up and shout "Like hell it won't!" but we also need to keep the goals of this thread in perspective.

If I'm not mistaken, the main goal of this thread is to develop an EG formulation that allows anyone to build a decent quality machine on a tight budget and without needing access to expensive equipment.

With that goal in mind, I don't see degassing as being essential, though I strongly recommend it. Degassing and heat curing make such a tremendous difference and are just so cheap and easy that I wouldn't dream of skipping either one, especially when you have as much material at stake as is required for a machine base.

Hopefully you all will forgive me when I feel compelled to chime in with one of my "That's only true if....." posts or other less than humble opinions.

Pete

[ckelloug]

The outgassing question from Jack wasn't really about de-airing under vacuum. Jack ran a test where he thoroughly deaired a batch of 37-127/37-606 and it did not cure correctly. He inferred that some portion of the hardener had boiled off altering the chemistry.

I agree with Pete that E/G that requires oodles of vacuum and precision machined high vacuum molds will not be practical for many of our readers. I'll try some vacuum experiments because I am curious about how well it works but aside from deairing the epoxy in a vacuum chamber, I'm not sure it will turn out practical to do vacuum infusion into molds for machine parts.

Regards all,
Cameron

[MrStainless]

Hi, I'm a newby here, currently looking to build a low cost cnc router.

I like the Drawer Slide solutions and would welcome links to cheap stepper motors. (sorry, off topic)

I am sure the EG style of cast tables and frames are a possible way forward. I noted the "Filled Weldment" idea.

Way back, when I was working with metal finishing equipment, we looked at making a modern version of a 2 metre wide linishing machine. We considered a hefty fabrication of massive box section steel, FILLED WITH CONCRETE. It would have worked and have provided the mass needed to match the original's cast iron construction. In practice used machines (1950's vintage) were cheaper to import from USA.

However, I think that - for smaller machines - there are two areas worth investigation.

The first may seem "off-the-wall" until you work with it, but Polymer Plaster is amazingly hard and easy to work with. I recently needed to copy some architectural details - small, 200mm x 200mm x 20mm - and did a time honoured toughness test with the spare castings after they had aged just a week - smack several times with Inertial Modifier (Hammer) - VERY Tough. This could work for small machines, although it doesn't have the mass of Granite. I am sure and might suit a production run for club/school needs.

The second is just another type of EG. In indusrty there are many concrete additives which make exceptionally strong floor sufaces and screeds. I bet there is someone out ther who can tell us a concrete mix which would serve our needs at a fraction of the cost of EG, but with a substantial proportion of its mechanical properties - maybe enough for our needs?

Keep up the good work, you've got me hooked.

[ckelloug]

Welcome Mr. Stainless,

Most of the merry band here is concentrating on producing an open literature E/G formula that is very good and reasonably doable by folks without half a million pounds or dollars worth of machinery to devote. The research activities documented here are a lot more difficult than we hope the final product will be to use.

E/G won't be the solution to all problems in home made machinery but when made right it is strong and dimensionally stable under the influence of both heat and atmospheric moisture. It also has the ability to be molded to a very high tolerance. Some special formulations we've postulated about here should allow the production of reference surfaces that are flat to the extent of earth curvature (around .0001 inch per foot) with no finishing work. Finally, many of the regulars here, including me, find working on this fun.

I just got back from a quick lab visit where my surplus Leybold Sogevac SV25 vacuum pump let out an oil geyser on it's inaugural run hosing down me and several items like my spool of o-ring cord. I am expecting a shipment of cutting tools today so that I can complete the sample mold I've been working on to replace the one that melted in the oven. Some days you win, others you don't.

Regards all,

Cameron

[greybeard]

H Mr. S.
I'd like to echo Cameron's welcome, but also ask if you have any more info on the polymer plaster. A pm would be welcome, and would reduce the danger of too many of us going off on yet another tangent

For myself, as a self-confessed knowledge geek, I'm always on the look-out for alternative ideas. That's my excuse for taking two (or is it 3 ?)years to get from thought to action.
Regards
John

[ckelloug]

ServoWizard mentioned plaster back on page 112. (I'm not psychic, I have the first half of thread stored locally on my computer so that I can search it with unix grep instead of the useless board search. I also have written software that can take translate to the page and post# from the arcane number vbulletin puts in the URL.)

This thread is all about knowledge and that which we've gained in so many areas so any thoughts even on plaster are certainly welcome.

See
http://www.cnczone.com/forums/showth...30155&page=112

Regards all,

Cameron

[MrStainless]

Cameron, John, Thanks for your relplys.

FYI Polymer Plaster is Dental Plaster with an acyrylic polymer additive in the mixing water. It's Art stuff for intricate casting. Alec Tiranti http://www.tiranti.co.uk sells it at Theale, as do Specialist Plasters http://www.specialplasters.co.uk/ind...ewCat&catId=15.

I was surprised by its strength.

Also Glasplies at Southport are competitive and sell Epoxies and Polyester casting goops. They have a Stone Casting resin for Statues which is designed to take a lot of filler, ie Sand, Granite etc. They have been around for decades, Mr Rankin - founder - discovered GRP after the war when he ran an amphibious ex-Army DUKW off the beach and could fix the rusty holes with GRP between tides! www.glasplies.co.uk not much of a web site, but proper practical people.

I don't have an interest in the above companies although I have been a customer of Tiranti and Glasplies.

Bill

[greybeard]

Thanks Bill.
I did suspect that as your my side of the pond you may have been referring to something slightly different.
Know Tiranti well, but the other one seems worth a look, even though Stockport is a bit off my track.

You might find www.tomps.com worth a look, especially for epoxy.
Regards
John

[craigl2]

A`

[alex_ku]

Hi guys!

I'v found video on my comp, which maybe helps to someone...
here we are:
<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/vrgbCrhkJTI&hl=ru&fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/vrgbCrhkJTI&hl=ru&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>

WBR,
Alex

[Zathras]

Hi guys,

This is really a question for Cameron.

I've been trying to find an aggregate supplier here in Oz to make my own surface plate (TT epoxy layer on the E/G block as has been done by one the guys here). I will (hopefully) be running air bearings on it eventually.
This company is the closest I have fond so far; http://www.sunstatesands.com.au/sand_gradings.htm
The data sheets are here; http://www.sunstatesands.com.au/product_data.htm

It seems at first sight, to my untrained eye, the spread of fractions would not be enough. Four orders of magnitude spread with 4 fractions was it not?
Is there a mix your sim could come up with that would be worth while for the gradings shown?

Thank you!

-Mark

[Zumba]

Great video, Alex!

[ckelloug]

Zathras,

I'll take a look at this in the next few days. If you're just trying to make a surface plate by making an E/G chunk and pouring some tabletop epoxy on it, the exact E/G formula isn't going to be super critical unless you've got some very high point loads on it or something. The 4 orders of magnitude and 4 sizes rule of thumb is for getting an E/G material that has as high a compressive modulus as possible with minimal epoxy usage.

My instinct is that if the plate is well supported on the bottom, most of the deflection that is likely to occur would be from compression of the tabletop epoxy rather than the deflection of a thick E/G plate. Unless there you have an overwhelming need to make the entire plate out of E/G, it might be cheaper and less work to get a steel plate from a local metal supplier, bolt it to a thick wooden table like a butcher block and then pour the tabletop epoxy on that being careful about the edges. There's no arguing that a 4 inch thick E/G base wouldn't make an excellent support for Tabletop Epoxy if you want to go through the trouble and expense.

Note:
I've been scarce around here lately as I'm almost a man month (100+hours) into producing my Mark I vacuum tight epoxy test mold. This leaves very little time to do anything besides work, eat, sleep, and fabricate the mold.

It's made from two plates of precision ground 1/2 inch thick A-2 tool steel separated by a 1/2 inch thick spacer ring with dual o-ring seals. The plates are mirror finished for the front and back cavity surfaces. It started with 6 pieces which were fabricated into 3 held together with 4 welds, 30 allen head cap screws and 8 dowel pins.

It will produce test pieces about 8in x 8in x 1/2in when completed. It is amazing to me how hard it is to make things out of steel accurately. I'll shoot some pics when I get done.

Regards all,

Cameron

[Zathras]

Hi Cameron,

Seriously, if you are that busy please don't worry about it.
Thanks for your suggestion too.

I think I'll just try what the German guys did. Just for those who don't know or missed it;

30% Basalt 2-4mm
30% Filler Sand 0-2mm
30% Quartz Sand 0.1-0.4mm
10% Epoxyharz R&G Epoxy. (Or what ever I can find similar of course)


Actually I would really like/need the damping properties of E/G, as you said the strength is not that important.
I dunno what 1" steel plate costs but I do remember 20mm Aluminium costs(some years ago) something like $750/m2. That would make it about $400 just for my top.
Planning on 900x600x100mm plate so my calculations suggest 5.4litres of epoxy. Have to find out how much that epoxy is, I know it isn't cheap though.(nuts)
I'll do my homework first.

Thanks for your response Cameron, now get some sleep man!


-Mark

[Kenrick]

Hi guys sorry about this but i just started to use this website....

Any way CAN YOU HELP ME I JUST STARTED TO USE DECKCNC at work we just got a 3 axis cnc getting it up and running was so easy, untill i started to use deckcnc man it is hard can any one help me by?

here are some of the things i would like to know
1. how to make the cnc work in mm if i can (i mean how to make the axis work in mm)
2. how to input DXF file and start the cnc running
3. just anything that can help me get my head around the deckcnc software and the running of the cnc it self HELP ME PLEASE

many thanks kenrick from Mo-sys

[greybeard]

Hi guys sorry about this but i just started to use this website....

Hi Kenrick, and welcome.
I suppose one of the first things to learn on this site is which forum to post your messages to.
Go to the Home page, then look for a forum that is a bit more appropriate.

Good luck, there's an aweful lot to read.
John

[ckelloug]

Zathras,

I will get to modeling your question it in the next day or so. I'd like to learn a linear algebra technique called singular value decomposition which on implementation should lower the kludge factor in the modeling/optimizing code so your question is the perfect excuse. I like practical questions like yours because they force me to learn new things and to fix things.

Good point by the way on the cost of steel. I always forget that steel is expensive compared to E/G because I have a machine tool addiction and E/G lab work always seems to require machine work and the opportunity to break expensive cutting tools is always present. I broke $65 worth of 1/8 endmills on the o-ring grooves in the mold alone :boxing:

On your project, all I can say is that epoxies with hardeners based on amidoamines are worth avoiding.

Anyway, I just finished retapping the epoxy and vacuum inlets in the mold after having bungled the threads the first time by getting the 1/8 NPT tap in crooked. An hour of making a tap guide bushing out of a chunk of 1.5 inch S-2 tool steel corrected the problem of crooked tap entry and I only broke one size Q drill in the process of making the bushing. Lesson of the day: don't bother starting to tap a hole without making a guide bushing for that tap size first.

I finished polishing the mold cavity with 3000 grit diamond paste last night after about 12 hours of lapping on the 128 square inches of surface area going through the following grits on both halves: 120, 200, 220, 320, 400, 600, 800, 1800, and 3000. Now I guess I need to get some vaseline to lubricate the O rings for testing purposes and go off to the lab to see if anything works and check for leaks. This should be done with vacuum grease but helpful supplier of vacuum grease seems to have shipped it from Oz (not really) or done something helpful to make it take two weeks to appear.

Thank the dieties for a long holiday weekend here in the states!

Regards all,
Cameron

[ckelloug]

First, we have the low force materials test machine:



Next we have the original sample mold that melted in the oven.



Here's the giant oven.



Here's the Leybold Sogevac SV25 vacuum pump.


Here's the new A2 tool steel sample mold in pieces on the bench.


Here's the mold with the vacuum lines connected.


Here's the polishing supplies used to take the shiny mold up to 3000 grit polish.


Here's the big surplus surface plate used in testing parts for flatness and for lapping mold parts on sandpaper.


Here's my epoxy bench with some epoxy samples.


Here's a better view that shows the soon to be re-gasketed vacuum chamber.


In conclusion, I've been pursuing the vacuum approach suggested by Tony and so far, what I would say is that building vacuum apparatus is very difficult and not for those without heavy machine tools. Unless there is a reliable way to vacuum bag E/G, vacuum molding in hard molds is likely to be a non-starter for folks that don't already have an army of machine tools.

So Chris, my progress is on the table. How's stuff in your sector?

Regards all,

Cameron

[PoppaBear10]

I have read the Index and this thread, and was wondering. Is there a "Final version" of the formula and process to use to make E/G Machine bases? I saw many advances and was hoping that there was an Aha moment.

I have a large machine, concept that I would like to try this on, if the process/fromula has been ironed out so to speak. (Please dont throw EG stones at me).

scott

[Eson]

Ive been thinking of using mineral/motor oil for release agents. Would that work?
I'm worried that multiple layers of wax might destroy any precision tolerance surfaces.
With oil you can try different viscosities. Also when the epoxy heats up, the oil will get thinner.